Can EM Radiations Exist without a Source?

In summary: So, so far, we can safely concluded that every electromagnetic fields have sources in order to exist. But given that atoms are everywhere in the universe, even in the most perfect vacuum, there will be also electromagnetic fields everywhere. Is that... correct?
  • #1
wonderingchicken
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Can electromagnetic radiations exist on their own without any source (i.e light existing on its own without flashlight). If light can't exist on its own so sources are necessary for light or any EM radiations in order to exist, how about the EM fields?
 
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  • #2
wonderingchicken said:
Can electromagnetic radiations exist on their own without any source (i.e light existing on its own without flashlight). If light can't exist on its own so sources are necessary for light or any EM radiations in order to exist, how about the EM fields?
Any light that you 'see' must have come from a source of charges and energy changes. Otoh, I think you could consider the Cosmic Microwave Background Radiation as having been there for the life of the Universe. But even that would have had an origin in the Big Bang so, apart from a chicken and egg situation at the start of things, the answer to your OP is No.
 
  • #3
sophiecentaur said:
Any light that you 'see' must have come from a source of charges and energy changes. Otoh, I think you could consider the Cosmic Microwave Background Radiation as having been there for the life of the Universe. But even that would have had an origin in the Big Bang so, apart from a chicken and egg situation at the start of things, the answer to your OP is No.
Hi, @sophiecentaur. What about the Hawking radiation? A pair of photons are created from vacuum due to vacuum fluctuation, and then one of them falls back to the black hole while the other one escapes. Could that be the light without a source?
 
  • #4
sophiecentaur said:
Any light that you 'see' must have come from a source of charges and energy changes. Otoh, I think you could consider the Cosmic Microwave Background Radiation as having been there for the life of the Universe. But even that would have had an origin in the Big Bang so, apart from a chicken and egg situation at the start of things, the answer to your OP is No.

Same goes for any electromagnetic fields too except for the CMBR?
 
  • #5
wonderingchicken said:
Can electromagnetic radiations exist on their own without any source (i.e light existing on its own without flashlight). If light can't exist on its own so sources are necessary for light or any EM radiations in order to exist, how about the EM fields?
Light can exist without a source. Such situations are called vacuum solutions. The sources of light are charges and currents. So a vacuum solution is one that contains an EM field without any charges or currents.

The light that we see today probably all has a source. Even the CMB has a source, which is called the surface of last scattering. So the idea that light can have no source is mostly theoretical. Meaning it is compatible with known physics but not actually observed.
 
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  • #6
Since a photon has energy, and travels at the speed of light, the question could be rephrased to,
“must propagating energy have a source”. What gives, can we dismiss conservation of energy?
 
  • #7
Dale said:
Light can exist without a source. Such situations are called vacuum solutions. The sources of light are charges and currents. So a vacuum solution is one that contains an EM field without any charges or currents.

The light that we see today probably all has a source. Even the CMB has a source, which is called the surface of last scattering. So the idea that light can have no source is mostly theoretical. Meaning it is compatible with known physics but not actually observed.
If I understands you correctly, vacuum solutions had never been observed in reality but are just hypothetical then?
 
  • #8
Baluncore said:
Since a photon has energy, and travels at the speed of light, the question could be rephrased to,
“must propagating energy have a source”. What gives, can we dismiss conservation of energy?
Everything just changing form from another to another, that's understandable. So, every propagating energy have sources then?
 
  • #9
wonderingchicken said:
If I understands you correctly, vacuum solutions had never been observed in reality but are just hypothetical then?
I think that is a fair assessment. Of course, we don't always know the source of every EM wave we have ever observed, so I would be hesitant to say "never". Certainly we have never determined that an observed EM wave had no source.
 
  • #10
Dale said:
I think that is a fair assessment. Of course, we don't always know the source of every EM wave we have ever observed, so I would be hesitant to say "never". Certainly we have never determined that an observed EM wave had no source.
So, so far, we can safely concluded that every electromagnetic fields have sources in order to exist. But given that atoms are everywhere in the universe, even in the most perfect vacuum, there will be also electromagnetic fields everywhere. Is that correct?
 
  • #11
If you are going somewhere with this, please tell us the destination and we can all enjoy the trip...
 
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  • #12
hutchphd said:
If you are going somewhere with this, please tell us the destination and we can all enjoy the trip...
I just want to understand whether EM fields or EM waves, etc. can exist on their own without sources. Sometimes I think some EM fields or EM waves can exist without sources somewhere in the universe including the emptiest parts of universe.

Get it...?
 
  • #13
wonderingchicken said:
whether EM fields or EM waves, etc. can exist on their own without sources.
This has already been answered. What remains?

In principle/theory, yes they can exist without sources. In practice, they all have sources as far as we know. Just because something can happen doesn’t mean that it does happen.

This has all been stated already.
 
