When I was a teenager I read Stephen Hawking’s A Brief History of Time. Instead of taking this beautiful book as a path to something useful, like a career in theoretical physics, I mainly used it as an excuse not to tidy my room. And I don’t mean I sat there screaming “Mum! Not now, I’m reading a book!”: if I understood it correctly, A Brief History of Time said that tidying my room would (in an absurdly, ridiculously tiny way) hasten the end of the universe. Surely, I argued, a tidy room wasn’t worth that…
That the argument was asinine should go without saying, but an argument can be asinine and still technically correct.
My story relied on a few big ideas from A Brief History. The first big idea is that any attempt to impose order on the universe actually increases disorder overall. (Throughout this piece, when I talk about “disorder,” I’m really talking about entropy). Take ice, for example. By putting a tray of water in the freezer you’re transforming it from a less organized state (a liquid sloshing around in the container) to a more organized state (a beautiful crystalline solid). But to make that happen your freezer has to create a large amount of heat, which agitates air particles, which (for example) causes a cup of water elsewhere in your kitchen to evaporate a little faster, transforming into the less-organized state of water vapor.
We can certainly make things more organized locally, thank goodness: for example, I’m grateful that somebody took a bunch of disordered sand and made it into the very well-ordered silicon chips in my laptop. But while we can’t always say precisely where the corresponding increase in disorder happened, we know that any local increase in order necessarily means more disorder in the universe on net. This is called the Second Law of Thermodynamics, and it’s a very big deal.
Another big idea I learned from A Brief History was that — from the understanding of scientists at the time — the end of the universe would essentially be a vast, lukewarm soup of completely disorganized matter. Everything humans want to do involves taking some substance (such as petroleum or sugar) that has accessible energy and using it in a way that does useful work but leaves the energy in a less-accessible state, such as in ever-so-slightly hotter air. (Energy cannot be created or destroyed, only transferred or transformed). If the universe becomes a lukewarm soup it will be impossible to do anything new, because there won’t be any “free energy” left to do work with. (Humans will be long dead by that point, which will be another major impediment to getting anything done). This end-time scenario is known as the Heat Death of the Universe, which also seems like a pretty great name for your new heavy metal band.
But now we arrive at the truly important question: how does this relate to tidying your room? The logic I had was pretty simple: tidying your room is an example of trying to create order, and therefore (necessarily) it means creating more disorder in the universe overall. The heat death of the universe will happen when everything is in total disorder, so if tidying makes disorder increase a little faster then tidying (ever so slightly) hastens the heat death of the universe.
You might already have noticed that this argument isn’t specific to room-tidying, and that in fact you can use it for almost any human activity. Your friend pesters you to come for a jog? “Um, I’m sorry, I thought you liked the existence of the universe.” Someone at the bar asks you out on a date? “I’m sorry, I’d love to, but I’m trying to lower my entropic footprint.”
Now, it’s true that on a practical level these arguments are junk because human activity is completely, incomprehensibly negligible from the point of view of the universe. But while our impact is inconsequential, that doesn’t mean that the room-tidying argument is wrong. Imagine drinking a super-sized sugary soda and then refusing to eat a grape because you’re “cutting down on sugar”; everyone can tell that you’re arguing in bad faith, but it is still technically true that eating the grape would increase your sugar intake. The difference is just that your relationship to the universe is less like a grape to a sugary soda and more like a grape to more soda than has ever been produced in the history of the world … and, honestly, that still doesn’t come close.
Now, of course, “not necessarily wrong” doesn’t mean anything close to “right.” So, with a pang of guilt about the genuinely useful things I was probably distracting them from, I tracked down some of the world’s best physicists to hear what they thought.
It turns out I wasn’t totally off track. It also turns out that tenured professors of astrophysics are less cocky in their views about arbitrary astrophysics topics than annoying teenagers who have only read one book.
Sean Carroll, a theoretical physicist at the California Institute of Technology and author of several excellent books about the universe, told me that my argument sounded “essentially correct, although to be honest I haven’t worked out any equations or anything. The Second Law says that entropy goes up, but it doesn’t say how quickly it goes up. Roughly, I would expect that any time you “do something” — whether it’s writing an email or cleaning your room — entropy probably increases a little faster than it would if you weren’t doing anything.” The point Carroll makes is that we can’t assume tidying your room increases entropy faster than the relevant alternative activity: it seems probable that sitting still and meditating will cause less of an increase in entropy than writing an email or cleaning your room would, but a real physicist still wants to check that rigorously instead of assuming.
But my argument soon faced knottier problems. While it’s probably true that in any particular moment my decision to tidy the room (instead of lying very still on my bed) would lead to higher entropy (that is, more disorder), what if we zoom out a little and think about the larger context? Teenage me had failed to realize that my opposition in the eternal room-tidying debate could use my argument too. Scott Aaronson, an MIT complexity theorist and phenomenal blogger, points out that “your parents could fairly argue that you increased entropy when you made your room a mess in the first place, so that’s what you shouldn’t have done and should never do again.” Now, my teenage self would have retorted here that you can’t change the past and once the room is already a mess the only reasonable solution is to leave it that way forever, but I do take Aaronson’s larger point that two can play the entropy blame-game. (Aaronson is himself a parent; I probably should have anticipated where his loyalties would lie.)
Unfortunately, things only got worse from there. David Tong, a professor of theoretical physics at the University of Cambridge, broke the news that my eschatology was also woefully out of date. There’s now “pretty compelling evidence that the universe is not going to end in heat death, no matter how often you tidy your room. About 15 years ago, we discovered that the expansion of the universe is speeding up. We don’t really understand this, but the evidence is clear. It means that the universe is likely to keep expanding forever … The ultimate fate of the universe will then be a cold, miserable, lonely existence in which the remnants of burnt-out stars get further and further apart.” That’s bad news on all fronts: “a cold, miserable, lonely existence” doesn’t sound like fun, and it doesn’t even give me a useful excuse to make a mess.
Margaret Geller, a pioneering scientist at the Harvard-Smithsonian Center for Astrophysics, was similarly amused but unconvinced by my shenanigans. “The ‘heat death of the universe’ has always struck me as an odd and not particularly useful concept,” she told me, because “entropy has at best an unclear meaning in a gravitating system.” If I was interested in the end of days I would need to start thinking bigger, because “human beings have essentially nothing to do with it.”
So there you have it: the “Argument From Entropy” against tidying your room (or doing almost-anything else) is almost certainly inaccurate given what scientists now believe about the far-off end of the universe. And even at its best, what does the argument really tell us? As Professor Aaronson, the MIT complexity theorist, nicely put it, “when all the stars have gone cold, and the universe has degenerated into radiation (and black holes, but those will eventually evaporate into radiation too), there will be no free energy left. What can one say about this, except that we should try to enjoy the ride while it lasts?”
We should try to enjoy the ride while it lasts. That’s why I’m still not tidying my room. •