Einstein spent 30 years of his life searching for one thing: the “unified field theory” – or the theory of everything. A big problem for physics is that its two main ideas - quantum mechanics and Einstein’s theory of general relativity - don’t work together. This has troubled physicists for decades, and the question of whether our observations of the subatomic and macroscopic worlds can be married together into one simple, unifying rule has led to some bizarre ideas. Some physicists – such Stephen Hawking – have argued that the quest is hopeless, but it nevertheless continues relentlessly onwards.
Quantum mechanics describes the interactions of the vast array of subatomic particles (such as electrons, quarks and gluons) and the electromagnetic, strong and weak nuclear forces. It’s famously mind-boggling, and is built on the principle of wave-particle duality. This states that all particles are also waves and vica-versa, and that forces also have associated particles (such as gluons, which contain the strong nuclear force). It describes why electrons occupy certain bands (energy levels) around a nucleus, and has opened new technologies such as semiconductors (essential for computers) and superconductors (used in MRI machines).
Einstein’s theory of general relativity is used to describe the way objects behave on a larger scale. Gravity is caused by objects interacting with the fabric of spacetime, which includes our three dimensions of space and one of time. Mass warps spacetime (like a ball placed onto a suspended blanket forming a circular crater in the material because of its weight) and therefore drags everything – even light – into it. This explains various phenomena, such as the problems calculating the orbit of Mercury using Newton’s theory of gravity (which mistakenly led scientists to believe that a new planet named Vulcan was giving it a gravitational tug), gravitational lensing and the fact that time slows down the further you are away from a gravitational source.
The main driving force behind the search for a theory of everything is that our observations of reality don’t seem to play well together. If you try to combine the mathematics underpinning the theories of general relativity and quantum mechanics, you are left with “meaningless infinities,” as Dr. Michio Kaku puts it. This doesn’t cause much of a problem in most cases, because both operate effectively within their own domains, but in situations like black holes when both are required, things generally break down. Likewise, mysterious phenomena such as dark matter and dark energy also present additional issues which baffle modern physicists. This indicates that they must be missing something inherent in nature, which explains observations on all levels, some unifying concept which guides the universe.
The contenders: string theory
Arguably the most popular contender for a theory of everything is string theory. This basically states that all matter is made up of imperceptibly miniscule one-dimensional strings, which vibrate at different frequencies. Like a guitar string producing different musical notes, the things we experience in our reality are only the stable frequencies at which the strings vibrate. Matter and the forces (or the associated particles which come with forces - like photons containing electromagnetism or gravitons of gravity) are created by the varying vibrations of loops of string. Although this unifies relativity and quantum physics, it has received staunch criticism for many reasons, such as the fact that eleven dimensions are required to make the calculations add up.
The contenders: E8
Not all theories of everything come from antiquated university libraries and lives dedicated to the pursuit of a grand, unifying idea. Garrett Lisi spent most of his time surfing in Hawaii, but still managed to come up with one of the most compelling theories of everything in physics. It’s based on a complex mathematical pattern called E8, which is a 248 point shape. He found that after some “weird equations” he could plot each of the fundamental particles and forces (including quantum variations like spin) onto it. There are also plenty of relationships observed in reality that are explained by rotating the shape and performing some basic geometric functions.
When the particles included in the standard model are plotted onto E8, there are 20 free spaces, but these actually serve as predictions for the theory. He aims to calculate the masses of the particles and associated force-particles that would fill the spots, and if they are found at the Large Hadron Collider they would be compelling evidence for his claims. It isn’t without criticism though, and Lisi admits that it’s an “all or nothing” idea.
Is it worth it? Does it even exist?
Despite the fevered pursuits for the Holy Grail of physics, not everybody is convinced it’s even worth it. Stephen Hawking and Leonard Mlodinow, two respected physicists and authors, are fronting a movement that believes several theories working together is the best way to model the universe for our needs. They favour an approach more related to observed reality, rather than an absolute reality. As an example, they use Neo from the Matrix, who had no reason to question the fact that his reality wasn’t actually reality, but could still function within it. Perhaps Einstein’s dream of a simpler reality was mistaken or even misguided, but the great minds of physics will undoubtedly continue to whirr away and potentially come up with something he would have been proud of.