Is the universe fine-tuned?


Is the universe fine-tuned? In other words, were physical laws and constants of nature somehow chosen to allow complex life to arise?

In the past sixty-five years, science has gradually revealed a shocking lesson: by every right, you shouldn’t be alive — none of us should.

It was only too easy for something to have gone wrong. For instance, had gravity been a little stronger, or had carbon been slightly different, or had neutrinos not existed — in all cases the result is disaster:

A dead universe — devoid of chemistry, life, and consciousness.

Yet somehow, through incredible luck, divine intervention, or otherwise, we dodged every bullet to enjoy a universe with life.

Among possible universes, ours is among the rare few that permit life.
Among possible universes, ours is among the rare few where life, of any kind, is possible.

Against all odds, the universe is a place where life is possible. To what can we ascribe this great fortune? How can it be explained?

What really interests me is whether God could have created the world any differently; in other words, whether the requirement of logical simplicity admits a margin of freedom.

Albert Einstein

Why is the universe the way it is? Could it have been any other way?

First Clues

In the past century, cosmologists and particle physicists developed a nearly complete understanding of our world and cosmos.

Our current understanding now covers a range from the astronomical scales of superclusters down to the subatomic scales of quarks.

Between the 1960s and 1980s, cosmologists developed a model of the history and initial conditions of the universe, known as the Lamda-CDM model, which is also known as the standard model of cosmology.

The Lambda-CDM model has recently been confirmed by satellite observations, including observations made by the COBE, WMAP, and Planck, satellites. Image Credit: Wikipedia
The Lambda-CDM model has recently been confirmed by satellite observations, including observations made by the COBE, WMAP, and Planck satellites. Image Credit: Wikipedia

Likewise, between the 1950s and 1970s, particle physicists developed a model that describes fundamental forces of nature, and all known elementary particles. It is called the standard model of particle physics.

Aside from describing known particles, this model predicted particles that had never been seen. For instance, it predicted the Higgs boson.

The Large Hadron Collider at CERN, detected the Higgs boson in 2012 – 48 years after it was predicted – earning Peter Higgs and François Englert the 2013 Nobel Prize in Physics.
The Large Hadron Collider at CERN, detected the Higgs boson in 2012 — 48 years after it was predicted — earning Peter Higgs and François Englert the 2013 Nobel Prize in Physics.

But these new theories also disturbed physicists and cosmologists.

The more they came to understand the particulars of our universe: the properties of particles, the strengths of the forces, the initial conditions of the big bang — the more they realized we shouldn’t even be here.

As we look out into the universe and identify the many accidents of physics and astronomy that have worked together to our benefit, it almost seems as if the universe must in some sense have known we were coming.

Freeman Dyson in “Energy in the Universe” (1971)

A Perfect Balance

In the 1960s, cosmology transitioned from a loose set of unconfirmed speculations into a hard science backed by observation. In this emerging field, cosmologists found a coincidence that couldn’t be brushed off as mere luck — it demanded explanation.

In 1948, Ralph Alpher and Robert Herman were the first to predict that if the big bang happened, space should be filled with a uniform radiation emanating from all directions in the sky — a primordial heat remaining from the earliest moments of the universe.

At the time, there was no technology to detect this radiation. Alpher’s and Herman’s prediction soon fell into obscurity and was forgotten.

Sixteen years later, the chairman of physics at Princeton, Robert Dicke, rediscovered this prediction. With his colleagues Jim Peebles and David Wilkinson, they planned to build a device able to detect this radiation. They could thereby confirm or disprove the big bang.

But as fate had it, they were beaten to the punch by two radio astronomers: Arno Penzias and Robert Wilson of Bell Labs.

In 1964, Penzias and Wilson spent a frustrating year trying to isolate the source of a signal interfering with their observations, to no avail. A mutual friend suggested that they reach out to Robert Dicke, who was a short drive away from their facility in Holmdel, New Jersey.

Penzias and Wilson called Dicke who was in his office with Peebles and Wilkinson. After hearing the details of this interference signal from the Bell Labs researchers, Dicke turned to his colleagues and said, “Well boys, we’ve been scooped.”

The Princeton team drove to the Bell Labs facility to hear the signal for themselves. The signal had all the right characteristics. It’s temperature, distribution, consistency, directionality, and intensity — all matched perfectly with predictions of the big bang theory.

They listened to a cosmic hum of radiation that had been traveling through space for billions of years — the universe had a beginning.

Arno Penzias and Robert Wilson stand on top of the Holmdel Horn Antenna, the site where the first evidence for the big bang was detected.
Arno Penzias and Robert Wilson stand on top of the Holmdel Horn Antenna, the site where the first evidence for the big bang was detected.

It was one of the greatest scientific discoveries of the 20th century. It earned Penzias and Wilson the 1978 Nobel Prize in physics.

But this wasn’t the end of the story.

In 1969, Dicke recognized an unsettling consequence of the big bang and the expansion of the universe: it is highly unstable.

Dicke realized that the density of the universe must sit almost exactly at the critical density.
Dicke realized that the density of the universe must sit almost exactly at the critical density.

Had the density of the universe been slightly greater, the universe would have collapsed billions of years ago, long before life formed. Had the density been slightly less, the universe would have expanded too fast for galaxies and stars to form.

It was as though the universe sat on a knife edge. Had it not been so balanced, it would have fallen to either side and we wouldn’t be here.

Why the universe's density is perfectly balanced is known as the flatness problem – since according to general relativity, a perfect balance implies that spatial curvature of is zero (flat).
Why the universe’s density is perfectly balanced is known as the flatness problem — since according to general relativity, a perfect balance implies that spatial curvature is zero (flat).

Modern observations confirm space is flat to within the precision of our measurement abilities (within 1%). Due to the unstable nature of the balance, it implies that earlier, the balance was even greater.

Calculations reveal that if the curvature is below 1% today, then one second after the big bang, it would have been 10^{15} times less.

The situation is analogous to rolling a bowling ball down a lane so long that the ball could roll for billions of years. If we find the ball drifted less than 1% from center after rolling for billions of years, it suggests the ball must have been even closer to center when it started.

If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, it would have recollapsed before it reached its present size. On the other hand, if it had been greater by a part in a million, the universe would have expanded too rapidly for stars and planets to form.

Stephen Hawking in “A Brief History of Time” (1996 edition)

It appears as though we are the winners of a cosmic lottery. Had there been just slightly more mass, then the universe would have collapsed billions of years ago. Had there been slightly less, there would be no galaxies, stars, planets, or humans — there’d be no time for any structures to condense out of a rapidly expanding interstellar gas.

Our universe is a ‘Goldilocks’ universe where the density is just right.

Monkeying with Physics

As long as human beings have looked up at the night’s sky, we’ve wondered what the stars were and what makes them shine.

But despite wondering for hundreds of thousands of years, only in the last 80 have we come to understand how and why the stars shine.

In 1920, Arthur Eddington speculated that fusion of hydrogen into helium powered the stars. But it wasn’t until 1939 that Hans Bethe did the math to prove it, earning Bethe the 1967 Nobel Prize in physics.

The only chemical elements produced in the big bang were hydrogen and helium along with trace amounts of lithium and beryllium.

It was believed that stars could account for the production of the 88 other naturally occurring elements. The elements we know and love, which form our bodies and are necessary for our existence.

These include carbon, nitrogen, oxygen, sodium, iron, and so on.

But there was a problem. In 1939, it was discovered that there is no stable element with an atomic mass of 5. This is known as the mass-5 roadblock. Like a staircase missing a step, it prevented heavier elements from being built up adding one hydrogen nucleus at a time.

Instead, the process would halt at helium-4 (a helium atom with two protons and two neutrons). Perhaps two helium atoms could fuse to make beryllium-8, and thereby “jump” over the missing fifth step.

But this didn’t work either.

In 1932, John Cockcroft and Ernest Walton found that beryllium-8 is unstable. It lasts for less than a thousandth of a trillionth of a second. Their work won them the 1951 Nobel Prize in physics for transmuting the elements — realizing the long-held dream of alchemists.

There are no stable elements with a mass number of 5 or 8. "The mass gaps at 5 and 8 spelled the doom of Gamow's hopes that all nuclear species could be produced in the big bang one unit of mass at a time." – William Fowler
There are no stable elements with a mass number of 5 or 8. “The mass gaps at 5 and 8 spelled the doom of Gamow’s hopes that all nuclear species could be produced in the big bang one unit of mass at a time.” — William Fowler

So yet another step was missing. With no known mechanism to get over the hurdle of the mass-5 and mass-8 roadblocks, there was no explanation for how elements necessary to life came to be.

This problem led the cosmologist Fred Hoyle, in 1953, to make what’s described as “the most outrageous prediction” ever made in science.

In the triple-alpha process, three helium nuclei fuse together at once to make carbon. Image Credit: Wikimedia
In the triple-alpha process, three helium nuclei fuse together at once to make carbon. Image Credit: Wikimedia

Hoyle’s outrageous prediction was the existence of a yet undiscovered excited energy state of the carbon-12 nucleus, which had somehow been missed by all the particle physicists in the world.

If this state existed, it would allow the triple-alpha process — the simultaneous collision of three helium-4 nuclei to yield carbon-12.

If carbon could be made this way, the mass-5 and mass-8 roadblocks could be cleared, and then other heavier elements could be built one hydrogen or helium nucleus at a time. Without this state, carbon would be many millions of times rarer, and we wouldn’t be here.

So, Hoyle reasoned, this state of carbon must exist.

In 1953, Hoyle traveled from Cambridge, England to visit William Fowler’s nuclear physics lab at Caltech. Hoyle asked that Fowler’s lab do the experiments to check for this state of the carbon-12 nucleus, which he predicted should be at an energy level of 7.68 million eV.

I was very skeptical that this steady state cosmologist, this theorist, should ask questions about the carbon-12 nucleus. […] Hoyle just insisted — remember, we didn’t know him all that well — here was this funny little man who thought that we should stop all this important work that we were doing otherwise and look for this state, and we kind of gave him the brush off.

William Fowler in interview (1973)

But Hoyle succeeded in convincing a junior physicist at the lab, Ward Whaling, to check for it. Five months later, Hoyle received word.

Whaling confirmed the existence of the excited state of carbon-12, and it was almost exactly where Hoyle predicted: at 7.655 million eV!

Hoyle’s prediction is remarkable because he used astrophysics (the physics of stars) to find unknown properties in nuclear physics (the physics of atoms and their nuclei). Fowler was an instant convert.

So it was really quite a tour de force, that a man who walked into the lab predicted the existence of an excited state of a nucleus, and when the appropriate experiment was performed it was found. And no nuclear theorist starting from basic nuclear theory could do that then, nor can they really do it now. So Hoyle’s prediction was a very striking one.

William Fowler in interview (1973)

Fowler took a year off from his post at Caltech to work with Hoyle in Cambridge. Together with two astronomers, Margaret and Geoffrey Burbidge they worked out a complete theory of element formation, showing how every element is produced and explaining the relative abundances of the elements as found in nature.

Their work was revolutionary and it made a name for the authors.

For this work, Fowler received the Nobel Prize in physics in 1983. Hoyle, however, did not share in the prize, creating controversy.

In any event, no one denied the significance of their accomplishment.

With their 1957 paper, humanity finally had an understanding of where all the matter, which makes up our world, our food, our shelter, our very bodies, came from — the innermost depths of long-dead stars.

Carl Sagan - Cosmos- Stars - We Are Their Children
This is what Carl Sagan meant when he said “We are star stuff harvesting star light.”

We are literally the ashes of long dead stars. If you’re less romantic, we are the nuclear waste from the fuel that made those stars shine.

Sir Martin Rees in “What We Still Don’t Know: Why Are We Here” (2004)

And so, the world as we know it is owed to the carbon-12 nucleus having this chance property. Like the delicate balance of the density of the universe, the existence of this state hangs in a delicate balance.

As it happens, the energy level of this state is at 7.655 MeV. Had the energy level of this state been less than 7.596 MeV or greater than 7.716 MeV, there would be almost no carbon in the universe.

The minor miracle of the carbon-12 nucleus having this excited state and it being in exactly the right range did not go unnoticed.

Some super-calculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of nature would be utterly minuscule.
[…]
A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.

Fred Hoyle in “The Universe: Past and Present Reflections” (1982)

The balancing of the universe’s density, and the fortune of the carbon-12 excited state were just the first of many “cosmic coincidences.”

The more scientists probed the inner workings of the universe, the more lucky coincidences they found. With each one, evidence gathered to support the idea that the laws of physics are finely-tuned to permit the emergence of complexity, and with that complexity, life.

Cosmic Coincidences

The expansion rate of the universe, and the existence of the excited state for the carbon-12 nucleus are due to fundamental physical forces.

For instance, the expansion rate of the universe is governed by the strength of gravity and the energy of the vacuum. Likewise, the excited state of carbon-12 is determined by electromagnetic and nuclear forces.

So far, particle physicists have identified 25 dimensionless constants in the standard model, while cosmologists have identified five others.

Like positions of a dial, these dimensionless constants could have taken other values.
Like positions of a dial, these dimensionless constants could have taken other values.

A universe where these fundamental constants have different values is just as mathematically and logically consistent as our own. They represent other universes among the set of possible universes.

Accordingly, these constants are considered free parameters.

Of the 30 known fundamental physical constants, very few of them can change to any significant degree without leading to a barren universe. For instance, universes of only hydrogen, universes with no aggregations of matter, or universes of only black holes.

Let’s review the fragility of our universe to tweaks to these constants.

Chemistry and Life

Our universe has a rich chemistry. The 92 naturally occurring chemical elements can combine in a nearly unlimited number of ways.

Atoms assemble into molecules that encode digital information and can even self-arrange into structures that reproduce themselves.

Shortly after the big bang, there was no carbon, oxygen, nitrogen, nor any of the other elements necessary for life. There was only hydrogen and helium. Image Credit: BICEP2
Shortly after the big bang, there was no carbon, oxygen, nitrogen, nor any of the other elements necessary for life. There was only hydrogen and helium. Image Credit: BICEP2

Three minutes after the big bang, the only elements in the universe were hydrogen and helium. The universe remained this way for hundreds of millions of years — a thin haze of light gas.

It’s doubtful that any life could arise in a universe with only these elements. Helium is chemically inert and by itself, hydrogen can only make dihydrogen. Without chemistry, the universe would be lifeless.

Fortunately, the fusion in stars gave us 90 other elements, and with them, new ways to combine, react, and generate complexity.

Of the 92 stable chemical elements, 60 can be found in your body. Of those, around 30 are believed to play a biological role in humans.

The King of the Elements

Some elements are more important than others when it comes to supporting life. Of those, carbon is the most special. For its unique role in chemistry, carbon’s been called the king of the elements.

Elemental carbon can appear in several forms, including graphite, coal, fullerenes, and diamond. Image Credit: Wikipedia
Elemental carbon can appear in several forms, including graphite, coal, fullerenes, and diamond. Image Credit: Wikipedia

Carbon is the only element that can link up 4 other atoms, and also form unlimited chains made of links with itself. Carbon is therefore the glue that binds large and complex molecules together.

Nearly every molecule with more than 5 atoms contains carbon.

This includes essentially all biomolecules: carbohydrates, fats, proteins, RNA, DNA, amino acids, cell walls, hormones, and neurotransmitters.

Without carbon, there could be no life as we know it.

There could be no life based on molecules, since complex molecules are impossible without the glue of carbon to hold them together.

That carbon exists at all is due to the miracle of the Hoyle state, which depends on properties of nuclear and electromagnetic forces.

A Desert Universe

After hydrogen and helium, oxygen is the most abundant element in the universe. By mass, it makes up 89% of the oceans, and 50% of Earth’s crust. It even makes up the majority of your weight.

For every 100 pounds someone weighs, 65 pounds are oxygen.

Carbon reacts with oxygen to produce carbon dioxide and energy.
Carbon reacts with oxygen to produce carbon dioxide and energy.

Oxygen is important to life for its reactivity. It reacts with every element except for fluorine and the noble gasses. Without oxygen, there could be no H2O — and the whole universe would be a desert.

We owe our existence not only to the presence of oxygen in the universe, but to the availability of oxygen outside the cores of stars.

With the exception of five lightest elements, all naturally occurring chemical elements are dispersed into space by the explosions of stars. Image Credit: Wikimedia
With the exception of the five lightest elements, all naturally occurring chemical elements are dispersed into space by the explosions of stars. Image Credit: Wikimedia

All our oxygen came from the cores of massive stars. When these stars exhausted their fuel, their cores collapsed under their own weight.

