If we look into a far off distance at an object travelling towards Earth, shouldn’t we be able to see both the light from the object at some time t plus the light at some later time (t + delta t)?
Let’s also assume that the object is traveling fast enough that it is discernable. This point might be moot, since I’m not sure if such a situation is possible. I know that Rayleigh’s criterion could give us a lower bound for how far the images of the object has to be, though I’m not sure how complicated it would be to throw redshift into the mix.
This seems like one of those “Whoa this feels see weird causally but it’s just a natural consequence of things we’ve observed thus has little repercussions as to what limitations physicists actually work around.” Actually, I could see perhaps long exposure photos (or the telescope equivalent, if it exists) could run into issues.
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Anything can be lensed into an einstein ring or einstein cross if you’ve got the right amount of mass between you and the object you’re observing.
Here is a picture of a supernova that is seen 4 times due to gravitational lensing by the foreground galaxy:
Not using special relativity (the object would have to travel faster than light in order to overtake the photons it’s already emitted)—but using general relativity, some of the photons could be bent and/or redshifted by a massive object en route (aka gravitational lensing).
Hmmmm, I guess that the premise was probably wrong then, since the object necessarily has to have mass and travel slower than c (I mean, a massless object would be constrained the by c anyways). The gravitational lensing is a good addition! I have no idea how I forgot, but I remember a hs physics class where this came up for new telescope images
Maybe I’m misunderstanding your description but I’m imagining an object moving in a straight line and pulsing information perpendicular to its path at a constant rate. If there’s even a slight curvature to the objects path the perpendicular lines will converge on the inside of the curve. Wherever 2 perpendicular lines intersect there’s a “potential” for information from 2 different positions to arrive at the same time, but that is not guaranteed. For this to be the case the information from position at T and T+∆T must reach the intersect point at the same time, this means that the objects postion at T+∆T itself must be closer to the point by the distance the information has to travel in ∆T along its own perpendicular path. Since the objects path is a curve (no infinite acceleration) and the closest distance between position at T and T+∆T would be a straight line. Because this line is the hypotenuse between the 2 positions and the information’s perpendicular position at T+∆T, it will always be longer than the distance the information has traveled in ∆T. My intuition tells me that the objects speed must therefore be faster then the speed of the information itself to essentially “cut the curve”.
I imagine something like that is possible with sound and going hypersonic but not with light, since their is no sonic boom equivalent.
I wonder if such a situation could occur if we were in some huge medium where Cherenkov radiation could occur
