Re: [Phys-l] how to prove relativity

["John Clement" <clement@hal-pc.org>]

> > What's missing, for me personally, is to add a discussion of
> > relativity of simultaneity.
>
> That's another thing that's easy in the spacetime
> approach (and not otherwise).
>
> As the saying goes, learning proceeds from the
> known to the unknown ... so let's start by
> reviewing some things we already know:
>
> Fact 1:  In the XY plane, suppose you start out
> with a vector purely in the X direction relative
> to your frame of reference.  Then you rotate your
> frame CW a little bit.  Relative to the new frame
> the vector has picked up a small projection in the
> Y direction.  No problem.  No surprise.

To the non physicist this is already gobbledy gook.  It will not convince
anyone such as a psychologist.  Again I must insist that you have to start
where the student is, not where you are.  While the analysis is quite clear
to anyone who understands vectors, non physicists (or non other related
sciences) find vectors impenetrable.  Look at the ADAPT reports.  One of the
biggest failures was trying to get students to understand vectors.  They
found that the weeks spent on it were fruitless.

Students are good at simulating understanding by using memorized sequences,
and most problem solving tests do not reveal this problem.  So we have
fooled ourselves into thinking they have better understanding than they
actually have.

Some of the hardest people to convince are actually engineers who have had a
firm grounding in classical mechanics.  I remember an electrical engineer
who was taking a QM course and totally disbelieved the uncertainty
principle.  He used classical EM arguments to show the uncertainty principle
was not true.  The case of the psychologist is someone who believes in
"absolute reality", but probably understands how we construct our own views
of it.  So relativity violates their view of reality.  What they are not
realizing is that reality is what we currently construct and that relativity
is another construction which we made up to be able to make sense of the
data.  Incidentally from my experience engineers are often very rigid in
their views and will not tolerate ambiguity, so they will tell you that your
method of teaching is wrong just because you used different terminology than
the engineering courses.  They also are probably more prone to become young
Earth creationists.

Part of the problem is that experts in one field will often think they are
likewise expert in other fields.  So expert dentists think they are
scientists and promote antievolution ideas.  Expert psychologists think they
are experts in "physical reality" without realizing they have huge gaps
there.  Expert scientists think they are expert teachers because they know
the subject matter, but they have very low understanding of how learning
actually proceeds.  The TX board of education has many experts, but none in
science or history.  So they think they are experts in these fields and
promote very bad pedagogical standards.  They overrule real experts.  The
MDs at Los Alamos complain that their patients come in with squirrely ideas
that they insist are correct, and of course a large fraction of the patients
are PhDs.

A very simple example of this type of thing is that scientists are easily
taken in by magicians such as Uri Geller or other quack mystics.  But fellow
magicians easily see through the tricks.  Teams of scientists and magicians
are even more powerful.  Johnny Carson, a fellow magician, easily debunked
Geller by providing him with ordinary materials that were no pre-prepared.
Geller realizing this used some mumbo jumbo to say the vibes were not right
so he couldn't perform his mystical feats.  Carson sprang the material on
Geller!

So I repeat that I have not seen very cogent sequences which will convince
non physicist experts.  And the whole idea of different trips along
different paths will most likely be dismissed as obvious nonsense by experts
on other fields.  If you want to convince a psychologist start with what
that person already knows, and build on that.  Incidentally the so called
paradoxes of relativity are some of the most interesting parts to the
budding experts, and the simple elegant analyses are not very convincing.  I
can remember how we could get excited over the paradoxes.  We would discuss
the paradoxes, and never the math analysis.

I do not know what sequence would convince an expert psychologist, but until
someone asks them the right questions to we can not really find out.  You
must first find out what the person knows and why they think a certain way
before designing a sequence to bridge over to new ideas.  That is why I
suggest looking at Clement/Camp "Preconceptions in Mechanics" and also at
associated John J. Clement articles in JRST.  They have come up with very
powerful learning sequences that bridge from student knowledge to new
concepts.  Unfortunately they do not have sequences for relativity, but they
do show a method that is very powerful in convincing students of things they
do not believe.

So do start proceeding from "known to unknown", but you have to start with
the subject's "known", not your known.

John M. Clement
Houston, TX