‘God doesn’t roll dice’, Einstein once quoted. He probably angered a lot of people, but this is what Physicists also believe. But then why does the universe work as it does and how? While scientists are working on it, it is actually very difficult to explain this fully, without breaking any laws of physics. The way to move forward has been to breakdown a big problem into smaller chunks and rationalise the concepts for these smaller chunks. This has worked out brilliantly in explaining some of the unsolved problems in physics, but relating each of the theory with other, is difficult. When a theory will, it would be, the ‘Theory of Everything‘. Precisely it would be, the theory of ‘everything’. It is the ultimate goal. It will tell us how the universe works and explaining all the observed and non-observed phenomena and the future of the universe.
To get into a bit of details to understand what we currently know about the universe, is imperative that I discuss the Standard Model of Physics as we know it. Here, you might need some unlearning, and then learning new theories. These theories are in fact very old, but have not been taught in schools in great depths. Whatever we learnt in school, was related to macroscopic entities, which is known as Classical Physics. Classical physics fails to reason the phenomenon’s at Quantum level, and is known as Quantum Mechanics. Quantum can be understood as nanoscopic particles, which we can never observe, but only theorise.
I have read quite many literatures, and collated the Standard Model of Physics, with the Theory of Everything, representing the interactions between particles and different forces, in a single flowchart, as below. I strongly recommend to open it in a new window while you read the text, or print one off on A3 for reference.
You must admit this is a fairly complex chart, and you would need to read it left to right, and at the same time right to left, up-down and vice versa. For now, forget the orange dotted lines and the pie chart.
Starting from the very left, Elementary particles are categorised as Fermions and Bosons. Fermions and further categorised at Matter and Antimatter particles, while Bosons are classified as Force Carriers and Scalar Bosons. Interestingly, Bosons are named after the Indian scientist and Nobel Laureate Satyendra Nath Bose. We all know from science fiction that Matter + Antimatter = Anhilation. Matter is further subdivided into Quarks and Leptons. There are 3 generations of each, 6 quarks and 6 leptons, as displayed in the image. They have different charges, but all are 1/2 spin. We will stop right there, and even forget the Bosons. Now, start reading from the very right. Everyday matter consists of molecules and atoms as we know, and there is some force interaction between them. Atoms are in fact made of more fundamental particles. A fundamental particle is one, for which we do not know if a substructure exists for it. This means, it cannot be broken down into further sub particles; or at least we are not aware of it.
The atom itself can be thought of as a nucleus core, with electrons rotating around it. Initially we thought that the nucleus just consists of Protons and Neutrons, and cannot be further sub divided, but now we know it is in fact made up of subatomic particles. The nucleus of atoms is made up of Baryons, which is a combination of 3 Quarks. The electrons are Leptons. Any combination of Quarks is called Hadrons. If there are 3 quarks, they are Baryons and hence Nucleus, if there is 1 Quark-Antiquark pair, it is known as Mesons.
Going back to Bosons, and hence we are at the middle-bottom of the flowchart. We know of 4 forces, Strong force, Electromagnetism, Weak force and Gravitational force, in accordance with their strengths. Strong force is responsible for binding atomic nuclei, and acts at very small distances. Weak force is responsible for radioactivity and nuclear fusion. There are particles (which also behave like waves) responsible for each of the above 4 forces. Gluons to Strong Force, Photons to Electromagnetism, W & Z bosons to Weak force and the hypothetical Gravitons to Gravitational force. These have a spin of 1, and different charges as represented in the table. Another category is the recently observed Higgs Boson, which is a scalar boson, meaning, no spin particle. Not all particles are massless, but it was difficult to also include masses of particles in the complex image, so I have left it out for now. Only Gluons and Photons are massless. These 4 forces particles interact with everyday matter as we discussed earlier, as shown in the dotted lines, which I believe is self-explanatory.
So far, scientists have been able to reason all 4 forces individually, and were able to combine Weak Force with Electromagnetism, forming the Electroweak theory. Further, as I understand, with some degree of confidence, the Electroweak theory has been merged with Strong Force to form Grand Unified Theory (it is not that grand). However, Gravity has kept them working. Scientists still have not been able to relate all the 4 forces, that is, combining Grand Unified Theory and Gravity. The theory that will be capable of doing so, will be the ‘Theory of Everything‘. There have been probable candidates for the ‘Theory of Everything’, like String theory, super-symmetry, and likewise, but none of them have been accepted fully. I guarantee that whoever comes up with a well-accepted ‘Theory of Everything’, will get a Nobel Prize in Physics. Until then, we can’t truly understand our universe.
Also on the image, in the top right corner, I have added the mass-energy composition of the universe. Everyday matter, as we see, which I discussed above only makes up 4.9% of the universe, while Dark Energy and Dark Matter make up 68.6% and 26.5% respectively. Food for thought, a discussion for another post.
Leave your comments below, and let me know what you would like to discuss. I have aimed to keep the text very simple to understand, so please leave feedback of your opinion. Next discussion is the ‘Scale of the Universe‘.