Entropy and electromagnetic radiation

In summary: I don't want to be responsible for spreading bad physics.In summary, the conversation discusses the concept of entropy and how it affects the energy of the universe. It also touches on the dispersion of electromagnetic radiation in space and the Hubble red-shift. The conversation highlights that entropy cannot decrease in a closed system and that the expansion of space-time affects the dispersion of electromagnetic radiation. However, the writer is unsure about the source of their ideas and the expert is cautious about providing accurate information without knowing the purpose of the writer's questions.
  • #1
tarakan
53
2
I don't understand this:

According to what modern physicists believe to be true, there is entropy that slowly converts all energy of the universe into heat that cannot do any work. Than this heat is radiated as infrared light into space. Correct?

Besides infrared heat radiation, start also produce other spectrums of light and all that goes out into space and escapes the universe for ever, if it doesn't happen to run into planets, stars, dust or other space objects on its way out.
Correct?

Because of some phenomena (what is the term that is used for it?) the frequency of electromagnetic waves decreases over time as they travel through space and all the light that escapes stars slowly becomes infrared heat radiation. Correct?

When frequency of electromagnetic radiation decreases, the energy is lost. Why?

Thank you.
 
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  • #2
Welcome to PF;
tarakan said:
I don't understand this:
That is hardly surprising - it doesn't make sense. Where did you get these ideas from?

According to what modern physicists believe to be true, there is entropy that slowly converts all energy of the universe into heat that cannot do any work. Than this heat is radiated as infrared light into space. Correct?
No.

Entropy is a measure of the amount of disorder in a system.
The amount of disorder in a closed system increases over time - simply because there are many more ways for something to be disordered than ordered.

There is a subtle thing here which may not be intended: "modern physicists" do not go around "believing" things. At least not in the sense that someone may "believe" in a God, or Astrology. That would be counter productive. But, sometimes, someone will mean "believe in xyz" as a shorthand for "the weight of opinion favors xyz as most consistent with the available evidence and most useful for building new theories from"... which is a bit tedious to keep saying.

Besides infrared heat radiation, start also produce other spectrums of light and all that goes out into space and escapes the universe for ever, if it doesn't happen to run into planets, stars, dust or other space objects on its way out.
Correct?
No - nothing leaves the Universe - that is what "Universe" means.

Because of some phenomena (what is the term that is used for it?) the frequency of electromagnetic waves decreases over time as they travel through space and all the light that escapes stars slowly becomes infrared heat radiation. Correct?
Kinda - you could be talking about two things here ... dispersion of EM radiation in space, or the Hubble red-shift.

The first is understood in terms of the field becoming more distributed in space and the second in terms of the expansion of space-time.

When frequency of electromagnetic radiation decreases, the energy is lost. Why?
Because that is how it works - high frequencies have higher energy.
You can try it with physical objects - you have to work harder waving things back and forth at a high frequency than you do waving them at a low frequency.

Light does not magically change frequency though ... the energy has to go somewhere.
Where it goes depends on how the frequency change happened. eg. high frequency light can be absorbed by something which distributes the energy among its component parts, warming it up ... each part later radiates some of the energy. So you get high energy light in and low energy light out.
 
  • #3
Simon Bridge said:
Welcome to PF;
That is hardly surprising - it doesn't make sense. Where did you get these ideas from?

No.

Entropy is a measure of the amount of disorder in a system.
The amount of disorder in a closed system increases over time - simply because there are many more ways for something to be disordered than ordered.

There is a subtle thing here which may not be intended: "modern physicists" do not go around "believing" things. At least not in the sense that someone may "believe" in a God, or Astrology. That would be counter productive. But, sometimes, someone will mean "believe in xyz" as a shorthand for "the weight of opinion favors xyz as most consistent with the available evidence and most useful for building new theories from"... which is a bit tedious to keep saying.

No - nothing leaves the Universe - that is what "Universe" means.