These cores are roughly the size of our moon, but have the mass of our sun. Accordingly, their gravitational field is 200 billion times stronger than Earth gravity. It’s so strong that infalling matter reaches a quarter of the speed of light by the time it hits the center.

In 10 seconds, 10% of the star’s mass is converted into energy. The result is a type II supernova, also known as a core collapse supernova. The star’s outer layers falling in would create a black hole and lock away all oxygen forever — except this doesn’t happen.

According to Chinese and Japanese astronomers, in 1054, a "guest star" appeared in the sky. It shone as brightly as the moon and was bright enough to be seen in the day. In 1999, NASA pointed the Hubble space telescope in the direction this light was reported. It saw the aftermath of a great explosion: the crab nebula. The remains of an exploded star.
According to Chinese and Japanese astronomers, in 1054, a “guest star” appeared in the sky. It shone as brightly as the moon and was bright enough to be seen in the day. In 1999, NASA pointed the Hubble space telescope in the direction this light was reported. It saw the aftermath of a great explosion: the crab nebula. The remains of an exploded star.

In the last moments of collapse, interactions by the weak nuclear force trigger a bounce that blows away the outer layers of the star.

Had the weak force been stronger, this bounce would happen too early. If it had been weaker, then the bounce would happen too late. In both cases, the result is a disaster. The entire star, along with all of its oxygen would fall into a black hole and never be seen again.

Without oxygen, chemistry is crippled. There would be no water, acids, bases, sugars, carbohydrates, fats, proteins, alcohols, nor any respiration, combustion, or photosynthesis as we know them.

Our lives are indebted to yet another precise balance. This time, it is a balance of the seemingly inconsequential weak nuclear force.

Every breath you take contains atoms forged in the blistering furnaces deep inside stars. Every flower you pick contains atoms blasted into space by stellar explosions that blazed brighter than a billion suns.

Marcus Chown in “The Magic Furnace: The Search for the Origins of Atoms” (2001)

Particle Physics and Life

The chemical properties of elements are set by properties of smaller parts, called particles. These include protons, neutrons, and electrons.

Diagram of an atom. In this case, the element lithium. Image Credit: Wikimedia
Diagram of an atom. In this case, the element lithium. Image Credit: Wikimedia

The nucleus of the atom is made of nucleons (protons and neutrons), while the outer shell of the atom is composed of electrons. Nucleons are themselves made of more fundamental particles called quarks.

The standard model contains 17 known elementary particles. Image Credit: Wikimedia
The standard model contains 17 known elementary particles. Image Credit: Wikimedia

Nearly every particle in the standard model of particle physics has to exist, or else we would not be here. Moreover, in most cases, the properties of each particle, such as its mass, had to be just so.

A World of Electrons

Electrons, being so small and light may seem remote and abstract, but the world we know is primarily the world of electrons.

The light we see is emitted by electrons. Sounds we hear are carried by electrons bouncing off each other. Tastes and smells we experience are caused by chemical reactions driven by electrons. Every time we touch something we feel the repulsion of that thing’s electrons.

In both plasma globes and lightning bolts, the path of electrons is visible.
In both plasma globes and lightning bolts, the path of electrons is visible.

Every chemical reaction is activity between electrons. Accordingly, the properties of elements, the compounds they can form, their level of reactivity, all of it, is determined by the properties of electrons.

If the mass or charge of electrons had different values, all of chemistry would change. For example, if electrons were heavier, atoms would be smaller and bonds would require more energy. If electrons were too heavy there would be no chemical bonding at all.

If electrons were much lighter, bonds would be too weak to form stable molecules like proteins and DNA. Visible and infrared light would become ionizing radiation. They would be as harmful as X-rays and UV are to us now. Our own body heat would damage our DNA.

Luckily for us, electrons weigh just enough to yield a stable, but not sterile chemistry.

The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron. […]
The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life. For example, if the electric charge of the electron had been only slightly different, stars either would have been unable to burn hydrogen and helium, or else they would not have exploded.

Stephen Hawking in “A Brief History of Time” (1988)

A Starless Universe

Electrons are very light compared to the protons and neutrons:

  • The proton’s mass mp is 1,836.15 times the mass of an electron me
  • The neutron’s mass mn is 1,838.68 times the mass of an electron me

In a ton of coal, the electrons contribute little more than half a pound.

We’ve seen how electron weight is of critical importance to chemistry. But so too are masses of other particles. It was important that:

  1. Protons and neutrons be close in weight: mpmn
  2. Yet differ in mass by more than one electron: |mpmn| > me
  3. And also that neutrons be heavier than protons: mn > mp

As it happens, all three of these conditions hold true. Had any of them not been met we end up with a universe devoid of life.

Particle physics provides no explanation for why neutrons are heavier than protons, rather than the other way around, except if protons were heavier, there could be no life like us.
Particle physics provides no explanation for why neutrons are heavier than protons, rather than the other way around, except if protons were heavier, there could be no life like us.

A free neutron is a neutron not part of an atomic nucleus. Free neutrons are unstable. They have a mean lifetime of ~15 minutes. Left alone, a free neutron will decay into a proton and electron.

Such decay is possible because neutrons weigh more than a proton and electron put together. Had instead, protons weighed more, then neutrons would be stable and protons would be unstable. A free proton would then be able to decay into a neutron and a positron.

But most of the hydrogen in the universe has a nucleus that is nothing but a free proton. If protons were unstable then hydrogen is unstable. Little hydrogen would survive to today. There would be no stars as we know them — only neutron stars and black holes.

Picture of the M87 black hole. Properties of subatomic particles at the smallest scales, determine the course of events of the universe at the largest scales. If neutron's weighed ever-so-slightly less, there would be no stars. Image Credit: Event Horizon Telescope
Picture of the M87 black hole. Properties of subatomic particles at the smallest scales, determine the course of events of the universe at the largest scales. If neutron’s weighed ever-so-slightly less, there would be no stars. Image Credit: Event Horizon Telescope

It was also necessary that neutrons be unstable. Had protons and neutrons weighed the same, or been within one electron’s weight, then both nucleons would be stable. There would have been equal numbers of protons and neutrons in the first minutes following the big bang.

Again the result is disaster.

With equal numbers, each proton could pair with a neutron to form hydrogen-2. Hydrogen-2 rapidly reacts to form helium-4. There would be no more hydrogen of any kind in the universe: no fuel to power stars like our sun, no water, no organic chemistry, no life.

A Universe without Atoms

Photons are particles of light and carriers of the electromagnetic force.

Photons are the reason: the sun warms you, like magnets repel, electrons bind to nuclei to make atoms, and why your eyes can see.

A laser beam consists of photons – so too are all gamma rays, X-rays, ultraviolet light, visible light, infrared, microwaves, and radio waves.
A laser beam consists of photons — so too are all gamma rays, X-rays, ultraviolet light, visible light, infrared, microwaves, and radio waves.

Of all known particles, only two are massless. One is the gluon. The other is the photon. It was necessary for life in the universe that photons be massless. Had they not been, there would be no atoms.

Virtual photons carry the electrostatic and magnetic forces. Because photons are massless, virtual photons can act over any distance.

If on the other hand, photons had mass, then virtual photons could only act over short ranges, on the order of the size of a nucleus.

There would then be no attraction or repulsion by electrons and nothing to bind them to atoms. There would be no chemistry, only plasma.

Ghosts to the Rescue

Buried a kilometer under a mountain in Japan, thirteen thousand electronic eyes sit vigil over a tank of ultra pure water.

The Super-Kamiokande detector at the Kamioka Observatory in Japan.
The Super-Kamiokande detector at the Kamioka Observatory in Japan.

Each eye is 20 inches wide and sensitive enough to detect single photons. They wait, in total darkness, shielded from radiation by the mountain, submerged in 20 Olympic-sized swimming pools of water.

The eyes wait patiently for a flash of light to appear in the water. If they’re lucky this happens maybe once every 100 minutes. But what could cause a flash of light out of total darkness? — ghost particles.

The flashes are due to a tiny particle known as the neutrino. Neutrinos are so small and light, it takes half a million of them to equal the weight of one electron. Further, they have no electric charge and so can pass straight through normal matter, even whole mountains.

A wall of lead one light-year thick would only block half of them.

Neutrinos are really pretty strange particles when you get down to it. They’re almost nothing at all, because they have almost no mass and no electric charge. They’re just little wisps of almost nothing.

John Conway in PBS interview (2011)

The infrequency of neutrino detection at the Kamioka Observatory is not because neutrinos are rare. Neutrinos are everywhere. Each second, 100 billion neutrinos pass through the tip of your thumb.

On Earth, most neutrinos come from the core of the sun. About 2% of the Sun’s energy is radiated away as neutrinos. To neutrinos, the Earth is transparent. Day or night, they pass through us, unnoticed.

This has earned neutrinos the nickname of ghost particles.

This is why neutrinos are so hard to detect. Only once every few hours, is a neutrino stopped by the massive water tank in Kamioka.

But on February 24th, 1987, something strange happened. It had not happened before nor has it happened since: in the span of 10 seconds, the Kamioka observatory registered 12 separate flashes.

It was not a problem with the equipment. At the same time, and on the other side of the world, the IMB detector in Ohio also saw a flurry of flashes in their neutrino detector during those same 10 seconds.

Something, somewhere, released an incredible burst of neutrinos.

As it turned out, the source of this neutrino burst was something far away and long ago — the death of a star beyond our galaxy.

The remains the supergiant star some 168,000 light years away.
Image Credit: ESA / NASA / Hubble
The remains of the supergiant star — some 168,000 light years away.
Image Credit: ESA / NASA / Hubble

These neutrino labs were the first to detect the explosion. Astronomers wouldn’t notice the event until several hours later. Today, a network of neutrino labs now form our supernova early warning system.

In 2002, Masatoshi Koshiba, who directed the neutrino experiments, and Raymond Davis Jr., who built the first neutrino detector, shared the Nobel Prize in Physics for the detection of these neutrinos.

Given their ghostly nature, it would be easy to write off neutrinos as playing no important role in the universe, and having no relevance to life. But we owe our existence to the tiny neutrino.

It is the neutrino that rescues oxygen and other vital elements from disappearing into the collapsing core of a dying star. During a core collapse, 100 times more energy is released in 10 seconds than our sun will emit in her 10 billion year life.

Around 99% of this energy is released as neutrinos.

Only a ghost particle could escape from the core and reach the outer layers of the collapsing star. There they deposit a little of their energy, giving the outer layers enough of a push to blow the star apart and save elements like oxygen from otherwise certain doom.

There would be no oxygen, no water, and likely, no life, if it weren’t for the neutrino and the role it plays during the deaths of these giants.

A very interesting question to me is: is the universe more complicated than it needs to be to have us here? In other words, is there anything in the universe which is just here to amuse physicists?

It’s happened again and again that there was something which seemed like it was just a frivolity like that, where later we’ve realized that in fact, “No, if it weren’t for that little thing we wouldn’t be here.” I’m not convinced actually that we have anything in this universe which is completely unnecessary to life.

Max Tegmark in “What We Still Don’t Know: Why Are We Here” (2004)

Fundamental Forces and Life

There are just four fundamental forces in nature:

  1. Electromagnetism
  2. Gravity
  3. The Weak Nuclear Force
  4. The Strong Nuclear Force

These forces drive all movement and every physical interaction. In each of them, scientists have noticed an inexplicable balancing act.

Electromagnetism and the “Greatest Damn Mystery in Physics”

Movement of a compass's needle is driven by the electromagnetic force.
Movement of a compass’s needle is driven by the electromagnetic force.

The strength of the electromagnetic force is determined by a dimensionless constant called the fine-structure constant (\alpha).

\alpha = 0.00729351 \approx \frac{1}{137}

Due to \alpha having a value of \frac{1}{137}, the speed of an electron in a hydrogen atom is \frac{1}{137} the speed of light. It also sets the fraction of electrons that emit light when they strike phosphorescent screens at \frac{1}{137}.

Determining such fundamental properties as the speed of electrons in atoms means \alpha determines how large atoms are, which in turn determines what molecules are even possible.

A different \alpha would change properties like the melting point of water and the stability of atomic nuclei.

Physicists calculated that had \alpha differed from its current value by just 4%, the carbon-12 excited energy level would not be in the right place. There would be almost no carbon in the universe if \alpha were \frac{1}{131} or \frac{1}{144}.

It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it. Immediately you would like to know where this number for a coupling comes from: is it related to pi or perhaps to the base of natural logarithms?

Nobody knows. It’s one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the “hand of God” wrote that number, and “we don’t know how He pushed his pencil.” We know what kind of a dance to do experimentally to measure this number very accurately, but we don’t know what kind of dance to do on the computer to make this number come out, without putting it in secretly!

Richard Feynman in “QED: The Strange Theory of Light and Matter” (1985)

Gravity and the Lives and Deaths of Stars

The gravitational force between an apple and the Earth moves it toward the ground.
The gravitational force between an apple and the Earth pulls both together.

The strength of gravity is determined by a dimensionless constant called the gravitational coupling constant (\alpha_{G}).

\alpha_{G} = 5.907 \times 10^{-39} = \newline
0.000000000000000000000000000000000000005907

It is striking how small \alpha_{G} is. The smallness of \alpha_{G} means gravity is exceptionally feeble compared to the other forces — so much weaker, it’s an unsolved mystery of physics (called the hierarchy problem).

If \alpha_{G} were larger, you and everything else in the universe would weigh more. Conversely, if \alpha_{G} were smaller, everything would weigh less.

But if gravity weren’t so weak, we wouldn’t be here.

In 1947, the physicist Pascual Jordan noticed a strange coincidence. He described it in his book “The Origin of the Stars.”

The coincidence he noticed was that the mass of the sun is suspiciously close to the weight of a proton divided by {\alpha_{G}}^{3/2}. In fact, the mass of nearly every star is within a factor of ten from this number.

There is a reason for this.

The electrostatic repulsion between two protons is about 10^{36} times stronger than their gravitational attraction. Accordingly, once you have around 10^{36 \times (3/2)} or 10^{54} protons in one place (as in a star), the gravitational attraction between the star and a proton begins to eclipse the strength of two proton’s repulsion, sparking fusion.

But should the mass of a compact object increase much past this level, the star becomes unstable and will either blow itself apart or collapse into a neutron star or black hole at the Chandrasekhar limit.

The reason stars are so big is because gravity is so weak.

If gravity were stronger, everything miniaturizes. Planets, mountains, animals — even the observable universe — need to shrink to not collapse under their weight. (See: “Why are things the size that they are?“)

A stronger gravity not only decreases a star’s size, but also its life expectancy. A smaller star leaks heat more quickly. If gravity were ten times stronger, an equivalently hot star would live just one tenth the time. So if \alpha_{G} had 37 zeros, rather than 38, after its decimal point, a star like our sun would live not ten billion years, but one billion.

A small sun sets on a planet devoid of complex life.
Image Credit: NASA/JPL/Texas A&M/Cornell
A small sun sets on a planet devoid of complex life.
Image Credit: NASA/JPL/Texas A&M/Cornell

Short-lived stars doom complex life. It took billions of years for multicellular life to appear on Earth. The chance for life to appear at all only diminishes as \alpha_{G} increases.

The cosmologist Martin Rees described the astrophysics of a hypothetical universe where \alpha_{G} is a million times stronger than it is:

Heat would leak more quickly from these ‘mini-stars’: in this hypothetical strong-gravity world, stellar lifetimes would be a million times shorter. Instead of living for ten billion years, a typical star would live for about 10,000 years. A mini-Sun would burn faster, and would have exhausted its energy before even the first steps in organic evolution had got underway.

Sir Martin Rees in “Just Six Numbers” (1999)

Life owes its existence to weak gravity. But we should also be grateful that \alpha_{G} isn’t zero or negative. This leads to disaster of another kind.

With zero or negative gravity, no galaxies, stars, or planets form. There would be no place for life to begin for there would be no places at all.

The Weak Nuclear Force and the Biggest Explosions

The weak force is ultimately responsible for the eerie glow surrounding nuclear reactors.
The weak force is ultimately responsible for the eerie glow surrounding nuclear reactors.

The weak nuclear force causes particle decay. The decay rate is set by a dimensionless constant called the weak force coupling constant (\alpha_w).

\alpha_w \approx 0.000001 = 10^{-6}

Unstable particles, such as neutrons, muons, and pions, spontaneously convert (or decay) into other particles. For example, in beta decay a neutron decays into a proton, electron and neutrino.

A larger \alpha_w shortens the lives of unstable particles and accelerates radioactive decay. But altering \alpha_w has other consequences.

The value of \alpha_w causes the biggest explosions in the universe.

Russia releases secret footage of 1961 Tsar Bomba hydrogen blast

The biggest man-made explosion was the 50 megaton Tsar Bomba. It had a yield of 50 million tons of TNT. Its mushroom cloud rose to 42 miles, reaching the edge of space at five times the height of Everest.

