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About Time

  1. Oct 30, 2003 #1
    About Time!!

    This paper has such a obvious ring of truth about it, one can only hope that the misconceptions are finally laid to rest, and we can move forward, for there is Relativistic change in the air.


    Here is an interesting paragraph:In special relativity, redshifts arise directly from velocities. It was this idea that led
    Hubble in 1929 to convert the redshifts of the “nebulae” he observed into velocities,and predict the expansion of the universe with the linear velocity-distance law that now bears his name. The general relativistic interpretation of the expansion interprets
    cosmological redshifts as an indication of velocity since the proper distance between comoving objects increases. However, the velocity is due to the rate of expansion of space, not movement through space, and therefore cannot be calculated with the special relativistic Doppler shift formula. Hubble & Humason’s calculation of velocity
    therefore should not be given special relativistic corrections at high redshift, contrary to their suggestion.

    There is a simple thought experiment that can break a number of chains, I have been waiting for the right paper to surface with just the right amount of clarity so I can put the experiment into a perspective frame. I will dig out from my annuls of paperwork, and place it here for inspection.
  2. jcsd
  3. Oct 30, 2003 #2


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    Re: About Time!!

    Doppler shift works the same regardless of how you define the motion. If you are standing on the platform and the train is moving past you or the train is sitting still and you drive past it in a car, the doppler shift of the horn sounds the same.

    The reason the galaxies are moving apart is not important to redshift. The fact that galaxies are moving apart is.
  4. Oct 30, 2003 #3
    I'm curious as to what experiment or observation ruled out the possibility. - That of moving through space?
  5. Oct 30, 2003 #4
    Re: Re: About Time!!

    That's not really correct. You cannot use the special relativistic formula for velocity Doppler shift to calculate redshifts in an expanding space. So, for instance, you cannot account for the Hubble redshifting of distant galaxies by postulating recessional motion in a flat spacetime. That's the point of the cited paper.
  6. Oct 30, 2003 #5
    Ok I'll put the thought experiment up for grabs here, I do not want to make it longer than is needed, without compromising the bigger picture, Im in the middle of digging out the paperwork in my house-front living room, so Ill be back shortly.
  7. Oct 30, 2003 #6


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    The observation that the relationship between distance and redshift is tight and 'linear'; if the redshifts were due to movement through space, the Milky Way/Local Group would be the true centre of the universe.

    The cosmic microwave background is interpreted to be the highly redshifted black-body radiation from the era of decoupling of matter and radiation (protons captured electrons to form H atoms).

    Plug all the observations - these and many others - into your a thousand models of the universe and see which best match the data.

    Of course, some part of the observed redshifts of galaxies is due to motion through space; the richer the cluster, the greater the 'velocity' dispersion about the cluster mean, and there are some quite monsterous clusters!
  8. Oct 30, 2003 #7
    Niether of these observations rules out the possibility. They just add new possibilities. Although these are somewhat compelling - I'm looking for the knockout punch. What observation or experiment makes it impossible that objects are moving through space at a higher rate the further out you look? Surely there must be something, because nobody of standing in cosmology and whatnot considers it to be even a remote possibility.
  9. Oct 30, 2003 #8
    Yes, they do. Cosmological redshift expanding space predicts a different redshift-luminosity (or redshift-distance) relation than does Doppler reshift from recession a non-expanding space. See, for instance, exercise 29.5 of Misner et al.

    Anyway, if you're so curious about this issue, why don't you read the paper that started this thread?? They've got calculations, data, and everything.
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