The ‘M’ should stand for math, but it doesn’t. This despite the fact that the mathematics of M-theory boggles the minds of many mathematicians. Yet, M-theory may represent that Holy Grail of physics, a Theory of Everything that explains how the four fundamental forces-the strong, weak, electromagnetic and gravitational-fit together in the framework of the universe.
The story of M-theory begins with string theory-the idea that all matter, forces and energy result from tiny one-dimensional vibrating strings. Initially, string theorists considered string theory the path to a grand Theory of Everything, but it soon frayed into five contradictory theories. Each made different assumptions about the number and types of particles in the universe.
In the early 90s, as theorists mathematically explored more of each string theory, they realized that each seemed to describe the same underlying idea. It’s like an optimistic friend describing a half-filled glass as “half full” and a pessimistic friend describing the same glass as “half empty.” Both friends describe the same glass, but they describe it differently. Mathematically, the five string theories described the same underlying idea in different ways.
Theorists had not noticed this underlying idea because the theories rested on contradictory assumptions. For example, some theories assumed strings stretched for long distances; others assumed short lengths. Theorists learned that the unique properties of strings made contradictory concepts, such as long and short, mathematically equivalent. The contradictions that had kept the five string theories apart actually tied them together. Then, at a lecture in 1995, Dr. Edward Witten, a string theorist at Harvard, mathematically described the idea that strung the five separate string theories together, calling it M-theory. Unwittingly, Witten had ushered in the so-called second superstring revolution.
M-theory builds on string theory, predicting 11 dimensions instead of 10 and the existence of 2-dimensional objects called M-branes, similar to the D-branes of string theory. However, M-theory remains incomplete and untested. “We have the secondary equations, but not the primary equations they should have come from,” Witten told The Varsity.
Experimental tests of M-theory would require measurements at scales far smaller than an atom , or microscopic observations of black holes-feats far beyond our technological capabilities. Witten cautiously offered one suggestion. “It’s at the fringe of being barely conceivable,” he said, “that if the Big Bang produced large numbers of miniature black holes, we could see them evaporating in space.”
Practical difficulties aside, M-theory makes the math of string theory make sense. It may yet lead to a Theory of Everything. Furthermore, in discovering M-theory, theorists have realized that seemingly-impossible contradictions, like long = short, become possible realities. This has already affected the way scientists think about the development of massive phenomena like black holes and the Big Bang.
So what does the ‘M’ stand for? No one knows for sure. Current suggestions include matrix, mother and muffin. Witten has suggested it could stand for murky, since at the moment, much of M-theory remains shrouded in mystery.