Yet this explosion is pitiful next to the biggest explosions known.

The biggest explosions in the universe are core-collapse supernovae. They release the energy of 10^{28} Tsar bombs. If each sand grain equaled a billion Tsar bombs, and if every grain of sand on Earth’s beaches exploded at once, that would approach the power of a core-collapse supernova.

The neutrino luminosity of a core-collapse supernova briefly exceeds the light output of all the stars of [the observable] universe.

Craig Hogan in “Why the Universe is Just So” (1999)

As we’ve seen, these most-powerful explosions depend on the most ghostly of particles — the neutrino. But the explosions also depend on the neutrino having the right amount of ghostliness.

Ever so rarely, a neutrino interacts with a particle through the weak nuclear force. For instance, a neutrino might interact with an electron and give it enough energy to knock it away from its atom.

This electron, if travelling fast enough, creates a shock-wave of light — the optical equivalent of a sonic boom — known as the Cherenkov effect. The effect is named for Pavel Cherenkov, who first noticed it in 1934, earning him a share of the 1958 Nobel Prize in Physics.

This effect is responsible for the flashes of light neutrino detectors look for, and also the blue glow seen inside nuclear reactors.

Since neutrinos feel the weak nuclear force, the value of \alpha_w determines the ease at which neutrinos interact with regular matter — it sets the neutrino’s level of “ghostliness.”

Recent models show that had \alpha_w been less than half its current value, neutrinos would leave the collapsing core too quickly to forestall the collapse. Conversely, had \alpha_w been more than five times its current value, then neutrinos would be trapped in the core for too long. Again, they would be unable to prevent the collapse of the star.

How to blow up a star
Recent computer simulations reveal how the largest explosions in the universe are caused by otherwise unassuming particles.

Core-collapse supernovae are the source of all free oxygen in the universe. Every breath you take, and drop of water you sip contains oxygen from these stars, blown into space by neutrinos.

If \alpha_w had been a little bigger or smaller, elements necessary for life would stay forever trapped in the remnants of giant stars. Accordingly, life as we know it depends on \alpha_w being close to 0.000001.

The Strong Nuclear Force and Sticky Nucleons

The strong nuclear force reveals its power whenever atoms split or fuse.
The strong nuclear force reveals its power whenever atoms split or fuse.

The strong nuclear force is the glue that holds atomic nuclei together. The stickiness of this glue is determined by a dimensionless constant called the strong force coupling constant (\alpha_s).

\alpha_s \approx 1

Of the four fundamental forces, \alpha_{s} is the strongest. It is 137 times stronger than the electromagnetic force, and a million times stronger than the weak nuclear force. Unlike electromagnetism and gravity, the strong force is range-limited. It can only be felt at up to a few femtometers away.

A larger \alpha_{s} makes fusion easier and fission harder. With a smaller \alpha_{s}, the reverse happens. We are lucky \alpha_{s} is much larger than \alpha. If it weren’t, the strong force wouldn’t be able to overcome the electrostatic repulsion of protons, and nuclei of atoms wouldn’t stay together at all.

In such a universe, the only possible atom is hydrogen. Accordingly, if the strong force weren’t so strong, we wouldn’t be here.

In your body, only about 1% of your weight comes from the weight of your constituent particles. The other 99% comes from the binding energy of the strong nuclear force.
In your body, only about 1% of your weight comes from the weight of your constituent particles. The other 99% comes from the binding energy of the strong nuclear force.

The reason there are ~100 chemical elements is due to the fact that the strong force is ~100 times stronger than the electromagnetic force.

But it is a delicate balance. The strong force must not be too strong.

Had \alpha_{s} been 3.7% stronger, fusion would be too easy. All hydrogen would have fused into helium in the first minutes after the big bang. There would be no water, no organic compounds, nor fuel for stars like our sun.

Yet, if \alpha_{s} were 11% weaker, hydrogen-2 wouldn’t be stable. Hydrogen-2 plays a necessary role in fusion of stars like our sun. So with a slightly weaker strong force, again our sun doesn’t shine.

A more recent analysis has placed even tighter constraints on \alpha_{s}, given the details of how carbon and oxygen are produced in the cores of stars:

Even with a change of 0.4% in the strength of [the nucleon-nucleon] force, carbon-based life appears to be impossible, since all the stars then would produce either almost solely carbon or oxygen, but could not produce both elements.

Luke A. Barnes in “The Fine-Tuning of the Universe for Intelligent Life” (2011)

Why does \alpha_{s} have the value it does? No one can say. All we know is that if it didn’t, there would be no one here to speculate about it.

Cosmology and Life

We’ve seen how particle physics, operating at the smallest scales of reality, is littered with coincidences that make life possible.

But particle physicists are not alone in mystifying themselves with discoveries of this kind. Cosmologists, studying the largest scales of reality, and the origins of the universe, have found that had the initial conditions not been just right, none of us would be here.

Infinitely Intelligent Babies and Spacetime Dimensionality

Our universe is marked by having three dimensions of space (height, width, depth) and one dimension of time. Under Einstein’s relativity, space and time merge into a unified whole called spacetime.

Since there are 3 dimensions of space and 1 of time, physicists sometimes refer to this as a 3 + 1 spacetime. (See: “What is time?“)

Even the number and character of dimensions appear significant to life. In a 2-dimensional space like Flatland, topological constraints make certain vital structures difficult or impossible to form.

Two dimensions impose limits on complexity: for example a digestive tracts cut creatures in half! Further, wires, nerve cells, neurons, and blood vessels can't cross without intersecting.
2D space imposes limits on complexity: for example digestive tracts cut creatures in half! Furthermore, nerve cells, neurons, and blood vessels can’t cross without intersecting.

Difficulties of another kind appear when the number of spatial dimensions increases beyond 3. With 4, rather than 3, dimensions of space, Newton’s inverse square law becomes an inverse cube law.

In space with ≥4 dimensions, orbits are unstable. Planets either crash into their stars or drift away. Electron orbits also become unstable.

In 1997, the cosmologist Max Tegmark was the first to notice and describe the apparent necessity of 3 + 1 spacetime to life.

With more or less than one time dimension, the partial
differential equations of nature would lack the hyperbolicity property that enables observers to make predictions. In a space with more than three dimensions, there can be no traditional atoms and perhaps no stable structures. A space with less than three dimensions allows no gravitational force and may be too simple and barren to contain observers.

Max Tegmark in “On the dimensionality of spacetime” (1997)
Our spacetime falls into the one square where life is possible. Image Credit: Max Tegmark
Our spacetime falls into the one square where life is possible. Image Credit: Max Tegmark

This leaves three spatial dimensions and one time dimension as the only viable option. In other words, an infinitely intelligent baby could in principle, before making any observations at all, calculate from first principles that there’s a level II multiverse with different combinations of space and time dimensions, and that 3 + 1 is the only option supporting life. Paraphrasing Descartes, it could then think, Cogito, ergo three space dimensions and one time dimension, before opening its eyes for the first time and verifying its predictions.

Max Tegmark in “Our Mathematical Universe” (2014)

Dark Matter and the Cosmic Web

Cosmologists suspect there exists a particle even more ghostly than the neutrino. While neutrinos can feel both gravity and the weak force, particles of dark matter are thought to only respond to gravity.

There are many theories for what dark matter could be. Examples include axions, sterile neutrinos, and WIMPs. So far, all have eluded direct detection. If dark matter only interacts through gravity, it would be invisible even to such sensitive detectors as the Super-Kamiokande.

For all that is presently known, dark matter particles could be everywhere. Many might be streaming through Earth and our bodies right now. But if they are, we wouldn’t have the slightest clue.

The rotational speeds of stars within galaxies provided hints of dark matter's presence.
The rotational speeds of stars within galaxies provided hints of dark matter’s presence.

In 1884, Lord Kelvin analyzed the speeds of stars orbiting the galaxy. He found that stars moved so fast that they should fly off — there wasn’t enough gravity from visible matter to keep them in orbit. This led Kelvin to speculate that most matter is in dim or dark stars.

Current models suggest that by mass, dark matter makes up 84.5% of all the matter in the universe — “regular matter” is less common!

Modern detection efforts have mostly ruled out large aggregations of regular matter, (such as black holes, rogue planets, and brown dwarfs), as candidates for this missing mass. This finding has led most physicists to look to a yet undiscovered particle (or family of particles) as responsible.

Dark matter may be invisible, but that doesn’t mean it’s unimportant. On the contrary, dark matter appears necessary to our existence.

What exactly happened after the Big Bang?
Detailed computer simulations of the universe reveal the critical role dark matter plays in the formation of galaxies, stars, and life.

Gravity caused dark matter to coalesce in filaments, or tendrils, forming a great cosmic web. This web is the scaffolding for the structures of the universe. Regular matter, which makes up galaxies and galaxy clusters clumped along the filaments of this web.

I worked on trying to make universes without dark matter in a computer and they were always a disaster. They just never worked. So a universe without dark matter is just a failed universe. It’s a pretty boring barren place. Galaxies just don’t form, and if galaxies don’t form, stars don’t form, and if stars don’t form, presumably people don’t form.

It was only when we got the right chemistry, you know, the right mix of dark matter and ordinary matter that we suddenly came up with replica universes that for all intents and purposes look just like the real thing.

Carlos Frenk in “What We Still Don’t Know: Why Are We Here” (2004)
These are not actual galaxies, but objects found in computer simulations. Galaxy-like objects only appear with the right mix of dark matter in the simulation. Image Credit: Illustris Project
These are not actual galaxies, but objects found in computer simulations. Galaxy-like objects only appear with the right mix of dark matter in the simulation. Image Credit: Illustris Project

Without dark matter, and also the right ratio of dark matter to ordinary matter, our universe would be a “boring barren place.”

Universal Homogeneity and Unwelcome Stars

The 1964 detection of microwaves by Arno Penzias and Robert Wilson helped establish the big bang. Terrestrial measurements showed the signal had an equal intensity, coming from every direction in the sky.

But according to cosmological theories, the signal shouldn’t be uniform, there needed to be some density variations, or else gravity wouldn’t have caused any clumping into galaxies at all.

It took satellite-based measurements to give sufficient precision. The measurements painted a picture of the mottled nature of the CMB.

The cosmic microwave background or (CMB) is a map of the oldest radiation in the universe as it appears across the sky. Image Credit: Planck/ESA
The cosmic microwave background or (CMB) is a map of the oldest radiation in the universe as it appears across the sky. Image Credit: Planck/ESA

Project leaders behind these satellite measurements, George Smoot and John Mather, received the 2006 Nobel Prize in Physics. In the words of the prize committee, the measurements “marked the inception of cosmology as a precise science.”

The temperature of space across the night’s sky is nearly, but not perfectly, uniform. It varies by approximately two parts in 100,000. This has been termed the homogeneity constant (Q).

Q \approx 0.00002 = 2 \times10^{-5}

The variations in temperature are due to density variations in the early universe. Over time, these density differences became magnified through gravity to seed all the large-scale structures we see today: the web of dark matter, galaxy superclusters, and galaxies themselves.

We are very fortunate that Q is two parts in \text{100,000} rather than in \text{10,000} or \text{1,000,000} — in either case, we probably wouldn’t be here.

Q determines the size and densities of galaxies. A reduced Q leads to small and sparsely populated galaxies. Such galaxies wouldn’t have the gravity to keep and recycle the heavy elements bequeathed by previous generations of stars. If Q were much smaller, galaxies wouldn’t form at all.

A larger Q is no better. Had Q been larger, galaxies become so densely populated that stars often pass near each other. These unwelcome guests cause havoc for planets. They can permanently alter planetary orbits — even cause planets to be ejected from their star system.

This would be a disaster for any life developing on such worlds.

An artist's conception of a black hole drawing in matter.
An artist’s conception of a black hole drawing in matter.

If Q were even bigger, say one part in \text{1,000} then there would be no stars or galaxies: only monster black holes that quickly swallow all matter in the universe.

Again there would be no chance for life as we know it.

Fortunately, with Q = 2 \times 10^{-5}, our universe is neither too lumpy, nor too smooth. It’s just right. Stars are close enough to reuse elements from previous generations, but not so close they run into each other.

The Cosmological Constant and Einstein’s Greatest Blunder

Einstein's "greatest blunder" turned out to be a breakthrough.
Einstein’s “greatest blunder” turned out to be a breakthrough.

The strength of the force that drives the expansion of the universe is determined by a number called the cosmological constant (\Lambda).

\Lambda  \approx 2.888 \times 10^{-122} = \newline 0.00000000000000000000000000000000000000000 \newline
000000000000000000000000000000000000000000 \newline
000000000000000000000000000000000000002888

\Lambda is incredibly small. It has 120 zeros after the decimal point, and then a two. \Lambda is referred to by many names, such as quintessence, dark energy, vacuum energy, zero-point energy, anti-gravity, and the fifth force.

Regardless of what we call it, all names refer to the same phenomenon: that the universe’s expansion is not slowing but accelerating.

In 1917, in an effort to explain how the universe could be static and eternal (the prevailing belief at the time), without gravitationally collapsing, Einstein introduced \Lambda as a parameter to his equations of general relativity.

The system of equations allows a readily suggested extension which is compatible with the relativity postulate, and is perfectly analogous to the extension of Poisson’s equation. For on the left-hand side of [the equation] we may add the fundamental tensor g_{uv} multiplied by a universal constant, - \Lambda, at present unknown, without destroying the general covariance. […] This field equation, with \Lambda sufficiently small, is in any case also compatible with the facts of experience derived from the solar system.

Albert Einstein in “Cosmological Considerations in the General Theory of Relativity” (1917)

But observations by Vesto Slipher and later by Edwin Hubble and Milton Humason suggested the universe was not static, but dynamic. In 1922, Alexander Friedmann showed that the equations of general relativity could account for and describe an expanding universe.

In a final blow, Arthur Eddington, who ironically proved Einstein right in 1919 by performing the first test of general relativity, proved Einstein’s static cosmological model wrong in 1930. Eddington showed that a static universe is unstable and therefore could not be eternal.

Einstein was quick to change his mind. He said, “New observations by Hubble and Humason concerning the redshift of light in distant nebulae make the presumptions near that the general structure of the universe is not static.” He added, “The redshift of the distant nebulae have smashed my old construction like a hammer blow.”

According to George Gamow, Einstein said, “The introduction of the cosmological term was the biggest blunder he ever made in his life.”

Einstein likely considered it a blunder not for being wrong, but because he missed an opportunity. Had Einstein not tried to prove a static universe and instead looked at what his own equations implied, he might have predicted a dynamic universe before observational results came in. Einstein could have scooped Hubble.

The idea of a cosmological constant was abandoned.

But in 1980, it made a return with the theory of cosmic inflation. Cosmic inflation filled gaps in the big bang. It explained where all the matter and energy came from, why the universe is expanding, and why the density of the universe rests on a knife edge. (See: “What caused the big bang?“)

All inflation needed to get started was for the energy of the vacuum to be non-zero. If vacuum energy is non-zero, space expands on its own, exactly in the way that a cosmological constant predicts.

The repulsive gravity associated with the false vacuum is just what Hubble ordered. It is exactly the kind of force needed to propel the universe into a pattern of motion in which any two particles are moving apart with a velocity proportional to their separation.

Alan Guth in “Eternal inflation and its implications” (2007)

Inflation provided an answer to one fine-tuning question. It answered “Why is the density of the universe so close to the critical density?”

But in doing so, inflation reintroduced \Lambda. And the value of \Lambda highlighted a fine-tuning coincidence so extreme that it’s considered one of the greatest unsolved mysteries in physics.

John Wheeler and Richard Feynman estimated that there ought to be enough vacuum energy in the space of a light bulb to boil the Earth's oceans. Image Credit: Wikipedia
John Wheeler and Richard Feynman estimated that there ought to be enough vacuum energy in the space of a light bulb to boil the Earth’s oceans. Image Credit: Wikipedia

According to quantum field theory we expect the inherent energy of the vacuum to be 10^{113} joules per cubic meter. A type II supernova, by comparison, is just 10^{46} joules.

But when cosmologists measured the vacuum’s energy, they found it to be pitifully weak: one billionth of a joule per cubic meter. In this case, theory and experiment disagreed by a factor of 10^{122}!

This error is described as, “The worst theoretical prediction in the history of physics.” The question of why this prediction was so bad is called the cosmological constant problem, or the vacuum catastrophe. It remains one of the great unsolved mysteries of physics.

But there is at least one reason why vacuum energy is so low. You probably guessed: had it not been as small as it is, life could not exist.

