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Post by speakertoanimals on Nov 22, 2010 15:41:41 GMT 1
No, you miss the point -- suppose the rate of expansion (hence the recession speed of the galaxy) changes AFTER the light has been emitted. According to expanding space, the light will be effected, since the space it is moving through will expand differently. According to you, it should not be, since the change in velocity of the source occurs after the light has been emitted. Or are you still really trying to claim that a change in the velocity of the source can effect light that was emitted BEFORE that change occurred?
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Post by Progenitor A on Nov 22, 2010 17:54:51 GMT 1
No, you miss the point -- suppose the rate of expansion (hence the recession speed of the galaxy) changes AFTER the light has been emitted. According to expanding space, the light will be effected, since the space it is moving through will expand differently. According to you, it should not be, since the change in velocity of the source occurs after the light has been emitted. Or are you still really trying to claim that a change in the velocity of the source can effect light that was emitted BEFORE that change occurred? The rate of expansion is always changing as it is proportional to the distance of the star, and as that distance is continuously changing, so is the expansion. What we see, using the expansion theory, is the red shift that has occurred as the light passes though a continuum of expansions. This passage through varying expansions will be observed as a red shift - one red shift (per observation) Exactly the the same red shift can be obtained from a star that is is moving away with a velocity v that gives the same doppler red shift as the expansioin red shift. There is evidently no way of distinguishing whether the red shift is due to space expansion or doppler. We say it is due to expansion because that happens to fit in with Einsteins relativity quite well (even though he himself introduced a cosmological constant to stop the expansion that he so hated)
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Post by speakertoanimals on Nov 22, 2010 20:52:50 GMT 1
Wrong. The apparent recession speed is proportional to the distance of the galaxy.
So, suppose we have a space where all distances double in some time t. Then a galaxy at distance d will move to a distance 2d in a time t, giving an apparent recession speed of d/t. The greater the distance, the greater the speed, for a FIXED t, which here measure the rate of expansion (the time required to double in size).
You don't seem to have grasped the basics, which doesn't help...........
Not quite well -- extremely well, in that we can either ditch relativity (what else are we going to use to explain gravitational lensing then?), or keep relativity and accept what it says about universe uniformly filled with matter expanding or contracting. The question then is does the pattern of redshifts we see fit in with the predictions of such an expanding universe model?
But it realy isn't that arbitrary assuming that space is expanding, we had to explain the observed redshifts some way, and since relativity works well close to home, AND naturally predicts that space should be expanding, would seem daft not to test that prediction, and if it fits, hence accept the space-expanding scenario.
I don;t see what the problem is -- if you can accept space and time bending and cavorting all over the place to explain gravity, then adding in the fact that space can expand as well is a small leap. Of course, I know what the problem probably is, some people are still convinced the whole bending space idea is nonsense...........
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