To elaborate a **theory of everything** , one that manages to coherently match the laws of the world of particles such as electrons (the postulates of quantum physics), and the physics of great stars, (the theory of relativity) has been the challenge of physics par excellence for the great geniuses of the twentieth century, and continues to be so. While the latter is described by Einstein’s equations, the former is predicted with extraordinary precision by the so-called Standard Model of fundamental interactions.

**Perhaps the two most famous scientists of our time died sharing the same wishes: Albert Einstein and Stephen Hawking.**

Before he died, Stephen Hawking worked for years on something called ” **M-theory** .” For him, it was the best bet on a complete theory of the universe. But what does it consist of?

Our understanding of the cosmos is described by **four fundamental forces** . Two of them, gravity and electromagnetism, are relevant to us on a macroscopic level, we deal with them in our daily lives. But the other two, called strong and weak interactions, act on a microscopic scale, becoming relevant only when it comes to subatomic processes.

But when trying to combine the forces of both scales, **infinite ‘nonsense’ appears.**

To understand the basic idea of Hawking’s M-theory, we must go back to the 1970s, when scientists realized that instead of describing the universe based on point particles, you could describe it in terms of **small oscillating strings: the famous string theory.**

This new way of thinking about the fundamental constituents of nature worked to solve many theoretical problems. And unlike the standard theory of gravity, string theory can describe their interactions mathematically without getting strange infinities.

## Many universes

Another surprising feature is that string theory requires the existence of **ten space-time dimensions.** Currently, we only know four: depth, height, width, and time. We could be forced to live in a three-dimensional world without any access to the additional dimensions.

Or, the rest of the dimensions could be “compacted” on such a small scale that we don’t notice them. One possible solution is that our universe is just one of many in an infinite “multiverse”, governed by different physical laws.

## The weak points of string theory

But there was a problem that nagged string theorists: a comprehensive classification showed the existence of five different consistent string theories, and it was unclear why nature would choose one in five. **This is where Hawking’s M-theory comes into play.**

## What does Hawking’s M-theory say?

In 1995, physicists proposed that the five consistent string theories are actually just different faces of **a single theory that lives in eleven dimensions of space-time and is known as M-theory.** This theory, which is the most mathematically consistent , is considered by many scientists the definitive ‘theory of everything’.

## Lack of empirical predictions

However, **until now, M-theory has not been able to generate empirical predictions** , which can be tested through experiments.

But some of its characteristics, such as supersymmetry, are currently being tested in the Large Hadron Collider. If scientists find evidence of superpartners, then M-theory would definitely be strengthened. But it **remains a challenge for today’s theoretical physicists to** produce testable predictions, and for experimental physicists to set up experiments to test them.

But for the moment, until theoretical physicists come up with experimental proof, we cannot be sure whether Hawking or any other scientist has come up with the prized ‘theory of everything’.

Stephen Hawking’s illness prevented him from moving, but that does not mean that it prevented him from performing this feat for humanity. With his death, he orphaned the world of physics, but his contributions will continue to mark the lines of research that lead the knowledge of the cosmos.