The Theory of Everything - String Theory (Part 2)

For many years, the pioneers of string theory struggled with a theory that most physicist just didn't believe in. The basic problem that had most physicists questioning the validity of string theory was that for decades it was believed that the components of the atom could all be classified as point particles, with electrons orbiting around a nucleus of protons and neutrons, which themselves were made up of even smaller 'particles' deemed quarks. In essence, what string theory says is that what we believed to be indivisible point particles were in fact tiny vibrating strings. Furthermore, strings were elegant in their design because of their enormous versatility, for example, just as strings on a musical instrument can vibrate at different frequencies making individual musical notes, in the same way, all the tiny strings of string theory vibrate in different frequencies making up all the fundamental particles and their properties in nature (known as resonance of strings). If we could only understand the properties of these strings, we would be able to explain all the matter and all the forces of nature, from subatomic particles to massive galaxies in our universe. This is the potential of string theory to be the 'theory of everything'.

However, physicists managed to come up with not one, not two, but five string theories! The five theories had many things in common but they had many differences in their mathematics. It was almost embarrassing for string theorist, to say the least, to have five competing string theories that could potentially be the 'theory of everything'.

However, in 1995 at a conference for string theory at the University of Southern California, Edward Witten, an American theoretical physicist with a focus with a focus in mathematical physics, provided a completely new perspective of string theory. He proposed and showed that in fact what we thought were five theories, were just five ways of looking at the same thing. Therefore, all five string theories could be unified into one overall theory, now called M theory, a revolution in string theory, and a possible 'theory of everything'.

However, even M theory had its caveats. Before M theory, string theory consisted of 10 dimensions, with one dimension of time and the 3 dimensions that we are familiar with, plus 6 extra dimensions that are very small and virtually impossible. But M theory demands another spatial dimension, and therefore, there must be 11 dimensions!

Another concept involves the idea that dimensions all have to do with the independent directions in which they can move (called degrees of freedom) and the more dimensions you have, the more you can do. And it became fairly obvious that at the 11th dimension allowed the strings to "stretch" to something like a membrane. A membrane could even be 3 dimensional and with enough energy, a membrane could be as large as a universe! The existence of membranes and extra dimensions reveals a new idea: our whole universe is lying on a membrane inside a much larger higher dimension of space. This raises the possibility that our universe, lying on a membrane, is just a small portion of this larger space, and possibly lies right next to other membranes that contain 'parallel universes'. Some of these universes could be like our own, or it could likely have their own unique laws of nature.

But these parallel universes are not individual compartments in the higher dimensional space, there is one thing that physicists believe that can transverse between universes: gravity. But what makes gravity special? What makes gravity different from anything else in the universe? Following the development of M theory, physicists began to investigate objects other than just strings, one example being membranes. Physicists now believe that matter and energy are actually made up of open-ended vibrating strings with their ends tied down to our 3 dimensional membrane, restricting the matter or energy to our membraned universe. However, closed-looped strings still do exist, and one kind is responsible for gravity (called a graviton). This allows the graviton to travel between the other dimensions and membranes. And if this is the case, then it could be possible to "detect" parallel universes by analyzing these transversing gravitons. And if theoretically there are intelligent lifeforms in these parallel universes, then it could be possible theoretically for this parallel to be very close to us, and thus, theoretically we could "communicate" with these lifeforms using gravity.

This concept of parallel universes could also explain the origins of our very own universe. If we were to turn back time, going further and further back, where our universe was just a very small highly dense point in space we would see that all the laws of physics just break down, and are no longer valid. Not only that, but we also have the problem with the process that initiated the "creation" of our universe, the so-called Big Bang. One of the most imaginative models suggests that the origin of the Big Bang lies in the movement of the parallel universal membranes. According to this proposed model, some time before the Big Bang, two membranes began to drift towards each other until they collided at a specific point, releasing this incredible amount of energy, leading to the Big Bang, and eventually, our universe. What is even more intriguing is that scientists believe that this was not a special event. In fact, it could be absolutely possible that two membranes could've collided prior to the creation of our universe, other membranes could be colliding giving rise to other parallel universes, and this collision will continue to occur in the future. If this idea is true, then it means that somewhere out there is an adjacent membrane on a collision course with our very own universe. However, there is a major problem. The mathematics and laws of nature break down at these early time points, so it is almost impossible to predict what would happen if two membranes were to collide. Would it lead to another Big Bang, or are there other inter-universal possible scenarios?

Of course, these theories seem very amazing and elegant, but they mean nothing if they cannot be proved "in the lab", so to speak. Two of the world's largest particle physics laboratories, fermilab and CERN, are creeping ever closer to answers. The concept here is that hydrogen atoms are electrocuted with huge amounts of electricity, and then they are stripped of their electrons. These energized protons are accelerated through a long underground tunnel system, and just as these protons approach the speed of light, these protons are collided with protons travelling in the opposite direction. Most of the time, the collisions are just glancing blows, but occasionally, there is a direct hit and the result is an explosion of subatomic particles. The hope is that among these subatomic particles is the graviton, which is closed-looped according to string theory, and can travel into the extra dimensions and therefore, the absence of the graviton could be detected.

Another experiment on top of the list for both scientists at fermilab and CERN is the idea of super symmetry, a central prediction of string theory. In essence, super symmetry predicts that for every subatomic particle there exists a paired heavier superpartner (also called a sparticle). If these superpartners exist, they are likely extremely heavy, in fact they may be so heavy that they may not be able to detected with today's "atom smashers" at fermilab and CERN. Although the existence of superpartners won't prove string theory, it will definitely be circumstantial evidence that we are on the right track.

But what if we are unable to find the graviton, or superpartners or even extra dimensions? What if we are unable to find any evidence for string theory? Could string theory be incorrect and is not the road into the 'theory of everything'? The fact of the matter remains, about a century ago some scientists believed they had figured out the laws of the universe, but Albert Einstein came along and revolutionized our views of space, time and gravity. Quantum mechanics revealed a world of unpredictability and bizarre. Regardless of the obstacles, scientific curiosity will keep us going and we will continue to explore the unknown. Undeniably, these new theories of physics shows us the imaginative and creative potential of the human mind.