The discussion centers on the completeness of our knowledge regarding the electromagnetic spectrum, specifically whether there are unknown wavelengths or sources of light beyond the established categories from gamma rays to radio waves. Participants explore the implications of terminology, measurement limitations, and the potential for undiscovered regions of the spectrum.
Participants express a range of views, with no consensus on whether our knowledge of the electromagnetic spectrum is complete. Some agree on the limitations of current understanding, while others maintain that the spectrum is well-defined and continuous.
Participants note limitations in measurement resolution and the dependence on definitions when discussing the electromagnetic spectrum. The discussion also touches on unresolved questions regarding the behavior of photons at the Planck scale.
You need to realize that "radio waves" and "gamma rays" are arbitrary names given to the same phenomenon. There can be something "beyond gamma rays" or "below radio waves" only if we decide to give electromagnetic radiation above or below a certain wavelength a special name. Otherwise, you have electromagnetic radiation, with different wavelengths/frequencies.m_robertson said:What I mean is the different wavelengths of light. We have an understanding of the light spectrum from gamma waves all the way to radio waves, but is that the complete and entire picture? Or could there be things beyond gamma waves and radio waves which we have yet to detect with modern instruments?
If I were allowed to interpret this question as "is there a region in the EM spectrum whose interaction properties with materials is still not well studied?", then I would say terahertz region, this covers frequencies between far infrared and microwave. It's not trivial to generate radiation within terahertz due to the fact that this region sets the working limit of conventional electronics.m_robertson said:The question is pretty simple really, do we have a complete knowledge on the different wavelengths of light? Or are there possibly other sources of light out there that are unknown to us?
We could soon find ourselves in the classification game - ionising frequencies, 'photon' frequencies and good old RF, which electronics can deal with. All the same basic stuff though.blue_leaf77 said:If I were allowed to interpret this question as "is there a region in the EM spectrum whose interaction properties with materials is still not well studied?", then I would say terahertz region, this covers frequencies between far infrared and microwave. It's not trivial to generate radiation within terahertz due to the fact that this region sets the working limit of conventional electronics.
Be careful how you use that term.mfb said:... you get it from thermal radiation...
Where is the problem?Khashishi said:Be careful how you use that term.
This is what I was getting at. So it's just down to a matter of terminology? The fact that we don't know what happens to EM radiation at the Planck scale is the answer I was looking for, so there are elements to light that aren't understood?DrClaude said:You need to realize that "radio waves" and "gamma rays" are arbitrary names given to the same phenomenon. There can be something "beyond gamma rays" or "below radio waves" only if we decide to give electromagnetic radiation above or below a certain wavelength a special name. Otherwise, you have electromagnetic radiation, with different wavelengths/frequencies.
Currently, by definition, radio waves encompass the entire long-wavelength part of the spectrum, so the limit there would be a wavelength the size of the universe. At the other extreme, what happens to EM radiation of a wavelength comparable to the Planck length, nobody knows.
m_robertson said:This is what I was getting at. So it's just down to a matter of terminology? The fact that we don't know what happens to EM radiation at the Planck scale is the answer I was looking for, so there are elements to light that aren't understood?
It does not - you just need a larger accelerator. Or you can simply go to a different coordinate system to get any photon energy you want.Jon Richfield said:This implies that we cannot even in principle generate photons beyond a certain frequency.
Nothing new, unless there are new, undiscovered particles. Beyond something like 1 GeV, all you get are interactions of photons with elementary particles, and the Standard Model can describe them very well. While the types of particles that can get produced in those collision still changes if you go to higher energies, from a macroscopic point of view it always looks the same: photon hits other particles and creates an electromagnetic shower (with smaller hadronic components).Jon Richfield said:It seems to me that the question is not so much the light being different as its frequency increases beyond the gamma limit, as the question of what sort of material effect we could expect to observe from such near- ( or trans-?) Planck limited light frequencies.
mfb said:It does not - you just need a larger accelerator. Or you can simply go to a different coordinate system to get any photon energy you want.
Nothing new, unless there are new, undiscovered particles. Beyond something like 1 GeV, all you get are interactions of photons with elementary particles, and the Standard Model can describe them very well. While the types of particles that can get produced in those collision still changes if you go to higher energies, from a macroscopic point of view it always looks the same: photon hits other particles and creates an electromagnetic shower (with smaller hadronic components).
Yes, but it is orders of magnitude above the Planck energy. Like... 60 orders of magnitude.Jon Richfield said:1: There is a finite amount of energy in the observable universe.
That is exactly the idea of the Planck energy (you would need this as invariant mass, a single photon alone cannot make a black hole, so you better collide two photons).Jon Richfield said:Frankly I suspect that the gravitational effects of such a photon alone would present us with some intriguing problems. (Black hole on the cob, anyone?)
Build a massive linear accelerator for electrons, let them hit a target, some collisions will give photons close to the original electron energy. Do the same for the other side.Jon Richfield said:2: Even granting that we mustn't be greedy just for the sake of large scale physics, what sort of approach would you use to convert real-life diffuse sources such as condensed matter, not to mention plasma accumulations like the sun FTM, into a single photon? You would need some pretty fancy coordination, because you couldn't run after your photon, shouting "Wait, here are some tributary photons that you missed!" even if you compromised on producing TWO photons to conserve momentum, could you? That could seriously affect your options for collecting the energy from the rest of our local 10 billion-light-year diameter globe I reckon. Unless you happen to have news for me of course...
As I said, at the Planck scale we know something new will happen. Before that, there could be something new, but we don't know. It could be very boring.Jon Richfield said:Forgive me if I regard that assurance with reserve. There tend to be some very curious things that happen when one leaves known constraints; such as when we enter the scale of photons whose behaviour might be dominated by their own gravitational effects, and which will have to travel through some 5 billion light years of space that we have evacuated of particles to generate them. Something gives me a nasty feeling that something unexpected might happen, possibly even more unexpected than someone actually developing technology for creating even a mingy little 1-kg mass-equivalent photon, or even two of them. But don't hesitate to surprise me!
Still, I have a totally unsupported suspicion, not even a self-respecting speculation, that if you pumped up a photon too deeply into Planck limit territory, it would split itself into more, lower-frequency photons and that would be a behaviour not to be expected of plain vanilla gamma rays. We would be justified in calling such light a new type, just as we speak of gamma ray photons, we then could speak of Planckrayons. Try getting fun dings for relieving gamma boredom in that way!mfb said:...
As I said, at the Planck scale we know something new will happen. Before that, there could be something new, but we don't know. It could be very boring...