WEBVTT - What Is Entropy? 0:00:01.920 --> 0:00:06.600 Welcome to brain Stuff production of I Heart Radio. Hey 0:00:06.680 --> 0:00:10.280 brain Stuff, Lauren Bogle bomb here. You can't easily put 0:00:10.320 --> 0:00:14.280 the toothpaste back into the tube. You can't expect molecules 0:00:14.280 --> 0:00:17.639 of steam to spontaneously migrate back together to form a 0:00:17.680 --> 0:00:20.840 panful of water. If you release a bunch of corky 0:00:20.920 --> 0:00:23.880 puppies into a field, it's very unlikely that you're going 0:00:23.920 --> 0:00:25.400 to be able to get all of them back together 0:00:25.440 --> 0:00:29.479 into a crate without doing a ton of adorable fluffy work. 0:00:30.760 --> 0:00:34.320 These are the problems associated with the second law of thermodynamics, 0:00:34.400 --> 0:00:38.720 also known as the law of entropy. Thermodynamics is important 0:00:38.760 --> 0:00:43.120 to various scientific disciplines, from engineering to natural sciences, to chemistry, 0:00:43.159 --> 0:00:47.400 to physics, and even economics. A thermodynamic system is a 0:00:47.440 --> 0:00:50.680 confined space which doesn't let energy in or out of it. 0:00:51.920 --> 0:00:54.360 The first law of thermodynamics has to do with the 0:00:54.440 --> 0:00:57.480 conservation of energy. You know that the energy in a 0:00:57.520 --> 0:01:01.360 closed system remains constant. That is, energy can be neither 0:01:01.480 --> 0:01:05.840 created nor destroyed, that is, unless the system is tampered 0:01:05.880 --> 0:01:10.480 with from the outside. However, the energy in a system 0:01:10.520 --> 0:01:14.720 constantly changes. Forms of fire can turn chemical energy from 0:01:14.720 --> 0:01:19.520 a plant into thermal and electromagnetic energy. Battery turns chemical 0:01:19.600 --> 0:01:24.360 energy into electrical energy. The world turns and energy becomes 0:01:24.600 --> 0:01:28.640 less organized. This is entropy, and it's one of the 0:01:28.720 --> 0:01:33.800 laws that demonstrates how our universe works. So entropy is 0:01:33.840 --> 0:01:37.480 a measure of the disorder in a closed system. According 0:01:37.480 --> 0:01:40.760 to the second law of thermodynamics, entropy in a system 0:01:40.880 --> 0:01:44.680 almost always increases over time. You can do work to 0:01:44.800 --> 0:01:47.560 create order in a system, but even the work that's 0:01:47.560 --> 0:01:52.720 put into reordering increases disorder as a byproduct, usually in 0:01:52.760 --> 0:01:56.400 the form of heat. Because the measure of entropy is 0:01:56.440 --> 0:02:00.240 based on probabilities, it is of course possible for the 0:02:00.360 --> 0:02:03.640 entropy to decrease in the system on occasion, but it's 0:02:03.640 --> 0:02:08.239 statistically very unlikely. It's harder than you think to find 0:02:08.280 --> 0:02:10.919 a system that doesn't let any energy in or out. 0:02:11.520 --> 0:02:13.680 Our universe is as good of an example as we have, 0:02:14.440 --> 0:02:17.040 but after accounting for the fact that it's usually not 0:02:17.080 --> 0:02:20.919 going to be mathematically perfect, entropy does help describe how 0:02:20.960 --> 0:02:23.920 disorder happens in a system as large as the galaxy 0:02:24.120 --> 0:02:28.640 or small as a thermos full of coffee. However, entropy 0:02:28.760 --> 0:02:30.760 doesn't have to do with the type of disorder you 0:02:30.800 --> 0:02:33.320 think of when you lock a bunch of chimpanzees in 0:02:33.360 --> 0:02:36.000 a kitchen, it has more to do with how many 0:02:36.120 --> 0:02:39.560 possible permutations of mess can be made in that kitchen, 0:02:40.080 --> 0:02:43.680 rather than how big of a mess is possible. Of course, 0:02:43.720 --> 0:02:46.959 the entropy depends on a lot of factors, how many 0:02:47.040 --> 0:02:49.880 chimpanzees there are, how much stuff is being stored in 0:02:49.919 --> 0:02:53.399 the kitchen, and how big the kitchen is. So if 0:02:53.400 --> 0:02:56.600 you were to look at two kitchens, one very large 0:02:56.639 --> 0:02:59.880 and stocked to the gills but meticulously clean and organized, 0:03:00.240 --> 0:03:03.200 and another that's smaller, with less stuff in it but 0:03:03.360 --> 0:03:07.239 pretty baseline messy, it's tempting to say that the messier 0:03:07.320 --> 0:03:11.000 room has more entropy, but that's not necessarily the case. 0:03:11.880 --> 0:03:15.080 Entropy concerns itself more with how many different states are 0:03:15.120 --> 0:03:18.560 possible than how disordered it is at the moment. A 0:03:18.600 --> 0:03:22.480 system therefore, has more entropy if there are more molecules 0:03:22.480 --> 0:03:25.760 and atoms in it, and if it's larger, and if 0:03:25.760 --> 0:03:31.040 there are more chimpanzees. Entropy might be the truest scientific 0:03:31.080 --> 0:03:35.240 concept that the fewest people actually understand. Honestly, me sort 0:03:35.280 --> 0:03:38.920 of