In physics, we have what we call the “Standard Model” of particle physics. The Standard Model describes all of the fundamental particles in the Universe and the interactions that they have with each other. This includes the particles that make up the atoms around us such as electrons, and the quarks that make up protons and neutrons, but it also includes strange particles that don’t exist around us naturally – we have to create them using a lot of energy! It is basically a recipe for the Universe and so far, it has passed every test that we have thrown at it. There’s just one problem though – we know it can’t be the final story. The particles in the Standard Model only make up less than 5% of our Universe. We know that there must be other stuff there because of the way that galaxies behave and the way that the Universe is expanding – it just can’t be explained with what we already know. No matter what we try though, we haven’t found out where the Standard Model is going wrong so scientists are working really hard to test every single bit of it until we find where it falls down. That’s what I do every day in my job 🙂
Savannah has given a beautiful summary of our current understanding of particle physics. I just want to add a bit about speculative ideas that go beyond our current understanding. But, let me first list a few things that are puzzling about the Standard Model (SM) besides the glaring fact that it fails to account for 95% of the stuff in the universe! The SM model contains 19 numbers that must be specified in order to make predictions from that theory. Here are two numbers I had something to do with: the mass of the top quark and the mass of the Higgs boson. We have no idea what determines these two numbers, nor any of the remaining 17. They could just be random numbers that just happen to be right and thereby allow an ancient Universe to form, expand, and create creatures like us. Or these numbers could be the solutions to a big formula that we have yet to find. I like to think it is the latter. Now about some speculations. A big one is that the forces of Nature (gravity, weak, electromagnetic, and strong) and the particles of Nature (electrons, muons, taus, neutrinos, and quarks) are just different aspects of one set of entities. In other words, there is no real distinction between forces and matter. This idea is called supersymmetry. Another speculation is that the fundamental things in Nature are not particles at all, but microscopic strings whose vibrations correspond to the particles we know about, plus others yet to be discovered. And yet another is that all of the particles are just made up of more fundamental things. It is very likely that none of these speculations is correct…only time and further experimentation will tell…but, I have a hunch that Nature is much more subtle and amazing that we have so far been able to imagine.
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Harrison commented on :
Savannah has given a beautiful summary of our current understanding of particle physics. I just want to add a bit about speculative ideas that go beyond our current understanding. But, let me first list a few things that are puzzling about the Standard Model (SM) besides the glaring fact that it fails to account for 95% of the stuff in the universe! The SM model contains 19 numbers that must be specified in order to make predictions from that theory. Here are two numbers I had something to do with: the mass of the top quark and the mass of the Higgs boson. We have no idea what determines these two numbers, nor any of the remaining 17. They could just be random numbers that just happen to be right and thereby allow an ancient Universe to form, expand, and create creatures like us. Or these numbers could be the solutions to a big formula that we have yet to find. I like to think it is the latter. Now about some speculations. A big one is that the forces of Nature (gravity, weak, electromagnetic, and strong) and the particles of Nature (electrons, muons, taus, neutrinos, and quarks) are just different aspects of one set of entities. In other words, there is no real distinction between forces and matter. This idea is called supersymmetry. Another speculation is that the fundamental things in Nature are not particles at all, but microscopic strings whose vibrations correspond to the particles we know about, plus others yet to be discovered. And yet another is that all of the particles are just made up of more fundamental things. It is very likely that none of these speculations is correct…only time and further experimentation will tell…but, I have a hunch that Nature is much more subtle and amazing that we have so far been able to imagine.