The Pinetar Rag

January 30, 2013

Dark Energy II

Filed under: Canned Heat — mcgonnigle @ 11:05 pm

Allright, I’m upset tonight because of the 2-2 draw at Arsenal and then I pull a calf (pop really) in warmups and soccer season, and maybe career, is over.

The previous post was a lot of fun. It got some good discussions going. The 3rd comment contains the refutation. Here is that:

The whole piece is here and it’s well written:

http://curious.astro.cornell.edu/question.php?number=274

Here’s a snip:

Let me begin by saying that “expanding” isn’t really the best word to describe what is happening to the universe, although that is the word that is often used – a word choice which I think leads to a lot of unnecessary confusion regarding what is already a difficult topic! A more accurate word for what the universe is doing might be “stretching”.

The difference between “expanding” and “stretching”, for me at least, is that an “expanding universe” conjures up an image where there is a bunch of galaxies floating through space, all of which started at some center point and are now moving away from that point at very fast speeds. Therefore, the collection of galaxies (which we call the “universe”) is expanding, and it is certainly fair to ask what it is expanding into.

The current theories of the universe, however, tell us that this is not the picture we should have in mind at all. Instead, the galaxies are in some sense stationary – they do not move through space the way that a ball moves through the air. The galaxies simply sit there. However, as time goes on, the space between the galaxies “stretches”, sort of like what happens when you take a sheet of rubber and pull at it on both ends. Although the galaxies haven’t moved through space at all, they get farther away from each other as time goes on because the space in between them has been stretched.

So, the galaxies aren’t really moving! Ergo, there are no relativistic effects then, eh? This is really hard for me to grasp. There is clearly local motion–that’s ok. And they ARE separated, as there’s distance between them, but only the SPACE between them is expanding!? Err, ok, I guess.

My thoughts are that Einstein said that there is no universal frame of reference and motion can only be relative motion between bodies. So if these galaxies are receding FROM US, is that not ‘relative motion’? I really need this explained to where I can have the light go on.

And I form the thought: how do we know this is “space expansion” and not real motion? What is the experiment, thought or otherwise, that cinches that? Have we hit on the back end of that? If it were real motion, these faster galaxies would weigh more, and we don’t see evidence of that?

For the thing to work, you have the big bang happen where all the matter and energy emerges from a singularity. It cools, there are some lumps, it interacts and forms the structure we see now. Aren’t things traveling out away from this singular point at a pretty good clip? But that motion is constant and the other component is “space expanding”? I’m at a loss to envision it–I’m sure they’re right, but I don’t get it.

And then thinking some more, the whole thing implodes because you read that there are galaxies that are receding from us at faster than the speed of light, but it’s not real, only apparent. If there’s no absolute frame of reference, then there’s no way to measure that speed, except relative to us, but that’s not a real measure…you see how you think you’re getting it and it blows up?

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