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## My observable universe

I've been stretching the ol' grey matter recently tackling- how the universe is expanding in all directions, that wherever you are in the universe it will appear to be expanding in all directions etc etc
I understand that in whichever direction we look the universe appears to be homogeneous, and that my perceivable universe is limited by the amount of it that I can actually observe - that the further I look the longer I look back in time and the farthest viewable points away are those whose light has only just reached me here on Earth.
Does that mean then that if I were somehow able to look beyond the furthest images I can see that I would see a black sky where lights would blink on over time as the light from those objects reached me?
Also, if the universe if expanding faster than the speed of light, meaning I will never see the farthest objects as they are travelling away from me quicker than the light can make it back to me to observe, will I eventually reach a point where I can see so far that I can see no more? Are there any guess-timates to this threshold (if indeed it exists)?

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• #### Gordon Barker10+

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Apr 6 2013: You can only look back so far in time - not back to the big bang because until the universe cooled below about 3000 K it was a plasma that is opaque to photons. That wall is the cosmic microwave background.
If you are really patient and are watching an area that has a lot of gas and dust collecting, you would be able to see a star "switch on". Reeeeaaalllllyyyy patient.
Its significantly easier to find one about to switch off with a nova or supernova in comparison.
If current theories are correct and space is expanding at an ever increasing rate then at some point objects will be moving away from us at greater than the speed of light and will be forever invisible to us.
Likely long before that the light from those receding objects will be red shifted so much that it will be impossible to see anyways. Eventually so far that it cannot penetrate the gas around our own galaxy and so will become invisible at that point.
Eventually all we will be able to see is our own milky way galaxy and maybe the Andromeda galaxy if it hasn't already whammed into us.
• #### Andy Eppy

• 0
Apr 7 2013: Hi Gordon
Thanks for your comment. I didn't think we would be able to see back to the big bang - although presumably if we look away/back far enough you would see the early universe, and in every direction you looked!
I cant seem to get my head around the fact that the farther away we look, the further back in time we see
The universe is bigger now than it was, and expanding all the time
So when we look away/back we are looking at an earlier smaller version of the universe?!
Perhaps you would need to see the universe from outside of it to gain this perspective?

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