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The Center of the Universe...

Engage in discussions encompassing themes like cosmology, human evolution, genetic engineering, earth science, climate change, artificial intelligence, psychology, and beyond in this forum.
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Ken Hemingway

Re: The Center of the Universe...

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Why has nobody talked about the balloon yet? Alright, I will.Take a perfectly spherical balloon and put little dots on it in a square pattern, say with adjacent dots 1/4 inch apart
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Loricat
Laughs at Einstein
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Joined: Thu Mar 03, 2005 11:00 am
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Re: The solar system is not expanding

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Thanks!L "All beings are the owners of their deeds, the heirs to their deeds."
Ken Hemingway

Re: The solar system is not expanding

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Well, I haven't seen Doc around here lately so maybe I won't wait for him to point out what was wrong in what I said above.I'm not happy with the following:The problem, I think, is that we tend to think of "the expansion of space" as something that is happening now - that somehow the space between any two points in the universe is constantly getting bigger by some magical process we don't really understand.I'm saying that a better way to think about it is to recognize that when two galaxies are receding from each other at some rate (which we can measure by their red shift), they really are moving.This makes it sound as though after the big bang everything was in constant velocity motion through normal space and that that is all that is meant by the expanding universe - just matter flying apart from a central starting point. What is wrong with that is that were the case there would have to be a central point from which everything is diverging (back to Chris's' original question at the top of this thread). But pretty much everyone rejects that possibility, which is why we do have to think of space expanding, not just bodies flying away from each other.What I think we can retain from what I was saying though is that if you consider two bodies which are moving apart due to the expansion, for the purposes of analysing their future motion you really can treat them as just having an initial relative velocity which can be changed by gravitational effects just the way I described. So I don't think the analysis is wrong. It just needed its underpinnings to be clarified.
Ken Hemingway

Re: The solar system is not expanding

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So, now move on to the second case, in which any two heavenly bodies (say the earth and the sun) are not only moving away from each other, they are also being accelerated away from each other due to the accelerating expansion of the universe.Now, of course, they may also have an acceleration towards each other, because of gravity, and, in the case of the earth and the sun, the gravitational attraction obviously overcomes the expansionary acceleration
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