On 2010-07-05, OldGringo38 <> wrote:
> If light travels at 5,865,696,000,000 miles a year, do we have any way
> of knowing if light we see in outer space is still out there?
> http://www.csmonitor.com/Science/Coo...hole-slingshot
> Were talking about 80 Bullion light years away here.
We don't see light in outer space; we see light at the back of our eyes.
Any light that is 'here' isn't anywhere else. So your question as
expressed is meaningless.
If you mean "how can we know whether or not a star whose light gets here
today is still there today?" the answer is "we can't". As far as we know
at present, information cannot travel faster than light. What we can be
certain of (for all practical purposes) is that the light started out from
such-and-such a place at such-and-such a time. That's why astronomers can
claim to be able to 'see' almost all the way back to the 'Big Bang', which
must have happened a very very long time ago (if it happened).
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-- Whiskers
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