A theory of everything
String theory is an attempt to explain what all matter in the universe is made of. What does it have to say?
By TRAVIS JONES
A question considered by scientists and philosophers for thousands of years has been: what is everything made of?
Today we know that matter is made up of atoms and molecules. Atoms and molecules are made of protons, neutrons, and electrons. Protons, neutrons, and electrons are made of sub-atomic particles called quarks, and quarks are held together by gluons, and that's as small as science has verified so far.
But the ultimate answer to this question would be to find out what the universe’s quantum constituent is.
A quantum constituent simply means the discrete particle that is the most basic building block of all other particles that exist in the universe.
Once we have divided matter into this cascade of ever-smaller particles, the quantum constituent would be the theoretical particle that it would not be possible to divide any further.
Theoretical physicist Dr Brian Green explained in a TED talk in 2005 what the core of the theory was.
“It’s a theory that tries to answer the question: what are the basic, fundamental, indivisible, un-cuttable constituents making up everything in the world around us,” he said.
String theory suggests that the discrete element that all sub-atomic particles can be divided into are infinitesimally small vibrating waves of energy that String Theorists have named “strings”. The theory suggests that these strings vibrate in different ways in order to produce different types of sub-atomic quark.
Monash University Professor of Physics Michael J Morgan used a music metaphor to explain.
"Just like the string of a violin gives rise to music, the vibration of these fundamental strings gives rise to all matter and the forces by which matter interacts,” he said.
This is an attractive theory for physicists, as it marries quantum mechanics (the physical properties and interactions of atomic and sub-atomic particles) and general relativity.
Developed by Albert Einstein in 1915, General Relativity asserts that gravity is the result of warps and distortions in space-time stretching around large objects in space. This space- time membrane wraps around these bodies and exerts an inward force. On Earth and other planets, this is experienced as gravity.
However quantum mechanics and general relativity have been observed acting separately to each other, with quantum matter moving in unpredictable patterns seemingly unaffected by the force of gravity.
Queen Mary University lecturer in theoretical physics Dr David Berman said in his blog that quantum matter acted randomly. "This randomness appears when we look at particles at a small enough scale. The smaller one looks, the more random things become,” he said.
String theory suggests that there are other hidden dimensions exerting forces on these particles. The existence of dimensions other then the four perceivable ones (the three dimensions of space, and time) was first speculated in 1919 by Theodore Kaluza. Later in 1926, Oscar Klein suggested that they were hidden, but ever-present.
The mathematics behind string theory suggests that there are 10 dimensions of space and one dimension of time. String theorists suggest the different vibrations of these strings within the extra spatial dimensions can explain much of the nature of the physical world that we observe at the macro level, including the explanation for several universal mathematical constants.
“It involves elegant mathematics and deep ideas,” said Prof Morgan.
There have been several attempts to lift string theory out from its theoretical musings to real world applications. Experiments at the Large Hadron Collider (LHC) were promising.
It was hypothesised that if particles were smashed together at enormous velocity, the debris caused by the impact would fly off into other dimensions. These tests to date have been inconclusive.
The detection of gravitational waves by the LIGO Project in September 2015 holds some promise for string theory. At the press conference announcing the discovery, LIGO physicist Professor Kip Thorne said the team would, among other things, look for proof of the strings.
“Amazingly we are searching for gravitational waves – and have some hope of finding them – from cosmic strings, giant strings that reach across the universe that are thought to have been created by the inflationary expansion of the fundamental strings that are the building blocks of all matter,” he said.
So far however, efforts to demonstrate the effects of these dimensional forces or find the strings themselves have been in vain. This lack of evidence has lead to skepticism.
Astrophysicist Neil DeGrasse Tyson, who is director of the Hayden Planetarium at the Rose Center for Earth and Space in New York City, said in 2009 that science wasn't always neat.
“Just because they want it to be elegant, doesn’t mean the universe agrees,” he said.
During his appearance on Q & A, Dr Brian Greene said that he doubted proof of the extra dimensions would be found in his lifetime.
Many others have been critical because there is not a clear sign as to what benefit understanding what the fundamental particle of the universe will give us.
Prof Morgan disagreed. “One could equally ask what are the practical benefits of music, literature and art. None, but they enrich our lives, give new perspectives on our world and are part of the rich intellectual tapestry that makes the human journey worth undertaking!”
