Science Forums 2

[Freethinker]

Originally posted by: joe222
My question directly relates to how the speed and distance of the rocket effects the constant video transmission on earth.

I have been trying to struggle with my RF background (No not the snow we see on TV! lol). For one thing, if the ship was moving at the speed of light (ignoring all of the impossibilites of that) the RF transmission would be doppler shifted so low as to be unusable. Basically 0Hz would be my first guess. Thus no "information" (pictures) could be transmitted. Now if I try to move past that complication.

If we look at it on an instant to instant basis. A pict taken/ sent back from alpha centaury would take the same time whether it was taken by a stationary or moving ship (again ignoring doppler)

If we were to take a pict every X increment of time and send it back (again ignoring doppler) we would get the 1st image 2X later. This would be the time X at which the pict is taken and then the same time X for it's travel back to earth. The next pict taken at 2X, would take the additional 2x to return. So it would be seen 4X later. And so on. Thus the picts from each point would be twice the time of travel. 1X for the ship to get there and 1X for the signal's return trip.

What we would see from a "continuous" series of images (picts taken at regular intervals) is a logarithmic increase in time between images received.

The rocket only broadcasts for 4.3 years (until it reaches Alpha centaury) but because of the increasing distance from earth what the rocket sees, progressively takes longer to reach and appear on the video screen. For this to happen does the time frame of the video slow down as the ship moves away?

I think a lot of confusion comes from "the time frame of the video". My explanation above ignores any specific affect the movement would have on either images being picked up by the camera aim forward nor signals sent back out. Travelling at the speed of light would effectively stop either.