Cosmological Redshift and Heisenberg Uncertainty Principle

[e2m2a]

Has anyone conjectured that the redshift associated with Hubble's constant can be explained by Heisenberg's uncertainty principle? Another words, the further in space away from us a photon is emitted from a galaxy, the longer in time it takes for the photon to reach us. Since the photon has a certain energy E at the time it is emitted from its source and because it takes an astronomical amount of time to reach us, doesn't this require that the energy of the photon when it reaches us must decrease or its wavelength must increase to conform to this principle? Another words, the further away, the longer the time, the more diminishing of the energy.

I ask this because the uncertainty principle is invoked to explain the existence of the unfathomably enormous vacuum energy, the reasoning being: the shorter the time increment the larger the energy possible within a volume of space. Could not this principle be applied in reverse-- the longer the time interval, the smaller amount of energy possible within the space that comprises the source and the detection of the photon? When I say space, I mean if we imagined a long volume of space, such as a "tube' where one photon travels within from its source of emission to the point of its detection.

 

[Orodruin]

No, cosmological redshift has absolutely nothing to do with the uncertainty principle.

 

[e2m2a]

Ok. Let me just keep this in the domain of quantum physics. (Maybe I have this thread posted in the wrong forum.) Let's say we measure the frequency of a photon at its point of emission and then use an incredibly sensitive instrument (such as with the resolution of a LIGO detector) to detect the frequency of the photon at the point of reception at various lengths of travel of the photon far below astronomical distances. Would it be theoritically possible to detect a decrease in energy of the photon per HUP(Heisenberg uncertainity prinicple) in direct proportion to the travel time of the photon?

 

[Ibix]

You would get a decrease in energy over cosmological distances, certainly. That's the cosmological redshift.

The uncertainty principle doesn't say energy decreases with time. I don't know where you got that idea from.

 

[kimbyd]

Ok. Let me just keep this in the domain of quantum physics. (Maybe I have this thread posted in the wrong forum.) Let's say we measure the frequency of a photon at its point of emission and then use an incredibly sensitive instrument (such as with the resolution of a LIGO detector) to detect the frequency of the photon at the point of reception at various lengths of travel of the photon far below astronomical distances. Would it be theoritically possible to detect a decrease in energy of the photon per HUP(Heisenberg uncertainity prinicple) in direct proportion to the travel time of the photon?

The Heisenberg uncertainty principle doesn't produce any change in the energy of a photon over time, so this can't happen.

One way to see this is that the uncertainty principle stems from the wave nature of quantum particles. The classical description of electromagnetic waves, pre-quantum mechanics, fully describes this behavior, uncertainty principle and all. The only thing that quantum mechanics adds to the puzzle is the fact that the EM wave is made up of lots of discrete bits (photons). Classically, the "uncertainty" for an EM wave is not a measurement issue so much as a localization issue: an EM wave that has a distinct momentum is spread across all of space, while an EM wave that is very localized in space has components with many different momenta. In QM, we can interpret this spread as a probability of measuring the photon as being at a particular location, but that interpretation is irrelevant to how the wave travels, which is fully-described by the classical system.

 

[e2m2a]

Thanks for the explanation.