The main thing to realize about all this is that we’re talking purely about a question of interpretation: everybody (at least, everybody sane) agrees on the physics - the argument is only about what words to wrap around the physics. Hogg and I argue for the rehabilitation of the idea that the galaxies are moving and the observed redshift can be regarded as a Doppler shift. In the cosmological context, though, people often say that the observed redshift has a different explanation: they say that the galaxies aren’t “really” moving, but rather that space itself is expanding, which causes the light to be stretched out in wavelength. Most of the time, when you see a redshift, it’s a Doppler shift - that is, it’s caused by the fact that the observed object is moving away from you. This fact is the observational basis for the idea of the expanding Universe. The most important fact in cosmology is that the light from distant galaxies is redshifted. I’ll quickly recap the big idea, but then I want to comment on some followups to our paper: a blog post by Sean Carroll (from way back when we first posted our paper) and a recent paper by MichaÅ‚ Chodorowski.įirst the background. I said a bit about the argument of the paper in a previous post. The talk is based on the paper David Hogg and I wrote last year. #Redshift meaning how to#I’m giving a talk here in Paris tomorrow on the question of how to interpret the cosmological redshift. Frequently Asked Questions about Black Holes.Frequently Asked Questions About Black Holes.
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