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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]

#121

Post by ineptech »

Timon3 wrote: post #97
floatrock wrote: post #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 t…

> 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”. Right? I think this could be a really interesting basis for a sci-fi novel - the first space-faring civilization in the entire universe trying to force every form of life to keep "entropy usage" to a minimum, so…

Not exactly what you're describing, but this is along those lines: https://slatestarcodex.com/2015/06/02/and-i-show-you-how-dee... It's pretty silly but the ending is both satisfying and relevant.

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

#122

Post by hunter-gatherer »

Timon3 wrote: post #97
floatrock wrote: post #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 t…

> 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”. Right? I think this could be a really interesting basis for a sci-fi novel - the first space-faring civilization in the entire universe trying to force every form of life to keep "entropy usage" to a minimum, so…

Isaac Asmiov's short story "The Last Question" isn't super inline with your suggestion but is a short discourse on humanity's struggle against entropy.

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

#124

Post by spuz »

Timon3 wrote: post #99
spuz wrote: 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?

I might be completely off kilter here (please tell me if that's the case!), but what makes sense to me is to think about "how much entropy is left", as in "how much can entropy still increase between the current state and the highest entropy state". That flips the meaning to describe what you're talking about, and feels very intuitive to me.

When you say "how much entropy is left?" you make it sound like a quantity that is decreasing, not increasing. That seems incorrect, no?

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

#125

Post by tgv »

floatrock wrote: post #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 t…

Isn't there a theorem that says that the overall rate is constant in a closed system? If you look at the universe as a whole, it would be closed, and we wouldn't have any impact. However, I learnt about entropy decades ago, and never applied it, so don't take my word for it.

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

#127

Post by AlexandrB »

hilbert42 wrote: post #8
4ad wrote: post #2

I hate Veritasium's clickbait, and I think most of his videos are very poor, but this one is the exception. It's very well put together. The first ten minutes of the video is exactly how I introduce entropy to people. Of course I can't give him a pass on how crass it was telling that women he has a PhD in physics (he does not). The video would have been so much better without that two seconds of footage...

"I think most of his videos are very poor," Why do you think so? (Most to me seem reasonable but one on speed of electricity stands out as badly done (he redid the video but it too could have been better).)

I was quite disappointed by his video on self-driving cars. It presented a very one-sided view and felt like a puff piece (and, indeed, it was sponsored by Waymo). Tom Nicholas did a good job breaking down the problems with it: https://m.youtube.com/watch?v=CM0aohBfUTc&pp=ygUPdG9tIHZlcml...

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

#128

Post by Timon3 »

spuz wrote: post #124
Timon3 wrote: post #99

Earlier quoted context omitted.

I might be completely off kilter here (please tell me if that's the case!), but what makes sense to me is to think about "how much entropy is left", as in "how much can entropy still increase between the current state and the highest entropy state". That flips the meaning to describe what you're talking about, and feels very intuitive to me.

When you say "how much entropy is left?" you make it sound like a quantity that is decreasing, not increasing. That seems incorrect, no?

That's why I specified that it's meant as "how much can entropy still increase between the current state and the highest entropy state". If you can't read it in that sense, either ignore the shorter question or read it as "how much increase of entropy left". Or maybe "how much entropy left until max".

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

#129

Post by franky47 »

floatrock wrote: post #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 t…

> a space full of life tends toward more entropy faster than the same amount of space without life.

And a space full of children is exponentially faster at increasing entropy.

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

#130

Post by ithkuil »

Lichtso wrote: post #119
ithkuil wrote: post #107

Earlier quoted context omitted.

If you need to do work in order to revert to the previous state, does it imply you can extract work when going to the first to the second state? Given the scenario you just laid out it seems no work can be extracted just by letting mix two substances that are at the same temperature and pressure. But there is something about it that doesn't quite add up to my intuition of symmetry and conservation laws. Could you ple…

I think you can very well extract work from having a membrane and selectively let one substance mix into the other but not the other in the first [0]. It is called Osmosis [1]. [0]: https://en.wikipedia.org/wiki/Semipermeable_membrane [1]: https://en.wikipedia.org/wiki/Osmosis

I guess what's confusing me in this scenario is that we're not saying that the two halves of the cylinder contain particles with different properties (e.g. different velocities) but only that we can "tell them apart" as if they were coloured differently, but otherwise behaving in exactly the same way.

The former scenario is famously the setting for Maxwell's daemon. I was assuming this scenario is something else.

I'm confused because on one hand I can see that it requires work to reorder the particles once they have been shuffled around. On the other hand I don't see how one could extract work while they get shuffled around if they all have the same momenta.

Perhaps the answer is that we cannot have a system where the microscopic entities are at the same indistinguishable but also distinguishable. Perhaps if they had different "colours' it means they do interact differently with the environment? I'm still confused frankly

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