Hi Everyone
Does anyone here know of any circumstances in which an object of any temperature might emit a continuous stream of extremely low frequency photons? (less then 1Hz or much lower)
What, if anything, would block or absorb such photons?
Thank you very much.
Kind regards
Tim
Questions about extremely low frequency photons
Re: Questions about extremely low frequency photons
Less than 1Hz? If that's not a typo, it's a wavelength of the order of the distance to the moon! Super-long wavelength ELF radio waves (or even below ELF definitions). I know some ELF signals (although I think still quite a bit higher frequency than 1Hz) are used for communications with submarines because of how well they penetrate even large depths of water, so it would take quite something to block that. Given the scale, I'd wonder more about astrophysical origin if it's a real signal, although I can't think of a relevant process off the top of my head. What does come to mind however is the prospect of such an observation being electronic noise rather than an external signal - perhaps due to low frequency switching of some component.
Re: Questions about extremely low frequency photons
Hi Josephjneilson wrote: ↑22 Sep 2024, 05:40Less than 1Hz? If that's not a typo, it's a wavelength of the order of the distance to the moon! Super-long wavelength ELF radio waves (or even below ELF definitions). I know some ELF signals (although I think still quite a bit higher frequency than 1Hz) are used for communications with submarines because of how well they penetrate even large depths of water, so it would take quite something to block that. Given the scale, I'd wonder more about astrophysical origin if it's a real signal, although I can't think of a relevant process off the top of my head. What does come to mind however is the prospect of such an observation being electronic noise rather than an external signal - perhaps due to low frequency switching of some component.
Thank you very much indeed for your very informative reply.
No, it wasn't a typo. I am very curious about the extremes of radiation.
I have some more questions.
1. Do you have a rough idea of what is the lowest frequency of electromagnetic radiation that has ever been studied either theoretically or practically?
2. If you know the answer to the above question, what was the study all about?
3. According to theory, would a parallel beam of 1Hz (or much lower) photons be able to pass right through an object as large as a planet or star with very little, if any attenuation?
Thank you very much.
Kind regards
Tim
Re: Questions about extremely low frequency photons
Interesting questions. I don't know enough about that end of the EM spectrum to give definitive answers to this. This is more the domain of electronics engineers, telecoms engineers, and radio astronomers.
Submarine communications is the lowest frequency application of EM radiation I'm aware of, and that's somewhere around the 70-80Hz ballpark. That might actually be the lowest frequency used or studied, but there's a good chance there's something else I'm not aware of.
Of course you can theoretically achieve any low frequency you want - at 1Hz frequencies you'd typically think more in terms of producing a static field which you then gradually vary, rather than thinking of RF generation. The limitation is more the size of the antenna you need to effectively radiate such a signal - there's rules of thumb that your antenna needs to be sized as a certain fraction of the intended wavelength - the submarine comms transmitters use huge electrodes buried such that they effectively used hundreds or thousands of km of the Earth's surface as their antenna. For sub-1Hz, all I can say is good luck building something that stretches a good proportion of the way to the moon!
In terms of definitions, there's an arbitrary cutoff in the definition of radio frequencies at 3Hz; below that there's no official name for what EM radiation might be called. I've seen "subradio" and "TLF" (tremendously low frequency) proposed as names, but I think with no practical use in that range, it's largely irrelevant. I think websearching around those terms is going to be the best approach to find anything else that might be a record lowest frequency.
As to question 3, when you switch to thinking about photons from space, there's a massive change of refractive index to consider as the photons cross from vacuum into the atmosphere. Thinking about radio astronomy applications, I believe frequencies under a few kHz are mostly reflected off the ionosphere back into space with very little being transmitted - look up the radio astronomy "window" for more on that. My understanding is therefore that your photon beam would likely be reflected, but my knowledge is limited, especially at frequencies so low, so I'm not sure.
Submarine communications is the lowest frequency application of EM radiation I'm aware of, and that's somewhere around the 70-80Hz ballpark. That might actually be the lowest frequency used or studied, but there's a good chance there's something else I'm not aware of.
Of course you can theoretically achieve any low frequency you want - at 1Hz frequencies you'd typically think more in terms of producing a static field which you then gradually vary, rather than thinking of RF generation. The limitation is more the size of the antenna you need to effectively radiate such a signal - there's rules of thumb that your antenna needs to be sized as a certain fraction of the intended wavelength - the submarine comms transmitters use huge electrodes buried such that they effectively used hundreds or thousands of km of the Earth's surface as their antenna. For sub-1Hz, all I can say is good luck building something that stretches a good proportion of the way to the moon!
In terms of definitions, there's an arbitrary cutoff in the definition of radio frequencies at 3Hz; below that there's no official name for what EM radiation might be called. I've seen "subradio" and "TLF" (tremendously low frequency) proposed as names, but I think with no practical use in that range, it's largely irrelevant. I think websearching around those terms is going to be the best approach to find anything else that might be a record lowest frequency.
As to question 3, when you switch to thinking about photons from space, there's a massive change of refractive index to consider as the photons cross from vacuum into the atmosphere. Thinking about radio astronomy applications, I believe frequencies under a few kHz are mostly reflected off the ionosphere back into space with very little being transmitted - look up the radio astronomy "window" for more on that. My understanding is therefore that your photon beam would likely be reflected, but my knowledge is limited, especially at frequencies so low, so I'm not sure.
Re: Questions about extremely low frequency photons
Hi Josephjneilson wrote: ↑22 Sep 2024, 22:01Interesting questions. I don't know enough about that end of the EM spectrum to give definitive answers to this. This is more the domain of electronics engineers, telecoms engineers, and radio astronomers.
Submarine communications is the lowest frequency application of EM radiation I'm aware of, and that's somewhere around the 70-80Hz ballpark. That might actually be the lowest frequency used or studied, but there's a good chance there's something else I'm not aware of.
Of course you can theoretically achieve any low frequency you want - at 1Hz frequencies you'd typically think more in terms of producing a static field which you then gradually vary, rather than thinking of RF generation. The limitation is more the size of the antenna you need to effectively radiate such a signal - there's rules of thumb that your antenna needs to be sized as a certain fraction of the intended wavelength - the submarine comms transmitters use huge electrodes buried such that they effectively used hundreds or thousands of km of the Earth's surface as their antenna. For sub-1Hz, all I can say is good luck building something that stretches a good proportion of the way to the moon!
In terms of definitions, there's an arbitrary cutoff in the definition of radio frequencies at 3Hz; below that there's no official name for what EM radiation might be called. I've seen "subradio" and "TLF" (tremendously low frequency) proposed as names, but I think with no practical use in that range, it's largely irrelevant. I think websearching around those terms is going to be the best approach to find anything else that might be a record lowest frequency.
As to question 3, when you switch to thinking about photons from space, there's a massive change of refractive index to consider as the photons cross from vacuum into the atmosphere. Thinking about radio astronomy applications, I believe frequencies under a few kHz are mostly reflected off the ionosphere back into space with very little being transmitted - look up the radio astronomy "window" for more on that. My understanding is therefore that your photon beam would likely be reflected, but my knowledge is limited, especially at frequencies so low, so I'm not sure.
Thank you very much indeed for all of your help with this.
Kind regards
Tim
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