So our imaginary farm is really a model of a solid, with energy (sheep) shuffled between atoms (plots of land).īack to the farm. Just as the sheep wander about the plots of land in the farm, these packets of energy randomly shuffle among the atoms in the solid. In the quantum picture, you can think of every atom like a tiny bucket for energy, into which we can place any number of energy packets. ![]() But when you get down to the atomic level, quantum mechanics teaches us that energy comes in discrete chunks. We usually think of energy as something continuous, something that flows. When you heat a solid, you're adding energy to it. So why are we picturing this pastoral scene? Because we can use it to understand the physics of solids. Try to find them all, by dragging the sheep around below. There are 10 different ways that these 3 sheep can be arranged in 3 plots of land. And this farm is split into three plots of lands. These sheep are shuffling about in a farm, pretty much at random. First, I’d like you to picture some sheep. ![]() Going down this road leads us to some of the biggest unanswered questions about the cosmos: how did our universe begin, how will it end, and why is our past different from our future? Counting Sheep What is entropy, really? Why does it always keep increasing? Why don’t eggshells uncrack, or wine glasses unshatter? In this piece, my goal is to give you the tools to answer these questions. In other words, things are only allowed to happen in one direction - the direction in which entropy increases.īut this doesn’t answer the question, it just replaces it with a new set of questions. You might also have heard the phrase, “ entropy always increases”. You might’ve heard an explanation that goes like this: whenever you drop an egg, or melt an ice cube, or shatter a wine glass, you’ve increased the entropy of the world. But when we get to large collections of atoms, a one-way street emerges for the direction in which events take place. The atomic world is a two-way street.Īnd yet, for some reason, when we get to large collections of atoms, a one-way street emerges for the direction in which events take place, even though this wasn’t present at the microscopic level. At the level of microscopic particles, nature doesn’t have a preference for doing things in one direction versus doing them in reverse. So there’s a deep mystery lurking behind our seemingly simple ice-melting puzzle. The movement of every atom in this time-reversed egg would still be perfectly consistent with the laws of physics. ![]() The pieces of the egg could theoretically start on the floor, hurtle towards each other, reforming into an egg as it lifts off the ground, travel up through the air, and arrive gently in your hand. Every atomic motion taking place in this messy event could have happened in reverse. So why is the first gif an everyday occurrence, while the reverse one impossible? The movements of the atoms and molecules in the first gif are every bit as ‘legal’ (in the court of physical law) as those in the second gif. If you could film the motion of any particle, and then play that film back in reverse, what you’d see would still be perfectly consistent with the laws of physics. Imagine you could zoom in and see the atoms and molecules in a melting cube of ice. Ice melts on a warm day, but a glass of water left out will never morph into neatly-stacked cubes of ice.īut here’s the weird thing. But something about it immediately seems off. ![]() The second gif is just the first one played in reverse. Entropy Explained, With Sheep From Melting Ice Cubes to a Mystery About Time By Aatish Bhatia
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |