Timeline for What is the minimum wavelength of electromagnetic radiation?
Current License: CC BY-SA 4.0
15 events
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| S Dec 20, 2022 at 7:12 | history | suggested | Stephane Bersier | CC BY-SA 4.0 |
Fixed word typo
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| Dec 19, 2022 at 23:16 | review | Suggested edits | |||
| S Dec 20, 2022 at 7:12 | |||||
| Jul 25, 2019 at 4:42 | comment | added | Luboš Motl | Objects in their rest frame cannot be shorter than the Planck length... But even if you try to do things that are possible, it is indeed a possibility that the plan will fail due to the shortage of energy you mention. | |
| Jul 23, 2019 at 18:15 | comment | added | Edouard | @Lubos Motl Is it possible that an object of some length shorter than the Planck length might be seen only through magnification energies exceeding all the energy in a locality's observable region? (For the benefit of other participants, I have to say that this question is slightly different from the OP's, but you seem so so close to answering it--with the simple "Yes" I'm hoping for--that I'm asking it in a comment along the lines of a "suggestion of improvements" to the original question.) | |
| Jul 9, 2019 at 16:01 | comment | added | Luboš Motl | It's not a typo, it was an order of magnitude estimate. 20 micrograms is more accurate, see e.g. en.wikipedia.org/wiki/Planck_mass | |
| Jul 8, 2019 at 18:20 | comment | added | endolith | "The Planck mass is just 10 micrograms or so" I think that's a typo | |
| Nov 4, 2011 at 15:10 | comment | added | Ron Maimon | @Lubos: Yes, of course, I understand this, but it doesn't sit well--- it seems that there is a universal boosted limit. The question of whether you have a boosted universal behavior is whether you can tell the two apart in an unboosted frame. If you look at a string falling into a black hole, there is Susskind's stretching and winding, as the string relaxes on the horizon. If you probe a boosted string, it looks stretched and generic. | |
| Nov 4, 2011 at 11:45 | comment | added | Luboš Motl | Well, @Ron, it's surely possible to distinguish them in principle, even though it may be hard. The simplest way is when you accelerate a whole laboratory to nearly the same velocity as the object so the relative momentum becomes manageable, and then you use e.g. the LHC calorimeters etc. to figure out whether it was a photon or something else. | |
| Nov 3, 2011 at 17:08 | comment | added | Ron Maimon | @Lubos: The indistinguishability comes from collision experiments--- the photon will produce a black hole in any collision. As for the speed issue, if you have a Planck mass black hole with total momentum equal to 400,000 times the mass of the sun, how do you determine that it's not massless exactly? Is it possible in principle? | |
| Nov 3, 2011 at 10:10 | comment | added | Luboš Motl | Dear @BCS, it is completely irrelevant how a photon was generated. Whatever the circumstances of the birth were, you may always boost the whole arrangement and get a photon of a shorter wavelength than before. There is no lower bound on the allowed wavelength. If you are uncertain what is allowed with "large energy densities", "short wavelengths" etc. and if it looks like a conflict of many infinities, try to find a reference frame in which the situation doesn't look too extreme. That's what relativity allows you to do. You will see that a single photon is never "less or more extreme". | |
| Nov 3, 2011 at 10:07 | comment | added | Luboš Motl | Dear @Ron, I agree that the momentum conservation prohibits the emission of just one photon from a black hole; otherwise, nope. A photon is always distinguishable from a black hole. Its rest mass is zero; the rest mass of any black hole is always greater than the Planck mass (times a numerical constant of order one). | |
| Nov 1, 2011 at 23:01 | comment | added | BCS | I specifically left unspecified how the photon is generated and even what matter source is used to power the experiment. The only things I specified is the total amount of energy dumped into it. | |
| Nov 1, 2011 at 19:07 | comment | added | Ron Maimon | @BCS: you can't emit just one photon from a black hole, but if a supermassive black hole would decay into two photons going in opposite directions, both photons would be indistinguishable from highly boosted supermassive black holes themselves, unless you chase them with impossible speed. All boosted matter is eventually indistinguishable from a boosted black hole experimentally for stationary observers. | |
| Nov 1, 2011 at 15:34 | comment | added | BCS | Note that with regards to point 1, The energy density I'm referring to is not that cause by relativistic speeds (if a photon had such, it would be infinitely heavy) but rather just the energy of the photon it's self. For example, what would happen if a single photon was emitted using the total matter/energy conversion of an entire super massive black hole (or an equivalent mass)? | |
| Oct 31, 2011 at 6:34 | history | answered | Luboš Motl | CC BY-SA 3.0 |