Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Red Shift

  1. Sep 7, 2014 #1
    How do scientists know if something is traveling away from us at any given moment, yes, it might be red, but it could be just a red dwarf star? How do they know it is the Doppler Effect in action, not just its natural colour?
  2. jcsd
  3. Sep 7, 2014 #2
  4. Sep 7, 2014 #3


    User Avatar

    Staff: Mentor

    We look at the individual spectral lines. For every element, there are a few frequencies at which it naturally absorbs and radiates energy, and these show up as lines in the spectrum. These lines form recognizable patterns, so if we see one of these patterns displaced towards the red or blue end of the spectrum we know that we're seeing Doppler at work.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook