When I think about the fact that the universe—not the world, the universe—will end, eventually, inevitably, I don’t feel much of anything beyond a nodding solemnity. Yes, yes, of course. That sounds exactly right. I suppose this is in part because it doesn’t matter for me personally. Whether the whole of the universe ends by a Big Crunch, a Big Rip, or vacuum decay, by all calculations it will happen so far in the future that the earth will already have been consumed by an exploded supernova sun. Humanity will already be gone (unless, of course, we find a way off this planet, a way to thrive somewhere far away from here when the sun dies). But the end of the universe will likely not affect me or you or even our grandchildren's grandchildren's grandchildren. In fact, humans are much more likely as a species to make the earth inhabitable long before the sun will, so even the sun exploding is not at all a concern compared to climate change.
Still. In the face of total and certain annihilation, it's tempting to ask whether this has all been for nothing. This being our blip-like lives on a little planet that will someday be consumed by our own sun, which will in turn be consumed by whatever doom is prescribed by some law of science that has been theorized but that we haven’t fully worked out yet (ie, Big Crunch, Big Rip, vacuum decay). So, what is our impact on the universe? As a civilization and as individuals? Does any of this matter if it’s not going to last? As long as the universe stays put, conceivably someone somewhere in billions of years could still be reading something that I wrote (or looking at a painting you painted, or listening to a song you sung. Or, simply, our descendants will still be alive and thriving). But if the universe collapses, if all trace of us vanishes—except maybe our scattered atoms—does anything we do matter in the very, very end?
I have to say yes. Yes, emphatically, because we are more than a purpose to be served. We are here to experience and to learn, to simply be, so if we’ve done that, then it doesn’t matter if the universe ends because we’ll already have done what we came to do. The idea of the end could easily fill us with dread, but is there possibly a strange sort of comfort to be found in the idea that nothing at all is permanent? This too shall pass, and it’s extremely possible that the universe is cyclical, so even the end will pass and the universe will begin again. I don't know—maybe there is some comfort in that.
But what I find sad, the thing that really scrapes close to the bone, is the possibility of the Heat Death of the universe. This is the most likely end-of-everything scenario, and it follows the Second Law of Thermodynamics, meaning it has to do with entropy, or decay (not, as the name kind of makes it sound, that the universe will end in a fiery explosion of heat , but that there will be a complete lack of heat, the universe eventually reaching the temperature of absolute zero). The universe is expanding, and someday the space between all objects with mass will be so large that there can be no interaction between them. No gas to fuel new stars; no dead stellar remnants to grow black holes. The skies will go dark, and every galaxy will die isolated and alone. The universe reaches maximum entropy, with absolutely no available energy to exchange, and…that’s it. It’s done. Nothing new can form.
Just the thought makes me feel cold and panicky. No new stars, no new planets, no new life. It will all just stall, game over forever. That's why, when I mourn for the universe, it is not because it must end. It is because there will someday be so much space between everything that nothing anymore can be reached.
But remember—that's a long way off. In the meantime, let's make art. Let's not drift apart.
We always talk about the beginning of the universe—the Big Bang—but what about the end of it? Recently I read the End of Everything (Astrophysically Speaking) by Katie Mack, a nonfiction book written by an astrophysicist about all the possible ways the universe could end. It’s full of humor and unabashed nerdy exuberance about science, and though some of it was a bit hard to follow (in general, outer space stuff is just hard to wrap the mind around sometimes), it was overall very accessible and a short, well-written read. I highly recommend this for anyone interested in the cosmos, and especially in the study of the end of everything.