RE: How Do Scientists Know It's Space Expanding Not Galaxies Moving?
August 10, 2017 at 7:53 pm
(This post was last modified: August 10, 2017 at 7:55 pm by Gawdzilla Sama.)
(August 10, 2017 at 9:14 am)Alex K Wrote: When space expands, redshift is the sum of all expansion during the light travel. When Galaxies move, the redshift from the Doppler effect is the difference between movement speeds at the time of sending and receiving. Big difference.
That's the introductory level stuff?
(August 10, 2017 at 4:16 pm)Rhondazvous Wrote:(August 10, 2017 at 9:14 am)Alex K Wrote: When space expands, redshift is the sum of all expansion during the light travel. When Galaxies move, the redshift from the Doppler effect is the difference between movement speeds at the time of sending and receiving. Big difference.Wow, I only had to read this three times to understand it. I think I'll have a clearer understanding of what you're saying if I understood redshifting mathematically. I'm thinking of it as a color. The color may fluctuate in intensity because of varying circumstances, but I still don't know enough about it to think of it as having sums and differences.
Use the fire engine siren passing you example. The sound "builds up" in front of the truck and "fades away" behind it. Blue shift is the "build up", red shift is the "fades away".
