# Constant velocity vs accelerating source

## Main Question or Discussion Point

Would a signal sent from a transmitter, traveling at constant velocity toward an observer, arrive at the same time if it were accelerating toward that observer? The signals are sent at the same relative distance from the observer. Would the result be the same if the transmitters were receding from the observer?

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Would a signal sent from a transmitter, traveling at constant velocity toward an observer, arrive at the same time if it were accelerating toward that observer? The signals are sent at the same relative distance from the observer. Would the result be the same if the transmitters were receding from the observer?
Same proper distance from the recipient, yes. Which means at the same distance distance according to the recipient.

If you doing all the relative distances according to the transmitter, then no.

cheers,

neopolitan

brightonb, i don't think there would be a difference because the speed at which light travels (c) is constant and does not depend on the motion of the observer as long as the light is emitted at the same distance from the transmitter in both cases.

Would a signal sent from a transmitter, traveling at constant velocity toward an observer,
You have constrained you inquiry by the phrase "traveling at constant velocity" so of course any two signals traveling at the same constant velocity would arrive at the same time from the same distance.

I think your real question is
Would a signal sent from a transmitter arrive at the same time if it were sent from the same distance approaching as receding from the observer?
and the answer is "yes" because the speed of electromagnetic radiation (say, light) is independent of the speed of the source or the observer.

You have constrained you inquiry by the phrase "traveling at constant velocity" so of course any two signals traveling at the same constant velocity would arrive at the same time from the same distance.

I think your real question is

and the answer is "yes" because the speed of electromagnetic radiation (say, light) is independent of the speed of the source or the observer.
Only one source is moving at constant velocity, the other is accelerating but they both transmit a signal from the same location. e.g., the c.v. source could be moving at 100 mph while the accel source could be at 1000 mph at the transmission time.

Fredrik
Staff Emeritus