"M" Theory and physics...

Why have I not heard of "M" theory before last night? I was blown away watching the discovery science channel last night when they described "M" theory as re-defining the age old challenge of "a unified theory of everything" that mathmeticians and physics gurus have been searching for so long.

It seems Fredrick Neitzche was right, there are parallel universes in the eleventh dimension.

Looks like "A Brief History of Time" will need updating. Get at it, Stephen Hawking!!!

If you didn't see the show, they've been able to mathematically suggest the origins of the universe, and pre-universe (pre-big bang) using a new theory called Membrane theory. It's complicated and I won't pretend to explain it, but it's been able to provide an explanation for several mysteries in physics (including why gravity is so comparably weak compared to other forces of nature) including the origin of the universe, and "before."

Several mathemeticians now using "M" theory are now finding the answers to many supposedly unsolveable riddles.

Woah! Looks like Einstein was wrong. Eine suggested nobody would ever find a unified theory. Wrong.

My only question, why am I only finding out about this now? How many DU'ers are up on "M" theory?

And it's pretty cool. Here a few links:

When Branes Collide - origins of universe
http://www.findarticles.com/p/articles/mi_m1200/is_12_160/ai_79196969

Invisible Forces and Gravity
http://dailyrevolution.org/tuesday/gravity.html

Leaking Gravity May Explain Cosmic Puzzle
http://www.space.com/scienceastronomy/dark_energy_050228.html

On edit: Here's another one my son just passed along:
Finding the Ultimate Theory of Everything
http://www.rednova.com/news/space/132303/finding_the_ultimate_theory_of_everything/index.html

to take a closer look. What was the name of the special you saw?

It was on the Discovery Science Channel but I forget the title of it. Thanks for the links!

Recurrence?

I'm not totally up on "M", but I've read some tangential stuff on it. What was the name of the show you saw, I may have seen it, but I don't remember.

affectionately called P-branes by some physicists. There was an extensive article about this topic last year in Scientific American. It was a good read.

Did you know that in field theory, there is an interaction that is illustrated using a figure called a "Penguin diagram"? It is called this because the author was challenged to somehow work the word penguin into his next paper...

I put in my time a few months ago.. It eventually clicked, but not until I read about 10 different papers. It's fascinating stuff. I just wish Einstein was still around to see what's happening with M theory.

a bit hokey but very intriguing!

I hope that I'm not a neo-con repub in a "parallel universe"

taught.:puke:

The "M" theory (the M can actually stand for anything; Magical, Mystery, or Mother etc.) M theory evolved from string theory which was not well accepted at first.

Cambridge Relativity: Quantum Gravity

M-theory, the theory formerly known as Strings
The Standard Model
In the standard model of particle physics, particles are considered to be points moving through space, tracing out a line called the World Line. To take into account the different interactions observed in Nature one has to provide particles with more degrees of freedom than only their position and velocity, such as mass, electric charge, color (which is the "charge" associated with the strong interaction) or spin.

The standard model was designed within a framework known as Quantum Field Theory (QFT), which gives us the tools to build theories consistent both with quantum mechanics and the special theory of relativity. With these tools, theories were built which describe with great success three of the four known interactions in Nature: Electromagnetism, and the Strong and Weak nuclear forces. Furthermore, a very successful unification between Electromagnetism and the Weak force was achieved (Electroweak Theory), and promising ideas put forward to try to include the Strong force. But unfortunately the fourth interaction, gravity, beautifully described by Einstein's General Relativity (GR), does not seem to fit into this scheme. Whenever one tries to apply the rules of QFT to GR one gets results which make no sense. For instance, the force between two gravitons (the particles that mediate gravitational interactions), becomes infinite and we do not know how to get rid of these infinities to get physically sensible results.

String Theory
In String Theory, the myriad of particle types is replaced by a single fundamental building block, a `string'. These strings can be closed, like loops, or open, like a hair. As the string moves through time it traces out a tube or a sheet, according to whether it is closed or open. Furthermore, the string is free to vibrate, and different vibrational modes of the string represent the different particle types, since different modes are seen as different masses or spins.

One mode of vibration, or `note', makes the string appear as an electron, another as a photon. There is even a mode describing the graviton, the particle carrying the force of gravity, which is an important reason why String Theory has received so much attention. The point is that we can make sense of the interaction of two gravitons in String theory in a way we could not in QFT. There are no infinities! And gravity is not something we put in by hand. It has to be there in a theory of strings. So, the first great achievement of String Theory was to give a consistent theory of quantum gravity, which resembles GR at macroscopic distances. Moreover String Theory also possesses the necessary degrees of freedom to describe the other interactions! At this point a great hope was created that String Theory would be able to unify all the known forces and particles together into a single `Theory of Everything'.