In 1987, before \Lambda was measured, Steven Weinberg predicted that \Lambda must be nonzero, positive, and smaller than 10^{-120}. Weinberg reasoned that had \Lambda been negative, the universe would have gravitationally collapsed billions of years ago. Had instead \Lambda been slightly larger than it is, say around 10^{-119}, then the universe would expand too quickly for galaxies, stars, or planets to form.

In 1998, two teams of astronomers studying distant supernovae confirmed Weinberg’s prediction. They found that the expansion rate of the universe was not slowing down, but accelerating.

The observed rate of accelerated expansion places \Lambda at 2.888 \times 10^{-122}. This was exactly in the range Steven Weinberg had predicted, 11 years earlier. For their discovery, Saul Perlmutter, Adam Riess and Brian Schmidt received the 2011 Nobel Prize in Physics.

Eighty years after introducing it, Einstein’s cosmological constant was vindicated. The only difference is \Lambda is not at a value that keeps a static universe, but instead is slightly larger, and so it drives an expansion.

Vacuum energy manifests on Earth through the Casimir effect and van der Waals forces. These forces enable Geckos to climb walls and colloidal solutions like mayonnaise to hold together despite being a mix of oil and water. The same energy that holds mayo together pushes the galaxies apart.
Vacuum energy appears in the Casimir effect and van der Waals forces. These forces allow Geckos to climb walls and colloidal solutions like mayonnaise to hold together despite being a mix of oil and water. The same energy that holds mayo together pushes the galaxies apart.

But the probability of \Lambda having the value it does is so low that it was inconceivable to physicists. There appears to be no reason it should be so small, aside from the fact that a miniscule \Lambda is necessary for there to be any complex structures or life in this universe.

The fine tunings, how fine-tuned are they? Most of them are 1% sort of things. In other words, if things are 1% different, everything gets bad. And the physicist could say maybe those are just luck. On the other hand, this cosmological constant is tuned to one part in 10^{120} — a hundred and twenty decimal places. Nobody thinks that’s accidental. That is not a reasonable idea — that something is tuned to 120 decimal places just by accident. That’s the most extreme example of fine-tuning.

Leonard Susskind in “What We Still Don’t Know: Are We Real?” (2004)

How Lucky were We?

We’ve seen the near misses, good fortunes, and happy accidents that conspired to make life possible in this universe.

Life requires complex structures. Complex structures require large aggregations of matter and many ways to organize it. This requires a rich chemistry, and in this universe, a rich chemistry requires stars.

Stars need the right kind of particles with the right masses, a balance of the forces and precisely set initial conditions for the universe.

What are the odds everything would work out just right? How likely would it have been to get a life sustaining universe if the fundamental constants of nature were chosen at random?

The Right Particles

Without the right particles, of the right masses, we don’t have a chemistry. Chemical properties depend on three parameters:

  • The proton mass: m_{p}
  • The electron:proton mass ratio: \beta = m_{e}/m_{p}
  • The fine-structure constant: \alpha
ConstantDanger ZoneConsequences
Electron mass (m_{e})< 0.5 m_{e}
> 2.5 m_{e}
Stars too dim
No hydrogen
Proton mass (m_{p})< 0.999 m_{p}
> 1.002 m_{p}
Only hydrogen
Only neutrons
Photon mass (m_{\gamma})> 0No atoms
Neutrinos (v)non-existentNo free oxygen

The following graph depicts our island of habitability within the possibility space of two parameters, \beta and \alpha.

Constraints preventing life appear in the shaded regions. Life is possible in the unshaded area. If a grand-unified theory is true, <span class="katex-eq" data-katex-display="false">\alpha</span> must fall between the two vertical lines. The dashed line shows universes where stars are hot enough to emit light with enough energy to trigger chemical reactions (e.g. photosynthesis). Image Credit: Luke A. Barnes / Max Tegmark
Constraints preventing life appear in the shaded regions. Life is possible in the unshaded area. If a grand-unified theory is true, \alpha must fall between the two vertical lines. The dashed line shows universes where stars are hot enough to emit light with enough energy to trigger chemical reactions (e.g. photosynthesis). Image Credit: Luke A. Barnes / Max Tegmark

Across the range of every possibility, our universe occupies a position on the dashed line and in the unshaded region (marked by +).

Virtually no physical parameters can be changed by large amounts without causing radical qualitative changes to the physical world.

Max Tegmark in “Is ‘the theory of everything’ merely the ultimate ensemble theory?” (1998)

Balanced Forces

To get the right physics, having the right structures at the smallest scales of atomic nuclei, and the largest scales of stars and galaxies, the four forces had to have a finely-tuned balance.

ConstantDanger ZoneConsequences
Electromagnetism (\alpha)< 0.96 \alpha
> 1.04 \alpha
Little carbon
(No Hoyle state)
Gravity (\alpha_{G})\leq 0
> 10^{-36}
No structures
No long-lived stars
Weak Force (\alpha_{w})< 0.5 \alpha_{w}
> 5 \alpha_{w}
No free oxygen
(No rebound)
Strong Force (\alpha_{s})< 0.9 \alpha_{s}
> 1.037 \alpha_{s}
Stars don’t shine
No hydrogen

The following graph depicts our island of habitability within the possibility space of two parameters, \alpha_{s} and \alpha.

Life is possible in the unshaded area. If a grand-unified theory is true, <span class="katex-eq" data-katex-display="false">\alpha</span> must fall between the two vertical lines. If <span class="katex-eq" data-katex-display="false">\alpha_{s}</span> were slightly stronger, we run into the diproton disaster: nuclei of two protons become stable and there would be no hydrogen. Moving to the right, repulsion between protons becomes too strong. As a result, carbon and all heavier elements become unstable. Moving below the horizontal line prevents deuterium from forming, which has a key role in stellar fusion. Stars like our sun would not shine. Image Credit: Max Tegmark
Life is possible in the unshaded area. If a grand-unified theory is true, \alpha must fall between the two vertical lines. If \alpha_{s} were slightly stronger, we run into the diproton disaster: nuclei of two protons become stable and there would be no hydrogen. Moving to the right, repulsion between protons becomes too strong. As a result, carbon and all heavier elements become unstable. Moving below the horizontal line prevents deuterium from forming, which has a key role in stellar fusion. Stars like our sun would not shine. Image Credit: Max Tegmark

Across the range of possibilities, our universe sits squished between all these bounds, occupying a spot marked by the black square.

If any one of the numbers were different even to the tiniest degree, there would be no stars, no complex elements, no life.

Martin Rees

Precise Initial Conditions

A few cosmological parameters have no impact on biology or chemistry. We can therefore consider them independently tuned from other constants of nature like particle masses and force strengths.

These independent cosmological parameters are:

  • The density of dark matter: \zeta_{c}
  • The homogeneity constant: Q
  • The cosmological constant: \Lambda

These parameters drive the formation of galaxies, stars, and planets.

ConstantDanger ZoneConsequences
Spatial
dimensionality (S)
< 3
> 3
Too simple
No stable orbits
Dark matter
density (\zeta_{c})
< 0.5 \zeta_{c}
> 20 \zeta_{c}
No galaxies
No stars
Homogeneity
constant (Q)
< 10^{-6}
> 10^{-4}
No structures
Stellar intruders
Cosmological
constant (\Lambda)
< -10^{-121}
> 10^{-120}
Universe collapses
No structures

The following graph depicts our island of habitability within the possibility space of two parameters, Q and total matter density \zeta.

Life is possible in the unshaded region. If the density <span class="katex-eq" data-katex-display="false">Q</span> were slightly greater, galaxies would be too dense and dangerous to life-bearing planets. If <span class="katex-eq" data-katex-display="false">Q</span> were much less, galaxies wouldn't be able to condense out of intergalactic gas. Moving to the right, if the dark matter density is too high, stars can't fragment out of the gas within galaxies. Image Credit: Max Tegmark, Anthony Aguirre, Martin Rees, Frank Wilczek / Dimensionless constants, cosmology and other dark matters
Life is possible in the unshaded region. If the density Q were slightly greater, galaxies would be too dense and dangerous to life-bearing planets. If Q were much less, galaxies wouldn’t be able to condense out of intergalactic gas. Moving to the right, if the dark matter density is too high, stars can’t fragment out of the gas within galaxies. Image Credit: Max Tegmark, Anthony Aguirre, Martin Rees, Frank Wilczek / Dimensionless constants, cosmology and other dark matters

Across the range of all possibilities, our universe sits comfortably between these two extremes, occupying the spot marked by the star.

It seems clear that there are relatively few ranges of values for the numbers that would allow for development of any form of intelligent life.

Stephen Hawking

Between Order and Chaos

Life, or more generally, complexity, walks a narrow line between a suffocating simplicity and an untamable chaos.

On the side of simplicity, we have universes without structure — a universe that’s nothing but a diffuse gas, devoid of galaxies, stars, and planets. There are universes lacking heavy elements, chemical bonding, or atoms capable of linking into large and complex biomolecules.

On the side of chaos, we have universes lacking stability — stars that live fast and die young, galaxies swarmed by black holes, and planets plagued by passing stars, asteroid bombardment, and nearby gamma ray bursts and supernovae. There are universes where chemical bonds form and break too easily, and where all sunlight is ionizing.

Fortunately for us, ours is a universe that occupies a happy medium between simplicity and chaos. Here interesting things happen, but things are stable enough to reliably encode and copy information — a universal requirement for life, or anything that reproduces.

Of the dozen or so of knobs of particle physics and cosmology we've reviewed, every single one of them happens to be tuned to a position that is necessary for life to exist.
Of the dozen or so of knobs of particle physics and cosmology we’ve reviewed, every one of them happens to be tuned to a position that makes life possible.

To some of us, it looks like we have to live with the idea that the constants of nature, the laws of nature, everything that we know about, somehow, was influenced by our own existence.

Leonard Susskind in “What We Still Don’t Know: Are We Real?” (2004)

Counting our Luck

How lucky should we count ourselves? Are the odds of a life-supporting universe modestly small, like one in ten, or incredibly small like one in a hundred billion?

One way to estimate this is to consider the possibility space for each of the fundamental constants of nature, and then look to see what fraction of that range is compatible with life.

For life to be possible required not just one coincidence, but many. Each of the constants had to fall in a life-compatible range. Had any one been off, it would have sterilized the universe.

Each fundamental constant of our universe landed in the bull's eye.

If there are 12 fundamental constants important to life, then the fraction of life-supporting universes, having our laws of physics, could be calculated as the volume of the 12-dimensional space compatible with life divided by the total 12-dimensional space of possible values.

But 12-dimensional spaces are hard to imagine, and even more difficult to depict on paper. Alternatively, we can depict this as six 2-dimensional areas, and consider just two constants at a time.

For example, we might take any two constants: the weak force vs. the strong force, space dimensions vs. time dimensions, electron mass vs. proton mass, and so on, and graph six areas. Each area forms a dart board whose bull’s eye is the life-friendly range.

If the constants of nature were chosen randomly, then getting a life-friendly universe is equivalent to throwing a dart at a random spot at each of the six areas and having it hit the bulls eye all six times.

If the average area of the bull’s eyes is 10% of the total, then the odds of hitting it six times in a row for a random throw is one in a million. If the area of the bull’s eye is 1% of the board, the odds fall to one in a trillion.

For a typical dart board, the area of the bull’s eye is just 1/1296th of the board. The odds of hitting six bull’s eyes in six random throws are 1 in 4.7 million trillion — so low as to have never happened in the history of darts.

If thrown at random, the odds of hitting six bull's eyes is 1 in 4,738,381,338,321,616,896.
If thrown at random, the odds of hitting six bull’s eyes is 1 in 4,738,381,338,321,616,896.

But how big are the bull’s eyes in the case of fundamental constants? How big are the boards? Knowing both is necessary to compute the exact odds of a life-friendly universe.

Dartboards of the fundamental constants of nature. The bull's eye marks a life friendly range.
Dartboards of the fundamental constants of nature. The bull’s eye marks a life friendly range.

In the graphs of life-friendly regions the life-compatible areas represent a narrow fraction of the possibility space. This suggests that across the range of all possible values, combinations supporting life are few and far between.

Of course, there might be other forms of intelligent life, not dreamed of even by writers of science fiction, that did not require the light of a star like the sun or the heavier chemical elements that are made in stars and are flung back into space when the stars explode. Nevertheless, it seems clear that there are relatively few ranges of values for the numbers that would allow the development of any form of intelligent life.

Stephen Hawking in “A Brief History of Time” (1988)

But calculating the exact probability of life is complicated. In most cases, science lacks an understanding of the possible ranges different constants might take and how likely different values are. This makes quantifying the exact likelihood of life difficult.

But there is one constant whose range and likelihood are both known. Further, it can be considered independently from the other constants. It plays no role in determining nuclear physics, chemistry or biology.

The Finest Tuning

In the dart boards of the fundamental constants, some bull’s eyes are smaller than others. We might say these parameters are “more finely-tuned” — greater precision was required to set those parameters.

Among all the known fundamental constants, one of them is the most finely-tuned of all. This finest tuning is \Lambda.

The cosmological constant, \Lambda, is understood to be the inherent energy of the vacuum. According to quantum field theory, the vacuum is a collection of overlapping particle fields, with one field for each kind of particle. Particles then, can be understood as vibrations in their respective field.

Each of the few dozen particle fields contributes some amount of energy, which can be positive or negative, towards the energy of the vacuum.

What’s remarkable is that when all of these independent field energies are summed, they cancel out to 120 decimal places:

\Lambda  \approx 0.0000000000000000000000000000000000000 \newline
00000000000000000000000000000000000000000000 \newline
00000000000000000000000000000000000000002888

For there to be any structures, complexity, or life in this universe, it was necessary for \Lambda to be so small. But how likely was it?

Their smallness with respect to the [Planck scale] is not understood and is considered as ‘unnatural’ in relativistic quantum field theory, because it seems to require precise cancellations among much larger contributions. If these cancellations happen for no fundamental reason, they are ‘unlikely’, in the sense that summing random order one numbers gives 10^{−120} with a ‘probability’ of about 10^{−120}.

Authors of “Direct anthropic bound on the weak scale from supernovae explosions” (2019)

To get a feeling for how unlikely such an occurrence is, imagine we had an infinitely-sided die. That is, rather than a standard six-sided die we had one with infinitely many sides: a sphere.

An infinitely-sided die.

On this die, we can denote each of the infinite values existing between -1 and +1. We might do this by having black denote -1, white denote +1, and every shade of gray between them marking the continuous range.

Having the magnitude of the vacuum energy be less than 10^{−120} is equivalent to rolling this spherical die a few dozen times, and after adding the numbers finding the magnitude of the result is less than one in 10^{120}.

This is extraordinarily unlikely.

To put it in context, consider that the odds of winning a national lottery are about one in a hundred million — or one in 10^{8}.

Our universe won the ultimate lottery. The prize: life.
Our universe won the ultimate lottery. The prize: life.

One in 10^{120} represents equivalent odds to winning a national lottery 15 times in a row. We definitely are winners in a cosmic lottery!

Could it all be a coincidence?

At a certain point, luck becomes implausible as an explanation. If the same person won a national lottery 15 times in a row, we would look to other answers besides mere luck to explain it.

Perhaps someone rigged the game. Or perhaps the person used their winnings to continue buying up all possible tickets.

It is a mystery that demands an explanation.

The extraordinary odds we overcame to win the right to exist seem to be telling us something important about existence and reality.

But what?

Why the Universe is Made for Life

Sir Martin Rees is professor of cosmology and astrophysics at the University of Cambridge, Master of Trinity College, former President of the Royal Society and the current Astronomer Royal.

Rees has spent much of his life on the question of why the universe is suited for life. He authored one of the first papers on the subject, wrote a book on it, and even hosted a television show exploring the topic.

In his book, “Just Six Numbers”, Rees describes three known answers to the question of why the universe is finely-tuned for life:

  • Coincidence
    • We’re just incredibly lucky and there is no explanation or reason.
  • Providence
    • Our universe was designed, chosen, or created to allow life.
  • Multiverse
    • There are many universes, most are barren, but some permit life.

Let’s consider the implications for each of these answers.

Coincidence

However small it may be, there is a chance that there is a single universe, neither designed, nor one of many, which just happens to have physical laws and constants that are life-permitting.

Perhaps, things are not so hopeless for life as we estimated. It might be that “life finds a way” in a large fraction of possible universes.

If so, then we shouldn’t be so surprised.

But there are reasons to doubt this. Life requires a special environment. Life must be capable of maintaining, repairing, copying, and mutating its information patterns. The environment must allow life to arise and self-assemble and also self-replicate.

Across possible environments, few appear to support both needs. Most seem to miss the necessary balance between simplicity and chaos.

