Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Entropy: A little understood concept in physics [video]

youtube.com

Post reply on HN
Print view View original

171–178 of 178 posts

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

#171

Post by [deleted] »

kergonath wrote: post #155
dekken_ wrote: post #149

Earlier quoted context omitted.

You can say what you like. Science is not about certainties. You can only control experiments to a particular degree and have no control of confounding factors which might interfere with your experiments. Do you really want to compare the totality of all universal processes to such trivial examples? I find it absurd.

You did not qualify the complexity below which it is acceptable to be certain of something so this is unlikely to be productive. You said that certainty was impossible and I gave you examples of certain things. Besides, both a ball and a glass of water are insanely complex systems. I am not sure we have the same definition of science, to be honest.

[deleted]

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

#172

Post by guga42k »

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

Indeed you can extract work from this system. But because of energy conservation it will result to temperature drop. In case if you want to revert the system to its original state you will have to reheat it (return previously extracted work back) AND also spend some work to reorder particles (reduce entropy).

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

#173

Post by spiralx »

Lichtso wrote: post #115

I think the most unintuitive even unsettling aspect of entropy is that the entropy of black holes is proportional to their surface area, not their volume [0]. That is only briefly mentioned in the video and not discussed any further. [0] https://en.wikipedia.org/wiki/Holographic_principle#Black_ho...

The surface of a black hole is also the most efficient information storage possible - each 2x2 Planck lengths area can store a single bit. Of course there's no way to read that data...

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

#174

Post by hilbert42 »

pxeger1 wrote: post #21
hilbert42 wrote: post #8

Earlier quoted context omitted.

"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).)

He seems to exaggerate the importance of things when they make for a good story and sound interesting. This is a classic flaw in popular science but I think he's got a lot more egregious with it over the years. The worst example I remember, which is actually what drove me to unsubscribe, was when he said that the golden ratio was "a pretty five-y number" because it can be written as 0.5 + 0.5 * (5^0.5). Anyone with a…

"The whole context and presentation seemed like it was designed to make the viewer feel like they'd learnt something even though nothing of substance was really delivered in those 20 seconds. He does that a lot."

I can't disagree with that. He's not only a YouTube presenter but also a documentary maker, His documentary Uranium: Twisting the Dragon's Tail https://www.imdb.com/title/tt4847012/ has been repeated on TV where I am, I think, at least three times. He's also made others.

Unfortunately, that type of presentation is all too common in modern docos (probably couldn't get it past the director otherwise). As you'd know, this and similar techniques (which I find highly irritating) are also used to pad out half-hour shows to an hour and or to multi episodes when one would do adequately (thankfully, my PVR comes to the rescue and I rarely watch them in real time).

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

#175

Post by kergonath »

hilbert42 wrote: post #164
kergonath wrote: post #142

Earlier quoted context omitted.

That’s exactly it. Except that equilibrium will never be reached, it’s more like tending towards a steady state.

Right, better stated than me. It would help if we could convey this across to the lay public. No doubt, the minutiae is complex and involved and the details will be argued over for years but at the high level it's pretty straightforward. Seems to me many balk at climate science because the figures seem to magically appear from nowhere—they just pop out of climate scientists' mouths without explanation. A simple under…

The basic principles are simple: stuff goes in from the Sun and the inside of the Earth; stuff goes out through the atmosphere. Greenhouse gases trap stuff in the atmosphere, which results in the accumulation of stuff in the oceans and atmosphere. No need to delve into entropy and free energy here: the concept of heat is enough*.

The details are insanely complex and I would not claim to understand the beginning of it, though.

* the concept of heat is of course horrendous from a scientific point of view and we do use things like enthalpy and entropy in modern thermodynamics. But there’s a reason why heat is used in vulgarisation and introductions. It is intuitive and useful if you don’t dig too far, so perfect to explain things to laymen and 5 years olds.

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

#176

Post by dangitnotagain »

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?

Emergence.

If entropy is the distribution of potential over negative potential, emergence is that where an outcome creates potential (of some discrete domain).

The mystifying relationship with thermodynamic entropy is that through accelerating entropy in other domains (burning), the entropy in the primary domain (eternal drag) is supplanted by the potentials provided by the external domain.

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

#178

Post by topologie »

dist-epoch wrote: post #45

Sabine Hossenfelder also had a video recently on entropy: > I don't believe the 2nd law of thermodynamics. https://www.youtube.com/watch?v=89Mq6gmPo0s

Beat me to it...

I posted it without realizing somebody else had already posted it.

Gotta love Prof. Hossenfelder.

Post reply on HN