Timeline for Do gravitational lenses act as prisms?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 16, 2021 at 19:26 | comment | added | Derek Seabrooke | It seems to me that even a microscopic difference of angle between light of different colors would become significant after lightyears of travel? | |
| Feb 15, 2021 at 18:03 | comment | added | QCD_IS_GOOD | I wonder what the order of magnitude estimate for the dispersion would be? I suppose that the relevant scales would be $\Delta E$ the energy difference between two test photons, maybe the Ricci scalar, and a length $L$ that the photons travel over; perhaps the deviation in length between the two photons goes something like $\delta L \sim L R \Delta E \frac{8 \pi G}{c^4}$? I probably got my units wrong, but a derivation of a relation like this would be interesting to see | |
| Sep 18, 2020 at 14:18 | comment | added | TimRias | Agreed, the effect should be absolutely tiny. However, there is an important distinction between "the effect should not exist at all in principle" vs "the effect exist in principle but is practically almost zero". | |
| Sep 18, 2020 at 13:36 | history | edited | Michael Seifert | CC BY-SA 4.0 |
added 609 characters in body
|
| Sep 18, 2020 at 13:32 | comment | added | Michael Seifert | @mmeent: That's true, but it's true in the same sense that a hammer takes a little less time to fall to the ground than a feather does when released from rest, because the hammer pulls the Earth upwards to it harder than the feather does. It's hard for me to imagine that such effects would ever be practically measurable; the test particle approximation is an excellent approximation for a lot gravitational physics problems, including this one. (That said, edited to reflect this.) | |
| Sep 18, 2020 at 13:22 | comment | added | TimRias | The geodesic equation however, is only valid in the test particle limit, i.e. when the gravitational field of the particle itself can be ignored. In principle there could (and should) be energy dependent correction to the scattering angle. | |
| Sep 18, 2020 at 13:12 | history | answered | Michael Seifert | CC BY-SA 4.0 |