Scientists report asymmetry between heating and cooling • Hacker News Board

Re: Scientists report asymmetry between heating and cooling

#131

Post by akira2501 » Wed, Jan 24, 2024, 5:52 AM UTC

m463 wrote: post #128

akira2501 wrote: post #49

Earlier quoted context omitted.

A lot of our experiences are with symmetrical physical phenomenon. So, we're modeled that way. Time does not "move." Yet we need to conceptualize it. So our language here gets sloppy. You can recognize this by using the modified "if time can move forward, it should be able to be stopped." The obvious incongruity of this defies the idea that we're attempting to impose ourselves. In terms of Entropy, the universe does…

I guess it depends on the second law of thermodynamics if you believe it. I thought the universe wants to be maximum entropy, which is disordered and not ordered. I'm not saying that that the universe doesn't want to cool off, just that it seems ok to think it would be faster to warm up than cool off.

> which is disordered and not ordered.

Which would like a bunch of randomized almost undetectable energy near absolute zero. So, I'm out on a limb past my comfort zone here, but my working model is:

Higher temperatures mean higher velocities mean the particles are less likely to interact with other particles and so their amount of entropy decreases, they become more predictable, have fewer possible future states, than they had before.

The second law just implies that work energy will always escape the system as heat because heat always moves from space with higher temperatures to space with lower temperatures. In a sense the universe is trying to move the hot things away from each other because it wants to be cold.

Re: Scientists report asymmetry between heating and cooling

#132

Post by darkerside » Wed, Jan 24, 2024, 10:04 AM UTC

Ma8ee wrote: post #126

nyrikki wrote: post #122

Earlier quoted context omitted.

You are using a didactic oversimplification as an absolute truth while it is more nuanced. An individual molecule in an open system can freely exchange energy with its surroundings and can/does have a temperature.

You can call the limitations of your knowledge about the exact state of a molecule a temperature, but that doesn't mean that any single molecule has an actual physical temperature in the same way as a collection of particles. You can say that a passing car had a speed between 60 mph and 70 mph because you couldn't measure it more exact, but the car has at any given moment an exact speed independent of your knowledge…

You may be right about the molecule, but the car absolutely has a distribution of speeds depending on what you are measuring in relation to.

Re: Scientists report asymmetry between heating and cooling

#133

Post by darkerside » Wed, Jan 24, 2024, 10:09 AM UTC

Ma8ee wrote: post #110

darkerside wrote: post #83

Earlier quoted context omitted.

At the boundary between water and air, molecules are constantly snapping back and forth between being liquid and vapor. It's just that an equilibrium has been reached that makes the system appear static.

A molecule isn’t liquid or vapour. A molecule doesn’t have a temperature.

Molecules don't have innate solid or liquid properties, but they do operate as a solid or liquid, correct? It has nothing to do with them having a temperature of their own, and everything to do with how they are currently acting with their peers. IIUC.

Re: Scientists report asymmetry between heating and cooling

#134

Post by jacquesm » Wed, Jan 24, 2024, 11:58 PM UTC

darkerside wrote: post #132

Ma8ee wrote: post #126

Earlier quoted context omitted.

You can call the limitations of your knowledge about the exact state of a molecule a temperature, but that doesn't mean that any single molecule has an actual physical temperature in the same way as a collection of particles. You can say that a passing car had a speed between 60 mph and 70 mph because you couldn't measure it more exact, but the car has at any given moment an exact speed independent of your knowledge…

You may be right about the molecule, but the car absolutely has a distribution of speeds depending on what you are measuring in relation to.

That is exactly GPS point: a car doesn't have a distribution of speeds unless you measure it relative to something else whereas a liquid or a solid does have a temperature, regardless of anything else. Depending on what the something else is that you measure your car's speed by you may decide it goes forward, backward or is motionless.

When you start talking about individual molecules, atoms or particles the whole concept of temperature becomes very counterintuitive. Think of it as a substitute for motion or vibration if you wish and even that is grossly inaccurate (but less so...).

