Entropy: The Invisible Force That Brings Disorder to the Universe

by Jesslyn Shields Mar 27, 2020

Entropy describes how disorder happens in a system as large as the universe or as small as a thermos full of coffee. Jose A. Bernat Bacete/Getty Images

You can't easily put the toothpaste back into the tube. You can't expect molecules of steam to spontaneously migrate back together to form a ball of water. If you release a bunch of corgi puppies into a field, it's very unlikely you're going to be able to get them all back together into a crate without doing a ton of work. These are the problems associated with the Second Law of Thermodynamics, also known as the Law of Entropy.

The Second Law of Thermodynamics

Thermodynamics is important to various scientific disciplines, from engineering to natural sciences to chemistry, physics and even economics. A thermodynamic system is a confined space, which doesn't let energy in or out of it.

The first law of thermodynamics has to do with the conservation of energy — you probably remember hearing before that the energy in a closed system remains constant ("energy can neither be created nor destroyed"), unless it's tampered with from the outside. However, the energy constantly changes forms — a fire can turn chemical energy from a plant into thermal and electromagnetic energy. A battery turns chemical energy into electrical energy. The world turns and energy becomes less organized.

"The second law of thermodynamics is called the entropy law," Marko Popovic, a postdoctoral researcher in Biothermodynamics in the School of Life Sciences at the Technical University of Munich, told us in an email. "It is one of the most important laws in nature."

Entropy is a measure of the disorder in a closed system. According to the second law, entropy in a system almost always increases over time — you can do work to create order in a system, but even the work that's put into reordering increases disorder as a byproduct — usually in the form of heat. Because the measure of entropy is based on probabilities, it is, of course, possible for the entropy to decrease in a system on occasion, but that's statistically very unlikely.

JAMES CLEAR

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