Monday, May 18, 2009

my thoughts about the stars

we are actualy seeing the light of stars which are some which were emitted some million years ago so its kind of that we are travelling back in time or the light is travellin back in time 
is this logically correct???????????????????????????

neither we are travelling nor light is travelling back in time.
we are getting light from stars that are 3000 million light years away from us.
that means we are watching their past. how & where they were 3000 million years back.
How may refer to their composition.
It is because light can only inform us about their existence. One can say light is conveying the information about them to us after 3000 million years as nothing can travel faster than light.

Please dont get confused.

if a star is very far away from us and it dies, would we still be able to see it even if its not there?

Yes. Looking up at the stars is actually looking back in time. Many of the stars that we see no longer exist but we are just observing the light that left their surface a millennium ago.
The speed of light is very high but not infinite and hence it takes some time for light to travel. Even the light from the sun takes around 8 minutes to hit the Earth so assuming that the Sun vanishes at this very instant, we wouldnt know anything about it till 8 minutes and for those 8 minutes the sun would still appear to be there.

yes exactly. but that is not the only phenomenon associated with it.
for example, as light bends in presence of a massive body, the light from that star may be reaching us after bending from a massive intermediate object.
So one can not be even sure of whether it is exactly on the straight line in which the light is coming.

Bending of light happens but it is not relevant to the discussion of the topic at hand. Irrespective of where the source may be, the "when" factor is due to the finite speed of light alone.
Gravitational lensing and gravitational opto-multiplication definitely happen but at large distances, the amount of deviation caused by stars is undetectable and only galactic clusters can be observed to exhibit this phenomena distinctly.

In some case it may also happen that the star would already have died before its light reaches us. Provided that the star is far away from us or it may be of bigger size or both. As we know bigger stars will have smaller life. 

Now in this case the light emitted by that star throughout its life would then reach us.
We will see that star which is already died. 

Please correct if I am wrong.

Thats correct. Bigger stars however do not burn out faster than smaller ones. The final fate of a star depends on the mass it contains but there are stars which are 100s of times greater than our sun and will also out live it by many thousand years. They will end up as supernovae however.

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