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Superstring theory unifies the laws of nature and explains all four known forces, including gravity. Strings vibrate to determine particle properties, and the theory requires six extra dimensions and an eleventh dimension for M-theory. The universe exists on a floating brane, and the Big Bang may have been caused by two branes colliding. Superstring theory has yet to be proven, but evidence of large strings has been discovered, and it could be the Theory of Everything.
Superstrings, or superstring theory, is an exciting field in physics sometimes called The Theory of Everything. Many think it is the elusive unifying explanation sought by Einstein that could explain all known forces in the universe.
Until the advent of superstrings, scientists had two opposing theories about how the laws of nature behaved: Einstein’s Theory of General Relativity and Quantum Mechanics.
General Relativity explains the world as we know it on a pretty massive scale. He describes spacetime as a fabric deformed by mass that takes into account orbital systems, galaxies and the force of gravity. But these laws break down at the quantum level, where a subatomic particle can’t be measured in terms of its exact position in space at any given moment. It’s also as likely to move backward in time as it is forward, and it can even appear to be in two places at once. The world of the infinitely small is so bizarre that scientists have coined the term “quantum weirdness” to describe it.
The problem for physicists was to find a theory that would unite the world we know with the quantum world. An explanation to account for all four known forces: gravity, strong and weak nuclear forces, and electromagnetism. Superstrings might be that answer.
Through mathematical equations it became obvious that the way we had previously thought of particles as “dots” or “balls” of energy was inaccurate. These tiny bits of matter actually acted more like strings that twitched and vibrated. Strings are so small that Brian Greene, a physicist and advocate, explains that if a single atom were the size of our solar system, a string would only be the size of a tree. Yet strings make up all matter from the quantum level up.
How strings vibrate determines the specific properties of each particle, likening the universe to a cosmic symphony of superstrings. But to rid the theory of mathematical anomalies, six extra dimensions were needed. The six extra dimensions form tiny 6D shapes curled up at every point in our space. Inside these 6D shapes are the strings of superstring theory. The extra six sizes, plus our three, meant there were really 9 sizes. Add one more at a time and the total is 10 sizes. Surprising as it was, it wasn’t the end.
In 1995 several superstring theories presented a conundrum until M-theory brought them together. The only trick? M-theory mathematically required an eleventh dimension. This presented a new picture of strings that, given enough energy, a string could stretch to become an extremely large floating membrane, called a brane for short. Branes can have different size properties and grow as large as a universe. In fact, according to the theory, our entire universe exists on a floating brane, just one of several floating branes that each support their own parallel universe. Each brane represents a slice of a higher dimensional space or mass.
Although the Standard Model of the 1970s already combined three of the four forces into a unified theory, gravity could not be reconciled with the three quantum forces. But a breakthrough in superstrings included the elusive force of gravity, whispering of the holy grail of physics. If a hypothetical massless particle responsible for the transmission of gravity – the graviton – existed at the quantum level as a closed string, this would have a direct gravitational link to superstring theory.
The theory predicts that strings can be open or closed. Open strings, or strings that look like tiny wriggling hairs, have at least one end “attached” to the membrane like a streetcar is attached by a top wire to a power line. Strings can move across the brane but can’t leave it, explaining why we can’t physically see out or reach our dimension. The atoms that make up our bodies are composed of open strings that have endpoints attached to our 3-D membrane. Another way to look at it is to consider a movie screen. People on a screen appear to be three dimensional, but they can’t actually reach the screen in our 3D world. They are stuck in their 2D world, just like we are stuck in our 3D world and can’t get to neighboring dimensions. Scientists refer to this as degrees of freedom.
But the graviton is different. Being a closed string or ring with no connected endpoints, it has been theorized that it might be able to escape our 3-D brane and penetrate other dimensions. This would explain why gravity is many times weaker than other forces.
However, what if the opposite were true? What if gravity on a parallel brane is as strong as the other forces, but here it’s weaker because it’s just seeping into our dimension? Mathematically, superstring theory again worked beautifully and finally provided a plausible explanation for the weakness of gravity while uniting it with the other three forces.
Only one obstacle remained: the unifying theory should also be able to explain the Big Bang. Four physicists traveling together on a train came across this topic casually. One of them asked the question, what would happen if two branes collide? The plausible mathematical answer turned out to be the Big Bang.
Detractors of superstring theory point to the lack of evidence and the difficulty of providing it. Is it just a beautiful mathematical construct? A philosophy? Or a true explanation of our world? No other theory has come close to mathematically unifying all four forces, much less providing an explanation for the Big Bang. But proving that other dimensions exist – floating branes and parallel universes – was a major sticking point.
However, believers in the elegant theory are eager to see it demonstrated, and scientists have since discovered that there may be observable evidence of astronomically large strings. Thus, superstring theory continues to gain ground. Eventually, if successful, from 11 dimensions to parallel universes to swirling galaxies to quantum soup, superstrings could indeed be the Theory of Everything.
