Re: SR examination question

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Hi all-
        I see no problem with the question.  I will translate it as
follows:  The muon has a lifetime of about 1 microsec (\mu_s).  A
beam of muons passes through my detector with a speed of 0.9c.  What
lifetime do I measure for the muons?
        I fail to see why this isn't the same question, with Peter
riding on the muons and Jane sitting in the lab.
                                        Regards,
                                                Jack



On Thu, 17 May 2001, Rick Tarara wrote:

> Read the original question again:
>
> Peter and Jane are each wearing a wristwatch with a second hand that takes
> one minute to make one complete revolution and Peter is moving at a speed
> of 0.9c with respect to Jane. When Peter observes the second hand on his
> watch to have made one complete revolution, how many revolutions will Jane
> observe the second hand of her watch to have made?
>
> Peter, moving (linearly) at .9c observes 1 minute to have passed.  During
> the time that Peter's watch has ticked off 1 minute AS OBSERVED BY HIM, how
> many minutes does JANE observe (in her frame--assumed to be at rest) to have
> ticked off on her watch?  That's what the question says to me.  Now if you
> want to read in complications--both are moving away from each other at .45c
> and Peter is reading Jane's watch and Jane is reading Peter's--feel free,
> but the question is still clear enough to me with no sexist (or even theist)
> overtones.  ;-)
>
> Rick
>
>
> ----- Original Message -----
> From: "John S. Denker" <jsd@MONMOUTH.COM>
> To: <PHYS-L@lists.nau.edu>
> Sent: Thursday, May 17, 2001 1:17 PM
> Subject: Re: SR examination question
>
>
> > Earlier today, someone who remain nameless wrote:
> > > I think it is quite clear what the question intends.
> > > Jane's second hand makes 2.29 revolutions while Peter's makes one.
> >
> > Ahh, so it is _quite clear_ that Peter's reference frame is preferred.
> >
> > I know how to explain this:
> >    1) It is obvious that girls can't be scientists.
> >    2) Therefore if we measure something, we must measure it in
> >       Peter's frame, not Jane's frame.
> >    3) Anybody who identifies with Jane (or even gives Jane
> >       equal standing) will have their homework marked wrong.
> >
> >
> > > ... and the observation is a 'God's Eye View' as is
> > > often the case when talking about time dilation.
> >
> > Wow, God prefers Peter, too.

--
Franz Kafka's novels and novella's are so Kafkaesque that one has to
wonder at the enormity of coincidence required to have produced a writer
named Kafka to write them.
                        Greg Nagan from "The Metamorphosis" in
                     <The 5-MINUTE ILIAD and Other Classics>