Nothing That Matters

How many dimensions of space-time a string theory predicts varies in different flavours of the theory. It started with a "Bosonic" model which explained only Boson Particles (Particles that explain the behaviour of Forces), no Fermions (Other particles that explain the material world). This theory was consistent only in 26 dimensions. (How cool!! These can be labelled from A to Z. Most scientist make their best contribution around this age. Einstein published his paper on General relativity at this age. My son was also born when I was 26 year old ;-)
Bosonic String Theory had some unacceptable predictions. Other theories followed to improve upon this, add Fermions and remove other inconsistencies. These are called by unimaginative names (quite rare in Physics) like I; IIA; IIB; HO & HE. These flavours agree on the number of dimensions - a perfect 10. (People of my age would recall Bo Derek!)
Efforts are on to integrate these flavours into a theory called M-Theory (Mother Of all Theories). Which requires an 11 Dimensional Space-Time. But to retain the advantages of earlier flavours, one of the dimension is assumed to be compacted (curled-up) into a small circle leaving only 10 significant dimensions.(Must have been invented by a Cricket-playing scientist : - where a team is complete if there are 11 players, but after 10 players are out, the 11th does not get to play.)
So how do we encounter only 4 dimensions, when the theory needs 10. The other 6 are compacted into a ball. Each point on our 4-dimensional space has a finite but minuscule 6 dimensional curled-up ball. These curled up dimensions would need very high energies (of the order available at the time of Big-Bang) to open-up, hence are beyond our perception.
What are differences and similarities between String Theory and Standard Model.
About that in subsequent posts.
Till Then. Enjoy the Ice-Cream!!

Posted by Girish Bhatnagar at 9:16 AM