Re: [Phys-l] geometry of spacetime (was: relativisitic mass ...)

[John Mallinckrodt <ajm@csupomona.edu>]

I wrote:

> ... the traveler him or  herself can reach objects over 30 billion 
> light years away, about  twice the size of the entire observable 
> universe by accelerating at that same rate for 25 years as measured 
> by his or her own clocks.

I should also have noted that, if the speed of light were a THOUSAND 
TIMES SMALLER, it would only take the traveler about two 
weeks--again, as measured by his or her own clocks--to reach those 
same objects.*  The worse that "relativistic speed limit" gets, the 
easier it is to get around!

* Formula
  d = (c^2/a) [cosh(at/c) - 1]

Where
  d is the distance traveled as measured by observers who remain "at rest"
  c is the speed of light
  a is the acceleration measured by the traveler (the proper acceleration)
  t is the time measured by the traveler (the proper time)