Strings To The Mother Or Magic Theory, What Is String Theory, M Theory & P Branes?

A long time back I explored quantum physics. I thought my head might explode doing that. but here I am today just about to explore string theory, which will, I am sure, push me closer again to boiling point.

String theory doesn’t sound so bad does it? We all know what a theory is and that a string is a long or short piece of flexible substance with two ends. If it is of the right length it can be used to hold your trousers up. A small bit cut in half could be used for shoelaces. Unfortunately it’s not that simple as the universe doesn’t like to be that obvious and, as far as we know, has no shoes.

Strings are incredibly small. Each is approximately the size of the Planck length, the smallest possible distance in spacetime (less than one billionth of one billionth the radius of an electron). Just as the strings of a violin can vibrate at different frequencies and produce varying musical notes, the tiny strings in spacetime can vibrate in many ways to create different types of elementary particles.

Super string theory

An elementary particle or fundamental particle is a particle not known to have substructure, which means it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. In the standard model quarks, leptons, and gauge bosons are elementary particles.

Besides making up all particles of matter in spacetime, according to the theory, strings also make up all the force-carrying particles that act on matter. Furthermore, the theory proposes that strings move within a curved spacetime. Therefore, string theory encompasses the explanation of gravity provided by general relativity (one of Einstein’s babys).

Physicists theorize that strings exist in two basic forms, open and closed. An open string has two free ends, while a closed string forms a loop with no free ends. Strings interact by splitting and joining, so that one string can break into two, and two strings can combine to form one. In addition, open strings can close up, and closed strings can break open. This means that the strings have a great time and the interactions and motions help determine the kinds of particles and forces the strings give rise to.

One prediction that string theory makes is that spacetime has more than four dimensions. In fact, the mathematical description of string theory doesn’t work unless physicists assume that strings vibrate in 10 dimensions. But where are these other dimensions, and why can’t we see them? Physicists working on string theory propose that we cannot see the extra dimensions because they are wrapped up in tiny balls. Each ball may be the size of the Planck length, and there is a ball at each point in the three-dimensional space that we observe. Physicists believe that the properties of these rolled-up dimensions determine some of the properties of the elementary particles that occur in nature.

String theories are classified according to whether or not the strings are required to be closed loops, and whether or not the particle spectrum includes fermions. In order to include fermions in string theory, there must be a special kind of symmetry called supersymmetry, which means for every boson (particle that transmits a force) there is a corresponding fermion (particle that makes up matter). So supersymmetry relates the particles that transmit forces to the particles that make up matter.

There are five kinds of superstring theories which are developments from the basic string theory idea. One theory is said to combine all theories and supersede them. That theory is M-theory which is an extension of string theory in which 11 dimensions are identified.

Large Hadron Collider

M-theory adds another fundamental bit – membranes. Like the tenth spatial dimension, the approximate equations in the original five superstring models proved too weak to reveal membranes. A membrane, or brane, is a multidimensional object, usually called a P-brane, with P referring to the number of dimensions in which it exists. The value of ‘P’ can range from zero to nine, which give branes dimensions from zero to nine – five more than the world we live in. Spooky, eh?

Strong evidence for string theory could come from the observation of short-lived, mini black holes at the large hadron Collider (LHC). But the chance of their appearing is extremely small, so a failure to see them would not be a death blow for the theory.

In 2006, string theorist Allan Adams of MIT in Cambridge, US, and others offered a more promising check. They showed that some particle collisions could reveal whether certain fundamental assumptions underlying string theory are wrong.

Now, another team has shown that the energies needed to reveal such effects are achievable at the LHC. This is interesting, as the large hadron Collider has just started up and particles have travelled halfway around the Collider. The collider should be getting up to full power in early 2010, so perhaps we will have some answers and maybe this post will be completely inaccurate.

For the first time in the history of physics we therefore have a framework with the capacity to explain every fundamental feature upon which the universe is constructed. For this reason string theory is sometimes described as possibly being the “theory of everything” or the “ultimate” or “final” theory and in my eyes 42.