Entropy, in relation to thermodynamics, is the amount of randomness in a system. Defined more precisely, entropy is the energy of unordered molecular motion in a system that can’t produce useful work. Measured in joules per kelvin, systems with higher uncertainty tend to have higher entropy. Since only ordered, predictable motion can produce work, entropy offers a mathematical way to quantify the amount of wasted energy in a system.
When I was seven, the bubble man visited my elementary school. Arriving in a pink van with blue bubbles painted on it, he carried trays of soapy water and colorful plastic bubble wands to the gym stage. When it was time for the show, I sat packed in with four hundred kids on the rough carpeted floor. The lights dimmed and our eyes were glued to the stage as the bubble man blew a bubble the size of a car, filling the audience with oohs and aahs.
After the bubble man finished his bubble tricks, we clapped and cheered, and the air filled with a soapy smell. To me, the bubble man was like a god. How had he created a bubble trampoline, merged two bubbles into one, and filled a bubble with fog without it popping? Was there a special mixture of soap and water he used? And how could I get a fog machine like his?
Fascinated, I wanted to devour the secrets behind bubbles to become like a god myself.
When the bubble man left, he packed his things away and slammed shut his car door. I watched as he drove out of the parking lot, the hum of his engine fading into silence as his pink-and-blue van diminished to a point down the road and then disappeared. I wondered where he was going, what school he was going to next, and whether the kids at the next school would appreciate what he did as much as I did.
According to the second law of thermodynamics, the entropy of a closed system always increases. Order is created from the concentration of energy; physical processes dissipate energy to achieve equilibrium, increasing entropy. The second law sets fundamental constraints on what is possible, creating the notion of irreversible processes. Think of an ice cube in the hot sun. As the sun’s rays transfer energy to the ice, the cube melts from an ordered crystal solid into a disordered flowing liquid. Naturally, in this scenario, it’s impossible for any amount of liquid water to transform back into ice.
I gave Bob the snowman a pat with my mittens, although calling him a snowman was a generous compliment. Seven inches tall and made of two brown, sludgy snowballs, Bob wore dimpled eyes, a crooked smile, and two mismatched sticks for arms. Despite his underwhelming guise, after sculpting his final touches I jumped and laughed, my smile stretching from ear to ear; I had brought a new friend into the world. Running around Bob, I trampled the layer of half-melted snow which covered the bare dirt of the yard.
Then, from over the pine trees and behind a gray blanket of clouds, a sliver of rays emerged from a pocket of blue sky expanding to reveal the sun. A beam of sunlight focused on Bob, blasting his smile with what seemed to be a blinding intensity. He began to sag as he trickled brown water from his side. My feet nearly slipping, I rushed over and shoved snow onto his sides with my mittens, squeezing and padding his body. But the sun was too powerful. With a sinking feeling in my heart, I watched as Bob melted into a puddle of brown slush, his stick arms lying flat on the bare dirt.
Entropy and disorder are closely related to chaos theory. Researching weather models in the 1960s, meteorologist Edward Lorenz discovered that because many systems have inherent disorder, a microscopic change in the starting state could drastically change the ending state. In other words, without perfectly exact measurements, even with the strongest supercomputers weather would still be impossible to predict with certainty. This effect is commonly known as the butterfly effect—when systems are sensitively dependent on initial conditions, even changes as minuscule as the flap of a butterfly’s wings can dramatically affect the future of the system.
The wooden boardwalk creaked beneath my sneakers with every step. My eyes darted from tree to tree, drinking in the scenery. Thousands of orange monarch butterflies covered the leaves and branches of the tall eucalyptus trees at the Natural Bridges Monarch Grove butterfly sanctuary. A cool fall breeze wound its way through the trees, and the air was filled with the clicking flap of butterfly wings.
“The monarch butterfly migrates in the late fall from the interior of the United States to its winter habitat,” the tour guide told my group. “These amazing creatures fly over 3,000 miles to reach the California coast.”
