I’m a bit late, but I thought I’d write a few words about the Theory of Everything (the Physical concept, not the film). If you’re not that bothered about Physics (as if!) then you can feel free to skip to the last paragraph. Corrections are welcome!
A Theory of Everything seeks to unite the four fundamental forces of the universe. In order of obviousness, these are:
Gravity stops you from floating off into space, keeps satellites in the air, and provides ample material for science fiction. Any object in the universe with mass is attracted to every other object with mass and, in the absence of other forces, will be attracted to each other. Very large objects, however, don’t just attract other masses, they warp the fabric of space and time around them (the general theory of relativity) and causes weird things to happen like slowing time down and causing things to orbit around them.
I’ll be honest that my knowledge of this doesn’t go much beyond GCSE Physics but the fact you are reading this is surely evidence enough you are aware of its effects.
The Strong Nuclear Force
This essentially allows to protons (positively charged particles) to join together: normally they would repel each other because they are both positively charged electromagnetically. However, if you fire them at each other with enough speed, you can get them close enough to each other that the strong force, which is stronger than electromagnetic repulsion at small distances, will kick in and bind them together as a deuteron, thus allowing more complicated atoms to form. This is essential to the formation of stars (and, ultimately, pretty much anything).
The Weak Nuclear Force
Is rather difficult to explain, but it regulates certain things that happen within an atomic nucleus such as beta decay (when a neutron turns into a proton, an electron, and a small particle called an antineutrino, which changes the atom into that of a different element).
These forces arise from the way that particles “interact” with each other, and this is explained by an exceptionally clever and fiendishly complicated equation the Standard Model (which is much too complicated to put here).
The particles in question are quarks (of which there are 6), leptons (which includes electrons, there are also 6 of these), gauge bosons (gluons, photons, and the mysteriously named Z & W: these essentially “carry” the fundamental forces) and the now infamous Higgs boson (nicknamed the God particle, much to Peter Higgs’ annoyance).
Particles “get” mass when they interact with the Higgs Boson: however, the Standard Model states that gluons, which hold particles together (they cause the strong force), and photons, which carry light, have no mass.
I say it’s explained: as of now, there is still no room for Gravity in the Standard Model. This is due to the fact that it’s so far proved very difficult to re-write Einstein’s rules of gravity (which deal with big things) in a quantum (i.e. particle-related) context in a way that gives meaningful results.
The quantum point of view sees the motion of small particles as being random: if you know where a particle is at any point in time, it could be anywhere else in the universe in the next instant, while Einstein famously said “God does not play dice” meaning that if we know the initial conditions, we should know how an object is going to behave.
A Theory of Everything would arise if we could unite all the forces of the standard model into a unified Electronuclear force with a quantum interpretation of gravity in a meaningful way. This looks a long way off, but there are possible proposed solutions, including the possible existence of particles called gravitons which would regulate the gravitational force. However, the maths so far has proven it difficult to show how these particles can exist, never mind if they do.
The reason we would be interesting in finding a unified theory of everything is that it would go a long way to describing what happened at the start of the universe. But I am convinced no amount of maths will ever answer the question “why?” .