I Speed of information-carrying radiation

[Speady]

How can an approaching observer receive the information from a source at a higher rate (as an accelerated recording), while the information-carrying radiation could not?

 

[PeterDonis]

How can an approaching observer receive the information from a source at a higher rate (as an accelerated recording), while the information-carrying radiation could not?

I'm not sure what you mean. Can you be more specific about the scenario you have in mind?

 

[FactChecker]

How can an approaching observer receive the information from a source at a higher rate (as an accelerated recording), while the information-carrying radiation could not?

It's not clear what you are asking, but keep this in mind: Although the information-carrying radiation will travel at the constant speed of light, c, the density of information or frequencies in the radiation can change. There can be red or blue shifts and the information content density (rate) can decrease or increase.

 

[Speady]

2 observers A and B watch the same film that is broadcast from station S. A and B see the first fragment of the film next to each other. A remains at a fixed distance from S and B travels from the beginning of the film at a uniform speed of 30 km/s to S.

After 02:46:55 hours B sees the last fragment of the film. The last fragment has to travel another 299,792.458 km to reach A. One second later A also sees the last fragment. B has seen a film from 02:46:55 hours and A has seen a film from 02:44:56 hours. (B sees the same film as A, but a sped-up recording, with a difference in duration of a whole second).

The same information must have arrived at B at a higher rate than at A. The information had a higher velocity relative to B than relative to A. Ergo: the information-carrying radiation had a higher velocity relative to B than relative to A.

I think the conclusion must be that radiation has a variable velocity relative to an observer, depending on the motion of the observer in the direction of the source. (If time dilation existed, it would be negligibly small in this example.)

 

[russ_watters]

This is just the doppler effect. "Information velocity" is not a thing, and no individual signal/packet of data traveled faster than C. Different packets travel different distances so they take different amounts of time to arrive.

 

[Speady]

@FactChecker: I see what you mean, about the density of information, but notice that both observers received the same total information with a difference in time of one second. To achieve that difference, the information at B must have arrived faster, right?

 

[Dale]

The information had a higher velocity relative to B than relative to A

Why do you say this? It doesn’t seem correct to me. Be sure to show your work and keep track of the units. So far I don’t see anything in your discussion with units of m/s other than c.

 

[Speady]

@russ_watters: Speed of information is just a thing. Doppler effect is also correct. No faster than c applies in any case with respect to the source and with respect to the remotely fixed observer A. Your last sentence is also correct. Only the speed of the information and implicitly the speed of the radiation with respect to B I miss in your answer.

 

[Speady]

@Dale: what exactly are you missing or what is not entirely clear to you in my message #4?

 

[PeterDonis]

@Dale: what exactly are you missing or what is not entirely clear to you in my message #4?

@Speady you have had multiple previous threads all pushing the same mistaken understanding on your part. Nothing has changed since those previous threads. Your claim here...

I think the conclusion must be that radiation has a variable velocity relative to an observer, depending on the motion of the observer in the direction of the source.

...has already gotten you one misinformation warning. This topic has been discussed more than enough. If you post about it again you will receive another warning which will result in a temporary ban from PF.

Thread closed.