I dong know much about physics, but I was curious about the red shift effect. I think I have the basic idea of it down in that as an object 1 accelerates from object 2 the light from object 1 will appear more red to object 2 because it stretches the light between them. My question is how fast is the red shift effect? If object 1 and 2 are viewing each other and are stationary with say one light year between them and object 2 suddenly accelerates away from object 1, how soon could object 1 see the light from object 2 shift red? My thinking was that if there was no lag that you could potentially use it to transmit information over vast distances with a sort of red shift mores code.
1 Answer
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There is lag, and the lag is precisely the time it takes for light to travel the distance (at light speed). In your example, that would be one year.
The red shift (or blue shift, for objects approaching) Doppler effect changes the frequency of light waves but not their speed, so you will only observe it once the light from the moving object reaches you.