Kinda - you could be talking about two things here ... dispersion of EM radiation in space, or the Hubble red-shift.

The first is understood in terms of the field becoming more distributed in space and the second in terms of the expansion of space-time.

Because that is how it works - high frequencies have higher energy.
You can try it with physical objects - you have to work harder waving things back and forth at a high frequency than you do waving them at a low frequency.

Light does not magically change frequency though ... the energy has to go somewhere.
Where it goes depends on how the frequency change happened. eg. high frequency light can be absorbed by something which distributes the energy among its component parts, warming it up ... each part later radiates some of the energy. So you get high energy light in and low energy light out.


Entropy increases over time in the Universe as start convert mass into energy through fusion?

Isn't dispersion of EM radiation in space affected by the Hubble red-shift?

I am sorry for asking questions like this. I am a writer.
 
  • #4
tarakan said:
Entropy increases over time in the Universe as start convert mass into energy through fusion?
The rule is: entropy in any closed system cannot decrease. However it can stay the same.

The Universe is the ultimate closed system and it contains a great many processes which increase the total entropy - one of which is nuclear fusion in stars.

Mass is also energy.
Fusion does convert mass into other forms of energy.

Isn't dispersion of EM radiation in space affected by the Hubble red-shift?
The Hubble red-shift is the effect, on dispersion, due to the expansion of space-time.

What are you trying to figure out?
Where are you getting these ideas from?

There is an odd wording in your questions which makes me cautious about the kind of answers I give you.
 
Last edited:
  • #5


I can explain this concept to you. Entropy is a measure of the disorder or randomness in a system. In the case of the universe, entropy is constantly increasing as energy is converted into heat and radiated out into space. This process is known as the "heat death" of the universe.

Electromagnetic radiation is a form of energy that can be emitted or absorbed by matter. This includes infrared light, as well as other spectrums of light such as visible light, ultraviolet light, and x-rays. As you mentioned, all of these forms of radiation can escape the universe if they do not encounter any objects in their path.

The phenomenon you are referring to is called redshifting, which is the decrease in frequency of electromagnetic waves as they travel through space. This is due to the expansion of the universe and the stretching of the wavelengths of light. As the frequency decreases, the energy of the radiation also decreases. This is why all light eventually becomes infrared heat radiation.

In terms of energy being lost, it is important to remember the conservation of energy principle. Energy can neither be created nor destroyed, but it can change form. As electromagnetic radiation travels through space, its frequency decreases and it loses energy. This energy is not truly lost, but rather converted into a different form (heat).

I hope this explanation helps you understand the concept of entropy and electromagnetic radiation better. Please let me know if you have any further questions.
 

1. What is entropy and how does it relate to electromagnetic radiation?

Entropy is a measure of the disorder or randomness of a system. In the context of electromagnetic radiation, it refers to the distribution of energy and wavelengths within the radiation. As entropy increases, the distribution of energy becomes more random and less organized.

2. How does entropy affect the behavior of electromagnetic radiation?

The increase of entropy in electromagnetic radiation leads to a decrease in the coherence and directionality of the radiation. This means that the radiation becomes more diffuse and less focused as entropy increases.

3. What is the relationship between entropy and the second law of thermodynamics?

The second law of thermodynamics states that the entropy of a closed system will always increase over time. This is also true for electromagnetic radiation, as it tends to disperse and become more random over time, leading to an increase in entropy.

4. How does the concept of entropy apply to the universe as a whole?

The concept of entropy also applies to the universe as a whole. According to the laws of thermodynamics, the universe is constantly moving towards a state of maximum entropy, where all energy is evenly distributed and no work can be done. This is known as the "heat death" of the universe.

5. Can entropy be reversed or decreased in electromagnetic radiation?

In general, entropy cannot be reversed or decreased in electromagnetic radiation. However, in certain situations, such as in a laser, energy can be concentrated and organized to create a lower entropy state. This requires an input of energy and is only temporary, as the radiation will eventually disperse and increase in entropy again.

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