🚀 go-pugleaf

In article <1992Jul21.141253.17366@jlc.mv.com> john@jlc.mv.com (John Leslie) writes:
>In article <mcirvin.711673227@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:
>>dk@imager (Dave Knapp) writes:
>>
>>In fact, I think that a more important issue than the definition of
>>mass is the use of four-vectors in introductory classes teaching SR,
>>which I think should be encouraged, since it brings beauty and
>>simplicity to something which otherwise looks like an algebraic junkheap  
>>built on a shifting foundation of paradoxes. 

Nice statement.  The "algebraic junkheap" was how I viewed it when I first 
tried to work through SR back in high school.  Of course, the following 
query tells you why intro classes do not use this particular formulation...

>   Could someone have mercy on those of us whose college physics is
>twenty or more years in the past?  What is "four-vectors"?

A "four-vector" is a vector with 4 components, normally used in physics 
when one wants to treat space and time as the 4 components of a single 
vector space called "space-time" for short.  It works just like regular 
geometry with "three-vectors" except the meaning of the distance between 
two points is altered in a significant way.  What is nice about this 
approach (besides the fact that it is crucial to use it if you want to 
do general relativity) is that it makes it very clear that the Lorentz 
transforms are just a rotation in this 4-space, and nothing more.

--
J. A. Carr                                    |  "The New Frontier of which I  
jac@gw.scri.fsu.edu                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)