Why does anything exist? Why is there something rather than nothing? Would it not have been easier for there to be nothing at all?
Is the universe fine-tuned? In other words, were physical laws and constants of nature somehow chosen to allow complex life to arise?
What is time? Few things are so familiar and mysterious. Our lives are governed by time, and yet we have so little understanding of it.
How big is the universe? While it is generally known that the universe is very big, the latest science reveals that its true size defies all comprehension.