October 28, 2009
Old Bang

Astronomers are reporting the discovery of the oldest celestial object found to-date. The massive interstellar explosion measures out at a record 13 billion light years away, when the universe was only about 5 percent of its current age. I think that means that, less than 600 million years after the big bang, the universe was already 13 billion light years across?

Posted by scott at October 28, 2009 07:19 PM

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No, 600 million years after the Big Bang, the (observable) universe was 600 million light years across, just like you'd expect.

What you have to realize is that after the Big Bang, space itself expanded, and continues to expand. Light travels through space at the speed of light, but the space between us and this object has been expanding at almost the speed of light. It's like trying to catch up to the leader in a race. If you're just a little faster than the leader, it can take a long time to catch him. In this case, 13 billion years.

The reason that light can't escape from a black hole is that the massive gravity of the black hole sucks in space faster than the speed of light. Light, traveling through space at only the speed of light, just gets sucked in slower. It's like trying to paddle a canoe up Niagara Falls.

In relativity, nothing can travel faster than light. But space, in this definition, is not a thing: it's nothing. It can expand or contract faster than light.

Posted by: Bob Hawkins on October 29, 2009 09:30 PM

Well, now, except for that whole inflation thing. Which, as I understand it (as a toddler understands a turbine), was when the universe blew out all to hell in fractions of a second.

Regardless, it all makes my head as'plode

Posted by: scott on October 29, 2009 09:49 PM

Bob - dammit. I came in to work all geared up (well, as geared up as one can get on a normal Friday after a weekend of traveling) to get things done and then I read your post. My head now hurts from attempting to contemplate what you've written.

I'll have my boss send you an invoice for the lost productivity.

Posted by: Ron ap Rhys on October 30, 2009 08:31 AM

Not entirely true. Matter and energy cannot travel faster than light, it's true, as it would take an infinite amount of energy to accelerate either to that point. But the edge of a wave propogation has been modeled (and experimentally confirmed) to be able to move faster than the speed of light, in certain space-time conditions.

It's kind of like the question of a frictionless tube stuffed with identical snooker balls, long enough to wrap around the world three or four times. You stick another snooker ball in one end, and a snooker ball pops out the other instantly... apparently faster than light itself can move. No, the snooker ball didn't actually move faster than the speed of light, but the wave propogation through the unique material (a frictionless tube full of identical snooker balls) did.

This way, information can in fact move faster than light, even though light itself cannot. They've actually done something similar with supercooled and photon-charged composites (replace "frictionless tube" with "superconductor," and "snooker balls" with "photons").

Posted by: Tatterdemalian on October 30, 2009 01:41 PM
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