Re: [Phys-l] how to explain relativity

[John Denker <jsd@av8n.com>]

On 06/18/2010 07:06 PM, Jeffrey Schnick wrote:

> I don't get this, it seems to be inconsistent with your statement that
> <<all the fundamental laws of physics commute with translation>>.  If
> they both have the same a(tau) profile, I think that whenever they are
> both coasting, their clocks will agree with each other.  Please explain
> how their clocks become offset by a constant.

That's an important question.  The answer that the
principle is still valid.  It disallows some things
but allows others.  In this case, each observer can say
"If I accelerate to the right, everybody to the left of
me gets redshifted."  Such a statement upholds translation
invariance.  

It also upholds rotation invariance, which is equally 
mandatory.  That is, acceleration dot separation is a
rotationally-invariant scalar.