From what I understand, red-shifting is when light from a distant source travels through expanding space which stretches out the wave making it appear more red by the time it reaches earth.
So if a light wave traveled far enough, would it “red-shift” all the way down the EM spectrum eventually losing its waviness and becoming a straight line?
In: Physics
No. Red shifting is only caused by the observer also moving, similar to the Doppler effect on sound. Otherwise, light will continue to travel infinitely at a constant rate because energy cannot be created or destroyed.
What you are describing would mean the observer would have to be traveling at the speed of light in order for it to essentially shift into net 0, but if you are traveling at the speed of light in front of a particle traveling at the speed of light then you will never be able to observe the particle in the first place. If you were going very close to the speed of light, on the other hand, the redshift would be a lot, but only ever approaching 0, never actually 0, if that makes any sense.
That is put very simply. Red shifting is actually caused by the expansion of the universe, but the idea still holds true. The rate of expansion of the universe would have to be the speed of light for the particles to no longer exist on the spectrum, but that has a few other challenging implications.
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