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  • #14
OK. I think every known bit of E M energy in the universe can be traced to a nonzero source. It is not unusual to dismiss allowed solutions because they do not match the boundary conditions.
Whether this source still "exists" is a question fraught with the usual relativistic issues.
 
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  • #15
Ok, so the answer remains so far "electromagnetic activities (EM field, EM waves, etc.) can be traced to nonzero sources". Then, everywhere in the universe there are particles and resulting EM fields/waves.
 
  • #16
wonderingchicken said:
Get it...?
Hmm. But do you get it?
You don't define what you mean by a source - so there can't be an answer. The only waves that your question could refer to would have had to originate 'before' the Big Bang. These would presumably have to be low frequency (?).
If you want'spontaneous generation' of waves in the context of 'vacuum' then you'd just have to look for evidence. Afaiaa, the jury's still out on that and you should be careful of anything that's published about it without a lot of support from recognised bodies. Only time will tell.
 
  • #17
sophiecentaur said:
Hmm. But do you get it?
You don't define what you mean by a source - so there can't be an answer. The only waves that your question could refer to would have had to originate 'before' the Big Bang. These would presumably have to be low frequency (?).
If you want'spontaneous generation' of waves in the context of 'vacuum' then you'd just have to look for evidence. Afaiaa, the jury's still out on that and you should be careful of anything that's published about it without a lot of support from recognised bodies. Only time will tell.
You seems upset. Sorry if I indeed making you upset.

The sources can be anything. Charge, flashlight, etc. But as what you guys already said above, so far EM activities (EM field, EM waves, etc.) must have sources in order to exist at least in reality. But hypothetically, EM activities without source are possible but not observed yet.
 
  • #18
wonderingchicken said:
You seems upset.
Nah. Not upset. Just a bit frustrated that you seem to be looking for an answer that's exclusively on your own terms. You will be very lucky if you find that kind of answer.
 
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  • #19
sophiecentaur said:
Nah. Not upset. Just a bit frustrated that you seem to be looking for an answer that's exclusively on your own terms. You will be very lucky if you find that kind of answer.
It's okay, so far every answers are useful.
 
  • #20
wonderingchicken said:
Can electromagnetic radiations exist on their own without any source (i.e light existing on its own without flashlight). If light can't exist on its own so sources are necessary for light or any EM radiations in order to exist, how about the EM fields?
wonderingchicken said:
The sources can be anything. Charge, flashlight, etc.
If by "sources" you mean the object(s) from which the light came, there's nothing that says the "sources" still have to exist for electromagnetic radiation to exist. As an example, if a particle and a corresponding antiparticle get annihilated, they will cease to exist and this process will produce gamma rays. See e.g. Positron Annihilation (HyperPhysics).
 
  • #21
Dale said:
Light can exist without a source. Such situations are called vacuum solutions. The sources of light are charges and currents. So a vacuum solution is one that contains an EM field without any charges or currents.

The light that we see today probably all has a source. Even the CMB has a source, which is called the surface of last scattering. So the idea that light can have no source is mostly theoretical. Meaning it is compatible with known physics but not actually observed.
What about the Casimir effect between two plates? Would that not in effect constitute a direct observation of the reality of 'light without a source' meaning vacuum fluctuations? Also related are van der Waals forces.
 
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  • #22
bob012345 said:
What about the Casimir effect between two plates? Would that not in effect constitute a direct observation of the reality of 'light without a source' meaning vacuum fluctuations? Also related are van der Waals forces.
Well, I think that I would attribute the Casimir force to the plates and the van der Waals force to the molecules. But you do make a good point about the vacuum expectation. I had not considered that above.
 
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  • #23
Haorong Wu said:
Hi, @sophiecentaur. What about the Hawking radiation? A pair of photons are created from vacuum due to vacuum fluctuation, and then one of them falls back to the black hole while the other one escapes. Could that be the light without a source?
@Haorong Wu The "virtual particle pair" description of Hawking Radiation is not an actual description of what happens. It is a heuristic created by Hawking himself who said that it was the only way he could figure out how to say in the English language what really can only be said in the math.
 
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  • #24
bob012345 said:
What about the Casimir effect between two plates? Would that not in effect constitute a direct observation of the reality of 'light without a source' meaning vacuum fluctuations?
I disagree that these are "sourceless". Each requires the presence of matter containing charges and some source of Energy (temperature?) to produce measureable effect I believe. Does not pass the "no source" test in my book
 
  • #25
hutchphd said:
I disagree that these are "sourceless".
And I disagree that it's "light".
 
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  • #26
Vanadium 50 said:
And I disagree that it's "light".
The OP actually mentions light or any EM radiation... I used the word lightly. But I think the virtual photons would include optical frequencies.

https://arxiv.org/pdf/0804.2554.pdf
 
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  • #27
hutchphd said:
I disagree that these are "sourceless". Each requires the presence of matter containing charges and some source of Energy (temperature?) to produce measureable effect I believe. Does not pass the "no source" test in my book
Of course the Casimir effect and the van der Waals force requires matter. But the matter is not the source of the virtual photons which exist independently as I understand it.
 
