Tuesday, July 5, 2011

Too Big for One Post: part 2

A couple of decades ago I was poring through that mainstay of American coffee tables, National Geographic, and found an article on the universe.

It wasn't as big an article as you might think.  It didn't even take up the whole magazine.  That part didn't cross my mind until much later, but let's stay focused.  It did include a map.  I can't recall if it was an insert, which by itself is one of the most awesome features of NG.  With one magazine subscription alone, you could slowly paper your bedroom with posters of stars, maps of distant countries, arrays of sharks and whales.  It was a source of decor, albeit a somewhat dry and highbrow kind of decor.

Anyway.  The map I found wasn't of anything you could walk to.  It was of the universe.  Again I say, I'm surprised they were able to find a piece of paper big enough.  The map featured an image of the local star cluster, shrunk to fit into a scale of the galaxy, shrunk to fit into a scale of the local cluster of galaxies, shrunk to fit into a scale of a broad array of galaxies, shrunk to fit into a scale of the known universe.

The known universe surprised me and being a much, much younger and rather more naive person then than I am now, I marveled at how the known universe seemed to fit into a fairly well-defined cylinder.  That cylinder was a mere 28 billion light-years across.  If you were to write that out longhand, that would be "17" followed by 22 zeroes.  If you could hop into your Volvo and start driving, it would take you 334 quadrillion years to drive from one edge to the other.

I say Volvo because you're going to want something both sturdy and safe.

Anway!  Twenty-eight billion light-years, really?  That's all?  At the time I couldn't understand how scientists could be so sure.  It didn't make sense.  Now I finally get it: light speed is the limiting factor.  We only know about 28 billion light years worth because we've only had this universe for about 14 billion years.  Light goes this way for 14 billion years, and that way for 14 billion years, and we only see what's up to 14 billion light years away from us because anything farther away than that, the light hasn't reached us yet.  The known universe is so sharply bounded because any farther away than that and the light simply doesn't exist for us, not yet.

Imagine peering into a large optical telescope, observing the far distant reaches of space, and suddenly seeing a glimmer where none was before.  The light of a star has made its debut for us here on earth, a star no one ever suspected.  That would be quite something to experience.

The actual experience would be much drier than that. Hardly any heavy-duty astronomy takes place with people looking through eyepieces anymore.  The telescopes are monitored by optical recording systems that don't blink, so no awakening star will be missed.  It might be missed of course, the recordings have to be examined by humans so there's plenty of room for error, but any light coming from the edge of the universe is going to be awfully faint.  The naked eye combined with the world's most powerful optical telescope simply can't see anything that dim.

So the point here is that there may well be a lot more to the universe than what we can see simply because it hasn't been seen yet.  And the likelihood of recognizable humans being around to see anything new isn't high in my opinion, all of humanity sits crouched on one lonely rock dangerously close to a large asteroid belt, a rock that itself hasn't experienced a large meteor strike in quite some time.  Anything could happen.  Apophis could happen.

Next time: wondering about time.

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