Re: General Theory of Relativity

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

Careful here.  Special relativity does not prohibit the two objects from
approaching each other at a relative velocity (as viewed by a stationary
observer) of greater than c.  What SR says is that if a light beam is
emitted by object 1 and observed by someone riding with object 2 that person
will measure the velocity of the light beam to be c.  You have to apply time
dilation and in some cases length contractions (depends on source of light
and measurement techniques) into both object's frames of reference to see
how this happens--both the source and observer will experience the SR
effects.   It is not particularly easy to do this.  It is similar to the
barn paradox which is conveniently explained in terms on non-simultaneity,
but requires quite a bit of calculation to show that the moving observer's
slowed clock and contracted length _can_ produce the necessary effects such
that he/she can interpret the barn as moving and being contracted to an even
smaller size.

Rick

***********************
Richard W. Tarara
Associate Professor of Physics
Department of Chemistry & Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

Free Physics Instructional Software:

NEW WIN 95/98/NT SOFTWARE NOW AVAILABLE!

see  http://www.saintmarys.edu/~rtarara/   for details.

****************************
-----Original Message-----
From: kevin sonntag <kevin_sonntag@KIMBERLY.K12.WI.US>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Friday, December 11, 1998 2:54 PM
Subject: General Theory of Relativity


> I have a question if anyone has ideas on how to present to introductory
> level students , the concept of  when two objects are approaching each
> other close to the speed of light that their combined speed between them
> cannot be greater than the speed of light. I have tried to relay the
> concept to my students, but I am not reaching them.
> Any help would be great
>
> Kevin Sonntag
> KHS