Some of the stars you see with the naked eye may no longer exist, but chances are a little slim until you're at big telescope distances. I read somewhere that maybe one in a million stars we can see just in our own galaxy may actually already be gone.
A Black As from Antoninus Pius: Antoninus Pius As Bronze, 26 mm, 11.72 gm, Catalog: RIC 900a Cohen 729 Struck: AD 152-153 Rome Obverse: Laureate head right ANTONINVS AVG PIVS PP TRP XV Reverse: Salus standing left, extending bowl to serpent rising from altar SALVS AVG COS IIII, Large S-C
Mind boggling! But if we were to see the same galaxies through space at different periods of time, wouldn't we be seeing them on a continuum , and wouldn't they then appear as linear streaks of light rather than discrete bodies?
That's sort of what I think - if we did see multiple views of a specific galaxy at various points in its life all at once (and I don't think we can), the images would be like overlays of each other, with maybe some slight variation in their position due to the universe expanding....and that would make for a very blurry image, I think, because I don't think their position changes all that much from our point of observation. To show up as linear streaks of light, I think we would need a lot more time between images, and a lot more images, before we could see that kind of "movement" of something so far away.
Actually, what we are able to see is only the light which emanates from the galaxy at a particular point in time. If a galaxy is one billion light years from us, we can see only its image of light that left it at a specific time one billion years ago. If there happens to be an inhabited planet one billion light years farther away from us (2 billion light years from that galaxy), they will see what we see today in one billion years. Should the entire galaxy become extinguished and we would cease to see anything at all, those on that other planet would continue to see the galaxy for an additional billion years. Thus , we would never see multiple images of the same galaxy in different times of its existence. The only exception to this that I can think of could possibly be worm holes in which space-time may be actually folded upon itself.
SYRACUSE - Black AE Octopus SYRACUSE 2nd Democr 466-405 BCE Æ Tetras 2.7g 15mm c.425 BCE Arethusa dolphins - Octopus 3 pellets SNG ANS 376 Calciati II.21.1
Here's the full moon and Mars from last night. Mars will be closer tonight. No more black holes but here is a new black one! Ionia, Smyrna. Æ24 Pseudo-autonomous. Time of Gordian III, AD 238-244(?). Æ 24mm. Third Neokorate. Draped bust of the Senate right / Tyche standing left, holding rudder and cornucopia, within tetrastyle temple with annulet in pediment.
Hole RImp Spain Lepida-Clesa Lepidus 44-36BCE C Balbus L Porcius Colonia Victrix Ivlia Lepida Victory - Bull holed RPI 262 plate 19
Gravitational lensing. If there's a massive object between us and the distant galaxy, it bends the light coming from that galaxy, and we see the distant galaxy "smeared" along an arc. If things are positioned correctly, we see multiple images of the distant galaxy. In principle, if light bent along one path has to travel a longer distance than light bent along another path, we'd see two images of the distant galaxy from two different times. I don't know whether there are any gravitational lenses arranged in such a way as to make this happen. You'd almost need a convenient supernova in the distant galaxy to check for it, and even then it might be difficult.
This tetradrachm, an imitation of Athens, I believe, is about as dark a coin as I have. 17.1 grams And, she comes with a musical accompaniment:
As it turns out, actual factual astronomers are on the case, apparently: https://iopscience.iop.org/article/10.3847/1538-4357/aaa975 Even the abstract is a heavy lift for me, but it seems to indicate 1-2 day delays on one of the sources they studied. In other words, light that went around the lens one way took a day or two longer than light that went the other way.