Why Is radiation the highest form of entropy?

[memento]

Hello everyone, I have heard in a sminar that radiation is the highest form of entropy. Why?
I was wondering too if all matter would transform at the end in radiation somehow

 

[Demystifier]

Hello everyone, I have heard in a sminar that radiation is the highest form of entropy. Why?

Because photons have zero mass.
Larger entropy means larger number of different states with given energy. The smallest possible energy of a given particle is equal to its mass (times $c^2$), so when particles do not need to "spend" a part of their energy for having mass, more energy remains for contributions to the entropy.

 

[memento]

Thank you. Do you know how is the entropy involved in combustion (the heat emited in form of radiation)? More exactly, why are the photons entangled in this procces?

 

[Demystifier]

Thank you. Do you know how is the entropy involved in combustion (the heat emited in form of radiation)? More exactly, why are the photons entangled in this procces?

Entanglement is related to the conservation of energy, momentum, and angular momentum. For example, if a radiated photon has certain energy $E$, then the source must have energy reduced by the value $-E$. This means that their energies are correlated. For quantum systems, the correlation is described by entanglement.

Is your question motivated by a desire to understand radiation by black holes?

 

[DrDu]

Hello everyone, I have heard in a sminar that radiation is the highest form of entropy. Why?
I was wondering too if all matter would transform at the end in radiation somehow

You can't say this in general. For example, laser radiation has very little entropy.

 

[Demystifier]

You can't say this in general. For example, laser radiation has very little entropy.

Of course, but in this thread it was implicit that it is about thermal radiaton.

 

[sciencejournalist00]

Because it is dispersed in a very large volume. Unlike it, laser is highly directional.

 

[memento]

Entanglement is related to the conservation of energy, momentum, and angular momentum. For example, if a radiated photon has certain energy $E$, then the source must have energy reduced by the value $-E$. This means that their energies are correlated. For quantum systems, the correlation is described by entanglement.

Is your question motivated by a desire to understand radiation by black holes?

Not exactly, but the physical meaning of the conservation of information in quantum mechanics. If something related with black holes or anything cast light to the subject, please let me know,

Thanks

PD: Following the reasoning of high entropy of ligh I suppose that conversion of mass into light is spontaneus, why don´t we see it?

 

[Demystifier]

conversion of mass into light is spontaneus, why don´t we see it?

We do see it, but it is perhaps not so obvious because the process of mass reduction is usually quite slow.

 

[DrDu]

There are also conservation laws for charge, baryonic number etc. which don't allow for the conversion of mass into light.

 

[A. Neumaier]

the conservation of information in quantum mechanics

This is a misunderstanding. Entropy is not conserved in Nature.

the heat emited in form of radiation

is something completely classical, unrelated to entanglement.

 

[A. Neumaier]

if all matter would transform at the end in radiation somehow

This is impossible since baryon number is conserved.

 

[Demystifier]

Entropy is not conserved in Nature.

This is both true and wrong, depending on the precise definition of entropy.
For example in classical statistical mechanics, fine grained Gibbs entropy is conserved but coarse grained Gibbs entropy is not conserved.
Similarly in quantum statistical mechanics, von Neumann entropy of a closed system is conserved, but von Neumann entropy of an open system is not conserved.

 

[A. Neumaier]

fine grained Gibbs entropy is conserved

But post #1 makes sense only in the context of macroscopic (hence coarse-grained), increasing entropy. (Even then only superficially, since it ignores conservation laws that are actually valid.)

 

[memento]

This is a misunderstanding. Entropy is not conserved in Nature.

You can neither destroy the information, nor create it, I think entropy reflects the state of this information.

 

[Demystifier]

But post #1 makes sense only in the context of macroscopic (hence coarse-grained), increasing entropy.

I agree. But to understand how can it be compatible with conservation of information in QM, one has to have in mind the existence of different kinds of entropy.

 

[memento]

We do see it, but it is perhaps not so obvious because the process of mass reduction is usually quite slow.

Really? Could you give me more information about the velocity of this process, a formula would be nice, thank you

 

[memento]

There are also conservation laws for charge, baryonic number etc. which don't allow for the conversion of mass into light.

I supposse this conservation law don´t allow convert light into matter, but this is FALSE, since in 2014 was announced that this year we will see it!

 

[Demystifier]

Really? Could you give me more information about the velocity of this process, a formula would be nice, thank you

I'll not give you a formula, but a physical idea. The Sun needs a few billion years to convert a significant fraction of its initial mass into light.

 

[DrDu]

I supposse this conservation law don´t allow convert light into matter, but this is FALSE, since in 2014 was announced that this year we will see it!

Before judging, I would propose at least to wait whether this prophecy becomes reality. Btw. from whom is this announcement?

 

[Ronie Bayron]

Hello everyone, I have heard in a seminar that radiation is the highest form of entropy. Why?
I was wondering too if all matter would transform at the end in radiation somehow

It's the end state of material-energy and there's no known process reversing radiation to materialization, yet. Even so, that there is(artificial and man made-like plasma), if it's not by nature, then its still generates entropy. Entropy is like, you spent some heat and effort baking a bread, but you only use a portion of the calorie brought by the sugar from the bread. There may be success of radiation materialization but there is no remedy for the lost on the process. It's always there.

The only interesting thing to investigate is to simulate the end state and probably the beginning also at the same time. That means looking through the end process of a black hole.--may be, just may be, radiation itself recycles becoming a material.IMO.

 

[memento]

Before judging, I would propose at least to wait whether this prophecy becomes reality. Btw. from whom is this announcement?

http://phys.org/news/2014-05-scientists-year-quest.html Imperial college

 

[DrDu]

This is the reverse process, i.e. the generation of matter from light. In this process, particles and anti-particles are created in equal amounts with their total charge and baryon number being 0. However, in our universe, we observe practically only matter and no anti-matter. Hence there is no anihilation process possible.

 

[memento]

I'll not give you a formula, but a physical idea. The Sun needs a few billion years to convert a significant fraction of its initial mass into light.

I found a sentence in this forum "Fusion reactions generally release energy as we build up larger nuclei until we get to iron-56, and fission reactions generally release energy as we turn larger nuclei into smaller until we get down to iron-56" and I think it´s true.
Beacuse of this, the end of the universe cannot be to convert all the matter into light, because fission is spontaneous for heavy nuclei.

Kind regards

 

[Demystifier]

Beacuse of this, the end of the universe cannot be to convert all the matter into light, because fission is spontaneous for heavy nuclei.

Well, if nuclear reactions were the only kind of reaction, you would be right. But there are also other forces, much weaker and therefore much slower, due to which even iron-56 may not be stable at much longer time scales.

For more details about the appropriate time scales see
https://en.wikipedia.org/wiki/Timel...he_Earth.2C_the_Solar_System_and_the_Universe
In particular, iron-56 is at $10^{1500}$, but that's not the end.

 

[memento]

Well, if nuclear reactions were the only kind of reaction, you would be right. But there are also other forces, much weaker and therefore much slower, due to which even iron-56 may not be stable at much longer time scales.

For more details about the appropriate time scales see
https://en.wikipedia.org/wiki/Timel...he_Earth.2C_the_Solar_System_and_the_Universe
In particular, iron-56 is at $10^{1500}$, but that's not the end.

It´s amazing, I was closed xD, but we will have to wait a long time to see that, probably dead.

Again, thank you