This means that light emitted from a radially moving source changes the rate at which wavefronts arrive at the observer, and the number of wavefront peaks that pass the observer in a given time are what frequency is, and hence the observed frequency of the light changes.Īs mentioned in comments, the intensity also changes because the rate of photon impacts changes but this is a separate and independent effect, and is hard to use in those terms because in practice, the number of photons in an emission of a macroscopic amount of energy is hard to determine.

The relevant aspect of light here - especially in the classical context Relativity is formulated in - is not the quantization that talking about 'photons' makes prominent, but that it is spatially extended waves in the EM field. The property of light compressing in the direction that a photonĮmitter is moving on spreading out on the other side should justĬhange the rate at which the observer receives photons. I'm probably just missing something really simple about special relativity, so please don't go too hard on me in the answers. The property of light compressing in the direction that a photon emitter is moving on spreading out on the other side should just change the rate at which the observer receives photons, meaning that the light will get brighter/darker.Ī similar question to this one was asked in this Physics SE post, but their question was more 'how could it be possible that the energy of photons is dependent on observers, which is what red-shift would imply?', but mine is more asking why the energy of the particle changes, since seemingly to me it has no reason to. The wavelengths of the photons being emitted from a source do not change as the source moves, and so the observer should see the exact same color of light. We believe that the redshift and blueshift are not entirely due to the Doppler's Effect, but also due (as in the light bending) to the medium composition (medium that could be formed by waves, particles, plasma, dust, gaseous, fluids, solids, etc.), to the medium density, to the medium heterogeneity, to the medium structure, and to the electromagnetic and gravitational fields contained in that medium that may interfere with the light that passes through.In physics class today we were learning about the doppler effect for sound, and the teacher said that blue-shift and red-shift are the exact same thing but for light. But Doppler's Effect itself is actually an appearance to a Subjective Observer, because the frequency is the same all over (if one considers the Absolute Observer). The General Theory of Relativity asserts that the redshift and blueshift are entirely due to the Doppler's Effect, which is caused by the motion of light source: if the source is moving away from the observer the frequency received is lower, but if the source is moving towards the observer the frequency received is higher. And, reciprocally, the blueshift is the shift from longer wavelengths towards shorter wavelengths.

The redshift is the shift from shorter wavelengths towards longer wavelengths.

Blue shift light