What is entropy?

Hi everyone,

Jonathon Riddell here. Today we outline what entropy tells us about the world we live in and how to interpret it.

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Jayne's paper:

Recommended textbooks:
Quantum mechanics:
Statistical mechanics:
Quantum information:

[SynysterKezia]

Great video! I also like to think of entropy as a quantified form of ignorance. It's the mathematical price we pay for not keeping track of all particles at all times (i.e. not knowing exactly which micro state we're in).

Also, I think there's a 60 symbols video that points out it's possible to contrive systems wherein a more ordered state has more entropy than a less ordered state. So the usual "entropy is a measure of disorder" way of thinking can lead you astray sometimes.

[Galileosays]

Thanks for this video. In the shown example of spins the microstates are numerable and therefore the probabilities for these states easy to compute. It becomes hard in the description of an ideal gas.  The positions and velocities of all molecules are infinite, so there is an infinite number of however

[alejandra]

Is there a limit on the particle number (or number of microstates) that can be studied by researchers? I was wondering if there is a computational and/or theoretical maximum for particle numbers that we can use the statistical inference approach for calculating entropy. Is this why the temperature argument comes up so often when discussing entropy?

[xjuhox]

Quantum mechanics, as a fundamentally statistical theory, seems to follow from the maximum entropy principle. But "who" is doing the inference and where is that information stored? If we do a double-slit experiment and add more and more interacting gas molecules into the vacuum, then the inference pattern slowly disappears. Thus, it seems to me that the information is objective and somehow universal; every entity is doing its part in processing and storing of information.

[parthasarker]

Please raise the sound volume of the video