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Looking back in time

r.t.swing

By r.t.swing
in The Astro Lounge

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r.t.swing

r.t.swing

Posted
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So I Hubble can take a picture of galaxy's 13billion years or so ago, and as our galaxy is much younger than than that. If some being in that old galaxy looked towards us what would they see? Nothing?:) As our light could not have traveled that distance.

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Jonobiwan

Jonobiwan

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Great I'll sleep easy

I'm glad you will!!!

Still find myself sat there some days thinking how mental it all is. There's places we're looking at that might not even be there now! We could be looking at the dawn of an alien race but is now extinct!

My head hurts now :)

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MontyUK

MontyUK

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There is a theory that the universe itself is expanding and that makes the speed we are separating from the outer reaches of the universe more than the speed of light. Even though nothing can travel faster than the speed of light. The image quoted is that of a balloon with pen marks drawn on it. No, I don't understand it either. But if it is the case, your friends on that old galaxy will never, ever see you wave.

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geordieskies

geordieskies

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There is a theory that the universe itself is expanding and that makes the speed we are separating from the outer reaches of the universe more than the speed of light. Even though nothing can travel faster than the speed of light. The image quoted is that of a balloon with pen marks drawn on it. No, I don't understand it either. But if it is the case, your friends on that old galaxy will never, ever see you wave.

if it was expanding at more than the speed of light we'd be unaware of its existence surely?

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MontyUK

MontyUK

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All galaxies are moving away from each other and the further apart they are, the faster they are separating, so at a point they are going faster than the speed of light. There is a boundary at the edges that we cannot see beyond and are unaware of. I've read a few books about it, but don't understand it in detail. The concept of space itself expanding is beyond me - as is the relationship between space and time and that they are related - as in 'before the big bang time did not exist'.

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iamjulian

iamjulian

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All galaxies are moving away from each other...

Only if you exclude their own independent motion. Andromeda and our galaxy are moving towards each other due to gravity. And our local group is being pulled at a stupid speed towards the nearest big galaxy cluster.

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Starblazer

Starblazer

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Ahhhhhhhh but if we can look back in time to 13 billion yrs ago, surely a being on a planet 13 billion LY away if they saw us.................wouldnt they be looking into the future?

No, they would have to wait 13billion LY for the light that is reflected off us to reach them. So they would be seeing what was going on 13 billion LY previous, only this isn't quite right as in that amount of time the universe will have expanded enough for it to take a little longer.

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LukeSkywatcher

LukeSkywatcher

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No, they would have to wait 13billion LY for the light that is reflected off us to reach them. So they would be seeing what was going on 13 billion LY previous, only this isn't quite right as in that amount of time the universe will have expanded enough for it to take a little longer.

Of course. Silly me. We were not here 13 billion years ago.

And of course if they are 13 billion LY away...........they are "old" in terms of the universe.. We (Earth) are only 4 billion yrs old so we are "young", so they also would be looking back in time, and not into the future.

Or something.

God i confuse myself (and others no doubt).

They looking out and seeing us would have to be about 17 billion LY away?.

But light has only reached 13 billion LY out thus far so they would have to wait another 4 billion yrs to see us and by that time we would also have traveled another 4 billion LY, so they would be 17 billion LY away from the point of the big bang and we would only be 8 billion LY away from the same point and this is where i am gonna leave it cuz my head hurts.

A friend of my nephew is studying theoretical physics in college. Just for fun (yes i am a sadist) i'd love to sit down with him over a few beers and just listen to him talking about it.

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r.t.swing

r.t.swing

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So, let me get this strait. We are closes to the point of the bang, than a galaxy 13 billion LY away. But when we look back in time (13 billion years only a short time since the Big bang we are actually looking the other way?

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John S

John S

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Yes I thing we are looking the other way but back in time to the beginning of the universe when the first proto stars formed exploded then the second generation stars formed and exploded then the sun formed about 5 billion years ago.

The milky way is about 13.2 billion years old so I think the Hubble deep field is the same as us then and we are the same as them now.

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wolfytom

wolfytom

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Only if you exclude their own independent motion. Andromeda and our galaxy are moving towards each other due to gravity.....

That's really good news.

By the middle of next week I should finally get a really good view of Andromeda through my 10x50s.

In colour.

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