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Re: Hewitt Special Relativity Example (Long)



At 22:01 -0700 10/19/02, John Mallinckrodt wrote:

Having said all of this, I'm not sure I find Hewitt's example all
that compelling since students simply have to take his word about the
results of the relativistic Doppler effect and keen-eyed students
like yours may not be so easily seduced.

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'll have to go break that video out and look at it again. It's been
a couple of years since I've seen it, and I'm fuzzy on the details,
but I recall that I had no trouble following the development without
having to worry about the speeds. Students, on the other hand, did
have some trouble following it. Mostly, I suspect because they were
really unfamiliar with the concepts so they were spending their
effort at trying to figure out what he was doing and couldn't absorb
the ideas. Something like that.

The whole trouble with relativity is that it is so counter-intuitive
that it takes a long time to get used to it enough that you can even
think straight about it, let alone be able to do problems in it. And
this on top of them just learning all the stuff about Newton's laws,
and now they have to toss it out and do it all differently. About
this time of the course, many of them lose it completely.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

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