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  • #28
Interesting to know that particles can appear out of absolute nothing, such as vacuum fluctuations. Are there any experiments out there that already demonstrated these phenomena?
 
  • #29
wonderingchicken said:
Interesting to know that particles can appear out of absolute nothing, such as vacuum fluctuations. Are there any experiments out there that already demonstrated these phenomena?
There are several insights articles on the common misconceptions of virtual particles.

In a nutshell, they are a calculation device and not real particles that could be detected.
 
  • #30
PeroK said:
There are several insights articles on the common misconceptions of virtual particles.

In a nutshell, they are a calculation device and not real particles that could be detected.
So, objects appear out of nothing never actually happened in reality at all even in physics? Then, what is actually happened when vacuum fluctuations happen?
 
  • #31
wonderingchicken said:
So, objects appear out of nothing never actually happened in reality at all even in physics? Then, what is actually happened when vacuum fluctuations happen?
Read the Insights article(s) on vacuum fluctuations.
 
  • #32
PeroK said:
Read the Insights article(s) on vacuum fluctuations.
Any links?
 
  • #34
PeroK said:
Read the Insights article(s) on vacuum fluctuations.
Wow, great. There is a lot to read and it will take some time. But I am just curious, what really happens in the process such as in Feynman diagrams? Is the answer is that we know how physically describe the whole process, and we build mathematical tools to calculate it but we do not know its true nature?
 
  • #35
Haorong Wu said:
what really happens in the process such as in Feynman diagrams?

We don't know. With every process there are associated infinitely many diagrams, and that thing alone makes it clear (for me at least) that Feynman diagrams are not representations of "what really happens". All we know is that we prepare particles in certain states (in-states), we collide them, and measure what comes out (out-states). We don't know happens during the collision.
 
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<h2>1. How can electromagnetic radiations exist without a source?</h2><p>Electromagnetic radiation can exist without a source because it is a natural phenomenon that occurs due to the movement of electrically charged particles. These particles can be found in atoms, molecules, and other structures, and their movement creates electric and magnetic fields, which in turn produce electromagnetic radiation.</p><h2>2. Is it possible for electromagnetic radiations to exist in a vacuum?</h2><p>Yes, electromagnetic radiation can exist in a vacuum because it does not require a medium to propagate. This is because it is made up of oscillating electric and magnetic fields, which can travel through empty space without the need for a physical medium.</p><h2>3. Can electromagnetic radiation exist in different forms?</h2><p>Yes, electromagnetic radiation can exist in a wide range of forms, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. These different forms have different wavelengths and frequencies, which determine their properties and interactions with matter.</p><h2>4. How do we detect electromagnetic radiation if it exists without a source?</h2><p>Even though electromagnetic radiation can exist without a source, we can still detect it using various instruments and devices. For example, radio antennas detect radio waves, while X-ray machines detect X-rays. These instruments are designed to measure the electric and magnetic fields produced by the radiation and convert them into signals that we can interpret.</p><h2>5. Can electromagnetic radiation be harmful if it exists without a source?</h2><p>Yes, electromagnetic radiation can be harmful if it exists without a source in high levels or certain forms. For example, exposure to high levels of X-rays or gamma rays can damage cells and cause health problems. However, most forms of electromagnetic radiation are harmless in small doses, and some, like visible light, are essential for life.</p>

1. How can electromagnetic radiations exist without a source?

Electromagnetic radiation can exist without a source because it is a natural phenomenon that occurs due to the movement of electrically charged particles. These particles can be found in atoms, molecules, and other structures, and their movement creates electric and magnetic fields, which in turn produce electromagnetic radiation.

2. Is it possible for electromagnetic radiations to exist in a vacuum?

Yes, electromagnetic radiation can exist in a vacuum because it does not require a medium to propagate. This is because it is made up of oscillating electric and magnetic fields, which can travel through empty space without the need for a physical medium.

3. Can electromagnetic radiation exist in different forms?

Yes, electromagnetic radiation can exist in a wide range of forms, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. These different forms have different wavelengths and frequencies, which determine their properties and interactions with matter.

4. How do we detect electromagnetic radiation if it exists without a source?

Even though electromagnetic radiation can exist without a source, we can still detect it using various instruments and devices. For example, radio antennas detect radio waves, while X-ray machines detect X-rays. These instruments are designed to measure the electric and magnetic fields produced by the radiation and convert them into signals that we can interpret.

5. Can electromagnetic radiation be harmful if it exists without a source?

Yes, electromagnetic radiation can be harmful if it exists without a source in high levels or certain forms. For example, exposure to high levels of X-rays or gamma rays can damage cells and cause health problems. However, most forms of electromagnetic radiation are harmless in small doses, and some, like visible light, are essential for life.

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