Following on from the question below

[Bazile]

Oh geez ( in an american accent - similiar to that of that sherrif , on holiday in that james bond film ) there you go again muxing my brain up when it comes to this subject .

Am I correct in saying that the reason why hubble can look back in time to see events that occurred billions of years ago is because -

The universe started from the size of the palm of your hand and expanded ( like a baloon being blown up ) at a rate far out stripping that of the speed of light . The earth is at a point on that baloon , where the light from those earlier events ( i.e stars that have formed etc ) are just reaching us

[gen2]

Yes, Some of that light is only just catching up with us.

[Buenchico]

A 100% accurate, and very straightforward, answer from Gen2.

I'll simply add that it's not a case of Hubble being able to look back in time, it's simply that Hubble is restricted to looking back in time. Even when you simply look at the night sky (with the naked eye) some of the stars you see no longer exist (and haven't done so for millions of years). It's just that the light from them (when they did exist) has finally arrived here.

Chris

[sidkid]

Does that then mean that we cannot guarantee that ANY of the stars we can see actually still exist - I believe even our nearest star Proxima Centauri is over four light years away so could have exploded/died during the last four years and we wouldn't know......

[Clanad]

As our youngest teenager would say,skidkid... Exactomundo!...

[Bazile]

- Could some of these stars ( which have died already) have been in existence for longer than the earth has being in existence , and the light from when they were alive is only just reaching us ?

- Is the reason that we cannot quite look back to the big bang - because the light from the event has already passed us by ?

[jake-the-peg]

Yes, although many of the stars that we see ene in our own galaxy have been there longer than the Earth has been around. The "population II" stars in globular clusters are particularly anciennt and consist of the first stars that formed after the big bang.

I'll just throw one more stick in here. The expansion of the universe meRecent research shows that the expansion of the universe is accelerating. This means that the universe most likely has an event horizon. Stars can exist so far away and moving so fast that light can never reach us from them , it's possible that stars are crossing over this invisible barrier all the time. (as you describe in your second paragraph)

Just remeber though that the big bang happened everywhere but we need to look back a long way to see light that was created then.

It's a bit like archeology. The Romans were where you stand today but we have to dig down to get to their preserved remains. Light from a long way off is the fossilised remnants of the early Universe