# Cosmological Redshift and Heisenberg Uncertainty Principle

• I
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
Staff Emeritus
Homework Helper
Gold Member
No, cosmological redshift has absolutely nothing to do with the uncertainty principle.

Ok. Let me just keep this in the domain of quantum physics. (Maybe I have this thread posted in the wrong forum.) Lets 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
2020 Award
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