If the environment is too simple, there’s no hope of getting self-arising, self-replicating forms. If the environment is too chaotic, there’s no hope of preserving information across generations.

John von Neumann's self-replicating machine was a first example of artificial life. Image Credit: Wikipedia
John von Neumann’s self-replicating machine was a first example of artificial life. Image Credit: Wikipedia

John von Neumann created the first self-replicating machine. It was designed to operate within a cellular automaton, a specially crafted environment having its own set of rules — i.e. its own “laws of physics.”

But in the set of possible cellular automata, only a small fraction has the right balance of complexity and stability to support self-replication.

It seems plausible that, even in the space of cellular automata, the set of laws that permit the emergence and persistence of complexity is a very small subset of all possible laws. […] The point is that, however many ways there are of being interesting, there are vastly many more ways of being trivially simple or utterly chaotic.

Luke A. Barnes in “The Fine-Tuning of the Universe for Intelligent Life” (2011)

As Richard Dawkins put it, “however many ways there may be of being alive, it is certain that there are vastly more ways of being dead.”

Even in a life-friendly universe like ours, we find ourselves in a very special place. Most of the universe is intergalactic space. A cold, dark, void — having just one hydrogen atom per cubic meter.

Our environment is some 10^{30} times denser than average. As Max Tegmark noted, “only a thousandth of a trillionth of a trillionth of a trillionth of our Universe lies within a kilometer of a planetary surface.” It’s doubtful life could arise in the near vacuum of intergalactic space, nor is it likely to exist in the hot cores of planets or stars.

Most of our universe is inhospitable. Life can’t always find a way.

Earth is a lone Eden. Trillions of miles sit between her and the nearest, plausibly hospitable, locations. Kepler-22b, which may have liquid water, is 6 thousand trillion kilometers away.
Earth is a lone Eden. Trillions of miles sit between her and the nearest, plausibly hospitable, locations. Kepler-22b, which may have liquid water, is 6 thousand trillion kilometers away.

The rarity of life in the universe speaks to how uncommon life may be across the set of possible universes. Even where life is known to be possible it appears to be exceedingly rare. (See: “Are we alone?“)

The sensitivity of life to the smallest changes in the fundamental constants further suggests it takes a rare mix of particles, forces, and initial conditions working together to make a universe with life.

It is logically possible that parameters determined uniquely by abstract theoretical principles just happen to exhibit all the apparent fine-tunings required to produce, by a lucky coincidence, a universe containing complex structures. But that, I think, really strains credulity.

Frank Wilczek in “Physics Today” (2006)

But if incredible luck is not the answer, then someone, or something, must have set things up just right.

Providence

Divine providence is another possible answer to the mystery. This is the belief that the universe was designed and created with intention. Perhaps to be interesting, to support the existence of intelligent life.

Fred Hoyle, who had been a lifelong atheist, was led by his discovery of the carbon-12 excited state to believe in a “super-calculating intellect” who must have designed the properties of the carbon atom.

In this, he is not alone.

Arno Penzias, who discovered the cosmic hum of the big bang, said “Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying (one might say ‘supernatural’) plan.”

A life-giving factor lies at the centre of the whole machinery and design of the world.

John Archibald Wheeler in forward to “The Anthropic Cosmological Principle” (1986)

If there is one universe, with one set of laws, divine providence is a natural conclusion. So many bullets were dodged in the many fine-tunings that it all being a coincidence doesn’t hold water.

While some physicists were open to this possibility, most were unsettled by it. Fine-tunings suggest a fine-tuner. But once a deity is invoked as part of an explanation, further scientific progress halts — as any line of inquiry can be answered with, “it was God’s plan.”

This is a dislike of mixing religion into physics. I think they were somewhat afraid that if it was admitted that the reason the world is the way it is has to do with our own existence, that that could be hijacked by the creationists — by the intelligent designers. And of course what they would say is “Yes, we always told you so. There is a benevolent somebody way up high in the universe who created the universe exactly so that we could live.” I think physicists shrank at the idea of getting involved in such things.

Leonard Susskind in “What We Still Don’t Know: Are We Real?” (2004)

But the claim that creation or a creator is unscientific is now in doubt. Today’s scientists have already wet their toes in the area of creating universes. They do so in highly detailed computer simulations.

Simulation is indispensable to today's scientists. It enables them to create, experiment with, and explore cosmic evolution. It allows us to see inside the cores of collapsing stars, and understand the physics of alternate universes with different constants or initial conditions.
Simulation is indispensable to today’s scientists. It enables them to create, experiment with, and explore cosmic evolution. It allows us to see inside the cores of collapsing stars, and understand the physics of alternate universes with different constants or initial conditions.

The cosmologist Alan Guth even thinks it is possible in principle to create and split off an entire new physical universe in the laboratory.

The odd thing is that you might even be able to start a new universe using energy equivalent to just a few pounds of matter. Provided you could find some way to compress it to a density of about 10 to the 75th power grams per cubic centimeter, and provided you could trigger the thing, inflation would do the rest.

Such an achievement is obviously far beyond our technology, but some advanced civilization in the distant future might… well, you never know. For all we know, our own universe may have started in someone’s basement.

Alan Guth in “Physicist Aims to Create a Universe, Literally” (1987)

If our universe is the result of such an experiment, or if it exists as a simulation performed by a higher being or species, then our universe is life friendly because of the providence of our creator. The particular constants and laws would have been chosen with intention. (See: “Are we living in a computer simulation?” and “Is it possible to create new universes?“)

But even if this is the case, the mystery still remains. How did the simulator or universe creator come to be?

If the creator arose through natural processes, the universe hosting the creator would also have to have been finely-tuned. It pushes the question back one step, but does not ultimately answer it.

Though we cannot rule out providence as an explanation, this solution raises as many questions as it answers. Scientists wanting to progress on the mystery of fine-tuning sought a naturalistic explanation.

Multiverse

If we are not exceedingly lucky, and if our universe was not designed, there is one alternative: many, perhaps even an infinite number of universes exist. “There will be life in some, and not in others.”

If there are enough universes, each having different laws, no fine-tuning is needed.
If there are enough universes, each having different laws, no fine-tuning is needed.

We imagine our universe to be unique, but it is one of an immense number—perhaps an infinite number—of equally valid, equally independent, equally isolated universes. There will be life in some, and not in others. In this view the observable Universe is just a newly formed backwater of a much vaster, infinitely old, and wholly unobservable Cosmos. If something like this is right, even our residual pride, pallid as it must be, of living in the only universe is denied to us.

Carl Sagan in “Pale Blue Dot” (1994)

Under the multiverse explanation, our universe is just one of a much larger set of other, equally real universes. Each of these universes may be ruled by different physics: different forces, constants, particle types, dimensionality, and so on.

Most universes won’t have rules of a kind necessary for life. They will be empty. No one will be there to appreciate the splendor.

How many other universes might there be?

While we have no way to know the exact number of extant universes, it’s possible to estimate the minimum. It is equivalent to asking: How many lottery tickets are needed to have a good chance of winning?

The answer: more than the inverse of the likelihood that a single ticket is a winner. So if the odds per ticket are 1 in a hundred million, you need around a hundred million tickets for a high chance of winning.

Let’s use this same logic to consider how many universes are needed to make up for the unlikelihood of \Lambda falling in a life-friendly range, whose improbability was on the order of 1 in 10^{120}.

Weinberg’s approach for explaining the cosmological constant only works if we’re part of a multiverse in which there are a huge number of different universes; their cosmological constants must fill out some 10^{124} distinct values. Only with that many different universes is there a high likelihood that there’s one with a cosmological constant that matches ours.

Brian Greene in “The Hidden Reality” (2011)

This number, 10^{124}, is far greater than the number of atoms in the observable universe, estimated to be 10^{80}.

Where does all this stuff come from?

Is the multiverse theory even scientific when we cannot observe or interact with these other universes? As Paul Davies said, “invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator.”

But as Max Tegmark points out, the idea of parallel universes is not a theory, but a prediction made by several existing theories, which are themselves testable and falsifiable, and thus scientific.

Examples include:

Independent of the search for answers to fine-tuning, various fields of science are increasingly pointing in the direction of many universes — a multiverse.

In 1996, Tegmark went one step further. In his mathematical universe hypothesis, he put forward the idea that the equations of string theory may not be the only equations that can define universes.

According to his radical idea, equations of string theory represent just one of an infinite number of self-consistent physical equations, and all consistent sets of equations correspond to physically real universes. (See: “How big is the universe?” and “Why does anything exist?“)

But how do parallel universes explain why this universe is made for life?

The Anthropic Principle

The existence of other universes, by itself, does not explain why the universe we are in is finely-tuned to support life. To get there we need one extra ingredient, the anthropic principle.

This term was coined by Brandon Carter in his 1974 paper detailing the coincidences in cosmology, but the idea predates this.

My Princeton colleague, Robert Dicke, expressed it this way: “What good is a universe without somebody around to look at it?”

John Archibald Wheeler in “From the Big Bang to the Big Crunch” (2004)
The places where life is possible may be few and far between. But wherever life exists, it is only found in places where it is possible for life to exist. This applies whether it in a life-possible universe, on a hospitable planet, or by a pool of water in a vast desert.
The places where life is possible may be few and far between. But wherever life exists, it is only found in places where it is possible for life to exist. This applies whether it is in a life-possible universe, on a hospitable planet, or by a pool of water in a vast desert.

The anthropic principle is the self-evident truth that life only finds itself in places compatible with its existence. Therefore, it’s no surprise we find ourselves in a universe having a rare combination of life-friendly laws — so long as the number of universes is large enough.

The analogy here is of a ready-made clothes shop. If there is a large stock of clothing, you’re not surprised to find a suit that fits. If there are many universes, each governed by a differing set of numbers, there will be one where there is a particular set of numbers suitable to life. We are in that one.

Sir Martin Rees in “Why is There Life?” (2000)

Solving the Fine-Tuning Mystery

We’ve considered three possible answers to the mystery of why the universe is made for life. Which one is right? How could we ever tell?

Here we can apply a technique known as Bayesian inference.

First we divide the decision into three answers that are mutually exclusive (at most one is true) and collectively exhaustive (at least one is true):

  • Coincidence: There is one universe, not designed for life
  • Providence: There is one universe, designed for life
  • Multiverse: There is not one universe

When framed in this way, there is zero uncertainty whether one of the answers is true. The only uncertainty is which one is true. If we were to divide up our certainty as to which answer is correct, then if we are consistent the sum of the certainty across the answers must add to 100%.

We all know this intuitively. When you hear there is a 30% chance of rain tomorrow, you can infer that there is a 70% chance that it will not rain tomorrow. Raining and not-raining are mutually exclusive as they can’t both happen. Raining and not-raining are also collectively exhaustive, as at least one of those possibilities must occur.

We can use this method to narrow down an answer.

Is there one Universe, not Designed for Life?

Before considering any evidence, we might equally divide our level of certainty across the three possible answers:

  • Coincidence: 33.33%
  • Providence: 33.33%
  • Multiverse: 33.33%

We could also group answers up any way we like, for instance:

  • Coincidence: 33.33%
  • Providence or Multiverse: 66.67%

Or equivalently:

  • Coincidence: 33.33%
  • Not Coincidence: 66.67%

According to the rules of Bayesian inference. Any time new evidence is taken into consideration, we must update our certainty accordingly.

Say you originally assumed even odds of rain. You would begin with 50% certainty it would rain, and a 50% chance it would not rain. But upon learning new evidence, you revise your certainty. If you hear there’s not a cloud in the sky, your certainty might shift from a 50% certainty of rain to a 5% certainty of rain, and 95% certainty of no rain.

Similarly, evidence of fine-tuning acts like learning there’s not a cloud in the sky. It forces us to revise downwards our initial certainty in the answer that there is one universe which is not designed for life.

If fine-tuning evidence causes us to revise our certainty in the coincidence answer from 33% to 1%, then our confidence in not coincidence or equivalently (providence or multiverse) rises to 99%.

  • Coincidence: 1%
  • Providence or Multiverse: 99%

The lower the probability of coincidence, the more certain we are that providence or multiverse is true, since all must add up to 100%.

Fine tuning evidence suggests that the odds of coincidence may be in the neighborhood of 1 in 10^{120} or less. This means we can with overwhelming certainty rule out coincidence as the answer.

This leaves two possibilities, and we can conclude with overwhelming certainty that either providence or multiverse is correct.

Most sets of values would give rise to universes that, although they might be very beautiful, would contain no one able to wonder at that beauty. One can take this either as evidence of a divine purpose in Creation and the choice of the laws of science or as support for the strong anthropic principle.

Stephen Hawking in “A Brief History of Time” (1988)

Is there one Universe, Designed for Life?

If there is only one universe, and we rule out coincidence, that leaves one alternative: providencethe universe was made for life.

Anthropic fine tuning is too remarkable to be dismissed as just a happy accident.

John Polkinghorne in “Science and Theology” (1998)

If it’s not a coincidence that life is possible then there had to have been a tuner — be it a simulator, universe creator, super-calculating intellect, intelligent designer, or deity. Its purposes led it to choose, from among the many possibilities, one set of physical laws where life is possible.

But concluding providence as an answer requires the assumption that there is only one universe. Ruling out coincidence can bring us towards certainty in either (providence or multiverse), but it can’t tell us which of these two remaining answers is right.

Is there not one Universe?

Once coincidence is ruled out as an answer, we can say, either:

  1. There is a designer, or
  2. There is a multiverse.

Could there really be more to reality than we can see? Are there other universes, with different laws, constants, particles, and properties?

An artist’s conception of the observable universe. We cannot see everything that exists. Given the finite speed of light, we are not even in a position to see all of our universe.
Image Credit: Pablo Carlos Budassi/Wikimedia Commons

Though we are not in a position to survey all of reality, nature has provided us hints. Cosmic inflation, string theory, and fine-tuning all suggest our universe is part of a vast and variegated reality.

The most important scientific revolutions all include, as their only common feature, the dethronement of human arrogance from one pedestal after another of previous convictions about our centrality in the cosmos.

Stephen Jay Gould

But should a vast, possibly infinite, reality exist, this leads us back to the notion of a creator — an entity able to design and make universes.

According to Martin Rees, our universe may be far from optimal in terms of its potential for complexity. If so, then there exists within the multiverse some universes having a greater capacity for complexity, computation, and intelligence than our own.

We can imagine universes that might be more propitious. These of course would be potentialities far beyond the powers of our brains to conceive, but we can’t assume in this grander cosmos that there couldn’t be other universes displaying more complexity than ours.
[…]
We know that over a few decades computers have evolved from being able to simulate only very simple patterns to being able to create virtual worlds as it were, with quite a lot of detail in them. If that trend were to continue then we can imagine computers which will be able to simulate worlds perhaps even as complicated as the one we think we’re living in.

Sir Martin Rees in “What We Still Don’t Know: Are We Real?” (2004)

Final Thoughts

Was the universe made for life?

This one question threads together humanity’s desire to understand its origin and place in the cosmos, and to know whether we were created with intention and purpose, or through blind luck and happenstance.

Reaching a point of progress on this question took the culmination of some of the greatest scientific discoveries of the past century. But we can now say with confidence that life, of any kind, is rare and precious.

Life’s rarity speaks to the existence of something beyond what we can observe — a reality that transcends this universe. A reality which is potentially infinite and contains all possibilities.

If not coincidence, is the answer providence or multiverse?

To our surprise, we find that regardless of which answer is right, both lead to the same place: a belief in something greater than ourselves.

If providence is the answer, then we get a creator outright.

If multiverse is the answer, then we get an infinite reality containing universes greater than our own, with beings greater than ourselves. Such beings would be in a position where they could create other universes, either directly or via computer simulation, thereby becoming the source of divine providence to those beings they create.

The infinite and comprehensive reality of the multiverse might even contain all things. The hypothetically omniscient mind of God, likewise contains all things, or at least knowledge of all things.

Is there a difference between the two? Might they be the same thing? (See: “Does God Exist?“)

As the philosopher J. J. C. Smart reminds us, “If we postulate God in addition to the created universe we increase the complexity of our hypothesis. We have all the complexity of the universe itself, and we have in addition the at least equal complexity of God.”

But Smart tempered his statement, adding, “If the theist can show the atheist that postulating God actually reduces the complexity of one’s total world view, then the atheist should be a theist.”

So it may be with the belief in an infinite reality.


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4 Replies to “Is the universe fine-tuned?”

  1. These distinct bubbles that we call the level two multiverse, contain an infinite number of universes as in level one, but this time, the physics governing each level two multiverse might not be the same. It is thought that the symmetry break was responsible for creating everything that we see in our universe; from the number of dimensions to the physical-constants that we hold as being set in stone.