included. The concept of entropy can be very confusing, 0:03:39.240 --> 0:03:43.880 partly because there are actually different types. The Hungarian mathematician 0:03:44.000 --> 0:03:47.960 John von Neumann lamented the situation by saying, whoever uses 0:03:47.960 --> 0:03:50.960 the term entropy in a discussion always wins, since no 0:03:51.000 --> 0:03:53.800 one knows what entropy really is, so in a debate, 0:03:54.040 --> 0:03:58.120 one always has the advantage. We spoke via email with 0:03:58.160 --> 0:04:02.320 one Marko Popovich, a post auctoral researcher in bio thermodynamics 0:04:02.320 --> 0:04:04.920 in the School of Life Sciences at the Technical University 0:04:04.960 --> 0:04:09.080 of Munich. He said, it's a little hard to define entropy. 0:04:09.120 --> 0:04:13.280 Perhaps it's best defined as a non negative thermodynamic property 0:04:13.480 --> 0:04:16.120 which represents a part of energy of a system that 0:04:16.200 --> 0:04:20.800 cannot be converted into useful work. Thus, any addition of 0:04:20.880 --> 0:04:23.320 energy to a system implies that a part of the 0:04:23.400 --> 0:04:27.440 energy will be transformed into entropy, increasing the disorder in 0:04:27.440 --> 0:04:31.839 the system. Thus, entropy is a measure of disorder of 0:04:31.880 --> 0:04:36.720 a system. But don't feel bad if you're still confused. 0:04:37.080 --> 0:04:40.400 The definition can vary depending on which discipline is wielding 0:04:40.440 --> 0:04:44.159 it at the moment. For example, in the mid nineteenth century, 0:04:44.240 --> 0:04:47.640 a German physicist named Rudolph Classius, one of the founders 0:04:47.640 --> 0:04:50.719 of the concept of thermodynamics, was working on a problem 0:04:50.800 --> 0:04:55.000 concerning efficiency in steam engines, and he invented the concept 0:04:55.000 --> 0:04:58.599 of entropy to help measure useless energy that cannot be 0:04:58.680 --> 0:05:03.279 converted into eve full work. A couple decades later, Ludwig 0:05:03.360 --> 0:05:07.520 Boltzman entropies other founder used the concept to explain the 0:05:07.520 --> 0:05:11.599 behavior of immense numbers of atoms, like even though it's 0:05:11.600 --> 0:05:15.000 impossible to describe the behavior of every single particle in 0:05:15.000 --> 0:05:18.040 a glass of water, it's still possible to predict their 0:05:18.080 --> 0:05:22.960 collective behavior when they're heated using a formula for entropy, 0:05:23.480 --> 0:05:27.640 Popovich said. In the nineteen sixties, the American physicist T. S. 0:05:27.760 --> 0:05:32.280 Jayne's interpreted entropy is information that we miss to specify 0:05:32.320 --> 0:05:35.960 the motion of all particles in a system. For example, 0:05:36.360 --> 0:05:39.800 one mole of gas consists of six times ten to 0:05:39.880 --> 0:05:43.400 the power of twenty three particles. Thus, for us, it 0:05:43.480 --> 0:05:47.000 is impossible to describe the motion of each particle, so 0:05:47.080 --> 0:05:50.159 instead we do the next best thing by defining the 0:05:50.200 --> 0:05:52.760 gas not through the motion of each particle, but through 0:05:52.760 --> 0:05:58.120 the properties of all the particles combined temperature, pressure, total energy. 0:05:58.320 --> 0:06:01.479 The information that we lose when we do this is 0:06:01.520 --> 0:06:07.280 referred to as entropy, and the terrifying and or fascinating 0:06:07.320 --> 0:06:09.840 concept of the heat death of the universe wouldn't be 0:06:09.880 --> 0:06:14.120 possible without entropy, because our universe most likely started out 0:06:14.200 --> 0:06:17.520 as a singularity, as an infinitely small ordered point of 0:06:17.600 --> 0:06:20.960 energy that ballooned out and continues expanding all the time. 0:06:21.520 --> 0:06:25.000 Entropy is constantly growing in our universe because there's more 0:06:25.080 --> 0:06:28.599 space and therefore more potential states of disorder for the 0:06:28.640 --> 0:06:33.880 atoms here to adopt. The scientists have hypothesized that long 0:06:33.920 --> 0:06:36.880 after you and I are gone, the universe will eventually 0:06:36.880 --> 0:06:40.640 reach some point of maximum disorder, at which point everything 0:06:40.680 --> 0:06:43.680 will be the same temperature, with no pockets of order 0:06:43.880 --> 0:06:48.760 like stars and chimpanzees to be found. And if that happens, 0:06:48.839 --> 0:06:56.080 we'll have entropy to thank for it. Today's episode was 0:06:56.080 --> 0:06:58.760 written by Josceline Shields and produced by Tyler Klang. For 0:06:58.800 --> 0:07:00.560 more on this lots of other top x visit how 0:07:00.600 --> 0:07:03.120 stuff works dot com. Brain Stuff is a production of 0:07:03.160 --> 0:07:05.480 I Heart Radio. For more podcasts from my heart Radio, 0:07:05.600 --> 0:07:08.159 visit the I heart Radio app, Apple Podcasts, or wherever 0:07:08.240 --> 0:07:09.520 you listen to your favorite shows.