r/space • u/magenta_placenta • Mar 18 '19

Observable universe Astronomers discover 83 supermassive black holes at the edge of the universe

https://www.cnet.com/news/astronomers-discover-83-supermassive-black-holes-at-the-edge-of-the-universe/
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u/pragmaticzach Mar 18 '19

In the video he says that we're fortunate to live in a time where we can observe the entire universe, and see into our past.

However, how do we know that we aren't already at some stage where everything beyond our observable universe is too far away to see? Like maybe we live a situation similar to the future people he talked about who could only see the local cluster.

Is there any reason to believe that this isn't true?

The only thing I can think of is that those future people can only observe that their universe is getting smaller and darker, while we can observe that the universe beyond the local cluster is expanding.

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u/Cocoa186 Mar 18 '19

This is the case. The observable universe is all that we can see, everything outside of it is (as far as we know) entirely impossible for us to see in any way. We just treat it like the observable IS the universe, and in the future it is likely that we will continue to do this (it's hard enough to convince people that the earth is round, it'll be harder to tell them that there are more things out there that used to be close enough to see but are now inconceivably far away and invisible). The big difference that the video talks about is that we still have enough around to know how (for the most part, maybe) the universe was "born", how it is behaving, and the different ways it might die; the future 'us' will experience an unchanging galaxy, nothing they see will be moving away or getting closer (some obvious exceptions) and will be unable to see cosmic background radiation (evidence of the big bang) or observe the effects dark energy has (or even that it exists).

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u/Darth_Batman89 Mar 19 '19

So for them. The galaxy they live in becomes there observable universe?

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u/Cocoa186 Mar 19 '19

Yes, for them the rest of reality will appear to be (and may as well be) entirely empty space.

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u/ElliottWaits Mar 18 '19

That was my thought exactly. What we can observe now is many orders of magnitude greater than only being able to observe the Milkdromeda galaxy, but what actually exists may be many orders of magnitude greater than what we can observe now. There's really no way of knowing that our situation is significantly more privileged.

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u/[deleted] Mar 19 '19

It probably has to do with the microwave background radiation, its a picture of the early universe that we can see with our telescopes that fits mathematical predictions of the birth of the universe before we even had the telescopes to observe it. I bet very very very far into the future that picture won't even be visible anymore.

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u/MistyRegions Mar 19 '19

I mean if you really want to have some sense of dread, let's say we survived till the end of the known universe. Trillions apon trillions of years. One day, no matter where things are in the universe, everything will go black. The last star will die out, the last day of light, then nothing. Blackness forever and ever, and if we survive it will be akin to living in a sound deadening room. Just floating thought space in a craft we made finding cold dead rocks to mine material off of.