Cosmology
# M Theory

## What is M theory?

## Who proposed the M theory?

## Backgrounds

## History

## Explanation of the M theory

## Characteristics

## What problems does the M theory present?

## Importance

**M theory** is the name for a unified version of string theory that was proposed in 1995 by physicist Edward Witten. At the time of the proposal, there were 5 variations of string theory, but Witten proposed the idea that each was a manifestation of a single underlying theory.

**Related topics**

The **M theory** or **super-string** theory is the one that determines that all elementary **particles** are made up of the same type of energy **filament** but that each of them has different **vibrations**.

The M theory was proposed in its beginnings by **Edward Witten**. Witten’s proposal was combined with the five theories of **super-string** and **super gravity** in eleven **dimensions** that already existed before. It has its origin based on **string theory**, according to which all particles are tiny strings that vibrate at a certain frequency. According to this proposal, particles are **strings** vibrating at a certain **frequency** in a **space-time** that requires at least ten different dimensions.

Many years ago, mainly during the **19th century**, the **atom** was believed to be the smallest particle of matter and the universe. It was long regarded as the **basic** and **indivisible element** of matter.

In the early years of the twentieth century, it was found that this atom had a series of smaller components that were called **protons**, **neutrons** and **electrons**, and that would be known as **subatomic** particles.

In the 1980s, it was discovered that protons and neutrons were made up of small particles called **quarks**. **Quantum theory** is the set of rules that describe the interactions of these particles.

Then, in 1980, a new type of mathematical model called string theory was consolidated which suggested that all **particles** and **forms of energy** in the universe could be hypothetically interpreted as “**strings**” or **one-dimensional** objects, which were perceptible at scales of length comparable to **Planck’s** length.

String theory said that the universe was made up of multiple **spatial dimensions**, compacted and perceptible on a very small scale. Strings vibrate in **multiple dimensions**, and according to how they vibrate, they could then be perceived in three-dimensional space as **matter**, **light**, or **gravity**.

In the mid-1990s, **Edward Witten**, a string theorist, considered that the five different versions of string theory were the same in different perspectives and proposed **unification** into a theory called “**M theory**,” in which the letter “**M**” is not specifically defined, but is understood as “**membranes**.

The M theory bases its **history** on the String Theory, from it, **Dr. Edward Witten** proposed the famous M theory, a **unifying** theory that could explain the whole **Universe** by interpreting the four forces of our Universe: **gravitational**, **electromagnetic**, **strong nuclear** and **weak nuclear**.

String theory, super-string or M theory, is the **unification** of all **theories** that relate to the four **forces** of nature.

This theory was developed by and to explain the **strong nuclear force**, but there was a much more relevant theory. The M theory is in charge of describing the universe with 11 **dimensions**. Of these spatial dimensions we have, one dimension is **time** and 6 dimensions are compacted in a Calabi-Yau space.

The M theory also postulates the existence of **branes** because according to it, the universe where we live is in a 3-dimensional brane, which would be found among other branes, side by side. The theory says that all matter is made up of **open strings**, and that it would be confined to our own **brane universe**. The branes would be next to each other, within a **hyperdimension** or **bulk**.

Branes would not be fixed but would be **undulating** and have **movement**. When 2 branes touch, a **Big Bang** would be produced and another **Brane universe** would be formed, expanding in opposite directions. Eventually, the branes could be touched again, and the **cycle** would begin again.

The main features of M theory are as follows:

- The M theory is much more than simple strings.
- It contains
**larger objects**as well as smaller objects. - The objects of string theory are called
**P-branes**where P denotes their**dimensionality**or D-branes. - Larger objects were always present in string theory but could never be studied before the
**Second**Super-string**Revolution**because of their**non-disturbing** - It is suggested that the
**Big Bang**was caused by the collision of two of these membranes, from which our Universe was born.

One of its problems is that the initial theory needed the existence of a multidimensional space, and our Universe only has **four dimensions** which are the three spatial ones and time. It was thought then that the dimension was very small in size and that it was **rolled** up or **compacted**.

The second problem with string theory was that it only worked for some types of particles, **bosons**; **fermions** like **quarks**, **electrons** and other interesting particles were then left out.

M theory is important for a better understanding about the **universe** and **humanity**. The impact of science also encompasses culture. The main objective of the theory is to unite the laws of **quantum** **mechanics** that refer to the laws of the “small” with the laws of **general relativity** that are basically the laws of the ” big “, in a same mathematically consistent framework. This is vital because in the standard formulation the union of **quantum mechanics** and **general relativity** leads to mathematical **inconsistencies**.

Written by Gabriela Briceño V.