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STRING THEORY : A Beginner's Guide...

String theory is one of the most famous ideas in modern physics, but it is also one of the most confusing.
At its heart is the idea that the fundamental particles we observe are not point-like dots, but rather tiny strings that are so small that our best instruments cannot tell that they are not points.
It also predicts that there are extra dimensions to space beyond the obvious length, breadth and depth, but we do not experience them because they are bunched up in tiny spaces.

String theory may predict our universe :
Why is our universe the way it is? If some of its fundamental laws were even slightly different, our world would be a strange and lethal place. Instead, it seems exquisitely tuned to make life possible. String theory could explain why.

The theory of everything: Are we nearly there yet?
Physicists believe that there was only one force just after the big bang, and as the universe cooled, it split into the four forces we now observe. String theory is the most popular idea for explaining why these four forces exist, but it has some serious competition.

Strings with a twist:
One of the most widely publicised aspects of string theory is its need for extra "tiny" dimensions of space. But these extra dimensions may not be necessary after all – at least, not if a 40-year-old idea called "twistor theory" has anything to do with it.

String theory could lead to multiple universes:
String theory describes 10500 separate universes, with different constants of nature and even different laws of physics. Many physicists think this is a weakness of the theory, but Leonard Susskind thinks it could actually help us understand why our universe is so well suited to life.

Can string theory accommodate inflation?
In its early days, the universe is thought to have expanded extremely rapidly through a process called "inflation". This is well accepted in physics, but it turns out that string theory has trouble producing inflation. It could be a problem for string theory – or for inflation.

The LHC could rule out string theory:
Particle collisions could reveal whether some of the fundamental assumptions of string theory are wrong. Once it's working properly, the Large Hadron Collider could achieve the energies needed to reveal these effects.

String theory: It's not dead yet:
Despite capturing the popular imagination, string theory is losing its public appeal. Sean Carroll argues that, despite the difficulties of testing it, the theory has still given us many valuable results.

Ice-bound neutrino hunter may bolster string theory:
A neutrino experiment at the South Pole may be able to detect the predicted effects of string theory. The IceCube experiment will be able to detect up to 10 cosmic neutrinos per year. Those neutrinos may reveal the existence of extra spatial dimensions, which is a key prediction of string theory.

String theory fights back :
Faced with accusations that their mathematical models cannot be tested, string theorists are retaliating with a host of thoughts on how to verify their ideas. These include looking for gravitational waves and scrutinising the results from particle accelerators.

Cosmic string: One of string theory's most dramatic predictions is that we should find cosmic strings. These would be billions of light years long, thinner than a proton and spectacularly dense. As they could reveal themselves in images of distant galaxies, the search is on.


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