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Re: [Phys-l] Relativity Question

I believe that the point is that the scientists on the train have NOT been lied to. In their reference frame, their clocks ARE synchronized. When you first introduce the setup to students, they don't realize that when we say that both sets of scientists don't really have synchronized clocks, we are reporting the facts from another reference frame, a third reference frame no more valid or less valid than that of the scientists on the two trains.

To take things further, you can consider a procedure that the scientists could use to ensure that the clocks on their own train were synchronized. Suppose that there is a star that is known to occasionally emit a burst of light at a specific frequency. And suppose you could design clocks that start running when exposed to that frequency. You could preset your clocks but with each clock set further ahead than the one before it. Then when the light from the star reached the individual clock, it would start the clock. The preset time differences would be to allow for the additional time it takes for the light to reach that train car.

If both sets of train scientists performed this procedure, they could each argue that their own clocks were in fact synchronized. And they would each argue that the other train performed the procedure incorrectly because that other train was in motion relative to the light source -- but we weren't. So in the final analysis, it is simultaneity that is relative and it leads to the other weird things about clocks and lengths.

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of chuck britton
Sent: Friday, May 15, 2009 8:45 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Relativity Question

Please elaborate a bit on this point.

Are you implying that the folks on the train can't 'really' have a
set of synchronized clocks?
or what is the swindle to which you refer?



On May 14, 2009, at May 14(Thu) 5:38 , John Denker wrote:

they involve some sort of swindle, such as lying to the
trainmen about their clocks.

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