    The symmetry break came about as a direct consequence of inflation and we know that there were chaotic quantum fluctuations that drove this inflation in our universe, meaning that the likelihood that these exact conditions would be replicated in another level two multiverse are nil: each level two multiverse would be unique!

    If the strength of the inflationary field varies in which other bubble universes are created then how is it possible that in another bubble universe that their would be an identical earth and identical copies of us in another bubble universe if the conditions if which they were created varies? Why is Dr matt brown saying that each bubble universe would be unique? If you get different laws of physics including a different value of epsilon and different constants of nature also a different density of dark matter, a different average density of normal matter, a different density of dark energy, a different ratio of dark matter to normal matter to dark energy and a different cosmological constant then how is it possible to have exact copies of us, earth and the observable universe in another bubble universe elsewhere in the inflationary multiverse? If there are an infinite number of ways that the laws of physics and the constants of nature be different and also an infinite number of ways that the density of dark matter can be different, an infinite number of ways that the average density of normal matter can be different, an infinite number of ways that the density of dark energy can be different, an infinite number of ways that the ratio of dark matter to normal matter to dark energy can be different and an infinite number of ways that the cosmological constant can be different as the condition in which they were created varies by the the strength of the inflationary field then how is it possible that there would be copies of us, earth and the observable universe in another bubble universe elsewhere in the inflationary multiverse?

    1. Hi James,

      I think there is an important difference between a nil (zero) and very very small. In Tegmark’s level 1 universe, the probability finding a repeated Milky Way Galaxy down to the quantum level in any randomly chosen location in space is close to zero, but importantly, it is not zero.

      By the Bekenstein bound, the amount of information encoded in the quantum states for an object of the mass and volume of the Milky Way is: (2.5769 * 10^43 bits/(kg*m)) * (3 × 10^42 kilograms) * (5 × 10^20 meters) = 3.87 × 10^106 bits.

      This is the amount of information that can be stored in the Milky Way. The number of possible states represented by this information content is 2 to the power of this number, or 2 ^ (3.87 × 10^106).

      So the odds of a Milky Way sized patch of space containing the Milky Way as we know it would be on the order of 1 in 2^(10^106). This is a probability far smaller than the getting the same string theory vacuum (same laws of physics), as the number of string theory vacua that have been counted, is by one estimate 10^272,000 (a number vastly smaller than the number of possible Milky Way mass-volumes).

      Given the comparatively smaller information content, (and correspondingly smaller number of possibilities), in the laws of physics compared to possible arrangements of matter and energy in space, I think that if one can accept repetitions of volumes of space within an infinite spatial volumes, then it should be easier to accept the inevitability of repetitions of physical laws arising across infinite bubble universes.

      Note that all this is conditioned on there being a small, *but non-zero*, probability of getting the same string theory vacuum through eternal inflation. If it is zero, then it becomes a fight between an infinity and zero, which is undefined absent further mathematical specification.

  2. In sort yes, the universe is fine tuned for live and for existence, and yes, there are a big chance of the existence of gods, spiritual beings, post-physical/extraphysical lifeforms, spiritual worlds, metaphysics/extraphysics, multiverses, mystics, esoterics, other dimensions and related things to exist, maybe they are outside the realms of hard-natural-empirical sciences, maybe they aren’t, but the thing is they all are for that field named “Spiritual Sciences”, that I used to talk since a long time, and yes, even if both things you told in the end are real, any of them would point out the existence of gods, spiritual beings and post-physical/extraphysical lifeforms, so yeah, it is an amazing thing. Sadly that atheist/skeptic/scientific zealots, militant atheists/skeptics/scientificists and neopositivists, as the ones on Quora, Facebook, Reddit, TikTok, Instagram and in the top 3 results of Google can’t realize that, but it’s not because them we will give up, we will keep theorizing and even argue with them if necessary. We will fight atheist/skeptic/scientific fanaticism, militant atheism/skepticism/scientism and neopositivism everywhere we can while we are alive in this world, and we will never give up from this struggle.

