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Scientists report asymmetry between heating and cooling

phys.org

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Re: Scientists report asymmetry between heating and cooling

#71

Post by mjevans »

Roark66 wrote: post #53
bmitc wrote: post #3

I always feel a little stupid or strange reading a lot of these science headlines and introductions. I wasn't aware that people considered there to be a symmetry between heating and cooling. I thought that the entire point of thermodynamics is that they are asymmetric. Even the article mentions that it's been known that heating is more efficient than cooling.

Exactly, I always thought heating raises the entropy of a system and cooling puts it back in the "more orderly" state. So of course it can't be symmetric. Just like breaking a wine glass, reversing that process takes a lot more effort. Of course I have no idea if the above makes any sense, it's just an "intuitive understanding" I somehow got.

My source of the same intuitive understanding; electric bills.

Power to heat, waste is more heat (just not where desired?).

Power to cool is used to move the state of one side of the system to another, ideally open, side.

Though this does raise the question of if it's possible to cancel energy out. I think that's likely stopped by Heisenberg's uncertainty of measurements (and exactly matching them even when measured).

Re: Scientists report asymmetry between heating and cooling

#72

Post by NoZebra120vClip »

leoqa wrote: post #32
foobarbecue wrote: post #26

Earlier quoted context omitted.

... lots of things are impossible?

name an impossible thing and a grant writer will propose a solution

Could God write a grant proposal so ambitious that He couldn't fund it?

Re: Scientists report asymmetry between heating and cooling

#73

Post by cmrx64 »

pitherpather wrote: post #14
bmitc wrote: post #3

I always feel a little stupid or strange reading a lot of these science headlines and introductions. I wasn't aware that people considered there to be a symmetry between heating and cooling. I thought that the entire point of thermodynamics is that they are asymmetric. Even the article mentions that it's been known that heating is more efficient than cooling.

> I wasn't aware that people considered there to be a symmetry between heating and cooling Same here. By analogy, while any chemical reaction is in principle reversible, the kinetics "forward" and "backward" are unlikely to be equally favorable. Likewise, with atomic nuclei, fission and fusion tend to be favored under distinctly different conditions. The article does mention "far from equilibrium." Could this be a ca…

No. This research is all about far from equilibrium systems, which also happens to be the realm of life. There IS symmetry near equilibrium, and I think a high school level of thermodynamics would expect it to be symmetric. In comparison with the high school chemistry which already considers enough phenomena to get meaningful asymmetry easily. I’m surprised at the level of surprise here, it seems motivated by some kind of certainty that I can’t tell the origin of.

Re: Scientists report asymmetry between heating and cooling

#74

Post by cmrx64 »

angiosperm wrote: post #39

We knew about this: some kinds of heating can affect all the molecules, but cooling generally only those colliding with the walls.

This explanation is unrelated to anything considered. It trivializes what the paper actually studies, we certainly had no such theorem before this work.

Re: Scientists report asymmetry between heating and cooling

#75

Post by cmrx64 »

rpmisms wrote: post #12
EGreg wrote: post #6

Does this have anything to do with volatility drag in trading? https://en.wikipedia.org/wiki/Volatility_tax

Considering that Brownian motion applies (chaotic movement, generally in liquids, caused by heat), yes, the market mirrors the laws of physics here.

The theorems of thermal kinematics derived apply to limited models with a quadratic energy potential, localized on a spatial manifold. is there any reason to believe the market is described by this sort of model?

Re: Scientists report asymmetry between heating and cooling

#76

Post by VMG »

geraldhh wrote: post #70
Ma8ee wrote: post #68

Earlier quoted context omitted.

No. Put a cold thing into something hotter and the thing will heat up without cooling.

the hot thing will get cooler. like to make something clean, you have to make something else dirty.

Is that true though? If I have say a box with mixed red and blue bricks and I sort them by color, both sides are "clean" now.

Re: Scientists report asymmetry between heating and cooling

#77

Post by Etheryte »

VMG wrote: post #76
geraldhh wrote: post #70

Earlier quoted context omitted.

the hot thing will get cooler. like to make something clean, you have to make something else dirty.

Is that true though? If I have say a box with mixed red and blue bricks and I sort them by color, both sides are "clean" now.

Sorting something is not the same as cleaning it, just like sorting an array doesn't sanitize its contents.

Re: Scientists report asymmetry between heating and cooling

#78

Post by HPsquared »

schiffern wrote: post #5

>And have questions like: 'Why don't we have a device like a microwave oven for fast cooling?'" Isn't that... just a blast chiller? (AKA a convection oven in reverse) It's not commonly found in households, but that's different from saying "we don't have a device" that does this. EDIT: Yes folks, I do understand how the principles of operation differ. Point being that the humble countertop convection oven definitely q…

For "cooling by radiation" there's, counterintuitively, laser cooling:

https://en.wikipedia.org/wiki/Laser_cooling

"Laser cooling relies on the change in momentum when an object, such as an atom, absorbs and re-emits a photon (a particle of light). For an ensemble of particles, their thermodynamic temperature is proportional to the variance in their velocity. That is, more homogeneous velocities among particles corresponds to a lower temperature. Laser cooling techniques combine atomic spectroscopy with the aforementioned mechanical effect of light to compress the velocity distribution of an ensemble of particles, thereby cooling the particles."

Re: Scientists report asymmetry between heating and cooling

#79

Post by ben_w »

VMG wrote: post #76
geraldhh wrote: post #70

Earlier quoted context omitted.

the hot thing will get cooler. like to make something clean, you have to make something else dirty.

Is that true though? If I have say a box with mixed red and blue bricks and I sort them by color, both sides are "clean" now.

In a sense that misses the metaphor, sure.

But the thing which is "dirtier" is the wider universe, where the energy you used to do that sorting has higher entropy.

At the scale of atoms and molecules in a gas, you can also sort them into high-energy particles on one side of a barrier and low-energy particles on the other side, and now there's a heat difference you can run a heat engine. This is totally a thing you can do with the right devices — but those devices will necessarily consume more energy than you get from a heat engine running on that heat difference.

https://en.wikipedia.org/wiki/Maxwell%27s_demon

Re: Scientists report asymmetry between heating and cooling

#80

Post by jackhalford »

VMG wrote: post #76
geraldhh wrote: post #70

Earlier quoted context omitted.

the hot thing will get cooler. like to make something clean, you have to make something else dirty.

Is that true though? If I have say a box with mixed red and blue bricks and I sort them by color, both sides are "clean" now.

That’s because the box isn’t a closed system, you’ve interacted with in and you have spent energy sorting the bricks. It’s the same story with humans on earth, things get sorted because of the energy inout from the Sun.
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