Re: Reflections on SR from a high school leaver

From: Bill Hobba (bhobba_at_rubbish.net.au)
Date: 11/29/04 

Date: Mon, 29 Nov 2004 22:05:27 GMT

"Dirk Van de moortel" <dirkvandemoortel@ThankS-NO-SperM.hotmail.com> wrote
in message news:fHIqd.4484$EP.243780@phobos.telenet-ops.be...
>
> "James Stokes" <dkjk@bigpond.net.au> wrote in message
news:a3ea3c76.0411290807.afc9528@posting.google.com...
> > Hi group,
> >
> > Well, I've finally completed my HSC (Australian equivalent of the
> > SATs) and have just returned from two weeks in China to celebrate for
> > schoolies. Anyway, now that I have an abundance of free time on my
> > hands, nerdy as always, I've decided to explore the intricacies of
> > spacetime using Taylor and Wheeler's Spacetime Physics. However,
> > throughout the course of my readings, several questions have arisen
> > about the nature of spacetime and events. As I understand it, the
> > spacetime of relativity is Minkowski space R^{3,1} comprised of the
> > set of quadruples of real numbers R^4 endowed with a form g : R^8 -->
> > R that defines the squared distance between two points in R^{3,1}.
> > Objects in spacetime are regarded as timelike subsets of R^{3,1} known
> > as worldlines so that the tangent vector v to any point in the
> > worldline obeys g(v,v) < 0.
>
> Since they define the interval as the time separation squared
> minus the space separation squared, that should be g(v,v) > 0.
>
> > When we transform from one inertial
> > observer to another, the components of the points comprising the
> > worldline change so as to maintain the value of g(v,v). Although the
> > worldline of an object changes from one observer to observer, it seems
> > to me that the object will pass through the same physical events
> > regardless of the observer.
>
> Actually, the *equation* of the worldline changes from one
> observer to another. The worldline itself is merely a collection
> of events and does not change. See below...
>
> > However, events in spacetime are defined
> > only in terms of points that are readily transformed into other points
> > in R^{3,1}.
>
> And events are defined as independent of any coordinate system, so
> they are not defined as elements of R^{3,1} or as elements of R^4.
> That should take away the objection you make below...
>
> > This appears to violate the ``Unity of Spacetime'' Taylor
> > and Wheeler attest to on the reverse front cover of their book. Do we
> > not need to add more structure to R^{3,1} to give events meaning, as
> > opposed to quadruples of real numbers? There are several other tidbits
> > I'd like to address but it's too late to rave on any longer. Let me
> > know what you think.
> >
> > Thanks is advance.
>
> Can I warmly recommend Robert Geroch's "General Relativity
> from A to B"? If not, sorry, too late ;-)
> It's an excellent introduction to Special Relativity as well.
> Part of sample chapter available at
>
http://www.amazon.com/gp/reader/0226288641/ref=sib_dp_pt/103-2973639-0603821#reader-link
> Check it out!
>

Hi James

Congratulations on your HSC. I am from Australia so I know what it is
about. I did terrible on my HSC, just passed and was ***** off at the time
about further study so I waited a few years before doing my degree. Those
few years we a real godsend - my scholastics turned right around and I went
from just passing to getting good marks. A lot has to do with how committed
you are.

I really can not expand on Dirks excellent response except to point you to
some modern derivations of the Lorentz transformations and treatments of SR
that emphasize the POR rather than the speed of light. I think it is
important to understand SR is not a theory about light - rather it is a
theory about symmetry.

See
http://arxiv.org/abs/physics/0110076,
and ancient, but I still think excellent post by Tom Roberts
http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=54jfst%24glp%40ssbunews.ih.lucent.com
and chapter 10 of
http://www.courses.fas.harvard.edu/~phys16/Textbook/
under the heading of Relativity without c.

If you post at sci.physics.relativity you will find we still have a number
of people that believe in aether theories and Tom Roberts did an excellent
series of posts examining these theories and why SR is preferred:

http://www.google.com/groups?selm=3838AC00.87B78404%40lucent.com
http://www.google.com/groups?selm=3838A838.81CE8090%40lucent.com
http://www.google.com/groups?selm=3838AA2A.829F46AD%40lucent.com

I recall when I was you age I was very intrigued by the idea that Maxwell's
equations can be derived from Coulombs Law and Special Relativity. A paper
that does that, if you are interested is:

http://www.cse.secs.oakland.edu/haskell/SpecialRelativity.htm

For general physics both myself and Dirk highly recommend you seek out a
copy of the Feynman Lectures in Physics.

Thanks
Bill

Relevant Pages

  • Re: Reflections on SR from a high school leaver
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