What If?: Serious Scientific Answers to Absurd Hypothetical Questions

by Randall Munroe

Our most lasting relic will probably be the layer of plastic we’ve deposited across the planet. By digging up oil, processing it into durable and long-lasting polymers, and spreading it across the Earth’s surface, we’ve left a fingerprint that could outlast everything else we do. Our plastic will become shredded and buried, and perhaps some microbes will learn to digest it, but in all likelihood, a million years from now, an out-of-place layer of processed hydrocarbons—transformed fragments of our shampoo bottles and shopping bags—will serve as a chemical monument to civilization.

But if you’re even more pedantic, it is true. The ocean is colder than space. Interstellar space is very cold, but space near the Sun—and near Earth—is actually incredibly hot! The reason it doesn’t seem that way is that in space, the definition of “temperature” breaks down a little bit. Space seems cold because it’s so empty. Temperature is a measure of the average kinetic energy of a collection of particles. In space, individual molecules have a high average kinetic energy, but there are so few of them that they don’t affect you.

Here’s a question to give you a sense of scale. Which of the following would be brighter, in terms of the amount of energy delivered to your retina: A supernova, seen from as far away as the Sun is from the Earth, or the detonation of a hydrogen bomb pressed against your eyeball? Can you hurry up and set it off? This is heavy. Applying Dr. Spector’s rule of thumb suggests that the supernova is brighter. And indeed, it is . . . by nine orders of magnitude.