/sci/ - Science & Math » Thread #12254265

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Anonymous Tue 20 Oct 21:27:13 2020 No.12254265 View Reply Original Report

Quoted By: >>12254270 >>12254275 >>12254314

Since some galaxies are moving away from each other faster than the speed of light, shoudn't we see their distance increasing? Shouldn't some of them disappear from our observable universe?
Is red-shift the only proof we have of the expansion of the universe?
That sounds like bullshit to me

Anonymous

Anonymous Tue 20 Oct 2020 21:30:31 No.12254270 Report

Quoted By: >>12254401

>>12254265
>Shouldn't some of them disappear from our observable universe?
im pretty sure this has happened already. someone will post sauce if true i gotta go

Anonymous

Anonymous Tue 20 Oct 2020 21:31:48 No.12254275 Report

Quoted By:

>>12254265
Yes but it takes a loooooong time for it to happen retard

Anonymous

Anonymous Tue 20 Oct 2020 21:43:07 No.12254314 Report

Quoted By:

>>12254265
Any observer, including us, will only see movement away from them up to c. Therefore, if we pick a galaxy that is on the boundary of our observable universe, it will take it's diameter in light years as how many years it will take for it to cross the boundary and disappear.
Even if it was possible to resolve galaxies that distant, do you want to stare at a dot for 90,000 light years until the moment comes that it vanishes?

Anonymous

Anonymous Tue 20 Oct 2020 21:57:44 No.12254390 Report

Quoted By: >>12254401

>Since some galaxies are moving away from each other faster than the speed of light, shouldn't we see their distance increasing?
Yes but distance estimates aren't accurate enough to see it currently. One indirect way to see this is that objects should very slowly increase in redshift. This is caused by galaxies being pushed further away, which means there is more expanding space between us and them so redshift slowly increases. This effect is tiny though, the change in velocity is about half a centimetre per second per year. It's thought that the new generation of ground based telescopes may be able to see this effect with high redshift quasars, but it will take decades and requires an extremely stable instrument.

>Is red-shift the only proof we have of the expansion of the universe?
Nope, there is also the Cosmic Microwave Background, time dilation in supernovae and the Tolman surface brightness test.

Anonymous

Anonymous Tue 20 Oct 2020 22:00:43 No.12254401 Report

Quoted By:

>>12254270
>>12254390
> Shouldn't some of them disappear from our observable universe?
I forgot to answer this question.
No. Objects do not immediately disappear. Instead their redshift would increase until it was infinite and invisible.

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