Baffled by Astronomy
 

Astronomers have discovered an enormous concentration of quasars and galaxies clustered across more than 600 million light years. It may be the largest structure in the observable universe, said Gerard Williger, a National Optical Astronomy Observatories researcher now working at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

My question is - if these things are 600 million light years away/across, and signals take that time to get to Earth – how do they know it’s still there?

They don't.

The galaxies in question may have exploded 599,999,999 years ago. We'll have to wait until next year to find out!

However we can hypothesise that galaxies don't usually explode just like that (stars sometimes do however), so it will most likely still be there.

[This message has been edited by ALKIN Hold (edited 09 January 2001).]

Alkin, loved the reply and had a good chuckle but this thread doesn't belong in this forum so off to Non Air Transport Issues with you.


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Capt PPRuNe
aka Danny Fyne
The Professional Pilots RUmour NEtwork

Apart from the fact that I got a bit keen with the '9' key - oh well, corrected now :)

agreed they do not know with certainty that the object in question is "still there". They do however conduct educated hypothesis etc based on star/galaxy information etc and they do know how these things work and when they are supposed to blow up etc. Even the voyager space probe may not exist anymore- it's signals take 20-30 hours??? to reach earth.