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superstrings



A very readable introduction to string theory:
http://theory.tifr.res.in/strings/dmw.html

The next level of detail, still quite readable, by
somebody who, shall we say, knows what he's talking
about:
http://www.theory.caltech.edu/people/jhs/strings/

====================

In case you are wondering whether I take string theory
seriously: I draw an analogy to the early history of
quantum mechanics
http://www-gap.dcs.st-and.ac.uk/~history/HistTopics/The_Quantum_age_begins.html

-- In 1900, how many correct predictions did QM make?
None. There was one correct postdiction, about the
blackbody spectrum.

-- In 1905, there were still no correct predictions. The
number of postdictions increased to two, including the
photoelectric effect.

-- In 1913 we got the Bohr model of the atom. It made
some predictions. Some of them were more-or-less right,
but many of them were wrong.

-- The Schrödinger equation didn't come along until 1926.

===========

This analogy connects to string theory as follows: Right
now string theory has been around for about 35 years. It
is currently in the state that QM was when QM was 10 or 12
years old. String theory makes no correct predictions,
but it makes some rather profound postdictions:
-- Gravitation is not inconsistent with QM.
-- The self-energy of the electron is not infinite.

String theory is so inchoate that one may reasonably
question whether it is a scientific theory at all. But
it might turn into a scientific theory one of these
days. I wouldn't be surprised to find that the first
predictions to come out of string theory are wrong, in
analogy to the Bohr atom.

One must not imagine that string theory is the "theory
of everything". Right now it is a theory of nothing.
It might remain so forever, or it might turn into
something important. Most likely there will be some
progress, then some backtracking (discarding some ideas
and recylcing others), and them some more progress, et
cetera.

I'm not putting all my eggs in this basket. But I'm
not giving up on string theory, either. After all,
QM turned out OK after a few decades of work.