Very distant objects

[DaveGarland]

Ok. Who can explain this to me so I can understand it? Objects that are observed, say 13 billion light years away are seen as they were 13 billion years ago as, of course, it takes light that long to travel that distance. BUT! 13 billion years ago, the universe was only a fraction of it's present size. So how are they seen to be that far away???

How? How? HOW???

[JamesF]

Oddly enough I'm trying to get my head around something that I think is related, but I'm not entirely sure and I don't know if it answers your question

If we accept that the universe is expanding, I'm heading towards the understanding that objects aren't actually moving away from each other relative to their surrounding space, but that in fact the "space" between them is "stretching". Perhaps as if more "space"/"space-time" is coming into existence between them.

In the context of your question, what that might mean is that whilst two objects (or, in our case, objects-to-be) might initially have been very close, the emitted light has still had to cover the space between us as it got "bigger" and to do so has taken 13m years. Perhaps in the first fraction of a millisecond the light travelled a significant proportion of the distance between us, but as the amount of space increases, it takes longer and longer to cover similar proportions of the remaining distance. Perhaps that also accounts for the fact that the further away objects are, the greater their red-shift.

It's seriously counter-intuitive stuff though, and I may have everything completely wrong.

James

[Theinvoker]

Measuring distances (hence travel time) in space is at best a tricky business. I guess the best way of thinking about it is we have been "running away" from the light for the last 13 billion years and now it has caught us up.

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