I have been known to ponder the mysteries of the Big Bang on more than one occasion. A recent news story about new telescopes giving us the ability to look deep into the universe’s past raised the spectre of those questions in my heart again.
“If the universe is 13 billion years old, then how is it that we are able to see light from stars 13,000,000,000 light-years away?” I asked once upon a time.
Fraser Cain, co-host of Astronomy Cast, dropped by on the previous occasion to point me toward that site’s archive of very interesting podcasts about astronomy and physics.
The show took on the subject of Inflation (the theoretical rapid expansion of the universe in the first phase of its existence) in October 2007.
Fraser’s co-host, Dr. Pamela Gay, described the process thus:
It’s all a matter of what is doing the moving. The idea is relative to the grid of space, I cannot move faster than the speed of light. I personally can’t get anywhere near the speed of light, but even the fastest, smallest particles — the things that can get the closest to going the speed of light, can’t ever go faster than it, relative to space.
Now, if instead space itself grows, that’s something different. One way to think about it is: imagine you have a little kid who is walking away from school on his way home. The little kid’s capable of moving at, say, four sidewalk blocks every couple of seconds. He can’t go any faster than that. His family might see him moving toward the house at four sidewalk blocks a second — no big deal. He’s going his typical speed.
Imagine there’s some crazy sidewalk builder building a hill of sidewalk blocks between him and the school. As the school watches, they see not just his motion but also all these new sidewalk blocks getting built.
Imagine that crazy sidewalk block-building machine is building sidewalk blocks at a rate of 10 sidewalk blocks every couple of seconds. As those new blocks appear between the school and the child, you now have the expansion of the sidewalk and the rate the kid is moving, added together.
So the school might see the kid moving at 14 sidewalk blocks every couple of seconds. That kid is moving faster than he’s allowed to go — but he’s not. It’s the sidewalk that’s growing not the kid that’s moving relative to the sidewalk. So you get these weird additive velocities coming in that cause things to be perceived as moving faster than they’re allowed to move. They’re not — it’s space moving instead.
So I get the metaphor, I think. As the sidewalk inflates, new blocks appear on both sides of the kid. At the beginning of his journey he could have started out with only 10 blocks to cross, but by the end of his journey he had to cross maybe 500 blocks.
This all starts to sound very much like one of Zeno’s paradoxes, where no matter how much distance you cover, there remains yet more distance to go before you can cross some threshold. And yet, our experience with movement tells us that we can cover an entire distance despite the paradoxes (I’m really paraphrasing badly to save time).
The thing about Zeno’s paradoxes is that eventually something has to stop or run out. In the case of Inflation, it was Inflation that stopped. The universe is still expanding but Inflation is not really affecting us any more (I think).
We apparently detect the after-effects of Inflation in the red-shifted starlight that reaches Earth from every possible direction in the universe. And that is what leads me to scratch my head yet again.
If the universe was at its very earliest point of existence nothing more than a point of existence, then when everything expand outward from that point, did it all expand uniformly in all directions (or even approximately uniformly) or did it expand in some non-spheroidal way?
By our observations, Earth must be at the center of the universe because we cannot see more of the universe in any one direction than in other directions. Of course, our observations can be misleading. After all, suppose we can only see a spherical portion of the universe within some larger shape?
Maybe the universe looks something like a spiraling cone and what we detect of it is just one small part of a spiral.
This must be the kind of stuff that keeps physicists awake at night. I am sure there is an insane asylum somewhere that houses former academics who blubber madly and scrawl obscene equations on chalkboards, occasionally yelling out things like, “Reverse Ontology Destabilizes The Molecular Continuum — Cogito, Ergo non Sum!“
It makes no sense to me, either.
What would it do to our understanding of the Laws of Physics (within this universe) if we could in fact pinpoint the region where the expansion began? Scientists are constantly revising their ideas of what the universe consists of — perhaps there is a place where new matter is still streaming into existence, pushing the portion of the universe we see farther out into whatever it is (or isn’t) that the universe expands into.
Things were simpler back when I was only thinking about how to steal the planet Venus and make it your own and colonizing mars.