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Old August 25th 05 posted to sci.astro,sci.physics
Ben Rudiak-Gould
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Posts: 1,116
Default Could the universe be older and bigger than we can see?

Yousuf Khan wrote:
If the universe is
expanding, and the further an object (e.g. a galaxy) is away from us,
the faster it is moving away from us. Are there parts of space so far
away from us that it's expanding away from us *faster* than the speed
of light?


You have to be careful of what you mean by "speed". It has units of distance
over time, but it's not the same as speed in special relativity. With that
caveat, the answer is yes.

Therefore the Cosmic Microwave Background Radiation isn't the cloak
that surrounds the secrets of the Big Bang, but just the curtain around
a part of the universe that is now out of contact with us.


The "speed" of the CMBR, in units of comoving distance over cosmological
time, is much larger than the speed of light. I think it's about 3.2c. This
means essentially nothing, since the speed of light has no special status
when talking about cosmological recession velocities.

-- Ben
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