Dialog from Annie Hall:
Doc: Why are you depressed, Alvy?
Mother: Tell the doctor … It’s something he read.
Doc: Something you read, heh?
Alvy: The universe is expanding.
Doc: The universe is expanding?
Alvy: Well, the universe is everything, and if it’s expanding, someday it will break apart and that would be the end of everything!
Mother(shouting): What is that your business? (to doctor) He stopped doing his homework.
Alvy: What’s the point?
Mother: What has the universe got to do with it? You’re here in Brooklyn! Brooklyn is not expanding!
I have seen this dialog used by physisists, in particular by Simon Singh in the Big Bang, stating that the fallacy here is that Brooklyn itself is not expanding, but rather, it’s like the universe was a bunch of galaxies and stuff painted on a balloon and the balloon is expanding.
I recommend The Big Bang as the number one current cosmology book for the masses. So I don’t want to say anything bad about it, and Simon Singh probably knows three orders of magnitude more than I do about the expansion of the universe.
But I’m pretty sure Brooklyn is expanding.
The reason I think this is because we can see (and by we, I mean people with enormous telescopes) stars that first emitted light a very long time ago but that are at present a Euclidian distance so great that this light could not have traversed that distance because of the limit of speed for anything in this universe.
It’s like you get the email from Netflix saying they just sent you your DVD and a few hours later it is in your mailbox. That is impossible.
The only reason that we can see this light is because Brooklyn, and everything else, has actually expanded. So the first part of the trip from that distant star to us was over a shorter distance than it seems by current observations, the next part still shorter but less so, and so on.
It’s like the Netflix Factory was originally next door to your house, and as the guy from Netflix started towards your house after sending the email, the distance got longer, but since he had a head start he still gets to your mailbox a preternaturally short time after the email was sent. His trip back to the factory will be problematic for him.
It also seems true that the galaxies and stuff have gotten farther away from each other because they have moved apart.
If I’m right (and I’m pretty sure of this so if you want to correct me make sure you have a PhD in something related) then it may be the case that understanding the expansion of the universe in “normal human” terms (instead of the mathematical terms that physicists normally deal in, and appropriately so) requires stating that TWO things are going on. One, large masses of mass (galaxies and stuff) are getting farther apart because they are literally moving farther apart; and two, the place in which these galaxies exist is getting larger (in a cosmic sense … without changing what we could call a “foot” or a “meter” or a “minute”). Brooklyn, the space between the galaxies, and the galaxies themselves are expanding as well.
Now, I want to add a quick caveat to this before all you Physics PhD’s hammer me. Actually, more a restatement than a caveat. Think of it this way. There is this phenomenon called “expansion” that is going on right now, but at one time in the past during the early days of the universe was much more apparent (did more) than now, by which the basic space within which stuff exists is growing “larger” in some cosmic sense. This largeness of growth is fundamental to the spacetime in which the speed of light is the speed limit for all things, and this is why we can see stars that we should not be able to see had the universe not “stretched out” as it were. There are other phenomena as well, including the attractive forces such as the Weak Force and the Strong Force that hold atoms and stuff together, and good ol’ Gravity which makes stuff fall down. So when you look at stuff and measure it, you are not going to see any real Weak or Strong force or Gravity out there in space where there is nearly no matter, but you will see Expansion. But in Brooklyn, the expansion may be minimal, largely overpowered by these other atomic or matter based forces.
It could be that the first part of this is wrong, and that all of the redshifts and other evidence of things moving away from us is all about expansion and that the galaxies are not moving apart from each other. There is an FAQ at UCLA that asks the question:
Are galaxies really moving away from us or is space just expanding?
and the answer is:
This depends … In one view, the spatial positions of galaxies are changing, and this causes the redshift. In another view, the galaxies are at fixed coordinates, but the distance between fixed points increases with time, and this causes the redshift….In the absence of the cosmological constant, an object released at rest with respect to us does not then fly away from us to join the Hubble flow. Instead, it falls toward us, and then joins the Hubble flow on the other side of the sky,…
In other words, to make this totally clear:
… D(t) measured at the cosmic time t, the acceleration is given by
g = -GM(r
So yea, that’s pretty much what I was thinking. RhotPD(t) and stuff.
But the second part is really true, I am not making it up. The “expansion” is universal at all scales, but pales in comparison to and/or is overwhelmed by other forces more obvious on the local level.
The reason I bring all this up to begin with is because of this. It got me thinking about how nobody who is an expert can really explain either cosmology or quantum physics … yet it seems so explainable. I watched The Elegant Universe (the DVD) which is based on an excellent book by the same name, with Julia, who is 11, and by the time we got half way through she had developed both a basic sense of the value of String Theory as well as it’s absurdity. (Which is apparently how the experts are thinking of String Theory these days.) The reason why she was able to do this is because no one told her it was not possible for her to get a basic grasp of these things (plus they cover the same material again and again and again in that particular documentary…)
OK so please feel free to hammer me as much as you like. I’m just one of those people who THINKS he understands a little of this. At least I don’t call in to Science Friday with my crazy theories every time Ira has a physicist on (if you have not done so, that is a lot of fun to listen to … such callers frequently get past the screeners…. Check out the Science Friday podcasts, which I used to RSS feed on this site until I realized no one ever clicked on them.)
Have you read the breakthrough novel of the year? When you are done with that, try:
or Paperback
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