(with thanks to Cat-eyes for provoking this interesting train of thought)
One of the biggest headaches in modern physics has been the utter incompatibility of two of our most imposing pillars of knowledge: General Relativity and Quantum Mechanics.
Einstein’s General Relativity beautifully describes the large-scale geometry of the Universe and shows that gravity is really the curvature of space-time in the presence of mass-energy. Meanwhile, Quantum Theory explicates the sub-atomic world as a frothy place where particles pop in and out of existence seemingly at random, but somehow balance out to produce the reassuringly ‘solid’ matter that we take so much for granted. The only problem has been that the mathematics of each these two theories completely break down and produce nonsensical answers when extended into the realms of the other!
Physicists have a high regard for symmetry and a certain ‘elegance’ when it comes to theories of ‘everything’, and this is decidedly a very UN-elegant state of affairs. While the math can get pretty hairy, the basic problem is simple: what happens when you divide by zero?… KA-BOOM!! <’Danger!… DANGER Will Robinson!‘>
One class of possible solutions to this conundrum has come to be called ‘String Theory’. Instead of point-like particles, sub-sub-atomic entities like ‘Quarks’ are envisioned as ultra-tiny* ‘string-like’ things, whose vibrational frequencies and harmonics produce the characteristics we previously associated with the zoo of sub-atomic particles. Immediate mathematical relief is to be had when these one-dimensional ‘strings’ replace zero-dimensional point-particles. No more dividing by zero!
As a musician, I must say that the image of cosmic vibrating ‘strings’ producing a veritable ‘symphony’ of ‘tones’ that in turn produce what we call ‘reality’ is a very attractive concept! I call it the theory of ‘The Big Note‘… ;-}
But this is just the beginning… as very smart people began to seriously apply the ‘string’ idea to the real world, they found that both Relativistic and Quantum effects fall quite naturally out of the theoretical framework! Eureka! But then, as things are so often wont to do, things got complicated again… It turns out that we needed 10 (count ‘em, TEN) spatial dimensions plus time for a grand total of 11 dimensions! YOWZA! And as if that weren’t bad enough, there are now things like ‘branes’ (from ‘membrane’) which are two-dimensional sheets of gossamer ‘stuff’. And there are several different formulations of string theory, only one of which can actually describe our Universe! Curiouser and curiouser!
The mathematical scaffolding being invented to describe such things is scary-hard. On a good day I can barely slog through simple differential equations, so the details are well beyond my humble abilities!
Happily though, Dr. Brian Greene has produced a very good book and a 3-part PBS/Nova special that explains things far better than I could. You can view the whole thing on-line here:
‘The Elegant Universe’
The Universe is not only queerer than we suppose, but queerer than we can suppose. – J.B.S. Haldane
* and I mean TINY! These entities exist at Planck scales (1.616252×10−35 meters). Sadly, we’ll probably never get to see a ‘string’!