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Re: Breakfast in LA - lunch in San Diego ( was Re: A Geometrical Pro of of the Non-invariance of the Spacetime Interval)



I answer the below according to SR



Okay. So, |x2'-x1'| != |x2-x1|, even for very, very small v.

Does |t2'-t1'| ~= |t2-t1|, for very, very small v?


If I read "!=" as "does not equal"

and "~=" as "approximately equals" then I agree for a itsy bitsy v. But
its important in SR that they aren't exactly equal, they have a fractional
difference of order v^2/c^2.

What is the magnitude of the four-vector? Is it (x2'-x1')^2 -
c^2(t2'-t1')^2 for F' and (x2-x1)^2 - c^2(t2-t1)^2 for F?

Yes.


Is the magnitude invariant?


Yes.


I know these questions are pretty naive and, perhaps, a tangent
to the thread, but I've been reading this thread for a while
and I'd like to be able to follow it.


I think bits and pieces of the thread were mangled (particularly early on).
I know I made a rookie mis-statement in an early post, so I don't think its
surprising that its hard to follow. Not to mention that there have been
about three seperate conversations going on, all with the same person (DR)
and using the same subject heading. Hence, the name change I introduced.

Joel R