Photon Energy Level At The Retina And Redshift Problem

[Mattzy]

According to theory, the retina responds to certain energy levels in incoming photons which are then interpreted as certain colours ie. red. Other energy levels between primary colours are not recognised and the eye then blends by proportion to secondary colours etc. (that's very basic but another topic).

If the wavelength of a receding star has a lengthened wavelength (redshift), its energy level is reduced - correct? But light is emitted at constant speed and wavelength, so redshift occurs at a device or retina at the point of reception. I can perceive lengthening of a wavelength where the carrier is arriving more slowly (doppler), but since emission from the electron the wavelength has not actually changed within the photon and its arrival speed is constant - the speed of light (maybe not?).

I'm running into perception problems. If light is emitted from a receding light source, it seems reasonable to assume that it will arrive at light speed minus its relative speed (going away from the receiver). But is it not the case that light always arrives at light speed? Maybe not. It seems unreasonable that light can speed up or slow down to satisfy this rule. So light speed is constant relative only to its point of emission?

Firstly can somebody please help me understand this redshift?  Could stars receding rapidly enough, become invisible due to photon energy drop being unrecognised by the retina?

[GAHD]

Might help you?

[rhertz]

According to theory, the retina responds to certain energy levels in incoming photons which are then interpreted as certain colours ie. red. Other energy levels between primary colours are not recognised and the eye then blends by proportion to secondary colours etc. (that's very basic but another topic).

If the wavelength of a receding star has a lengthened wavelength (redshift), its energy level is reduced - correct? But light is emitted at constant speed and wavelength, so redshift occurs at a device or retina at the point of reception. I can perceive lengthening of a wavelength where the carrier is arriving more slowly (doppler), but since emission from the electron the wavelength has not actually changed within the photon and its arrival speed is constant - the speed of light (maybe not?).

I'm running into perception problems. If light is emitted from a receding light source, it seems reasonable to assume that it will arrive at light speed minus its relative speed (going away from the receiver). But is it not the case that light always arrives at light speed? Maybe not. It seems unreasonable that light can speed up or slow down to satisfy this rule. So light speed is constant relative only to its point of emission?

Firstly can somebody please help me understand this redshift?  Could stars receding rapidly enough, become invisible due to photon energy drop being unrecognised by the retina?

 

1) The human visual system is not involved into the direct perception of red or blue shifting. It's a matter of spectrographic techniques developed since the times

    of Gustav Kirchoff, around 1859, and the discovery of absorption lines by different elements present in the gaseous enviroment surrounding the celestial body.

2) The shift of spectral lines of absorption is perceived for objects beyond a radius of about 50 Mly around Earth.

3) Since the availability of computing power everywhere (40 years), the calculations of shifting (z values) are performed with specialized software. Some programs

    are available for amateurs or observatories with low budget, as you can find googling about it.

4) It's not the retina which perceives colors, as it only perceives intensity of light. It's the macula, a 4 mm² organ within the eye involved in fine resolution. You

    can find more googling about it. Anyways, the eye doesn't detect spectrum shifting. Spectroscopy does, by indirect means.

[Mattzy]

Many thanks for that - especially the correction to the macula. I should edit the question accordingly. I should simply have said that the eye detects colour respective to photon energy level. I will ask some specific questions one at a time and see if anyone can help. Thanks again.