"sal" wrote in message news
On Wed, 01 Jun 2005 07:49:36 -0700, Astroguru wrote:

Well, I agree if we go by the theory and use lorentz equations than
probably we can not reach the speed of light. But is this restriction not
just imposed because of those equations ?

Sure it is! Absolutely! :-)

hehe... we seem to take a rather different point of view here.
Did you see my reply "Of course not" before you answered?


The equations define the "model" of the universe provided by the theory of
special relativity. According to those equations, there is a
_contradiction_ if there is an observer traveling at C. So, within the
"model" of the universe, there can be no such observer. End of that
part of the story.

Now, out in the real world, we ask if the model agrees with reality; and
that question is answered by experiment rather than by quoting equations.
In real experiments in the real world, things behave very much as the
model objects in the model provided by SR behave. So we conclude that, so
far as we know, reality behaves like the model of the world provided by
relativity. Since nothing which has mass can reach C in the model, we
conclude that, most likely, nothing which has mass can reach C in reality,
either.

So we do agree.
The only difference is that in my view the "theory" is put one
step higher than the equations. Reasons for doing so are because
the postulates aren't cast in equation form - they are rather
meta-equations - , and of course ultimately the theory can be
expressed without the equations. I mean, *very* ultimately.
Let's hope the OP doesn't get too confused by that.




I mean if I replace 'c' by 'x' (my own arbitrary constant equivalent to
three times 'c' for example) then the equations would still hold true
and then I definitely cannot reach 'x' but can achive 'c' for sure !! Is
it not possible that we just are unable to measure anything beyond 'c'
as of now and hence we are restricting ourselves to the 'c' ?

You are confusing the speed of light with the "c" in special relativity.
They happen to be the same value (as far as anyone can tell) but they
wouldn't have to be -- there's nothing about the basic model provided by
special relativity that makes electromagnetic radiation "special".
Relativity provides a model in which there is _some_ special speed which
can't be exceeded; that speed is called "c". It appears that
electromagnetic radiation travels at "c". If it turned out that EM
radiation travels at 0.999999*c, for instance, it might cause problems for
Maxwell's equations, but the Lorentz transforms would not be affected.

As to the "real" speed limit being 3 times the speed of light -- no way.
They've both been measured very precisely, and photons either travel at c
or travel only very slightly slower than c. Certainly they travel
far faster than (1/3)c.

Here we completely converge again :-)

Cheers,
Dirk Vdm