When was m theory created

Then, in , the physicist Edward Witten discovered the mother of all string theories. He found various indications that the perturbative string theories fit together into a coherent nonperturbative theory, which he dubbed M-theory.

M-theory looks like each of the string theories in different physical contexts but does not itself have limits on its regime of validity — a major requirement for the theory of everything. For such imaginary worlds, physicists can describe processes at all energies, including, in principle, black hole formation and evaporation. This basic sequence of events has led most experts to consider M-theory the leading TOE candidate, even as its exact definition in a universe like ours remains unknown.

Whether the theory is correct is an altogether separate question. The strings it posits — as well as extra, curled-up spatial dimensions that these strings supposedly wiggle around in — are 10 million billion times smaller than experiments like the Large Hadron Collider can resolve. Although this might seem a major obstacle, several solutions have been proposed and nowadays it is considered as a notable feature, rather than a problem.

For example, we could somehow be forced to live in a four dimensional world without any access to the extra dimensions. However, different compactifications would lead to different values of the physical constants and, therefore, different physics laws. This may seem odd, but a lot of theoretical physicists are coming around to this idea. If you are not convinced you may try to read the novel Flatland: a romance of many dimensions by Edwin Abbott, in which the characters are forced to live in two space dimensions and are unable to realise there is a third one.

But there was one remaining pressing issue that was bothering string theorists at the time. A thorough classification showed the existence of five different consistent string theories, and it was unclear why nature would pick one out of five. This is when M-theory entered the game. During the second string revolution , in , physicists proposed that the five consistent string theories are actually only different faces of a unique theory which lives in eleven spacetime dimensions and is known as M-theory.

It includes each of the string theories in different physical contexts, but is still valid for all of them. For example, in archery, perturbation theory is how we aim our arrows. So at first it appears hopeless that we could ever penetrate into the non-perturbative region.

For example, if every motion of our arms got bigger and bigger, we would never be able to zero in and hit the target with the arrow. But notice that because of duality, a theory of small e which is easily solved is identical to a theory of large g which is difficult to solve.

But since they are the same theory, we can use duality to solve for the non-perturbative region. The first inkling that duality might apply in string theory was discovered by K. Kikkawa and M. Yamasaki of Osaka Univ. Unfortunately, T duality was still a perturbative duality. The next breakthrough came when it was shown that there was a second class of dualities, called S duality, which provided a duality between the perturbative and non-perturbative regions of string theory.

Another duality, called U duality, was even more powerful. Then Nathan Seiberg and Witten brilliantly showed how another form of duality could solve for the non-perturbative region in four dimensional supersymmetric theories. However, what finally convinced many physicists of the power of this technique was the work of Paul Townsend and Edward Wit- ten.

They caught everyone by surprise by showing that there was a duality between 10 dimensional Type IIa strings and 11 dimension- al supergravity! The non-perturbative region of Type IIa strings, which was previously a forbidden region, was revealed to be governed by 11 dimensional supergravity theory, with one dimension curled up. At this point, I remember that many physicists myself included were rubbing our eyes, not believing what we were seeing.

This revived tremendous interest in 11 dimensional theories and p- branes. Lurking in the 11th dimension was an entirely new theory which could reduce down to 11 dimensional supergravity as well as 10 dimensional string theory and p-brane theory.

Since string theory is really a theory of Creation, when all its beautiful symmetries were in their full glory, the only way to test it, the critics wail, is to re-create the Big Bang itself, which is impossible. Nobel Laureate Sheldon Glashow likes to ridicule superstring theory by comparing it with former Pres. Actually, most string theorists think these criticisms are silly.

They believe that the critics have missed the point. The key point is this: if the theory can be solved non- perturbatively using pure mathematics, then it should reduce down at low energies to a theory of ordinary protons, electrons, atoms, and molecules, for which there is ample experimental data.

If we could completely solve the theory, we should be able to extract its low energy spectrum, which should match the familiar particles we see today in the Standard Model. Thus, the problem is not building atom smashers l, light years in diameter; the real problem is raw brain power: of only we were clever enough, we could write down M-theory, solve it, and settle everything. In the early s, string theory was in a bit of a theoretical pickle.

For decades, theorists had poured their hearts and minds into the idea that the fundamental building blocks of reality are tiny, vibrating strings. This was a potentially revolutionary idea, capable of uniting all the forces of nature and all the building blocks of matter into a single, harmonious picture. The pickle, however, was that there were five independent candidates for string theory, each one looking radically different than the others.

Which one was right? Related: Why string theory persists — despite the knotty physics. The five different string theories had a few commonalities. For one, they all involved strings. They also all required our universe to have 10 total dimensions : the usual three spatial dimensions, one for time and six more compact dimensions that are tiny and curled up on themselves at submicroscopic scales.

And in all the theories, the ways strings vibrate give rise to the richness of our physical world, from the forces of nature to the building blocks of matter to physical constants themselves. But when it comes to physical theories, details matter, and the five competing string models differed in the details. Some theories only had closed loops of strings, while others allowed open, wiggling strings. Some theories only allowed vibrations to travel in one direction on the strings, while others allowed both.