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Space Time

Posted: Mon Apr 07, 2014 7:43 pm
by Ruby
Can someone please answer this? If by looking at distant galaxies etc. back in time, about 13mil. light years is about as far as we can go. Now my understanding is that what we see is the light from that object as it was 13 mil. light years ago hence I understand that determines the age of the observable universe. Does this mean that that object is where we see it now as it was 13 mil light years ago, then how long did it take that object to reach that point from the time of the big bang? If the universe expands or expanded at the speed of light then does that mean it then took 13 mil. light years for that object to reach that point and thus the universe is then 26 mil. light years old? Sh..I`m now so confused!

Re: Space Time

Posted: Tue Apr 08, 2014 12:17 pm
by brian livesey
The universe is said to be some 18 billion years old, much further back than 26 million years.

Re: Space Time

Posted: Sun May 11, 2014 8:14 pm
by M54
Not easy to explain and really I am not going to try.
I would forget and relation between distance and time. That was true until Hubble found everything was moving away from us then they discovered that this movement was not the objects but the space-time that wwas expanding.
It has taken the light 13 million years to get to us, that is the time aspect.
The distance of it was I would say less.

The problem is that the space between us and it is expanding, so the light may have started out when the object was say 10 million light years distant, but in that 10 million years space-time has expanded enough to "add" another 3 million years travelling time.

It is not even required that the object actually be moving. Just the bit of space time that the object on "sat on" will be moving away from us. An example (simplified) of this is put a suit case on a rubber walkway at an airport, but you do not step on it. You are not moving, the case cannot move itself but it moves away from you. So 2 stationary objects that are moving apart.

There will be objects greater then the 13.4 billion (or whatever) lightyears distant from us. Space time is not limited to moving faster then light, just anything in space-time is limited to the speed of light.