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Old Nov 27th 2013, 07:50 AM   #1
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Measurement without redshift

Can we measure the expansion of the universe without relying on redshift?
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Old Nov 27th 2013, 11:32 AM   #2
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No - measurements of expansion rely on red shift, sometimes extreme (as with cosmic microwave background radiation).
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Old Nov 27th 2013, 11:38 AM   #3
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Originally Posted by ChipB View Post
No - measurements of expansion rely on red shift, sometimes extreme (as with cosmic microwave background radiation).
Could we not measure the apparent size of a galaxy and at a later time re-measure? What sort of time frame do you think would be required to have a measurement significant enough to determine if the galaxy was indeed receding?
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Old Nov 27th 2013, 12:03 PM   #4
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Originally Posted by Troll View Post
Could we not measure the apparent size of a galaxy and at a later time re-measure? What sort of time frame do you think would be required to have a measurement significant enough to determine if the galaxy was indeed receding?
Even though there are objects that are moving away from us at 1/3 of the speed of light the distances involved make the measurements you suggest impossible...the measured size simply doesn't change that much. You would have to take a measurement now and, say, another in 1000 years from now (or longer.) It's doable but I doubt anyone would be willing to fund it. (Institutions who fund "Big Science" want answers right away. It's a shame, really.)

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Old Nov 27th 2013, 12:21 PM   #5
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Easy enough to put some numbers on it. Given that the universe is about 14 billion years old, galaxies that are receding from us we would be expect to see their apparent angular size halved in another 14 billion years. You can expect a 1% change in about 140 million years. If your measurement gear is accurate to 0.001% then you only have to wait about 140,000 years. I doubt that we have the technology to do these measurements at this level of accuracy.
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Old Nov 27th 2013, 01:18 PM   #6
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So, we really have no way to validate red shift? That is it could be caused by another phenomenon?
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Old Nov 27th 2013, 01:29 PM   #7
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Occam's Baseball Bat

Just to be contrary,
The usual explanation for red-shift is the stretching of the wavelength due to the expansion of distance.
Could there not be other explanations,
For example what if the permeability of free space (the magnetic constant) and the permittivity of free space (the electric constant) are not constant (in cosmic time frames)?
Why are these parameters (for example) considered sacrosanct, while the very fabric of space is considered malleable?
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Old Nov 27th 2013, 01:37 PM   #8
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Originally Posted by MBW View Post
Just to be contrary,
The usual explanation for red-shift is the stretching of the wavelength due to the expansion of distance.
Could there not be other explanations,
For example what if the permeability of free space (the magnetic constant) and the permittivity of free space (the electric constant) are not constant (in cosmic time frames)?
Why are these parameters (for example) considered sacrosanct, while the very fabric of space is considered malleable?
If the universe is expanding at an accelerating rate and that expansion extends throughout time/space(that includes human observers), when we look at a very distant body we would be seeing it as it was when it was much more compressed and hence having a much greater gravitational field. The displacement would cause a much greater gravitational red shift than would be expected. If we adjusted for this distortion, the universe would be static(nothing would actually be receding). An observer that was not a part of this expansion would observe a universe that was expanding at an accelerating rate.
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