"The Elegant Universe" originated over here in the states, Public Broadcasting System TV station WGBH, for their "NOVA" series.
link --->
http://www.pbs.org/wgbh/nova/elegant/
The production is slick. Program host Brian Greene is a string physicist, best-selling author of the book with the same name as the program, and now something of a media darling, apprearing on nightime TV shows ,interviewed and publicized in magazines of wide circulation. He is recapitulating the glory of Carl Sagan in the role of science promoter, whose series "Cosmos" was broadcast in 1980. The style of this program shows it. Behind all the glitz and FX ("effects") lies an extremely sophisticated scheme of mathematics. The program featured several of the bright ones, pioneers and adepts, of string theory. The program does have flaws. Still, I think it is worth viewing several times.
The Quantum Cafe is an attempt to reduce 5,000 words about the smallest level of physical reality to a scene, without having to explain details like the uncertainty principles and instability. Maybe it doesn't work so well, but its importance is to enhance the point of the wide difference between the realm of the very small and the very large. It should be coupled with the scene at the bottom of the elevator shaft (a very Cosmos-like touch IMO) with those quantum fluctuations boiling up everywhere (but not disturbing the elevator itself, somewhat like Dr. Who's tardis). The important contrast is with the top of the elevator shaft, where serene cosmic smoothness of spacetime rules. This is the background for any theory for unifying the small with the large, not just string theory itself.
The 5 theories are actually 5 mathematical models that all satisfy the requirements that were set out for a string theory. There was little to guide a proper choice back in the 1980 era of string theory. But, by mid 1990s, the duality concepts of Witten and others tied these 5 models together in one supertheory, "M".
By the way, I'll wager that "M-theory" originally simply meant "Membrane Theory". The word "membrane" was shortened to "brane", similar to the way that "n-tuple" from the theory of relational databases was shortened to "tuple".
As someone else stated, there are open strings and closed strings. The theories that postulate breadsliced membranes for the regular 4D universe prefer open strings rooted on the slice, while gravity's gravitons seem to be closed. This was illustrated by the jelly vs. cinnamon-sugar scene in the program.
Something that is missing from all this is discussion of fields. Do these exist all around those vibrating strings? The size of these particles in physics comes from the measurement of interactions between particles, scattering and absorption patterns. From a higher scale, a vibrating string might act like a solid massive particle. Some of these, like electrons and quarks, don't seem to come apart.
Some other flaws in the program:
1. No mention was made that there are rival approaches to the problem of unification.
2. Einstein's work, illustrated in the first part of the program, really bears little relationship to the way unification is done since 1960. I guess he gets credit for trying to do it at all.
3. The planet rolls around the lip of the sink to illustrate unforced gravity by the sun. Sir Arthur Eddington loved this illustration too. But, properly, the planet should be a flat dot in the surface itself. The same thing is true of the sun. TV demands that one show something bigger, so the bodies are shown atop the surface.
4. The program doesn't really try to explain why there are 10 or 11 dimensions.
5. Related to this last point, the account of history is selective. In the 1970 period, when string theory was an orphan child, theoretical physicists borrowed the aspect called "supersymmetry" for an ordinary pointwise field theory called "supergravity". There they got used to extra dimensions- as many as 26. Part of the big raveup for string theory in the 1980 period was that fewer dimensions were required, and also something called "renormalization" became unnecessary by switching to strings instead of sticking with points. The program didn't get into any of this. Insufficient time, I reckon.
Despite this, I recommend viewing the program again (pour a nice pint of bitter; remember, it is entertainment). I recommend reading Greene's book, as much of it as you can stand. And I recommend coming back frequently to Physics Forums Strings, Branes & LQG topics to get the latest foibles and flummery of high-class thought, the leisure of the theory class.
