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Tremongulous_Derf t1_irhccop wrote

Distant galaxies are moving relative to us, and they will also be in a different gravitational field, so the combined effects of special and general relativity will cause their clock to move a bit differently from ours. The difference will be fairly small but it exists.

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the_ben_obiwan OP t1_irhdqhe wrote

Thanks, seems to be the general consensus. I was just unsure if the great distance would exacerbated the effects, as in- if we watched the twin fly into the distance, they might appear to slow down, even though they moving at a constant speed because their clock would be slowing down, so their movement would also appear slower. I'm not really sure if that's how it works, its just interesting to think about

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he_who_floats_amogus t1_irhfd1g wrote

Great distance will greatly exacerbate the effects, because the entire universe is expanding. The reason why there's a limit to how far we can see is that there is an event horizon beyond which objects are moving away from us FTL. Relative velocity is proportional to distance.

We've confirmed this experimentally by observing distant cosmological events of known types. At a vast distance, we can observe events that literally function as a cosmological clocks, and can verify that they adhere to the expected time dilation. At a distance that results in relative velocity of 50% speed of light, you'll see events take 15% longer.

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Vahelius t1_irh9vxb wrote

Short answer is no. If there was a giant clock next to a galaxy we can observe clearly we'd see it tick normally. A difference in the speed of the clock would be observed if it began to travel close to the speed of light.

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the_ben_obiwan OP t1_irhd7gp wrote

Thanks for the reply. It was just something I was thinking about and unsure of the answer.

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space-ModTeam t1_irhv6um wrote

Hello u/the_ben_obiwan, your submission "Are we watching distant galaxies the same speed they would actually be experiencing?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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SeginusGhostGalaxy t1_irh9o0j wrote

I'd assume not. We'd be watching their past, from my understanding. Sorta like video lagging when the audio is fine? Light (therefore appearance of objects) reaches us later than it occurs, so the same logic may be applied to observing them depending on where we do it from and what devices we use.

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the_ben_obiwan OP t1_irhd3ne wrote

Yeah, I get that it takes an extremely long time for the light to reach us, I think I was just curious about the speed effecting the light, but I suppose it's not fast enough, or close enough to the speed of light to warp time enough to be noticeable.
Just a thought experiment I was playing out in my head but didn't have all the pieces to make it work. Thanks

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