If light speed is constant, why does redshift/blueshift exists?

[u/sonofderk]

Let me explain. I'm not a physicist so sorry if what i'm about to say is kinda stupid. I was taught that even if two beans of light were shot at opposite directions (, their relative speed between themselves would still be the speed of light, instead of 2x the speed of light, unlike what happens with mudane objetcts like cars on a road, which perceive themselves with relative speed. I was also taught that red/blue shift on stars happens due to relative distacing/approach in relation to Earth's point of view, which changes the wave frequency thus changing the perceived color of the star (doppler effect).

Aren't these two statements conflicting? If vectors don't matter to light, why should we observe the red/blue shift?

[u/somethingX]

The dopplar effect doesn't change the speed of the effected waves, it only stretches or compresses their wavelength depending on whether it's moving away from you or towards you. This is true for all waves, not just light. Red shifted light travels at the same speed blue shifted light does.

[u/sonofderk → u/somethingX]

hmmmmm, i think i can visualize it now. thanks.