Lightspeed as a universal 'time capsule'

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Postby AndrewB » 08/09/04, 5:26 pm

"A galaxy 12 billion light years away is seen as it existed 12 billion years ago. Now look at your hand at arm's length." -Bob's sig

Explain this to me if I'm completely off the mark, but I have a problem w/ the concept that super far away stars represent images of long ago. My logic is this:

If the speed of light is finite and constant in a vaccuum, would it not be true that the (anti)matter expelled from the big bang would have had to initially travel MANY times faster than the speed of light, and then decelerated relitavely rapidly? The only way that light from a 12 billion-year old star's light could represent how it was 12 bill. years ago would be that: A) it was created MUCH later than some signifcant deceleration began to occur, and/or that B) all matter in the universe decelerates @ the exact same rate. Considering that varous celestial bodies have formed, creating varigated gravitational areas, etc. I highly doubt that. Also, the (anti)matter at the edge of the primordial "infinately dense sphere" (if it really did exist) would expand before the core did, giving it a head start.

Hmm... Since i've written all that, I think I'm beginning to piece things together. But now the question is, considering all the variables, how can we be certain that a "light-year" to us in this space-time environment is the same as other points in space-time? More simply, how do we know that light travels at a finite, consistent rate everywhere in the universe? If not, then guaging the age of celestial bodies such as stars via their energy radiation could be very unreliable indeed.
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Postby bob » 08/10/04, 4:04 am

<!-- BBCode Quote Start --><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class=postbody>Quote:</font><HR width=100% color=#333333 SIZE=1></TD></TR><TR><TD><FONT class=quote><BLOCKQUOTE>More simply, how do we know that light travels at a finite, consistent rate everywhere in the universe?</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR width=100% color=#333333 SIZE=1></TD></TR></TABLE><!-- BBCode Quote End -->

Tons of experimental evidence, which we extropolate to apply universally (since there's no reason to consider it as an abberation from the norm). In short, inductive logic.
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Postby Gerry » 08/10/04, 5:26 am

<!-- BBCode Quote Start --><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class=postbody>Quote:</font><HR width=100% color=#333333 SIZE=1></TD></TR><TR><TD><FONT class=quote><BLOCKQUOTE>
On 2004-08-10 01:26, AndrewB wrote:
More simply, how do we know that light travels at a finite, consistent rate everywhere in the universe?</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR width=100% color=#333333 SIZE=1></TD></TR></TABLE><!-- BBCode Quote End --> Well until somebody proves it wrong, that's what their sticking with. It's the same with everything. At one time we knew the Earth was flat. :-)
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Postby Don » 08/12/04, 12:57 am

I seem to recall from science lessons long ago the term; "redshift" has a lot to do with how they calculate these things.
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Postby SOD » 08/12/04, 9:55 am

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Postby SOD » 08/12/04, 10:06 am

According to AE and others this is true but light is the transmission line the carrier of the image. I think you would end up seeing distorted images. What you are trying to resolve is phase shift caused by external anomalies for the image to be resolute you may need a wave guide. TV transmitters use them. That would be one long ass wave guide!
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Postby bob » 08/12/04, 11:46 am

<!-- BBCode Quote Start --><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class=postbody>Quote:</font><HR width=100% color=#333333 SIZE=1></TD></TR><TR><TD><FONT class=quote><BLOCKQUOTE>Explain this to me if I'm completely off the mark, but I have a problem w/ the concept that super far away stars represent images of long ago. </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR width=100% color=#333333 SIZE=1></TD></TR></TABLE><!-- BBCode Quote End -->

Easy to explain, using sound. Ever see a stroke of lightning, then a few seconds later hear the thunder? They were both emitted at the same time. But because the speed of sound is slower (12 miles a minute, vs. 186000 miles per second), you don't hear it "immediately." It takes a while for the wave to arrive. In short, you're hearing a sound created a few seconds before (and yes, with the distortion Sod mentions, created as the shock wave travels, encountering obstacles which distort it).
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Postby bob » 08/14/04, 1:01 pm

We've got another set of posts about the time thing from a while back, but I can't find it.....
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Postby SOD » 08/14/04, 6:34 pm

I would like to see data on the shape of the wave.
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