Wayne Myrvold: Entropy Isn't Real; It's What You Don't Know
episodePreviously titled “Wayne Myrvold: A 2 Hour Deep Dive Into Entropy” — renamed by the publisher on Aug 3, 2026
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Is entropy a property of the system or of our knowledge?
Even though a lot of physicists will say second law says the total entropy is never decreasing, that can't be actually be the second law. That can't be a consequence of the second law. This
is a two-hour deep dive into entropy and the second law. Most talks on this subject are 10 minutes long, but today Professor Wayne Mirvold gives a tour de force, explaining entropy from multiple angles, dispelling myths, and even the stunning realization that the second law is
opposite to what you think. You will get both answers from perfectly competent physicists and on each side. We'll be absolutely certain that that is the right answer. Questions explored.
Why is thermodynamics better understood as a resource theory?
Are why is entropy not the same as disorder? What do popular accounts and even undergraduate texts on entropy and thermodynamics consistently get incorrect? Is the universe subject to the second law? Can you break these supposed entropic limits and why quantum mechanics changes everything? There's plenty of confusion and puzzles about entropy. Today I would like to talk about exactly what is entropy. And one of the questions that give conflicting answers is imagine in front of you you have some physical system. I believe this comes from Shelley Goldstein. Like let's just say you give this example, like a glass of water, for instance, and its physical state is clearly not completely known to you, but then something else appears to you.
You can be an intelligent person, an angel or what have you. It gives you a much better approximation of this glass of water than what you had before.
How does the second law rely on entropy, and not the other way around?
Then the question is, has the systems the glass of water has its entropy decreased?
Mm-hmm.
So there are broadly speaking two answers one can give. One is yes, obviously, because entropy has to do with the information of the system. So if you've gained information, the entropy has changed. Then the other is that's absurd. The entropy has something objective to do with the system. So why would your information about the system change its entropy? Take it away.
Yeah, absolutely. And you will get both answers from perfectly competent physicists and they will be absolutely certain that that is the right answer. Um so I mean I think the the best way to start even thinking about that is you raise a qu you you pose the question as what is entropy? And I think that's a bit of a misleading question because entropy is one of those words is used in different senses.
What was the historical shift from caloric fluid to molecular motion?
And um I mean we're used to that. We're not it's not unusual. Like if you open up a dictionary and like at a random page and point at any word at random, there'll probably be like two or three or maybe four definit different definitions. Very often in f in science, people will give a uh c coin a new technical term because they want uh something to have a precise, well agreed upon meaning. And that's actually what Clausius did back in um eighteen sixty five, I think it was. Um he he thought, okay, here's this important quantity that I and others have been batting around in thermodynamics. It's important
How does Maxwell’s demon challenge the absolute truth of the second law?
important enough it needs a night a a n a dignified name. And he's you know, his rationale was, Well, everybody sp studies the dead languages, right? We all know Greek and Latin. And so we don't want something like from English or German or Italian because then it becomes sort of nationalistic word. So let's coin something from the a Greek word. So he coined the word entropy from a Greek word for transformation. And he deliberately coined it to sound kind of like energy because it's closely related con um concept. If I had my way. We would respect Clausius and we would only use the word entropy in exactly the same sense that Clausius defined it.
Can information defeat entropy? – Landauer erasure and Maxwell’s demon
Okay, and that what's that would be what everyone means by entropy. But historically that's not what happened. There's been a number of different quantities that people call entropy, and they're all related, and they're all related in some sense to thermodynamic entropy, but they're just different things. If someone asks you the question, has entropy decreased, I think an actual question is, well, which entropy?
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Chapters
8 chapters
1
Is entropy a property of the system or of our knowledge?
0:00–0:42
2
Why is thermodynamics better understood as a resource theory?
0:42–1:35
3
How does the second law rely on entropy, and not the other way around?
1:35–2:34
4
What was the historical shift from caloric fluid to molecular motion?
2:34–3:15
5
How does Maxwell’s demon challenge the absolute truth of the second law?
3:15–4:00
6
Can information defeat entropy? – Landauer erasure and Maxwell’s demon
4:00–4:59
7
What’s the difference between Boltzmann and Gibbs entropy?
4:59–6:56
8
Is the heat‑death of the universe inevitable, and what does it mean for resources?
6:56–1:59:34
Speakers
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