Is Brian or Jim Wrong? (the science of Dr. Who)

[AtoMick-u235]

i made a comment on youtube =

It's only 4 minutes long, see the last minute

If Jim went away at 99.94 c, for 10 years, and we see him take 29 years, 1) what doe's that mean, it means that Jim's apparent speed from Earths veiw has to be slower than 99.94 c, because it took longer, it equals just 34.48 c, someone help me out here !!, , All processes that change with time, change at a slower rate when observed in motion, even speed, , you have to insert the new time in, S = D \ T, , ,
99.94% C = 28.87 x time dilation, so i don't know where Brian got 29 years from 10, , , it should be 288.7 years, , , 2 ) or maybe for Jim, he could be away for just 10 \ 28.87 = 0.37 years, so thats about 4 months, and from earths veiw we see him take 10 years,, , , all i can think is that brian got it wrong, it should be 1 year instead of 10, , ,

I think option 2 is correct, , ,

 

[PeterDonis]

If Jim went away at 99.94 c, for 10 years, and we see him take 29 years

Where does 29 years come from?

99.94% C = 28.87 x time dilation

Where does 28.87 come from? What does this mean?

 

[PeterDonis]

All processes that change with time, change at a slower rate when observed in motion, even speed, , you have to insert the new time in, S = D \ T, , ,

This is nonsense.

 

[AtoMick-u235]

Where does 29 years come from?Where does 28.87 come from? What does this mean?

Brian rounded 28.87 to 29 years, , ,i just put in the correct value

 

[AtoMick-u235]

This is nonsense.

Yes, , like i said Brian has it wrong

 

[PeterDonis]

Yes, , like i said Brian has it wrong

What you posted in post #3 that I said was nonsense, is not something Brian claimed in the video, as far as I can tell. It's something you claimed in your OP. And it's wrong. See further comments below.

Brian rounded 28.87 to 29 years

Ok. You are right that that's not correct given the other parameters he gives. See below.

i just put in the correct value

If you mean the figure of 288.7 years that you gave in your OP, yes, that is correct for the total round trip travel time as seen from Earth, given that the total travel time by Jim's clock is 10 years and that his speed relative to Earth is 0.9994c (which means a gamma factor of 28.87).

However, when you say...

Jim's apparent speed from Earths veiw has to be slower than 99.94 c

...you are wrong. The difference in travel times as seen by Earth clocks vs. Jim's clock does not mean the speeds are different; the relative speed is the same in both frames. The difference is the distance that is traveled.

In Jim's frame, the Earth moves away from him for 5 years (half of the total 10 year trip time), meaning that at its furthest Earth is just short of 5 light years away from Jim in Jim's frame.

But in the Earth frame, Jim moves away for 14.435 [Edit-144.35] years, so at his furthest, Jim is just short of 14.435 [Edit-144.35] light years away from Earth in the Earth frame.

 

[AtoMick-u235]

What you posted in post #3 that I said was nonsense, is not something Brian claimed in the video, as far as I can tell. It's something you claimed in your OP. And it's wrong. See further comments below.Ok.If you mean the figure of 288.7 years that you gave in your OP, yes, that is correct for the total round trip travel time as seen from Earth, given that the total travel time by Jim's clock is 10 years and that his speed relative to Earth is 0.9994c (which means a gamma factor of 28.87).

However, when you say...

...you are wrong. The difference in travel times as seen by Earth clocks vs. Jim's clock does not mean the speeds are different; the relative speed is the same in both frames. The difference is the distance that is traveled.

In Jim's frame, the Earth moves away from him for 5 years (half of the total 10 year trip time), meaning that at its furthest Earth is just short of 5 light years away from Jim in Jim's frame.

But in the Earth frame, Jim moves away for 14.435 years, so at his furthest, Jim is just short of 14.435 light years away from Earth in the Earth frame.

In option 1) i'm just stating brians reasoning, and that it is wrong , , and option 2) is correct

 

[phinds]

@AtoMick-u235 the moral of this story is never ever trust pop-sci presentations. They get a lot of stuff right a lot of time time but they get enough wrong that they are not to be trusted. They are entertainment, not science.

 

[PeterDonis]

In option 1) i'm just stating brians reasoning

No, you're not. None of this...

1) what doe's that mean, it means that Jim's apparent speed from Earths veiw has to be slower than 99.94 c, because it took longer, it equals just 34.48 c, someone help me out here !!, , All processes that change with time, change at a slower rate when observed in motion, even speed, , you have to insert the new time in, S = D \ T, , ,

...is said by Brian in the video. It's stuff you made up yourself.

The only incorrect statement Brian makes in the video is the 29 years; given the other parameters, it should be 288.7 years. I think that's more likely than Brian making a mistake and meaning to say 1 year instead of 10 (which would make 29 years correct), because he says Jim flies away for 5 years and then back for 5 years by his own clock, so he would have had to make several mistakes while he was describing the scenario, not just one. Whereas if he just mistakenly said 29 years instead of 288.7 years, that's just one mistake.

 

[PeterDonis]

in the Earth frame, Jim moves away for 14.435 years, so at his furthest, Jim is just short of 14.435 light years away from Earth in the Earth frame.

Now it's me forgetting to put in an extra factor of 10. It should be that Jim moves away for 144.35 years, so at his furthest he is just short of 144.35 light years from Earth in the Earth frame.

 

[PeterDonis]

After moderator review, this thread is closed.