Heat Death of the Universe

What would happen if the universe expanded indefinitely?

In 1967, an American-born writer and artist named Pamela Zoline published an unusually subversive short story in a British science fiction magazine entitled "The Heat Death of the Universe." It became an instant classic, even though it had none of the usual conventions of the genre.

There were no aliens, no inter-galactic wars, no massive explosions, no ravenous black holes, and no futuristic technology or robot overlords - just the seemingly disjointed musings, in neatly numbered paragraphs, of a young wife and mother named Sarah Boyle, "vivacious and witty... proud of her growing family which keeps her happy and busy around the house, involved in many hobbies and community activities, and only occasionally given to obsessions concerning Time/Entropy/Chaos and Death."

The title refers to a 19th century theory about how the universe will end based on the implications of entropy (a.k.a., the Second Law of Thermodynamics) - hence the "heat death" of the universe. In Zoline's story, it becomes a metaphor for the unending battle against disorder, decay and chaos, through the eyes of a disgruntled housewife on the brink of madness:

"Housework is never completed, the chaos always lurks ready to encroach on any area left unweeded, a jungle filled with dirty pans and the roaring of giant stuffed toy animals turned savage. Terrible glass eyes."

Much of the science is spot-on, certainly for 1967, with one notable exception. At one point, Sarah Boyle envisions the world ending in fire:

"Everything becoming warmer and warmer, each particle of matter becoming more agitated, more excited until the bonds shatter, the glues fail, the deodorants lose their seals. She imagines the whole of New York City melting like a Dali into a great chocolate mass, a great soup, the Great Soup of New York."

But the term "heat death" doesn't refer to actual heat, as Zoline leads us to believe. It's a throwback to the 19th century vocabulary of thermodynamics. All physical systems tend towards a state of equilibrium, in which there is no net flow of energy.

For instance, gas molecules are confined by the walls of their container, but when the gas is released, the molecules disperse outward, until they are evenly spread out into the larger space.

If the second law were extrapolated to its logical conclusion, the entire universe would eventually reach a similar state of thermal equilibrium, with a uniform temperature throughout its vast expanse. Change would stop, and therefore time as we know it would cease.

Chalk up Zoline's take to artistic license. Her short story is over 40 years old now, and the science of cosmology has come a long way. But the notion of a possible "heat death" of the universe is still viable, in light of the 1998 discovery that our universe's expansion is accelerating.

Scientists continue to debate the eventual fate of the universe, but if the accelerating universe theory holds up, so does our cosmos' eventual "heat death." All matter in the universe will grow further and further apart, until hardly any galaxies or stars will be visible from our tiny corner of the Milky Way.

In fact, some physicists estimate that, although there are roughly 100 billion galaxies in the universe, within 150 billion years only a few thousand would be visible from earth - not that we'd notice. By that time, our sun would have burned out long ago. Even black holes would evaporate away into energy.

It's the kind of thought that would drive poor Sarah Boyle to even greater depths of despair. But I'd encourage Sarah to take comfort in this thought: there's really no such thing as perfect thermal equilibrium. Even when the cosmos has been reduced to empty space, there will still be tiny fluctuations from time to time - and out of those fluctuations could very well spring another baby universe.

Infinity is a very long time, after all. Our heat death might just be temporary.

Image (top): Three possible futures for our universe. The "heat death" will occur with option number two ("Indefinite expansion"). Credit: NASA/STScI/Ann Feild.