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Entropy: A little understood concept in physics [video]

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Re: Entropy: A little understood concept in physics [video]

#51
post #18

Earlier quoted context omitted.

> how can there ever be a shortage of energy I think it's not so much a shortage of energy, but that there thermodynamic equilibrium and thus no available energy to do anything. I don't think this will ever happen tho, it's pretty clear to me that making energy more dense is a universal process.

Not really - look up “heat death” of the universe.

The "heat death" of the universe is a concept that deserves to die. The second principle of thermodynamics is true only if you ignore gravity. In the presence of gravity, systems tend to go towards lower entropy, just see how a planetary system can form out of a gas cloud.

Re: Entropy: A little understood concept in physics [video]

#52
post #39
post #27

I think the concept would be easier for me to understand if we talked about the inverse of entropy - i.e. some kind of measurement for the concentration of useful energy or "order". I think it would then be more intuitive to say that this measurement always decreases. Do we even have a word for the opposite of entropy?

> Do we even have a word for the opposite of entropy? I've always referred to the inverse as "information" or "order".

"information" is not a good term for the opposite. Entropy is a well defined concept in information theory (and can be connected to the physical concept). More entropy means more information, not less.

Re: Entropy: A little understood concept in physics [video]

#53

That's an excellent overall summary as he covers almost every aspect of the subject albeit in brief. It would be good if he produced a second video dealing with the low entropy of incoming energy from the sun and the higher entropy of radiated energy from earth and relate that to global warming. In all the debate over global warming little is talked about why say CO2 and other greenhouse gasses increase the earth's t…

My understanding:

Global warming occurs because the previous equilibrium between incoming and outgoing energy has been broken by changes in the composition of the atmosphere.

So until we reach a new equilibrium long after the atmosphere composition ceases to change, the outgoing energy will be less than the incoming energy.

Re: Entropy: A little understood concept in physics [video]

#54

Entropy only made sense when I learned it from the perspective of statistical thermodynamics. It's a very programmerly understanding, IMHO, and it's quite intuitive. EXCEPT that the language used is ridiculous: grand canonical ensemble indeed! Anyway, the idea that a system can be in some number of specific states, and that equilibrium is that unique situation where the number of possible specific states is at its ma…

I took a stat thermo class and it was basically all about entropy, which was expresed as ln W- the log of the number of ways (permutations) that a system can be ordered, which gives a convenient denominator when calculating the probability of a specific permutation. Here's the professor's book, which was still only in latex form when we took the class: https://www.amazon.com/Molecular-Driving-Forces-Statistical-...

Re: Entropy: A little understood concept in physics [video]

#55
post #39

Earlier quoted context omitted.

> Do we even have a word for the opposite of entropy? I've always referred to the inverse as "information" or "order".

"information" is not a good term for the opposite. Entropy is a well defined concept in information theory (and can be connected to the physical concept). More entropy means more information, not less.

> Entropy is a well defined concept in information theory (and can be connected to the physical concept). More entropy means more information, not less.

More entropy means more missing information.

https://iopscience.iop.org/book/mono/978-0-7503-3931-5/chapt...

Re: Entropy: A little understood concept in physics [video]

#56

Last night me and my wife were deciding if we should watch The Witcher or this video. I decided I didn't have the brainpower/mental capacity to think about The Witcher and that this video on Entropy would be easier to digest.

Not sure if you are humble bragging, but I agree The Witcher is more demanding. Layers of meaning, emotions, allegory, subtext. It’s no Shakespeare, but physics and math are simple in comparison especially in the wonderfully produced and easily digestible format of Veritasium.

Re: Entropy: A little understood concept in physics [video]

#57
post #11

A pithier way to introduce this topic: the first law of thermodynamics, a.k.a. the law of conservation of energy, is that energy cannot be created nor destroyed, only transformed from one form to another. In light of this, how can there ever be a shortage of energy? [Note that this is intended to be a rhetorical question advanced for the purposes of pedagogy. If you find yourself wanting to post an answer, you have m…

Why is this pithier than the video? I’m not entirely sure I see added pedagogical value. Asking the rhetorical question how can there be a shortage of energy sounds a little like someone sort-of intentionally misunderstanding what that phrase “energy shortage” means in any practical economic context. “Energy shortage” is an economics phrase, not a physics phrase. The first law of thermodynamics doesn’t suggest there can’t be energy shortages on earth, because the phrase “energy shortage” is not used to suggest a loss of energy to the universe, energy shortages are all about not having enough specific forms of energy in specific places at specific times [1], and it’s no surprise that we can’t capture dissipated heat, or that a local power system has a maximum limit at any given time, for example.

Something similar could perhaps be said for the video’s approach; “what do we get from the sun?” is an ambiguous question, not necessarily a fair setup to ask a lay person when you have entropy in mind as the answer. We do get energy from the sun, that is a correct answer, and we use some of it before it goes away. But, there is the nice a-ha that all the energy from the sun eventually leaves the earth, right?

[1] “An energy crisis or energy shortage is any significant bottleneck in the supply of energy resources to an economy.“ https://en.wikipedia.org/wiki/Energy_crisis

Re: Entropy: A little understood concept in physics [video]

#58
The part that was new to me was the bit about how a space full of life tends toward more entropy faster than the same amount of space without life.

Like the best ideas, it’s simple and makes sense if you think about it, but it’s still a really interesting framing that the complex machinery of life is really just the most efficient “entropy converter”.

If there’s something about the arrow of time that speeds towards the heat death of the universe, we’re just helping it go a tiny bit faster here on our floating speck of dust.

Re: Entropy: A little understood concept in physics [video]

#59
post #27

I think the concept would be easier for me to understand if we talked about the inverse of entropy - i.e. some kind of measurement for the concentration of useful energy or "order". I think it would then be more intuitive to say that this measurement always decreases. Do we even have a word for the opposite of entropy?

Exergy

Re: Entropy: A little understood concept in physics [video]

#60

Entropy only made sense when I learned it from the perspective of statistical thermodynamics. It's a very programmerly understanding, IMHO, and it's quite intuitive. EXCEPT that the language used is ridiculous: grand canonical ensemble indeed! Anyway, the idea that a system can be in some number of specific states, and that equilibrium is that unique situation where the number of possible specific states is at its ma…

Entropy is mathematical force to be honest.

Huh? "Force"?
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