From Strings to Superstrings
The particles known in nature are classified according to their spin into bosons (integer spin) or fermions (odd half integer spin). The former are the ones that carry forces, for example, the photon, which carries electromagnetic force, the gluon, which carries the strong nuclear force, and the graviton, which carries gravitational force. The latter make up the matter we are made of, like the electron or the quark. The original String Theory only described particles that were bosons, hence Bosonic String Theory. It did not describe Fermions. So quarks and electrons, for instance, were not included in Bosonic String Theory.

By introducing Supersymmetry to Bosonic String Theory, we can obtain a new theory that describes both the forces and the matter which make up the Universe. This is the theory of superstrings. There are three different superstring theories which make sense, i.e. display no mathematical inconsistencies. In two of them the fundamental object is a closed string, while in the third, open strings are the building blocks. Furthermore, mixing the best features of the bosonic string and the superstring, we can create two other consistent theories of strings, Heterotic String Theories.

However, this abundance of theories of strings was a puzzle: If we are searching for the theory of everything, to have five of them is an embarrassment of riches! Fortunately, M-theory came to save us.

Extra dimensions...
One of the most remarkable predictions of String Theory is that space-time has ten dimensions! At first sight, this may be seen as a reason to dismiss the theory altogether, as we obviously have only three dimensions of space and one of time. However, if we assume that six of these dimensions are curled up very tightly, then we may never be aware of their existence. Furthermore, having these so-called compact dimensions is very beneficial if String Theory is to describe a Theory of Everything. The idea is that degrees of freedom like the electric charge of an electron will then arise simply as motion in the extra compact directions! The principle that compact dimensions may lead to unifying theories is not new, but dates from the 1920's, since the theory of Kaluza and Klein. In a sense, String Theory is the ultimate Kaluza-Klein theory.

For simplicity, it is usually assumed that the extra dimensions are wrapped up on six circles. For realistic results they are treated as being wrapped up on mathematical elaborations known as Calabi-Yau Manifolds and Orbifolds.

M-theory
Apart from the fact that instead of one there are five different, healthy theories of strings (three superstrings and two heterotic strings) there was another difficulty in studying these theories: we did not have tools to explore the theory over all possible values of the parameters in the theory. Each theory was like a large planet of which we only knew a small island somewhere on the planet. But over the last four years, techniques were developed to explore the theories more thoroughly, in other words, to travel around the seas in each of those planets and find new islands. And only then it was realized that those five string theories are actually islands on the same planet, not different ones! Thus there is an underlying theory of which all string theories are only different aspects. This was called M-theory. The M might stand for Mother of all theories or Mystery, because the planet we call M-theory is still largely unexplored.

There is still a third possibility for the M in M-theory. One of the islands that was found on the M-theory planet corresponds to a theory that lives not in 10 but in 11 dimensions. This seems to be telling us that M-theory should be viewed as an 11 dimensional theory that looks 10 dimensional at some points in its space of parameters. Such a theory could have as a fundamental object a Membrane, as opposed to a string. Like a drinking straw seen at a distance, the membranes would look like strings when we curl the 11th dimension into a small circle.

Black Holes in M-theory
Black Holes have been studied for many years as configurations of spacetime in General Relativity, corresponding to very strong gravitational fields. But since we cannot build a consistent quantum theory from GR, several puzzles were raised concerning the microscopic physics of black holes. One of the most intriguing was related to the entropy of Black Holes. In thermodynamics, entropy is the quantity that measures the number of states of a system that look the same. A very untidy room has a large entropy, since one can move something on the floor from one side of the room to the other and no one will notice because of the mess - they are equivalent states. In a very tidy room, if you change anything it will be noticeable, since everything has its own place. So we associate entropy to disorder. Black Holes have a huge disorder. However, no one knew what the states associated to the entropy of the black hole were. The last four years brought great excitement in this area. Similar techniques to the ones used to find the islands of M-theory, allowed us to explain exactly what states correspond to the disorder of some black holes, and to explain using fundamental theory the thermodynamic properties that had been deduced previously using less direct arguments.

Many other problems are still open, but the application of string theory to the study of Black Holes promises to be one of the most interesting topics for the next few years.

Are there any predictions that derive from such a theory that we have the tools to observe?

Many people didn't give relativity any credence until the day the light from a visible star was actually observed to have bent under the force of gravity.