Re: Hewitt Special Relativity Example (Long)

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

Hugh Haskell wrote:

> I have that video and have used it several times. I think that it is
> compelling. The way he sets it up (and I'm working from memory here,
> so I can't remember the exact details), it isn't necessary to do the
> Doppler calculation and find speeds. Once he and specifies that the
> time between flashes in the spacecraft is twice what the sender is
> using on the outbound trip, it immediately follows that the time
> between flashes on the inbound trip is half the sender's frequency.

I don't see how this "immediately follows" unless one refers to the
relativistic Doppler shift formula.  It certainly isn't true for
sound.  But if there is a simple argument that has eluded me, I'd
like to hear it.  Hewitt offers none and even if these is one, I'd be
surprised to find that the result is "obvious" to the target student
population unless it is "obvious" for all the wrong reasons--e.g.,
"1/2 is the inverse of 2."

--
John Mallinckrodt        mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.