  3. Review fromAaron M
    1 star
    10/23/2021

    name aaron minch im separate from you and people because your all carnally minded and its death but to be spiritually minded life and peace and its sinful to think the way the world thinks and your carnal minds are enmity against god for it is not subject to the law of god neither indeed can be so you that are the flesh cannot please god but me i’m not in the flesh no more im in the spirit and the spirit of god dwells in me and im spiritually minded and i have life and peace inside me as long as i live and there is therefore now no condemnation for me because im in christ jesus because i walk after the spirit and the law of the spirit of life in christ jesus hath made me free from the law of sin and death and in troubled on every side yet not distressed and i look to the things that are unseen as long as i live because the unseen things are eternal but the things that are seen are temporal and i want to be alone with god in quietness and peacefulness away from the world and distractions and confusions from people and the world so i can worship god in spirit and in truth abiding in jesus and his words praying in faith as long as live and jesus is all need want and have forever not you and no man in this world and his presence goes with me and he gives me rest and i trust alone in jesus christ and i trust no one in this world and im not lucky im blessed everything have is because of gods grace and favor and i will never mur mur complain about anything i will be blessed grateful and thankful as long as i live and im separate from sinners and the world my kingdom is not of this world i have a home eternal home in heaven with god forever where i belong and im on my way home to spend eternal life with jesus christ in heaven forever where i belong when i die and im jesus sheep i hear his voice and i know him and he knows me and i follow him and he has given me eternal life and i will never perish neither shall any man pluck me out of his hands and god knows my heart and thoughts not you and no man in this world im separate from sinners and the world and im separate from smokers cussers blasphemers fornicators drunkards idolaters and i avoid strife and vain babbling empty constant worldly talk and chatter and empty discussions like god said to be separate in the bible wherefore i come out from among all of you people and i touch not the unclean thing and im separate saith the lord almighty like god said in the bible and i avoid arguing bickering like the bible says because i have a personal loving relationship with my heavenly father it causes pain to my unity and peace and joy that god gives me but will never take away my peace and joy of eternal life that god has given me through jesus christ by the power of his holy spirit in me and i rejoice in the lord always not in man for he is the God of my salvation and im in fellowship with jesus christ and communion with the holy spirit and i reject people who cause divisions within the body of christ after a second warning and have nothing more to do with such people i am the body of christ and i stay away from people who sow discord and i live a quiet and peaceful life in all godliness and honesty like god said in the bible and i will never be unequally yoked together with unbelievers because righteousness and unrighteousness have nothing and common just as light and darkness are opposites and i have received the righteousness of god through my faith and trust in jesus christ and im saved by gods grace through my faith and trust in jesus christ and the gift of god is eternal life through jesus christ our Lord and im on my way home to spend eternal life in heaven with sweet holy jesus forever when i die where i belong and i have forsaken everyone and everything for jesus name sake because jesus gave me eternal life and i live a quiet and peaceful life in all godliness and honesty like god said in the bible Romans 8 King James Version 8 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit. 2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death. 3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: 4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit. 5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit. 6 For to be carnally minded is death; but to be spiritually minded is life and peace. 7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. 8 So then they that are in the flesh cannot please God. 9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his. 10 And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness. 11 But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you. 12 Therefore, brethren, we are debtors, not to the flesh, to live after the flesh. 13 For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live. 14 For as many as are led by the Spirit of God, they are the sons of God. 15 For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father. 16 The Spirit itself beareth witness with our spirit, that we are the children of God: 17 And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together. 18 For I reckon that the sufferings of this present time are not worthy to be compared with the glory which shall be revealed in us. 19 For the earnest expectation of the creature waiteth for the manifestation of the sons of God. 20 For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope, 21 Because the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God. 22 For we know that the whole creation groaneth and travaileth in pain together until now. 23 And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body. 24 For we are saved by hope: but hope that is seen is not hope: for what a man seeth, why doth he yet hope for? 25 But if we hope for that we see not, then do we with patience wait for it. 26 Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. 27 And he that searcheth the hearts knoweth what is the mind of the Spirit, because he maketh intercession for the saints according to the will of God. 28 And we know that all things work together for good to them that love God, to them who are the called according to his purpose. 29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren. 30 Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified. 31 What shall we then say to these things? If God be for us, who can be against us? 32 He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things? 33 Who shall lay any thing to the charge of God’s elect? It is God that justifieth. 34 Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us. 35 Who shall separate us from the love of Christ? shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? 36 As it is written, For thy sake we are killed all the day long; we are accounted as sheep for the slaughter. 37 Nay, in all these things we are more than conquerors through him that loved us. 38 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, 39 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord. 2 Corinthians 3:17 King James Version 17 Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty. Paul has just urged the Corinthians to open their hearts to him again. Now he turns to a direct command: that believers in Christ not be yoked with unbelievers. The imagery of the “yoke” brings to mind the rigid harness used to keep livestock locked together and pulling in a consistent direction. The Old Testament used a form of the word to forbid mating cattle of different species (Leviticus 19:19). The Law also forbids harnessing together an ox and a donkey to plow a field (Deuteronomy 22:10). The point of this phrase will soon become clear. Those in Christ are something other than those who are not in Christ. They are not the same–spiritually–and should not be locked together into any kind of binding relationship. Paul begins to ask a series of questions to show the absurdity of a believer in Jesus being “unequally yoked” with an unbeliever. Paul asks: what cooperation can there be between virtue and wickedness? Those in Christ have “become the righteousness of God” (2 Corinthians 5:21). Those outside of Christ continue in their status as unrepentant, lawless sinners. The two cannot–must not–be joined together. To do so makes as little sense as trying to join light and darkness in fellowship. It can’t be done. As soon as the light arrives, the darkness must vanish. It’s essential to realize Paul is not saying believers should never associate with unbelievers, at all (1 Corinthians 5:9-10). Believers should continue to live and function in the world, which includes contact with unbelievers (1 Corinthians 10:25-26). He has written to the Corinthians previously, though, not to sue each other in pagan courts of law (1 Corinthians 6:1-11), not to join themselves sexually to temple prostitutes (1 Corinthians 6:12-20), and not marry unbelievers (1 Corinthians 7:39). Rather, Scripture’s teaching here is that Christians must not enter into binding, partnering agreements with non-Christians. Context Summary Second Corinthians 6:14-18 begins with Paul’s command to the Corinthians not to be ”unequally yoked” with unbelievers. Light and darkness cannot be in fellowship. Christ and Satan cannot work together. Christians are God’s temples on earth since His Spirit lives in them. That’s why they must separate themselves from any kind of formal, binding relationship with unbelievers. Paul references several Old Testament Scriptures to show that believers in Jesus must separate themselves from being ”yoked” to unbelievers since God is their Father and lives among them. Chapter Summary This passage appeals to the Corinthians not to miss the day of salvation. Paul insists that he and those who work with him have done nothing to keep anyone from believing in Christ. He points to the evidence that he has been a true apostle and representative of Christ and asks the Corinthians to open their hearts to him again. He commands them not to harness themselves to unbelievers since Christ can have nothing to do with Satan or darkness. God lives in them through the Holy Spirit, so they must separate from everything that is opposed to God. 2 Corinthians 6:14-18 King James Version 14 Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? 15 And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? 16 And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people. 17 Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you. 18 And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty. 1 Corinthians 5:9-11 King James Version 9 I wrote unto you in an epistle not to company with fornicators: 10 Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world. 11 But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolator, or a railer, or a drunkard, or an extortioner; with such an one no not to eat. It can be argued, as I have suggested in a previous volume, that the message of this great and most eloquent chapter really begins at verse 5. The first four verses sum up the argument of chapter 7; and here we have a new section which runs from the 5th verse to the end of the 13th verse. Let us remind ourselves that the object of the entire chapter, and therefore the object of every subsidiary section, is really to prove the contention of verse 1 namely, that `There is therefore now no condemnation to them which are in Christ Jesus’. That is the fundamental proposition. The Apostle’s purpose is to show the absolute certainty and finality of the full and complete salvation of all who are `in Christ Jesus’ – in other words, of all :who are in the realm of the Spirit, and in whom the Holy Spirit of God dwells. Of course this has its negative side – that this salvation only applies to such people as have been set free from `the law of sin and death’ by `the law of the Spirit of life in Christ Jesus’. They are the only people for whom there is no condemnation and to whom, therefore, this certainty of final and compete salvation applies. The Apostle has been reminding us in verses 3 and 4 of the way in which believers have been put into that position and thereby set free from the Law and all its demands, and all that it does to those who are unregenerate and `in the flesh’. Having done that, Paul can proceed to prove that it is essential that we should be `in Christ’, and in the realm of the Spirit, before this can possibly happen to us. He has made his great asseveration in verses 1 and 2; then in verses 3 and 4 he shows us how we get into that position. Now he wants to establish the fact that it is only to such people that this full and final salvation is guaranteed and is absolutely certain. We can put it in this way, that the object of verses 5 to 13 is to prove the contention of verse 4 in particular, and especially its second statement. He has told us that the object of salvation is `that the righteousness of the law might be fulfilled in us’. But, he says, `the righteousness of the law’ is only fulfilled in those `who walk not after the flesh, but after the Spirit’. Now he proceeds to show why he speaks in this way, why it is that only in those who walk `after the Spirit’ and not `after the flesh’ can `the righteousness of the law’ be fulfilled. A general analysis of this sub-section, verses 5 to 13, I suggest, is the following: Verses 5 to 8 give us a picture of the contrast between the Christian and the non-Christian, with the special object of showing that `the righteousness of the law’ cannot possibly be fulfilled in the non-Christian but only in the Christian. In verses 9 to 11 Paul applies this to the Roman Christians. He says: `But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his’ – that is to say, he is not a Christian at all. As far as they are concerned he knows that they are `in the Spirit’ and not `in the flesh’. So he shows them what their present position is in the light of that fact, and what their future glory is going to be as its outcome. Then in verses i z and 13 he gives them a practical exhortation because of all that is true of them. `Therefore, brethren, we’ – of whom all this is true – `we are debtors, not to the flesh, to live after the flesh; for if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.’ Two things, therefore, stand out very clearly here. The first is that in verses 1 to 4, as I have been careful to stress all along, the Apostle is describing and writing about all Christians, not merely some Christians. He gives no indication whatsoever that there are two classes of Christians. A popular teaching says that there are (2) `carnal’ Christians and `spiritual’ Christians, and that here Paul is talking only about the `spiritual’ Christians. This section will confirm and prove to the hilt our contention that in verses 1 to 4 the Apostle has been talking about all Christians, not certain special Christians only, not only Christians who have received some second experience. That `there is therefore now no condemnation to them which are in Christ Jesus’ is true of every Christian. This is quite basic because it determines, as we have seen, our view of sanctification. Verses 5 to 13 will prove that to us quite clearly and put it beyond any doubt whatsoever. The second principle that verses 5 to 13 bring out clearly is that a complete change in us is absolutely essential to salvation. If a man does not undergo a radical change, if he does not enter into the realm of the Spirit, `the righteousness of the law’ can never be fulfilled in him. Christianity, as the Apostle has told us so often, involves a complete, a radical change in the nature of the human being. These, then, are the two great principles on which we must keep our eyes. They stand out very clearly in the first sub-section of this section, verses 5 to 8. It is quite clear, I repeat, that here the Apostle is comparing and contrasting not two types of Christians but the non-Christian with the Christian. They that are `after the flesh’ are the non-Christians; they that are `after the Spirit’ are the Christians. It is a wrong interpretation to say that `they that are after the flesh’ are the so-called `carnal’ Christians; for we shall see that the Apostle says something about them which makes it impossible that they should be Christians at all. We must keep this particularly in view because the Apostle’s whole object is to show how utterly impossible it is to say of any man as he is by nature that to him there is `no condemnation’ or that `the righteousness of the law’ will be fulfilled in him. On the other hand, the moment a man is delivered from the condemnation of the law, and is changed, and in this new realm, his hope is certain, and nothing can ever rob him of it. That, then, is the theme we are going to consider. But instead of taking the passage verse by verse, and drawing out the contrast between the two types of persons verse by verse, it seems to me to be more advantageous to consider first of all what the Apostle tells us about the non-Christian; and afterwards to look at the Christian positively as a whole. This method will help us to follow the Apostle’s argument. We take first what Paul says here about the man who is not a Christian. His general description of him is that he is `after the flesh’. What does he mean by this? We have earlier explained that the word `flesh’ means fallen human nature, human nature as it is before the Spirit of God begins His work in a person. It is man left to himself, man born, developing and growing in life in this world outside the activity of God upon him. The non-Christian is `after the flesh’. The word `after’ is interesting. Some would translate it as `according to the flesh’, but the best translation is `under the flesh’. The word the Apostle uses carries the idea of being `under’ something else, under authority in particular. So we are told that the non-Christian is one who is habitually dominated by the nature with which he was born. Chapter 5 has already told us in a most amazing manner – and Paul has worked it out in detail in chapters 6 and 7 – that we are born like this because of our connection with Adam and because of Adam’s sin. Everyone born subsequent to Adam has been born `after the flesh’; we are born under the power, the domination of this fallen human nature which we inherit. The Apostle adds that it is something that is continuous – `they are after the flesh’. They are born in sin, they exist in sin, in sin they go on living. How does that show itself, and to what does it lead- The first thing is that such a man `minds’ certain things. `They that are after the flesh do mind the things of the flesh.’ That is a most interesting expression. In the Epistle to the Philippians the Apostle uses exactly the same expression several times. He says `Let us therefore, as many as be perfect, be thus minded: and if in any thing ye be otherwise minded, God shall reveal even this unto you’ (3:15). Verse 16 has the same word: `Nevertheless, whereto we have already attained, let us walk by the same rule, let us mind the same thing.’ Then Paul introduces it negatively in verse 19, where he is talking about people `whose end is destruction, whose God is their belly, and whose glory is in their shame, who mind earthly things’. ‘To mind’ is a term with which we are familiar, an expression that is quite commonly used. If a man is a busybody and puts too many questions to you and shows too great an interest in your affairs, you say to him ,`Mind your own business’. The expression means, therefore, the deliberate action of your mind on certain objects. That is why you say to the busybody, `Do not train your mind on me and on my affairs, switch it to your own affairs, mind your own business’. But the term includes not only thought and understanding, it includes the affections, the emotions, the desires and the objects of pursuit. In other words, it is a comprehensive term. `To mind earthly things’ not only means that non-Christians think about them occasionally, but that these are the things which they think of most of all; these are the things of which they think habitually, the trend or the bent of their thinking is toward them. `Earthly things’ are the things that please them most of all, the things that give them greatest satisfaction; and therefore the things which they seek after most of all. The term is comprehensive, and we must not limit it merely to the intellectual aspect. It is much wider than the interests of the mind, and takes in the whole personality. The Apostle John, in his First Epistle (chapter 2, verses 15 to 17) has the same idea though he uses a different term. He says: `Love not the world, neither the things that are in the world.’ He might equally well have said, `Mind not the world, neither the things that are in the world’. The first thing about the non-Christian, therefore, is that because he is dominated by his fallen human nature, he is a man who is deliberately interested in, and concerned about `the things of the flesh’. Once more we have to be careful that our understanding of this expression is sufficiently comprehensive. What are `the things of the flesh’? The danger is to limit the term to sensual pleasures and to the sins that belong only to the body. The term `the flesh’ tends to make us think immediately of physical sins, sins which belong primarily to the realm of our animal being. They are certainly included, but it is important for us to realize that the term is very much more comprehensive in its use, as we find when we turn to the Epistle to the Galatians chapter 5, verses 19 to 2 1. `Now the works of the flesh are manifest, which are these; adultery, fornication, uncleanness, lasciviousness’. Yes, but also `Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, envyings, murders, drunkenness, revellings, and such like’. We see that the notion is indeed a very wide one. Or go back again to the First Epistle of John, chapter 2, verses 15 to 17: `Love not the world, neither the things that are in the world’. What are they? The Apostle lists them as `the lust of the flesh, and the lust of the eyes, and the pride of life’. `The flesh’ is a big term, a widely inclusive one. What then does `the flesh’ mean? In a word it means `worldly mindedness’. That is a term which John Bunyan uses, and it is the term that some people would use here. ‘Worldly-mindedness’! It includes everything which is opposed to `the mind’ and `the life’ of the Holy Spirit. Another way of putting it is to say that `the things of the flesh’ means every aspect of life without God, everything in life from which God is excluded. It refers, in other words, to the life of this world only; it denotes a complete severance from all that is spiritual. It concentrates on the visible, the seen, and has nothing at all to do with the unseen. Or again, we can say that it means the temporal only, this world of time only; it has nothing to do with the eternal. Its reference is to life in this world only, to life bounded by the body and the various qualities and attributes of the fleshly mind, but to the exclusion of the spiritual element. The tragedy of the matter is that many people think that this description – `they that are after the flesh do mind the things of the flesh’ – applies only to open, obvious, profligate sinners, on the streets and in the public houses of great cities; the fact being that it includes also very highly intellectual people, very moral people, and people whom the world would describe as very noble. To `mind the things of the flesh’ includes political interests without God, social interests without God, cultural interests without God. That is what the expression means. Paul has in mind man’s highest pursuits, his philosophy, his art, his culture, his music, that never get beyond the flesh. God is outside it all, He is excluded from it; there is nothing spiritual about it. Men may write very cleverly, and in a very learned and interesting and entertaining manner about social conditions; they can tell us how to ameliorate bad conditions, how to improve them; they can write eloquently about forming some sort of Utopia, they can produce masterpieces of art and of literature and of music; but there is no soul there, there is no God there, no Spirit there. It is all `after the flesh’. How important it is to realize the truth of this matter! That is why that list in Galatians 5 is so important. Paul does not stop at drunkenness and adultery and murder and things of that type. He goes to the realm of the inner man; and there you find that his list is all-inclusive. So what the Apostle is really saying about the non-Christian is that it does not matter where he fits in this gamut of possible interests and behavior and conduct, he is still only minding `the things of the flesh.’ It is because the world does not understand this that it is not interested in the Gospel. The world’s good, moral people are admired so much today; and yet the Apostle’s words describe exactly where they stand. They are as much `after the flesh’ and they as much `mind the things of the flesh’ as does the man who falls into drunkenness or gives rein to his passions and lusts. It is purely a difference of degree. There is no essential difference at all. The good, cultured well-spoken moral man is as devoid of the Spirit as the most obvious and profligate sinner; he is outside the life of God as much as the other. He hates to be told this, of course; that is why he is the typical Pharisee. And that is why the Pharisees crucified the Lord Jesus Christ. He convinced them of being `after the flesh’ and `minding’ only the things of the flesh. What a terrible state this is and how alarming it is to realize that people can be in it without ever imagining it! They draw many distinctions and divisions; but there are none in reality. The only difference between the obvious so-called `sinner’ and the highly cultured good moral man is purely a social difference, a superficial one. Let me go a little further; it is perhaps a difference in the skin; the second man keeps his skin a little cleaner than does the first man. The first man has mud and filth and mire about him in abundance, the other takes baths very frequently, so his skin looks very white. But the difference is skin-deep only. In their inner beings, as men, and in their relationship to God, there is not the slightest difference between them; they both together mind the things of the flesh. All their thinking, all their interests, all their pursuits are entirely outside the realm of the spiritual and of God. That is what the Apostle tells us about them. The next thing the Apostle says about them is found in verse 6, where we find the words, `To be carnally minded is death’. The translation in the Authorized Version is most unfortunate; the expression should not have been changed. It should read, `The mind of the flesh is death’ or, `To have the mind of the flesh is death’. He has already said that non-Christians mind the things of the flesh; now he is saying that the people who do mind the things of the flesh, and have the sort of mind that does that, are dead. Here Paul is describing the quality, or the state of mind of people who only mind the things of the flesh. It is, he says, nothing else but sheer death. Our Lord gives us the best understanding of this in what He said to Peter on that occasion at Caesarea Philippi when the Apostle made his great confession in reply to our Lord’s question `Who do ye say that I am?’ Matthew records the matter in his 16th chapter. Peter said, ‘Thou art the Christ, the Son of the living God’. But a few minutes later, when our Lord began to tell the disciples about His approaching death, Peter said, `Be it far from thee, Lord’. Our Lord rebuked him severely and said, `Get thee behind me, Satan, for thou savourest not the things that be of God, but the things that be of men’. The word translated `savourest’, really means `to think’ – `thou thinkest not the things that be of God’. Indeed, it is the very word which is used in this sixth verse of Romans 8. `The trouble with you, Peter,’ said our Lord in effect, `is that your whole mentality is wrong, your whole way of thinking is wrong; you are not thinking the things of God, you are thinking the things of man: `Peter’, He seems to say, `what is the matter with you? You have just made your great confession, and I told you that “flesh and blood had not revealed it unto you, but my Father which is in heaven”. Now you are proving that I was right, because when I go on to make a great spiritual statement to you, you turn and say “That be far from thee, Lord”. Peter, the trouble with you is that you are now thinking, not after God, but after men; your whole outlook, your whole mentality, your whole process of thinking is sadly astray.’ That is the idea in the phrase `The mind of the flesh is death’. Let me illustrate this further, by what the Apostle tells us in the twelfth chapter of this Epistle in the second verse: `Be not conformed to this world: but be ye transformed.’ How? `By the renewing of your mind.’ It is absolutely essential that the mind be renewed. In the absence of a renewal of the mind man is entirely hopeless. You will find the same in Ephesians 4, verses 17 to z4, and also in the second chapter of the First Epistle to the Corinthians: `The natural man receiveth not the things of the Spirit of God.’ Why not? `Because they are foolishness unto him: neither can he know them.’ Why not? `Because they are spiritually discerned. But he that is spiritual judgeth all things, yet he himself is judged of no man’ 1 Corinthians 2: 14, is The statement that `The mind of the flesh is death’ means that the natural man is in a state of spiritual death. That is what the Apostle says everywhere about the unbeliever, about the man who is not a Christian. We find it mentioned at the beginning of the second chapter of Ephesians: `You hath he quickened, who were dead in trespasses and sins.’ ‘Dead’ l He repeats it again in verse 5 : `Even when we were dead in sins, he hath quickened us together with Christ.’ The Apostle is saying the same thing here. The man who is `under the flesh’, and governed and controlled by his fallen human nature, not only minds the things of the flesh -those worldly things out of which God is shut – but he does so because he is spiritually dead. He is alive physically, he exists, but spiritually he is a dead man. The Apostle’s statement means that the man is dead to God, he lives as if there were no God. Some of your greatest moral men, some of your most cultured men in the world are in that position. They are very able, very cultured, very much interested in life, they never get drunk, they are not guilty of adultery …. `Ah’, you say, `you cannot say that such a man “minds the things of the flesh”.’ I do just that! God is not in all his thoughts, he is completely dead to God, he is living as if there were no God. That is what is meant by spiritual death. Spiritual death is to be outside the life of God. Our Lord has settled the matter for us. In John’s Gospel, chapter 17, verse 3, we read: `And this is life eternal, that they might know thee, the only true God, and Jesus Christ whom thou hast sent.’ The man who has not got eternal life does not know God, he is outside the life of God; and that means that he is dead. The spiritual realm does not exist for him, he scoffs at it; spiritual realities mean nothing whatsoever to him; he is dead to them all. Ask him to read the New Testament, and he says that it is `nonsense’; draw his attention to spiritual things and he does not know what you are talking about. There is a well-known story which seems to me to supply a perfect illustration of this point. It concerns two great men, William Wilberforce the leader in the movement for the abolition of slavery, and William Pitt the Younger, one time Prime Minister of Britain. They were both brilliant men, they were both politicians, and they were very great friends. But William Wilberforce was converted and became a Christian, while William Pitt, like so many others, was but a formal Christian. William Wilberforce was very much concerned about his friend. He loved him as a man and was greatly concerned about his soul. He was most anxious therefore that Pitt should go with him to listen to a certain preacher, a London clergyman of the Church of England named Richard Cecil. Cecil was a great evangelical preacher, and Wilberforce delighted in his ministry, so he was ever trying to persuade Pitt to go with him to listen to Cecil. At long last Pitt agreed to do so. Wilberforce was delighted and they went together to a service. Richard Cecil was at his best, preaching in his most spiritual and elevated and exalted manner. Wilberforce was enjoying himself, and feeling lifted up into the very heavens. He could not imagine anything better, anything more enjoyable, anything more wonderful; and he was wondering what was happening to his friend William Pitt, the Prime Minister. Well, he was not left long in a state of uncertainty as to what had been happening, because, before they were even out of the building Pitt turned to Wilberforce and said, `You know, Wilberforce, I have not the slightest idea what that man has been talking about’. And he hadn’t, of course. As a man can be tone deaf to music, all who are not Christians are tone deaf to the spiritual. That which was ravishing the mind and the heart of Wilberforce conveyed nothing to Pitt. He was bored, he could not follow it, he could not understand it, he did not know what it was about. A man of great brilliance, a man of great culture, a man of great intellectual ability, but all that does not help l `The natural man receiveth not the things of the Spirit of God, for they are foolishness unto him; neither can he know them, because they are spiritually discerned’ (I Corinthians 2: I4). Richard Cecil might as well have been preaching to a dead man. The dead cannot appreciate these things, neither could William Pitt. He himself confessed it. It is not what Wilberforce says about him; it is what he said about himself. There are such people. They come to a place of worship, they listen to things that ravish the hearts of believers, but they see nothing in it at all. There are many such people in the churches now, as there always have been. They want whist drives and dances, entertainments and socials, and to meet one another socially. That is because they are not alive to spiritual things. They are dead, dead to God, dead to the Lord Jesus Christ, dead to the realm of the spiritual and all spiritual realities, dead to their own soul and spirit and their everlasting and eternal interests. They never think about such matters at all. That is their trouble. That is what the Apostle says here about them. This mind of the flesh shuts them out from the life of God and from all the interests that emanate from the life of God. The trouble with the unbeliever, the non-Christian, is that he is in a living death, he is merely existing. He is shut out from the life of God; and if he dies in that condition he will continue to all eternity shut out from the life of God. Nothing more terrible can be contemplated. That is the meaning of spiritual death. The Apostle then goes on to say another thing about the non-Christian in verse 7: `Because the carnal mind is enmity against God.’ Here, again, it is unfortunate that we have this translation in the Authorized Version, for in the original it still is, `the mind of the flesh’. `Because the mind of the flesh is at enmity against God.’ This explains why `the mind of the flesh’ is death. If a man is at enmity against God he is obviously outside the life of God; and that means that he is dead. Here we have one of our striking proofs that the Apostle is not comparing and contrasting two types of Christians, but is comparing and contrasting the non-Christian and the Christian. You cannot say of any. man who is a Christian that he is at enmity against God; it is impossible. A man cannot be at enmity against God and be a Christian at the same time. Why is he a Christian at all? Because he wants to be right with God. Why does he believe on the Lord Jesus Christ? Because he believes that the Lord Jesus Christ puts him right with God. Why did he ever want that blessing? Because he sees the consequences of being an enemy of God. So here the Apostle depicts a man who is at enmity against God. This is not a so-called `carnal’ Christian; there is no such thing. This is the non-Christian, this is a man who is not a Christian in any true sense, and this is the man Paul has been describing all along. He is contrasting the non-Christian with the Christian, any Christian. The Apostle says the same thing in many other places. In Colossians 1 : 2 1, for instance, we have: `You that were sometime’ ? once upon a time – `alienated and enemies in your mind by wicked works.’ They were once in that condition, but now it is no longer the case. Why so? Because they have become Christians. In other words, the contrast is between the non-Christian and the Christian. But let me emphasize once more that this state of enmity is that of every person who is not a Christian. `Ah but,’ you say, `I know certain people who say, “I would not like to say that I am a Christian, but I believe in God”; what about them?’ The simple truth about them is this, that they are at enmity against God. `But,’ you say, `they are interested in God, they believe in God, they read books about God, and they talk and argue about God. ‘No, they do not!`But how can you say that so dogmatically?’ I do so for this reason: they think they are interested in God, but their interest is not in God, it is in some figment of their own imagination, it is some product of their own philosophy and their own thoughts. `But why do you say even that?’ asks someone. I answer, the way to prove that such persons are not true Christians is quite simple. Say to them, `Do you believe in God?’ They reply, `Of course we believe in God; we have always believed in God’. Next confront them with the God of the Bible, who is not only love but also justice and righteousness; confront them with the God who not only shows mercy and compassion but also wrath; and you will find that they snarl their teeth at you. They will say that they do not believe in such a God! Of course they do not; they have never truly believed in God. What they believe in is a god whom they have constructed for themselves. They have made a god of their own, and for this they have no authority whatsoever, except that it fits in with their thoughts. They say, `The God I believe in is a God who is entirely a God of love’. Wrath? Of course not! Impossible ! But what is their authority for speaking in this fashion? They have none at all. It is simply that they, and people like them, agree in saying these things. The only true knowledge that we have of God is to be found in the Bible. God has revealed Himself. No man can know God of himself – `no man can see God, or has seen God, at any time’. If a man could understand God with his own mind he would be equal to God, if not greater. By definition God is absolute and infinite and eternal in all His attributes and qualities. We cannot arrive at Him of ourselves; He must reveal Himself. He has done so, in the Scriptures and in the Lord Jesus Christ. And the Lord Jesus Christ has taught us about the wrath of God, about the judgment of God, and about hell. Yes, but the moment these people who say they believe in God hear such things, they become furious and remonstrate against it; they hate it. Indeed, they hate God; as Paul tells us, this `mind of the flesh is enmity against God’. It wants a god after its own image, and it hates the God of the Bible, the God and Father of our Lord. Jesus Christ, the God preached by this Apostle Paul and all the other apostles. This is the all-too-common state of things today; alas, you find it in so-called Christian pulpits and churches. In the name of God and of Christ men are showing their enmity and their hatred of God, the living God, `the only true God’. Let us not therefore be misled or deluded by people who say that they believe in God; the question is, Do they believe in the God who has revealed Himself, who is the only God? All natural men, all who are not Christians, are `at enmity against God’. The fifth thing Paul tells us about non-Christians is that `they are not subject to the law of God’. What he means is that they do not submit themselves to it. How can they? If they hate Him why should they subject themselves to Him? Instead of submitting themselves as a soldier does to his commanding officer, to the General set over him, they rebel, they are antagonistic. They do not care what God has said; they do what they want to do. They are not taking orders, they are following out their own minds, and their own likes and dislikes, and their own understanding. Man by nature is an enemy of God, he is a rebel against God, he flouts the commandments of God. `All we like sheep have gone astray, we have all gone after our own devices.’ That is true of all men who are not Christians. They are trampling and spitting upon the Ten Commandments, and the moral law, and all the sanctities. .Of course they are! They are haters of God, and they hate His law; they abominate it; `they are not subject to the law of God’. Next the Apostle adds, `Neither indeed can be.’ `This mind’, he says, `is not subject to the law of God, neither indeed can be.’ Here we have a basic statement about the unbeliever. The unbeliever, says Paul, is not only like that, but he cannot do anything about it. `His mind is not subject to the law of God, neither -indeed can be.’ We find exactly the same idea in 1Corinthians 2: 14: `The natural man receiveth not the things of the Spirit of God, for they are foolishness unto him, neither can he know them.’ He cannot know them. Why? `Because they are spiritually discerned.’ A man who is tone deaf to music cannot create a ,delight in music in himself. He may desire it, but he cannot Attain to it; it is impossible. What the Apostle is saying is that this natural man, this non-Christian, not only hates God, and is not subject to the law of God; but he cannot desire to love God, he cannot desire to obey Him. He cannot choose to do so, he is totally incapable of any spiritual effort. I am not saying this; it is the Apostle Paul who says it. The popular teaching which says that we have to preach the Gospel to the natural man as he is, and that he, as he is, decides to believe on the Lord Jesus Christ; and that then, because he has believed, he is given new life, is regenerated, this, I say, is a complete denial of what the Apostle teaches here. The natural man, this man after the flesh, this unbeliever, cannot believe in God; he cannot believe in and on the Lord Jesus Christ. He is `at enmity’ against Him; he hates Him, he is altogether opposed to Him. He is shut out from His life, he lacks a spiritual faculty, he is incapable of spiritual good `neither indeed can be’. He is completely helpless; he cannot choose to love God. You cannot love God and hate Him at the same time. Why should a man who is at enmity to, and a hater of God, decide suddenly to love Him? There is no reason; his whole nature is against Him, his whole bias, his whole bent, everything in him is opposed to God; he is in complete and entire helplessness; he is dead. And there is nothing more final than that The man who is spiritually dead hates God, rebels against Him, and can do no other, for `the natural man receiveth not the things of the Spirit of God, for they are foolishness unto him, neither can he know them, for they are spiritually discerned’. And if you have not got the spiritual faculty you cannot discern them. If that is lacking in a man, and he is completely dead, how can he discern them – He cannot; and, of course, the world is proving that very thing today. Total inability ! What is the result of all this? It is stated in the eighth verse, `So then’ here is the conclusion, the thing the Apostle was really setting out to prove `so then, they that are in the flesh’ they are the same people, they are `after the flesh’, they are governed by `the mind of the flesh’ `so then, they that are in the flesh cannot please God’. His displeasure is upon them; they can do nothing at all about pleasing Him. They cannot bring forth any fruit unto God. As Paul has already said in chapter 7, verse 5, the righteous demands of the law cannot be fulfilled in them. `In the flesh’, `after the flesh’, governed by `the mind of flesh’, they are entirely and altogether outside God and His life; and there is nothing in them or about them that recommends them to God. Such are the unbelievers. How then does anyone become a believer? The answer has already been given in verse 2, and we shall proceed to work it out. `The law of the Spirit of life in Christ Jesus hath set me free.’ I have not done it; it has been done to me. It is God’s action. `By grace are ye saved through faith; and that not of yourselves: it is the gift of God.’ `We are His workmanship’ (Ephesians 2: 8-10). We can do nothing, it is all of God. And let us thank God that it is so, for it is because it is all of God that it is certain, it is safe, it is sure. We are not just believers, we have been `made anew’, born again; we are in the realm of the spiritual, we have been put there, we are `in Christ’, the Spirit of God has incorporated us into Him. It is His action. Thus far we have been looking at the negatives; and how important it is that we should do so! We shall never realize what we are as Christians until we first realize what we were as non-Christians, and what was absolutely essential before we could ever become Christians. If God had not quickened us we should still be dead. A dead man cannot give himself life. God quickened us, and because God has put life into us we are alive in Christ Jesus, and in the realm of the Spirit. 1 Corinthians 1:9 King James Version 9 God is faithful, by whom ye were called unto the fellowship of his Son Jesus Christ our Lord. Ephesians 2:18 King James Version 18 For through him we both have access by one Spirit unto the Father. 8 But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death. 9 And there came unto me one of the seven angels which had the seven vials full of the seven last plagues, and talked with me, saying, Come hither, I will shew thee the bride, the Lamb’s wife. 10 And he carried me away in the spirit to a great and high mountain, and shewed me that great city, the holy Jerusalem, descending out of heaven from God, Revelation 21:8-10 King James Version Holy Bible Romans 16:17-22 King James Version 17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them. 18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple. 19 For your obedience is come abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise unto that which is good, and simple concerning evil. 20 And the God of peace shall bruise Satan under your feet shortly. The grace of our Lord Jesus Christ be with you. Amen. 21 Timotheus my workfellow, and Lucius, and Jason, and Sosipater, my kinsmen, salute you. 22 I Tertius, who wrote this epistle, salute you in the Lord. Philippians 3:18-21 King James Version 18 (For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ: 19 Whose end is destruction, whose God is their belly, and whose glory is in their shame, who mind earthly things.) 20 For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ: 21 Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself. Titus 3:10-12 King James Version 10 A man that is an heretick after the first and second admonition reject; 11 Knowing that he that is such is subverted, and sinneth, being condemned of himself. 12 When I shall send Artemas unto thee, or Tychicus, be diligent to come unto me to Nicopolis: for I have determined there to winter.Paul’s epistle to Titus outlines the conduct, integrity, and maturity that should be the hallmark of spiritual leadership, both in the body of Christ and in the home environment. He also gives some instruction to the whole Body of Christ on living godly lives in this fallen world system – as we live in our local communities and interact with a wide variety of unbelievers. Throughout the New Testament, we are given helpful guidelines on our roles and responsibility, during our sojourn on earth. As Christians, we are in this world, but we should not be fashioned into a worldly way of living, for the whole world system is currently lying under the power of Satan – the wicked ‘god of this age’. The devil is already condemned by God, because Christ won an almighty victory over sin and Satan, through His sacrificial death on the cross. But Satan’s evil influence is still very much evident in this fallen world – and for that reason, we should be living in the world but not become part of the world. Our mission from on high is not to improve the world, but to act as salt and light within the world. Although it is good and right to help others, we are not instructed to share a social gospel, as so many teach today. We are not called to make the world a better place, but to share the good news of the gospel of grace, so that men, women, boys, and girls may be saved out of the world – by grace, through faith in Christ. The piece of advice that Paul gives to Titus, and to other Christians in this verse, is to reject a fractious man after a first and second warning. Having been justified by His grace and made children of God, we are to reflect the love and kindness of Christ to others… but we are not to seek out arguments or respond to argumentative or contentious people. Rather, we are called to avoid foolish controversies. We are to shun strife, legal conflict, and futile arguments. We should not be drawn into foolish doctrinal disputes about religious law or Church statutes. The Bible reminds us that such controversial interactions are unprofitable and worthless. Reject a fractious man after a first and second warning, Paul explains… knowing that such a man is perverted and is sinning – being self-condemned. Rejecting a factious man may appear in contradiction to the biblical instruction of turning the other cheek or forgiving someone seventy times seven… but whether aggressive conflict comes from an unsaved man or even a carnal Christian, whose primary desire is to promote discord, it is absurd to quibble or engage in fruitless bickering. It is unfruitful and unwise to partake in fractious arguments with someone, who is deliberately acrimonious or has entrenched opinions – like the Scribes and Pharisees of Christ’s day. The Lord Jesus likens it to swallowing a camel and straining out a gnat! Both within the church and in the wider world of the unsaved, there are those that have a particular bee in their bonnet about a certain doctrine or one aspect of biblical truth to the exclusion of everything else, and they consistently drag up their singular theological soap-box, with the intent of entering into mindless arguments or destructive debates… or deliberately causing disunity in the body of Christ. Paul describes this sort of person as divisive and fractious and states very clearly that we are to reject a factious man after a first and second warning. Grace demands that we do not assume someone to be a fractious man or a religious ‘nit-picker’ with their first quibbling comment. However, he makes it clear that we should be prepared to offer a clear warning if they continue with their critical attitude, their nonbiblical allegorising of Scripture, or their habitual preoccupation with some irrelevant issue, which only causes disunity. We are to reject the fractious man who maintains tunnel-vision, which is continuously critical of those that do not agree with his favourite dogmas and rabbit trails. It is particularly sad today, to hear of so many Christians that exhibit this fractious attitude towards their fellow believers over non-essential issues, or who delight in theorising truth or accusing others when presented with an alternative opinion. Indeed, in a world where social media, and other impersonal ways of communicating, have become the accepted norm, it is sad to see so many Christian brothers and sisters adopting this impersonal medium to post critical challenges or make contentious comments, in order to accuse and attack others or simply to instigate a fruitless argument or accusation. Let us be wise in our dealings with fractious men and divisive women, whether they are saved or unsaved. And although we should always be ready to give an answer for the hope that we have in Christ, we are not bound to respond to any contentious comments… nor should we feel obligated to answer some inane question, which is designed to instigate an argument. We should not waste our valuable time and effort in indulging the divisive tactics of someone whose prime objective is to cause division, within the body of Christ. Let us be wise with our time our talents and our teaching. My Prayer Heavenly Father, thank You for this wise advice from Paul.. to reject a factious man after a first and second warning. Lord, I confess that I have sometimes wasted valuable time, trying to appease certain people, whose obvious aim is to cause division or acrimony within the body of Christ… because of some pet preoccupation with one small doctrinal issue, in pursuit of a cherished ideal or to justify their some nonbiblical ideas. Help me to identify those that deliberately seeking to cause division in the body of Christ, and give me the grace and wisdom to remain silent, rather than being pulled into some unfruitful argument – this I ask in Jesus’ name, AMEN. Proverbs 22:24-25 King James Version 24 Make no friendship with an angry man; and with a furious man thou shalt not go: 25 Lest thou learn his ways, and get a snare to thy soul. NEW MAN VS. OLD MAN new-man-vs-old-man As we have learned in previous segments, Adam’s disobedience had a deadly effect on his entire being (spirit, soul, and body); a condition passed on to all his descendants “Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned…” (Rom. 5:12). Also revealed was the remedy; by means of God’s wonderful grace, a dramatic reversal of this condition takes place upon salvation. “Therefore if any man be in Christ, he is a new creature” (2 Cor. 5:17) Sealed with the Holy Spirit. “In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise…”(Eph. 1:13). At the moment of salvation, the Light of God floods in and reignites man’s darkened spirit, and a “new creature is born within; spiritual life is then restored. At this point, two spirits become one, “…he that is joined unto the Lord is one spirit” (1 Cor. 6:17) “…so is every one that is born of the Spirit” (John 3:8). As we have previously learned in the article entitled “In Adam vs. In Christ” the new believer is now supernaturally removed from Adam and placed, “in Christ” thereby uniting him to Jesus’ death, burial and resurrection, (co-crucifixion) (Gal.2:20, Rom.6:3-6). [Additional information see the article entitled “Co-crucifixion”] “For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit” (1 Cor. 12:13). The process also involves a spiritual, “circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ” (Col.2:11), whereby the soul is cut free from the corrupt body of flesh. [Additional information see the article entitled “Spiritual Circumcision”] In summary, upon salvation, man’s SPIRIT is quickened [made alive], his SOUL is redeemed, cut free from his dying BODY which shall be exchanged for a glorified body at the RAPTURE, “For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep. For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.” (1Thess. 4:15-17). “Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself. One Person Two Natures Due to the second birth, every born-again believer truly is a “new creature in Christ”, sealed with the Holy Spirit, possessing a “divine nature” (“new man”), “Christ in you, the hope of glory” (Col. 1:27). However, our old fleshly nature, (“old man”) which is opposed to God is not eradicated upon salvation… unfortunately, he remains alive and active. In reality, every believer is a spiritual being temporarily residing in sin-prone flesh. “An immortal life in dying flesh…a royal servant in a prison of clay.” The nature of the “new man” is that of the Holy Spirit, therefore He desires to love, obey and please God. The nature of the “old man” is that of the flesh, which manifests itself through self-centeredness; self-gratification, and self-righteousness. He is characterized by an attitude that is antagonistic to everything genuinely associated with God (although he will gladly wear the mask of religion to suit his self-righteousness) “Having a form of godliness, but denying the power thereof…”(2 Tim. 3:5). Rebelliousness, lust, worldliness, and pride are in his DNA. The “works of the flesh” (the old man) and “the fruit of the Spirit” (the new man) are set at contrast in (Gal. 5:19-23): “Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God. But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, Meekness, temperance: against such there is no law.” Hence, Paul’s declaration in Rom.7:18, “For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. Believers must learn to deal with the ever re-emergent force of the flesh…the “old man” is dead but buried in a shallow grave!” Understanding the Inner Struggle In Paul’s epistle to the Corinthians, he divides all Christians into two categories, the spiritual and the fleshly or carnal (1 Cor. 3:1-3). The two types consist of those who have learned to overcome the flesh and those who are overcome by the flesh; those who have matured and those who remain, “babes in Christ.” As previously stated, every born-again believer has TWO diametrically opposed natures struggling for control of the being. In Galatians 5:17 we read, “For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.” Romans chapter 7, verses 14-25, provide a window into the nature of the constant struggle between the “old man” and the, “new man” which began shortly after salvation. In these verses, the apostle Paul describes the inner conflict between two contrary forces, the indwelling Holy Spirit, and his sin-prone flesh. The battle for control of the being is a tug-of-war between a well-established nature and an emerging new nature…intense as hand-to-hand combat, although in this case, the battle is not against flesh and blood, the mind is the arena of conflict. [Additional in-depth information see the article entitled “The Mind is the Battlefield”] Who’s in Control? The below drawings are meant to illustrate the “inner realities” concerning the spiritual state of Christians. The two believers set at contrast are both related to the Lord by the “second birth”; however, one has a “relationship” with the Saviour, and the other doesn’t. The diagram on the left pictures a believer who is yielded to the Holy Spirit (walking in the Spirit). Because he has learned to “draw nigh to God” and resist the flesh, the new nature is dominating… he is “spiritually minded.” For to be carnally minded is death; but to be spiritually minded is life and peace. (Rom. 8:6). The eyes of his spiritual understanding are open and attuned to the motions of the Holy Spirit, therefore he is full of God’s Light, growing in grace and knowledge of the Lord. On the other hand, the diagram on the right depicts a believer who is grieving the Holy Spirit by yielding to the flesh. He has chosen the things of the world and self…neglecting the things of God, “carnally minded”(Rom.8:6). He may even deceive himself and those around him concerning his actual condition, but God sees the heart. Because he is out of fellowship with the Lord, his spiritual understanding is darkened, receptivity is minimal. Therefore, he is deprived of the many vital spiritual blessings enjoyed by those who “Abide in Christ.” Every believer is either walking in the flesh (yielded to the influence of the old man) or walking in the Spirit (yielded to the power of the new man)…there is no middle ground! “Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey…” (Rom. 6:16). That which separates the two types of believers is whether or not they have understood and obeyed the essential truths of Romans chapters 6-8. The Trilogy of Transformation Romans chapters 6-8 explain the crucial process of sanctification (growth) in

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