Did Anyone Get Confused By The Wording Of The Time Dilation Question (1 Viewer)

[walla]

adam you don't even understand that inertial frames are dealt with by special, not general relativity, let alone that in this question we have to consider the spaceship stationary to answer it

 

[ND]

Here's my interpretation:

The astronaut is accelerating away from the earth, and so has left the inertial frame of reference (you can't use the argument that it's the same for both observers, cos the astronaut can detect that he has left the inertial frame), so therefore his frame of reference is invalid, making the earth's observation the correct one. Hence the answer is D. Meh... that's my logic.

 

[walla]

i'm not convinced that he is accelerating
i mean no-one here even knows how to calculate things taking general relativity into account
let alone it being in the syllabus
so i dunno how you can say "hence D", because 16.7 was an answer you (and I) got by calculating according to special relativity (the wrong way)

 

[ND]

Originally posted by zoodboog
The best way to summarise it is this, from Bob Emery's site:


Note the use of the word "relative".

Earth and rocket are both inertial frames since they have constant velocity. (given)

Since they are in inertial frames they don't know which one of them is *really* moving. Thus the Spaceship could be considered as standing still and Earth moving away from it.

But they're not both inertial frames, i'd like to see you get to the moon without accelerating.

 

[ND]

Originally posted by walla
i'm not convinced that he is accelerating
i mean no-one here even knows how to calculate things taking general relativity into account
let alone it being in the syllabus
so i dunno how you can say "hence D", because 16.7 was an answer you (and I) got by calculating according to special relativity (the wrong way)

Yep i know, and i agree that this is a dodgy question (in the exam, i changed answers 3 times), but to me, D seemed the 'most correct', even though as you said, it's general relativity and you can't use special relativity equations.

 

[~TeLEpAtHeTiC~]

i get the feeling markers are gonna giv it either way now
i rekon majority of ppl would hav picked either (b) or (d).. oh well... i cant wait till the standards package comes out .. lol

 

[freaking_out]

Originally posted by ND
Yep i know, and i agree that this is a dodgy question (in the exam, i changed answers 3 times), but to me, D seemed the 'most correct', even though as you said, it's general relativity and you can't use special relativity equations.

yeah, we have ND on our sides!!!

 

[walla]

ND - what "general relativity equations" did you use????

 

[toknblackguy]

bugger this...we are all just speculating
can someone here get in contact with a marker or someone high up and ask em?

 

[freaking_out]

Originally posted by walla
ND - what "general relativity equations" did you use????

general relativity is not in the course, and its beyond the course!!!

 

[walla]

Originally posted by freaking_out
general relativity is not in the course, and its beyond the course!!!

umm that's exactly my point. ND is claiming that he got D by using general relativity

 

[ND]

Originally posted by walla
ND - what "general relativity equations" did you use????

I used that one i formulated in the 3rd year of my PhD.

edit: i'm not arguing that 16.7 is the correct answer, i'm arguing that BOS fucked the question, and that 16.7 is the answer that they'll mark correct.

 

[walla]

ok so you got d by using special relativity...but you claim that special relativity doesn't apply...how does that work?

 

[freaking_out]

Originally posted by ND
I used that one i formulated in the 3rd year of my PhD.

yeah, u gotta b einstein to use that. ...so its obviously outta the hsc exam/syllabus. :rofl:

 

[freaking_out]

Originally posted by walla
ok so you got d by using special relativity...but you claim that special relativity doesn't apply...how does that work?

well thats bcoz, if u really think abt. the spaceship had to have accelerated to reach its 0.8c speed...so therefore it is not exactly a inertial frame of reference as such.

 

[ND]

Originally posted by walla
ok so you got d by using special relativity...but you claim that special relativity doesn't apply...how does that work?

Read the edit in my post above.

 

[Inhuman]

my thought was that it's a multiple choice, you're meant to be able to do each one in about a minute or less, therefore just sub into the damn equation and get 16.7

 

[toknblackguy]

oooh
like ur quote inhuman!

 

[Bannanafish]

ok ok

EXPLANATION!!!

Acceleration of the spaceship, taking time for the astronaut to "see" the clock on earth, and any other "complications" are all irrelivant. This is a THOUGHT experiment, hence ignoring all these factors. Hell, if it weren't i'd argue how the hell could the astronaut see a clock so far away?? Also in Einstein's THOUGHT experiment, he never said anytihng about acceleration (which is obviously needed for his trains to travel so fast).

So since we can ignore all these things, think of the spaceship as a train.
Train is travelling at 0.8c
Goes past an observer
Observer looks in the window of the train and the clock inside is running slow (i.e. for every second on his watch, the clock is only going a fraction of a second)
The passenger on the train looks at the observer's watch and sees it as going slow (i.e. for every second on his clock, the watch is only going a fraction of a second)
If the observer sees something to take 10 seconds according to his watch, then he sees the clock inside the train go 6 second.
If the passenger sees something to take 10 seconds according to his clock, then he sees the watch on the observer to go 6 seconds.
Now if 10 seconds was 10 years, the PASSENGER'S clock READS 10 hours. THIS IS WHAT THE QUESTION GAVE YOU.
Now the PASSENGER looks at the OBSERVERS watch. THIS IS THE PERSPECTIVE THE QUESTION ASKED.
Therefore the OBSERVERS watch would say 6 years have passed.

Now if you can't understand this, i don't see how you can argue.

 

[Bannanafish]

*bump* for some reason my post didn't register as a new post