One of the biggest goals in physics is to answer the seemingly simple question 'What is the universe made of?'. For the last few centuries, we have found a better and better answer to this question but there is still lots of work to be done. For example, if a human is made of molecules and those molecules are made of atoms then what are atoms made of. Up until the middle of the 20th century this is what we thought the world consisted of, atoms. However, if atoms are the smallest things then what are they made of? Well, this is why you are reading about elementary particles is it not?! I will explain how elementary particles build the structure matter and how these particles are formed because the smart ones in the room are already asking about what elementary particles are made of if they are the smallest thing.
Spins, Colours and Flavours
Before I start talking about the particles and their properties I need to update first-time particles physicists on what some key terms mean when I get to them later on. The key characteristics that create the different groups of elementary particles are their spin, colour, mass, charge and flavours. Currently, there are 17 different elementary particles. The four fundamental forces, the quarks, the leptons and the Higgs boson.
There are 6 types of quarks which are the up, down, charm, strange, top and bottom quarks. 6 types of leptons including the electron, muon and tau leptons with a neutrino counterpart. The quarks and leptons make up a bigger group called the fermions. The 4 fundamental forces are gravity, strong nuclear force, weak nuclear force and the electromagnetic force. Also the Higgs boson.
The mass of these particles is measured in eV (electron-volts). The mass is so minute that 1 GeV(Giga-electron-volt) is equal to 0.00000000000000000000000178 grams and they are so small that light waves are actually bigger than them so we can't see elementary particles with light.
Each variety of elementary particle is given the term ' a flavour', this is just the name that the groups of particles were given to distinguish themselves. Each 'flavour' of elementary particle comes in three different colours, red, green, and blue. These 'colours' are more labels than literal meaning but refer to a unique difference in the same type of particle. These colours must cancel each other out to create white in a compound particle like a proton of otherwise they will not be able to join because of Pauli's exclusion principle or would rapidly decay. Pauli's exclusion principle concludes that no two fermions can have the same quantum mass, so in a proton, for example, one cannot have two red up quarks because they have the same quantum characteristics.
A particle's spin is like a planet spinning on an axis. However, quantum physics tells us that these particles do not have well-defined axises, but for the purpose of simplicity, they do in this scenario. The spin of a particle can tell us how a particle appears at different angles. Spin 0, for example, is like a perfect sphere, where no side is different from another. Spin 1, is like an arrow head, all the sides are different unless you rotate the arrow 360 degrees, a complete revolution, will it look the same. One of the most interesting pieces of the spin theory is the matter particles or fermions. These particles have a spin of 1/2 which means that it takes two full rotations to get the same side again. However, because particles are so small we don't actually know if they are spinning and so this 'spin' is less of a rotation and more like a path of velocity (movement with direction). This is important in the state of atoms because Pauli's exclusion theory also states that no two particles with the same velocity/spin and mass can exist at the same time.
Atoms make up every object you see, this includes your computer, bed, food, it's all just atoms! But to get a deeper understanding of the universe scientists had to uncover what made atoms, atoms! Now we have 12 fundamental matter particles that make up matter, these are called the fermions and consist of the six quarks and the six leptons. One key rule of fermions is that they can never exist on their own they always have to have another quark or antiquark. From Pauli's exclusion theory we now know that no two fermions that have the same quantum mass can coincide wit each other in a compound particle like a proton and that gives fermions different characteristics to determine if they can be in the same quantum state. Quarks can come in three different colours, for example,an individual particle has three different colours, all this information can now give us the building blocks of how atoms are made. In the nucleus of an atom there are protons and neutrons, and in orbit around the nucleus is the electrons. Now let's see how these compound particles are formed. A proton and a neutron have a formation of 3 quarks. The proton has a charge of +1 so now from all the information we have gathered we know that the charges of all the quarks have to equal 1 and they all have to be different variations. Protons are one of the smallest makeup of quarks so they can't be in the GeV in size so that excludes charm, strange, top and bottom, so they must be made of up and down. So from the chart we can see that the up quark has a charge of +2/3 and the down quark has a charge of -1/3. This means that two down quarks and one up quark will create a charge of zero of a neutral charge, creating a neutron. So a proton must be made up of two up quarks and one down quark. Also because the colours have to combine to create white one quark is green, one blue and one red. This is just a simple example of one set of the quarks. The electrons on the outside, however, are just an electron in the lepton group of the elementary particles but, if you know about electron shells, every atom apart from hydrogen has more than one electron. Electrons still have to follow the Pauli exclusion theory and so no two electrons on the shells of atoms are the same.Contact me if you would like me to add more detailed examples using other fermions.
Going back to the point I made about quarks always forming with another. The antiparticle is usually the one that appears in the formation. The antiparticle is basically the same as the normal particle but has the opposite electric or magnetic properties. For example, the antiparticle of an electron is a positron because it has the same mass as the electron but the opposite charge making it positive. The reason for why there is little antimatter left in the world is still very debatable but in the grand scheme of things even if antiparticles were the majority we would call them particles because we wouldn't know different as they are the opposite but have no different effects. So in theory, an electron could actually be the antiparticle to the positron but we would have no idea.
So if elementary particles are the smallest unit of matter then what are they made of?
Well, this is a really tough question to answer because it hasn't even been 100 years since we realised that atoms weren't the smallest things. This brings up the question that there might be particles making up the elementary particles. However, to test this has become harder and harder because we can barely see protons and neutrons and we can't see elementary particles so anything below an elementary particle will be hard to calculate. Most scientists believe we have almost found the end though. Electrons and other elementary particles have fields in which they are created. These fields are similar to that of space-time and could be motivated to create particles by disturbances of energy. However, it will be hard to tell at this current state in time but it definitely isn't impossible, only time will tell.