The structure of matter, that is, everything you see in the universe – you, me, the earth, stars happens to be made up of some core fundamental particles which are governed by four fundamental forces. Our best understanding of these fundamental particles and forces, is represented by the standard model of particle physics.
It is a stunning piece of work which explains nearly everything, But it has a gaping flaw, because it does not explain something that is fundamental to our existence. Not only that, it also happens to predict that our universe should NOT exist at all.
The standard model consists of 12 elementary particles known as fermions. The fermions are 6 quarks and 6 leptons. All non-fundamental particles like protons and neutrons are made of these elementary particles.
The guage bosons are force carriers and are responsible for three fundamental forces of nature. Gluons mediate the strong force which binds the nucleus of an atom. W and Z bosons mediate the weak force which is responsible for radioactive decay. Photons mediates the electromagnetic force which causes light and magnetism. And the Higgs Bosons gives all fundamental particles their mass by interacting with them.
And how do the forces manifest themselves?…it happens through the exchange of the guage bosons.So for example, if you bring two magnets together, the force is actually being manifested because of an exchange of photons between the positive and negative poles. You can’t see the with the naked eye, but they are there. Similarly the other guage bosons are being exchanged for the other forces.
Where is gravity? It is nowhere to be found. This is pretty important, because of course, without gravity, the universe, and we would not exist. So as impressive as the standard model is, it does not explain gravity.
All we have to do is find a new gauge particle called the “Graviton” – then we will have a model that explains everything right? Not quite, ven if we found a theoretical particle called the gravitation, it wouldn’t completely explain gravitation.
And why is Gravity so difficult to integrate into the standard model? Unlike the other forces which can be explained using the quantitized particles, gravity does not necessarily even need a particle, because at its fundamental level, it can be explained in geometric terms.
General relativity is about curvature of space rather than interaction of particles. We can only presume that gravity must have a quantum form – but maybe it does not. We don’t know. The other forces don’t seem to bend space and time, only gravity does – so that is what so far no one can explain and thus incorporate into the standard model.
String theory and loop quantum gravity provide the possibility of a quantum theory of gravity. And according to these theories, the Graviton MUST exist. But the major problem with these theories is that they do not make predictions that we can test. So they may just be random mathematical constructs that happen to model certain parts of nature.
The theory of gravity breaks down at the quantum level, so we have no way to explain the singularity of a black hole, or the events that led up to the big bang. But luckily for particle physics, when it comes to the minuscule scale of particles, the effect of gravity is so weak that it is negligible. Only when matter is in bulk, at the scale of the human body or of stars and planets does the effect of gravity dominate. So the Standard Model still works well despite its non explanation of a fundamental force of nature.
What we need is a theory of everything that unites relativity and quantum mechanics. It’s possible however that nature is messy at the irreducible level. It is also possible that space-time itself is not smooth as General Relativity presumes, but is itself made up of quantum particles. In any case, if the next Albert Einstein or Isaac Newton happens to be watching this video, and is inspired to come up with a quantum explanation for gravity, perhaps he or she could also explain dark matter and dark energy, because these are not explained by the standard model either.
And lastly, according to this model, there is certain problem of matter-antimatter symmetry. The model predicts that at the beginning of the universe, at the big bang, there should have been an equal amount of both matter and antimatter that should have totally annihilated each other, so that the universe would be a massive soup of energy consisting of nothing more than photons.
So perhaps the biggest flaw with this model is that it predicts that the universe does not exist. So it is clearly wrong…We do exist…don’t we?