Maybe this will help: a gas in a container has a pressure and a density as well as a temperature, all of which are properties of the gas and not of the individual gas molecules. A single molecule that the gas is made up from does not have a density, it doesn't have a temperature and it doesn't have a pressure. What it may have though is a speed relative to something else, and when it hits the something else it may impart some energy relative to that speed difference.

Re: Scientists report asymmetry between heating and cooling

#135

Post by darkerside » Thu, Jan 25, 2024, 1:41 AM UTC

jacquesm wrote: post #134

darkerside wrote: post #132

Earlier quoted context omitted.

You may be right about the molecule, but the car absolutely has a distribution of speeds depending on what you are measuring in relation to.

That is exactly GPS point: a car doesn't have a distribution of speeds unless you measure it relative to something else whereas a liquid or a solid does have a temperature, regardless of anything else. Depending on what the something else is that you measure your car's speed by you may decide it goes forward, backward or is motionless. When you start talking about individual molecules, atoms or particles the whole co…

It sounds like you're enthusiastically agreeing with me?

Re: Scientists report asymmetry between heating and cooling

#136

Post by taylorius » Fri, Jan 26, 2024, 7:02 AM UTC

sparrowInHand wrote: post #66

taylorius wrote: post #60

Earlier quoted context omitted.

But isn't that passing on of energy from one particle to the next, just conduction? Why wouldn't it apply in the same way when heating?

Particles in heat are more active, as in brownian motion puts them allover the place, the cooler things get, the smaller the ripples, the less likely to interact with another particle, by transfering that ripple. Now in solid materials, that neighbour is always there to distribute any energy to everyone equally. But from solid to gas, there is only the surface and a gases density is lower, so the transfer propability…

But that's hot vs cold. As I understood it, this article is talking about difference in rate of heating vs. cooling, from the same starting temperature.

Re: Scientists report asymmetry between heating and cooling

#137

Post by aeonik » Fri, Jan 26, 2024, 9:14 PM UTC

LeegleechN wrote: post #118

aeonik wrote: post #116

Earlier quoted context omitted.

If this were the case, then how can a solid have a temperature at all? Especially crystalline solids, where all the molecules/elements are bound in a lattice?

The molecules in a crystal still vibrate kinetically. A solid with no molecular motion would be at absolute zero temperature.

Wouldn't a fair amount of the thermal energy be hanging out in the bonds themselves? The stress in the system has to count for something.

I'm imagining a bunch of potential energy being stored in the fields at any given moment.

Re: Scientists report asymmetry between heating and cooling

#138

Post by i-use-nixos-btw » Fri, Jan 26, 2024, 11:58 PM UTC

pimlottc wrote: post #48

i-use-nixos-btw wrote: post #9

> While no immediate practical applications exist, the researchers envision enhanced efficiency in micromotors, microscale cargo transport, and materials that can self-assemble or self-repair. Everyone who has ever written a grant application will recognise this wording.

Do you mean this general sort of speculative wording or these specific applications? If so, why these applications and not others?

Yes and yes.

These applications specifically because anything that looks at anything on the micro scale includes these as “possible applications”. They sound cool and exciting, and the urge for making them has been around since before Feynman’s Room At The Bottom lecture.

But my comment is mainly surrounding the farce of making a cool discovery that progresses an area of understanding, and then being asked a question that is best posed to engineers: “but what can we do with it?” Wrong field, wrong people, wrong question.

Imagine if astrophysicists were asked these questions. “So you’ve discovered a new kind of star that is made entirely of sponge? What applications do you think will come out of this research?” “Well we hope it will help with Dyson Spheres, Astrology and sea navigation”

Re: Scientists report asymmetry between heating and cooling

#139

Post by ivalm » Tue, Jan 30, 2024, 5:50 PM UTC

aeonik wrote: post #137

LeegleechN wrote: post #118

Earlier quoted context omitted.

The molecules in a crystal still vibrate kinetically. A solid with no molecular motion would be at absolute zero temperature.

Wouldn't a fair amount of the thermal energy be hanging out in the bonds themselves? The stress in the system has to count for something. I'm imagining a bunch of potential energy being stored in the fields at any given moment.

Absolutely, but that’s not heat. Things like heat produced from burning wood is an example of potential energy of binds getting released as kinetic energy + photons.