Subject:
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Re: Relativity Question
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 8 Nov 2000 18:13:41 GMT
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Reply-To:
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mattdm@+saynotospam+mattdm.org
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Viewed:
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528 times
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Dave Schuler <orrex@excite.com> wrote:
> reference frame and one is not. Am I correct in thinking that the occupant
> of the ship will experience Doppler Shift of light while the "stationary"
> observer will not? Might that be the determining factor?
Maybe. I don't understand it well enough. Lemme think about the headlights
thing....
For someone standing on earth, light is moving away at about 300,000km/sec.
Then, say we have a spaceship, moving at half the speed of light relative to
earth, and the people on the spaceship turn on the headlights.
To the people on earth, the light from the spaceship moves away from earth
at 300,000km/sec, while the spaceship itself moves at 150,000km/sec.
However, to the people on the spaceship, the light from the headlights is
moving away from the craft at 300,000km/sec -- the speed of light is a
constant to all observers.
So, to the people on earth, for light to get 300,000km beyond where the
spacecraft is at a given instant takes one second, and in that second, the
spacecraft will have moved 150,000km. In two seconds, the spacecraft will
have moved 300,000km, and light 600,000km:
0km 150 300 450 600
***
0sec ***** <+>
***
***
1sec ***** <+> .
***
***
2sec ***** <+> .
***
But to the people on the spaceship, light is moving 300,000km *faster than
they are*. So to them, the third step above -- two earth seconds -- must
take only one second.
Ok, so far, so good, yeah? (Although really weird.)
So, what about, say, a laser signal leaving earth? (Again, time in the left
column is earth time.)
0km 150 300 450 600
***
0sec ***** <+>
***
***
1sec ***** . <+>
***
***
2sec ***** <.>
***
Now, the same thing from the perspective of the spacecraft:
0km 150 300
***
0sec ***** <+>
***
***
1sec ***** <.>
***
It only takes one second!
I dunno. Still feels like I'm missing something. What happens with a signal
leaving the spaceship for earth? Perhaps I'm all confused. :)
Anyone care to explain?
--
Matthew Miller ---> mattdm@mattdm.org
Quotes 'R' Us ---> http://quotes-r-us.org/
Boston University Linux ---> http://linux.bu.edu/
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Message has 1 Reply:
 | | Re: Relativity Question
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| Just looked this up in Britannica Online. (Search for "time dilation"). Acceleration definitely plays into it. *All* clocks in non-accelerating motion relative to an observer run slow by his/her frame of reference. (Thus potentially causing (...) (24 years ago, 8-Nov-00, to lugnet.off-topic.geek)
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Message is in Reply To:
| | Re: Relativity Question
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| (...) 8^) Certainly, but one of the two parties is moving relative to the inertial reference frame and one is not. Am I correct in thinking that the occupant of the ship will experience Doppler Shift of light while the "stationary" observer will (...) (24 years ago, 8-Nov-00, to lugnet.off-topic.geek)
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