# String theory and M-theory

Asked Jan 12, 2011, 02:46 PM — 4 Answers
What are the basic ideas behind the string theory? What about the M-theory : how advanced is it? Is it the truly unifying theory we all wish to see?

 TUT317 Posts: 657, Reputation: 395 Senior Member #2 Jan 13, 2011, 06:42 PM
Quote:
 Originally Posted by crisis87 What are the basic ideas behind the string theory? What about the M-theory : how advanced is it? Is it the truly unifying theory we all wish to see?
As Pythagoras would say," it's all mathematics". Mathematics way beyond what I can understand. Nonetheless, I'll give it a go.

One reason string theory was put forward was to solve the problem of singularities. As you probably know the laws of classical physics break down at distances smaller than a Planck length. What we end up is with are infinities. That is a point particle which is of infinite density. The concept of time also breaks down.

String theory postulates that the smallest units of matter are not point particles but rather vibrating strings. If correct it apparently solves a few problems. The most important being the unification of classical physics and quantum mechanics. I think it also solves the problem of quantum particle jitters. Strings smooth out these jitters.

In a similar fashion the classical laws of physics breaks down at the moment of the Big Bang. If String theory is correct then oscillating strings need extra dimensions to move through. The outcomes of this was there were 5 different string theories developed at more or less the same time each postulating different numbers of dimensions. It was obvious that all five theories could not be correct. They had to be united under a single theory. The idea was the five different theories were just five different ways at looking at the one reality. Eventually everything was united under one theory know as M-Theory. M-Theory calls for 11 dimensions.

Another implication for M theory is that there are an infinite number of universes existing on its own membrane. This does away with the need for the Big Bang. The Big Bang is simply membranes colliding. On this basis time and space don't have a beginning as such.

I am unable to provide you with a more detailed explanation.
 crisis87 Posts: 2, Reputation: 10 Junior Member #3 Jan 14, 2011, 05:06 AM
Thanks a lot! I found it quite useful.
 Capuchin Posts: 5,319, Reputation: 3601 Uber Member #4 Jan 14, 2011, 06:23 AM
It's important to point out that these aren't theories, but hypotheses. There is no evidence to back either of these ideas. They have a lot of hold because they turn out to be quite elegant solutions, and no hypothesis about these things has any evidence backing them currently.

But, the more we think about them and perform calculations on them, , we may find something that can be measured and matched to prediction.
 TUT317 Posts: 657, Reputation: 395 Senior Member #5 Jan 14, 2011, 12:52 PM
Quote:
 Originally Posted by Capuchin It's important to point out that these aren't theories, but hypotheses. There is no evidence to back either of these ideas. They have a lot of hold because they turn out to be quite elegant solutions, and no hypothesis about these things has any evidence backing them currently. But, the more we think about them and perform calculations on them, , we may find something that can be measured and matched to prediction.

Hi Cap,

Good point. Like all axioms/postulates they cannot be proven true. They serve as a starting point. I agree that it is important to keep this in mind.

Regards

Tut