Imagine you are sitting in a room. It is a magic room, protecting you from time. It has windows at which there are the most powerful telescopes ever made, enabling you to see to the edge of the visible universe. You will be able to survive there and observe reality for trillions of years.
Trillions of light years beyond you, there is a point beyond which you cannot see. That is because the universe is expanding, and at the very edge of this expansion, stars are moving away from you – relatively speaking – at the speed of light, so they fall behind this dark event horizon, beyond which you will never be able to see.
But the universe is continuing to expand because there’s not enough matter in it to slow it down or reverse it. In fact, the expansion is increasing. That means the event horizon is moving closer to you all the time. The edge is always falling away from you. In a few million years, the farthest objects you know will become unseen and unknown.
This expansion will continue, and at some point, in the far future, you might never have known any such thing as other galaxies exist, because the closest ones will have moved away from you at the speed of light, falling out of your sight.
But it doesn’t stop there. Eventually, the farthest stars in the galaxy will expand beyond your view. Closer and closer the event horizon will come. You look through the telescopes in the windows of your magic room, and the farthest objects you can see are the outer planets. Beyond that, all is dark. There are no stars.
But still, the expansion goes on. The outer planets fall out of your sight. Then the inner planets. Then, even the sun. It is moving away from you at the speed of light.
And there in your room, the farther points on the earth would fall behind the ever-approaching event horizon. And then your town. Everyone you know and love is expanding away from you at the speed of light, lost forever from your view.
And then, eventually, the walls of your magic room would go dark. And there you would be, alone in the darkest cold and the coldest dark that could ever be, infinitely far away from everyone and everything else that ever existed.
Eventually, your limbs will expand away from you. Then your senses. Then whatever it is that makes you, you.
This cold, dark emptiness is the final entropy, the profound death that awaits all that has ever existed.
Sometimes, science is like a teenager whose girlfriend just broke up with him.