astronomy concept

[nohorn]

I was wondering.....if we look to the night sky the light from the stars we see today, those stars aren't really existing anymore as the time it took for the light to travel here to our eyes, they have used their life span. They went whereever burned outstars go (black hole, etc.,) Now since any universe is dynamic, other stars should have taken their place.

However, those stars that have taken their place, by the time their light reaches out solar system, our sun will be burned out.

I know what I said was terribly simplified, was their anything wrong with the logic?

[VHG]

>>>>those stars aren't really existing anymore

Yes the light does take a long time to reach us ("light years"),

But start dont disappear and reappear that quickly, so the stars will almost certainly still be there.

Our sun (which is a star) has been there billions of years, and will still be there in billions of years.

[VHG]

>>>But start dont

Whoops, should be

But stars dont......

[jake-the-peg]

Not with the logic but with the scale

Pretty much all of the stars you can see are inr galaxy and that is something like 100,000 light years across

However most stars will live for many billions of years - the sun is about 4 Billion and will probably live another 4

So a few of he stars you are looking at now are almost certainly gone - stars like betelgeuse or eta carinae are large and very unstable so will probably be gone by now.

[heathfield]

I'd love to see Betelgeuse turn nova. Could happen any time now, it's said. Or maybe any time in the next couple of million years - no-one's sure.

[excelsior-1]

when i told my god-daughter one night, that she was essentially 'looking back through time' when stargazing - she was very amazed.

[Johnysid]

Here is a thought, the universe is older than most stars. It expands at the speed of light. This means that most of the energy from a star spends most of its time distributed in space rather than in the star itself...

[modeller]

If as is claimed the universe is expanding faster than the speed of light
then a time will come when the universe will be totally black although it is still there. In fact we may have already passed that point and most of the galaxies are already blacked out despite shining as bright as ever.

[modeller]

cont .
On the other hand what is happening within our own galaxy ? Is our galaxy the Milky Way expanding ? If it's not, then we will always see our stars in the same way as we see the sun i.e until they burn out.

[jake-the-peg]

//the universe is older than most stars.//

No it's older than all stars

// It expands at the speed of light.//

Not now but it probably has in the past

//This means that most of the energy from a star spends most of its time distributed in space rather than in the star itself...//

Despite the above errors the conclusion is correct it is a solution to Olber's paradox or "Why is the sky black at night"

[Johnysid]

JTP, your corrections are valid in the context of my brief "ponder". But the situation is too complex for brevity. The rate of expansion relative to the point of the big bang depends on the cosmological model - closed or open. But even at the edge of the closed model light will appear to go at light speed and appear to be able to travel in the opposite direction to the centre. A few collapsed stars may be only slightly older than the matter of the universe and composed of matter that dates from the beginning of elemental matter (barring a bit of neutron turnover).

[jake-the-peg]

Slightly older is a relative concept here isn't it - as I recall the first stars are formed about a million years or so after the big bang.

I am very confused by your expression "relative to the point of the big bang"

What do you mean

The big bang happened everywhere

[nohorn]

Thank you for all replying, it just boggles the mind. And the answers were all so interesting.

[jomifl]

Excelsior, everything that we see near or far has already happened so we are always looking back in time, we have no choice.

[Johnysid]

JTP "The Big Bang happened everywhere". Yes, when it happened but a spatio-temporal expansion can have a centre, though equally it may not.... - see: http://math.ucr.edu/h...tivity/GR/centre.html