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To: RightWhale
Someone above pointed out that the distant objects are receeding at faster than light speed and so can't be seen. This would put the observable limit of the universe at a particular distance from the observer

I recall that post, but I don't know ... it needs some clarification. I've read that the most distant objects are receding from us at about 70% of lightspeed, judging by their redshifts. (Perhaps those estimates are higher now, it's been a while since I read that.) But let's go with 70%, which means that if you look in the opposite direction and see another such object, those two objects are separating from one another at 140% of lightspeed. So the universe is expanding faster than c, but nothing seems to be receding from us at that speed. At least that's my understanding. I'm sure that if I've got it wrong -- as I often do -- a tactful correction will appear in due course.

162 posted on 04/25/2002 11:37:03 AM PDT by PatrickHenry

To: PatrickHenry
If the objects were moving then none would appear to be moving away at over lightspeed. But if space itself is expanding, the rules of relativity don't apply, even though the rule of redshift, for some reason, does. I probably have this pretty well confused. That's why Fred Hoyle is missed. He could explain things clearly, even if not accurately.
163 posted on 04/25/2002 11:41:56 AM PDT by RightWhale

To: PatrickHenry
So the universe is expanding faster than c, but nothing seems to be receding from us at that speed.

As it is to be expected. The distance at which the recessional velocity (caused by the expansion of space-time) is equal to "c" defines the boundary of an imaginary sphere around the point of observation, within which it is possible to observe objects. Objects beyond the boundary (if they exist?) would not be observeable to someone at the center of the sphere defined above, though they would still be part of the Universe, and would be observable from points located less than the previously defined boundary distance away from such objects.

I think "Physicist" referred to this distance as the "light horizon." It defines in a very practical way the limits of the observeable Universe, from a particular point of observation.

That was probably as clear as mud....

173 posted on 04/25/2002 1:12:38 PM PDT by longshadow

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