Electromagnetic (EM) radiations cannot exist independently without a source, as all observable light originates from charges and energy changes. The Cosmic Microwave Background Radiation (CMBR) and phenomena like Hawking radiation are often cited in discussions about source-less light; however, both have origins traceable to the Big Bang and black hole processes, respectively. Theoretical concepts such as vacuum solutions suggest the possibility of EM fields existing without sources, but these remain unobserved in practice. Ultimately, every known EM activity can be traced back to a nonzero source.
PREREQUISITESPhysicists, students of electromagnetic theory, and anyone interested in the fundamental nature of light and electromagnetic 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.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?
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?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.
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.
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.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?
If I understands you correctly, vacuum solutions had never been observed in reality but are just hypothetical then?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.
Everything just changing form from another to another, that's understandable. So, every propagating energy have sources then?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?
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.wonderingchicken said:If I understands you correctly, vacuum solutions had never been observed in reality but are just hypothetical then?
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?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.
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.hutchphd said:If you are going somewhere with this, please tell us the destination and we can all enjoy the trip...
This has already been answered. What remains?wonderingchicken said:whether EM fields or EM waves, etc. can exist on their own without sources.
Hmm. But do you get it?wonderingchicken said:Get it...?
You seems upset. Sorry if I indeed making you upset.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.
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.wonderingchicken said:You seems upset.
It's okay, so far every answers are useful.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.
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?
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).wonderingchicken said:The sources can be anything. Charge, flashlight, etc.
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.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.
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.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.
@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.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?
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 bookbob012345 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?
And I disagree that it's "light".hutchphd said:I disagree that these are "sourceless".
The OP actually mentions light or any EM radiation... I used the word lightly. But I think the virtual photons would include optical frequencies.Vanadium 50 said:And I disagree that it's "light".
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.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
There are several insights articles on the common misconceptions of virtual particles.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?
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?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.