/rel517ad                       9jan02

     We have an exciting brand-new textbook, Rindler's ``Relativity:
Special, General and Cosmological'', (Oxford 2001), on the shelves in
the UWM Bookstore and on order by Panther books (across Downer Ave.)---
evidently ``General and Cosmological'' bites off more than we should
chew in the course.  The book is up to Rindler's usual exacting
standards for accuracy, clarity, and above all, an absorbing style.
     But the course will follow my own outline, with Rindler for
reference, background, and for some problems.  (Problems: grading is
based on homework.  And you are encouraged to resubmit after I find
mistakes.  You can also earn points by correcting *my* mistakes...if
any...in class!)

     Einstein's 1905 title was
``On the Electrodynamics of Moving Bodies'': that a dynamo's behavior
reflects *relative* motion of its parts, was Einstein's decisive
inspiration.  In I hope this spirit I get as much as I can from
electric and magnetic fields directly:

The Lorentz transformation of electric and magnetic fields from the
    Lorentz force: Relativity from magnetism and compound interest!

But I start with an exercise lifted from my minicourse:

Learning relativity by drawing: see drawing.rel on my web page;
this amounts to presenting the facts before any
reason for accepting them, much like stating  ``Theorem'' before ``Proof''.

    We then see (or review) how electromagnetism introduces a constant speed:

``The speed of light is a law---hence is constant.''
Proof of the impossibility of *signals* faster-than-light.  (Because
``signal'' is *not*formally* defined, there is a screw loose which
we won't be able to tighten.  I.e. signal suggests information
hence entropy hence thermodynamics---a tangle I will only mention!)
Even so, the impossibility argument seems to have the force of a proof!

*The* constantly accelerating rocketship: *size* of the acceleration
depends on *where* in the ship you sit, so all accelerations need only
the one ship!

(Spin in the planetarium sky---a possible advanced topic near the
end.  But it opens up a way to compute with 2by2 complex matrices
instead of 4by4 real matrices, often easier.)

     Back to early basics:
The 4-vector idea suggests how energy and momentum transform: the
 story of ``E = mc^2''.
Mass without mass (2 photons)
    As Rindler does, we will use 4-vector labeling to bring it all
together, but I will build a lot first, without it.  That should make
people new to 4-vector labeling feel better about picking it up as a tool.
    The constantly accelerating ship and the story of parking a long
car in a short garage, both have involved Wolfgang Rindler's original
contributions---another plug for our textbook's author and quality.

    So do seriously consider registering for 754-517-001, MWF 11:30,
room 226, and rush to buy the book.

---   eli  (Elihu Lubkin, Associate Professor, Physics room 422)