Cosmological Redshift and Expansion of Space

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by tvanflandern</i>
<br /><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />it should then also mean that if expanded light waves enter our solar system, they should be shrunk back to the original size, i.e. no redshift should actually be observed at all, contrary to evidence.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">That is definitely not true. Entering, leaving, or being in space that has never expanded has no effect on light. Residing in space that is expanding or shrinking for a very long time will cause the light to do likewise.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

That seems to be a bit of a hand-waving argument to me. What determines quantitatively whether the time is long enough or not?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
So if a lightwave travels through expanding space for billions of years, it gets expanded too (redshifted). If it then enters the solar system, it stays exactly as it was -- redshifted. -|Tom|-
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What about my example with the light having bounced around in the solar system for the last few billion years then? Would the light be redshifted now or not?

Thomas

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />What determines quantitatively whether the time is long enough or not?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">When light is propagating in expanding space, the lightwave is always continually expanding too, but at an extremely slow rate. That rate is the Hubble rate: ~ 60 km/s per megaparsec traveled. It takes light about 3 million years to travel one megaparsec. So it takes a very long time before we can detect any of the redshift.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">What about my example with the light having bounced around in the solar system for the last few billion years then? Would the light be redshifted now or not?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">That's a very good example. The Big Bangers would be forced to conclude that it would not be redshifted because it was never in expanding space. I'm certain that it would, in reality, be redshifted. But I cannot think of any observation we might yet do that could test for this. The effect is just too small. -|Tom|-

The Hubble constant is what exactly? I assume its acceleration but no one agrees with that, so what is it?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />The Hubble constant is what exactly? I assume its acceleration but no one agrees with that, so what is it?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">It is the reciprocal of the age of the universe, which is the rate at which the "universe expands" (in BB theory) or redshift accrues (in alternative theories). -|Tom|-

If the Hubble constant is in any way related to the age of the universe and the universe is infinite would it not be zero rather than ~1nm/s^2 or what ever scale you want like the standard scale?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />If the Hubble constant is in any way related to the age of the universe and the universe is infinite would it not be zero rather than ~1nm/s^2 or what ever scale you want like the standard scale?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The Hubble constant is unrelated to the age of the universe in alternative cosmologies, only in the Big Bang and expanding universe theories.

In theory-independent terms, the constant measures the rate at which cosmological redshift increases with distance, on average. -|Tom|-