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Originally Posted by sanctus
Actually i do not see the link between metric expansion and shortening the wavelength of a photon for example.
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I was speaking proportionally (the proportion between the wavelength of the photon and the size of space). If space is larger than it was before (it has expanded) and the wavelength of the photon is the same size, the wavelength of the photon is now smaller in proportion to space than it was when the photon was emitted.
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It is usually the other way around, take for example the CMB (cosmic microwave background radiation) at the surface of last scattering (~300'000 after the Big Bang) they had a temperature of 3000K and then due to the expansion of space their wavelength increased until they got down to temperature of 2.7 K today...
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As the wavelengths of all matter and photons from this generation of matter/energy grow smaller (compared to the total amount of space) in synchronicity we would still see red shifts from metric expansion of space: it is only compared to the total size of space that the wavelength of matter/energy* becomes proportionally smaller.
*of this generation of matter/energy
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I'm pretty sure you know all this and I did not understand what you meant (the compared to space part?), but in case you don't I can explain...
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I hope the explanation above is sufficient (but a hopefully more coherent (...in my dreams) rewording follows*). I considered red shifts (including the CMB's) when trying to figure out if anything I knew rendered the idea invalid, false, or not even wrong.
* Suppose we have a (3 dimensions of space) universe with a space volume of 1000 units cubed (10^3).
A photon is emitted of wavelength 2 units.
When the space of the universe has increased in volume to 8000 (20^3) units cubed, the wavelength of the photon would still be the same (2 units) however at this point the ratio of its wavelength to the size of space in universe would be smaller.
The wavelength of a photon in relation to the wavelength of other matter/energy effects the interaction between the photon and the other matter/energy.
If a photon is red shifted or blue shifted in relation to other matter/energy, there is a measurable effect on its interaction with the other matter/energy.
The idea is that the photon is blue shifted in relation to the size (maybe 'wavelength'?) of space as space expands.
Other matter/energy in space is blue shifted in relation to space as well, at the same rate as the photon (equally). The expansion of space between matter clusters (galaxies) still redshifts photons emitted from distant galaxies in relation to other matter, as all matter/energy blue shifts in relation to space in synchronicity.
I hope my long winded explanation clarifies things a bit. If it didn't, I have to think of a better way of explaining the idea.
Still looking for anything similar that has been written, if anyone knows of something.
