Cecil’s column about how we know something is 1200 light-years away or whatever didn’t include the final step. By using knowledge of the distances of stars and galaxies from those methods, we were able to verify the Doppler effect and confirm that the farther away something is, the more its spectral lines are shifted in the red. Now we can simply look at how much red shift there is and calculate the distance, which is the method used for extreme distances, up to as far as we can see.
Howdy psycho. The article to which you refer is in fact a mailbag article, not one of Cecil’s columns. How do they figure the distance between celestial bodies? I think you will find that Doppler and such matters are already being discussed in this thread in the next forum down the hall.
picmr
Welcome to the SDMB, and thank you for posting your comment.
Since the article is a Staff Report, not a Straight Dope column, (and was written by our resident board physics genius Chronos, not Cecil Adams), this thread is leaving the «Comments on Cecil’s Columns» forum and going to visit my colleague CKDextHavn in the «Comments on Staff Reports or Mailbag Answers» forum.
moderator, «Comments on Cecil’s Columns»
This was actually the same question posed by the OP of the other thread, so I’ll just briefly re-cap my answer from there. The Hubble relation is useful, but you really do need those way far out points to calibrate it properly. This is espescially true since the relationship isn’t actually a straight line. The most distant galaxies we see are also very old, and the Universe was expanding at a different rate back then. Just how different the rate was is not something that we can theoretically derive, so we need those observations.
By the way, let me just say that I’m flattered… I think that this is the first time that I’ve been mistaken for the Great and All-Knowing Cecil.
Arnold, Karen is probably more of a physics genius than I, she just has a different specialty.