(April 8, 2019 at 5:19 pm)bennyboy Wrote: Red shifting is just the doppler effect-- if a star is moving away, its spectrographic spikes shift toward red. It doesn't necessarily imply a general expansion, unless a collection of bodies are ALL red-shifted-- which they mostly are. Pretty much everything we observe seems to be red-shifted.
Not true. Other *galaxies* tend to be red shifted. But the *stars* in our own galaxy can be either red or blue shifted. Most of what you see if you go out and look at the night sky, even with a good amateur telescope, will be stars in our galaxy.
Yes, there is an overall expansion of the universe at large. But 'at large' means galaxies that are over 5 million light years away (and we know of galaxies that are billions of light years away). But there are only three other galaxies that can be seen without a telescope: the Andromeda spiral, and the Large and Small Magellanic Clouds. All of these are gravitationally bound to our own and the Andromeda is *blue* shifted because it is approaching us.
Our own galaxy is about 100,000 light years across. The stars in it orbit the center and we know of stars that are approaching (blue shift). Sirius is one of them. There is an old claim of it being red shifted, but that goes back to the 1800's and the instruments weren't so accurate then. The measurements are also delicate and easy to mess up.
So, no, Sirius is NOT red shifted, no, a red shift for stars in our galaxy is NOT part of the universal expansion, and no, Not all galaxies are red shifted.