I paused momentarily as a large monarch butterfly fluttered to a stop on the wooden railing next to me. The brilliant bright orange and yellow spots on its large wings were interwoven with narrow black lines and surrounded by a thick black ring dotted with white spots. Clutching the wood with its short twig-like black legs, two twitching antennae grew out of its fuzzy white spotted body. The sunlight struck the butterfly in such a way that it appeared to glow golden as if it were radiating magical energy. Looking at the creature, I almost imagined its bulbous eyes staring back into mine. Then, as the moment passed, the monarch flapped its wings and danced away.
As we continued down the trail, my mind was full of wonder. Why here, and why now? Why did they come to this otherwise ordinary eucalyptus forest? How many thousands of them were here? I wanted them to stay here forever with their dazzling spectacle, hundreds of flashes of orange darting through the air, creating whorls, eddies, and dancing patterns of shadow. But deep down, I knew they would leave, carried away by the wind just as they had been carried here, leaving the eucalyptus trees bare once again. The butterflies generated chaos and disorder, but with a hidden order. Chaos, but with the sense of beauty only nature can possess.
Entropy operates on all scales, from the microscopic to the macroscopic. From the motion of subatomic particles to the melting of ice to the brilliant explosions of stars, the second law of thermodynamics provides a model to understand the world. Natural processes that decrease entropy, such as the freezing of water into ice, are counterbalanced by other processes that increase entropy, creating a net increase at the universal scale. All the planets, stars, and galaxies in the cosmos obey this universal law.
“Come, look here,” Dad said.
I crouched down in the tall grass on top of the hill. With only the dim glow of the city on the horizon, the dark night of the new moon cast my surroundings in black shadow, the silhouette of trees visible in the distance. The sound of chirping crickets filled the field and I could smell the fresh soil.
Glowing white streaks, orange nebulae, and black dust splayed across the cloudless sky in a giant milky band surrounded with points of yellow, red, and blue scattered like grains of sand. Closing my left eye, I pressed my face up to the telescope.
“Wow,” I whispered. In the circular viewport, a striped, brown sphere appeared, streaked with beige and russet from its equator to its poles and surrounded by sharp, paper-thin rings. “I didn’t think the focus on Saturn would be this good.”
A fan of astronomy, I knew Saturn was the second largest planet, and as a gas giant, its atmosphere was made mostly of hydrogen and helium. I knew the planet was less dense than water and would float in a bathtub. I knew its rings were split in the middle by the Cassini Division, a gap 4,800 kilometers wide. I knew its largest moon Titan was cold enough to have liquid methane lakes.
But looking at the planet through my telescope with my eyes felt magical as if I were Galileo discovering Saturn for the first time. Looking at its atmosphere and its rings which scientists had measured and studied gave me a sense of understanding, truth, and accomplishment as a member of the human species. That sitting there, in the tall grass, I could observe the outer reaches of our solar system, I could explore deep into the wonders of space, and I could understand our place as humankind in the mighty cosmos made me breathe a sigh.
In the heat death theory of the universe, scientists have taken the second law of thermodynamics to its natural conclusion. As the universe continues to expand and entropy continues to increase, energy and matter become more and more diffuse. In 100 million years, galaxies outside our local group will have moved so far away we can no longer observe them. After 120 trillion years, the last star will have fizzled out and dissipated its gas across the emptiness of space. After 100 quintillion years, even the last stellar remnants will have been swallowed by black holes. Beyond a googol years, the last black holes will have breathed their dying breaths.
The universe will have achieved maximum entropy, its energy dissipated across the unimaginable vastness of the expanding cosmos. No matter can be formed. Lone photons and quarks will have spread too far apart to interact with each other. Our planet Earth and the human species will long have ceased to exist. Our information, the language, literature, science, and culture we have created and that we will ever create will be gone, atomized across the void of space and time.
