I've heard everything from zero-dimensional points, to squares, and I would love to know what they really look like, or if they have any physical shape.
[Physics] What do quarks look like
elementary-particlespoint-particlesquarksstandard-model
Related Solutions
Yes, the 6 antiquarks are antiparticles of the 6 quarks – in other words, they're particles of "antimatter". The word "antimatter" sometimes represents just a relative label – antimatter of something (antimatter of antimatter is matter again), sometimes it means the antimatter of the particles we routinely see in the world around us.
Because the 6 antiquark flavors – anti-up, anti-down etc. – have the same properties as the quarks (up to the opposite signs), they're not counted as "independent types of elementary particles". Quite generally, we don't consider antiparticle species to be "independent species" because it's a completely general fact that every particle type has an antiparticle (although, in some cases such as the photon, Z-boson, or Higgs boson, they coincide with the original particle).
No one would ever say that there are "12 types of quarks" because of the antiquarks. We either consider antiquarks "not to be quarks" when we talk about "quarks" in a strict sense, or we do include antiquarks among quarks but the antiparticles are considered to be pretty much the same thing as the original quarks (despite the sign flip in all quantum numbers) which is why we still have just 6 quark flavors (the types are called flavors; each of them also has 3 colors and 2 spin polarizations).
Leptons are not composed of quarks. Leptons and quarks are two equally large but mutually disjoint sets of elementary particles – leptons plus quarks are known as "elementary fermions".
The four forces are mediated by the photons (electromagnetic), W-bosons and Z-bosons (weak nuclear force), gluons (strong force), and gravitons (the gravitational force). Physics is pretty much equally sure about all four or five of them. The only way in which gravitons differ is that gravity is such an extremely weak force that individual gravitons are pretty much undetectable. But they're detectable if they're coming in sufficiently strong beams or packages – gravitational waves – and the 1993 physics Nobel prize was given out for the evidence that gravitational waves existed exactly as predicted by Einstein's general theory of relativity.
The Higgs boson is a boson (i.e. not fermion) but it's the only boson in the list that doesn't mediate a fundamental force. It's still very important in the scheme of the Universe because it guarantees that W-bosons, Z-bosons, (charged) leptons, and quarks are massive – via the Higgs/BEH mechanism. The Higgs boson was discovered last July.
Quarks differ by their carrying a color - interacting via the strong force (one mediated by gluons and described by QCD). Leptons don't carry any color so they don't interact by the strong force – which is the reason why their name, "leptons", is related to words like "skinny" in Greek.
It is just simply really weird to me that they can have a fractional charge.
The quarks have a charge that is 1/3 or 2/3 of the charge of the electron. The charge of the electron is not an integer, it is
−4.80320451(10)×10^−10 esu
By this I mean that it is a convention, to call it an integer of 1 as charge, and it is true that any charge measured macroscopically will be an integer multiple of this.
While other elementary particles, such as the electron, carry an integer charge.
The proton also carries an integer charge in this convention, and that is one of the reasons that we can have matter as we know it, with atoms and molecules etc.
So logically I would expect charge to be made up in discrete packets of charge
It is true macroscopically, all charges measured in absolute number are integer multiples of the electron charge
just like energy is made up of discrete packets of energy called photons.
This is a misunderstanding. Energy is an attribute of particles, the same way their location is space is an attribute. Photons have energy as do protons and electrons and all matter. $E=mc^2$ for particles and $E=h\nu$ for the photons where $\nu$ (nu) is the frequency.
And spin in particles comes in integers for particles as well.
Well, fermions have spin 1/2, 3/2 etc, bosons spin 0,1,2 etc so this is another misunderstanding.
Does this mean you can break up all other integer values assigned to other particles or subatomic particles?
The only reason we are adopting the quark terminology is that it has been found out that the protons and neutrons are not elementary particles.
Physicists found out that atoms were composed of electrons about a nucleus containing protons and neutrons by scattering experiments. These experiments showed that the central nuclei had a hard core and were composite, and it was understood that the nuclei were quantum mechanically bound protons and neutrons in different configurations.
The scattering experiments are ongoing, with higher and higher energies, and have showed us that protons and neutrons are composite and made up by three quarks. The painstaking gathering of many data resulted in the standard model of particle physics, which is a theoretical model that explains practically all observations up to now. This model has the quarks inherent in the description of the strong force . The other elementary particles in the table
are mathematically on par with quarks in being the building blocks of the model.
Or is this just a freak of nature and only happens in this one instance?
If one considers compositeness a freak of nature than this is unique to the strong force: it holds the quarks in the protons and neutrons , and the spill over of that strength holds the nuclei together. As the real world is based on nuclei in atoms it is not one ignorable instance!
The number three comes from the study of the scattering experiments, and the symmetries displayed by a plethora of resonances .The 1/3 and 2/3 come from a higher order algebra, a group structure on which the standard model is based that makes consistent all the data we have of strongly interacting resonances and composite particles like the pions and kaons etc.
Best Answer
In physics quarks are point elementary particles. Their existence can only be inferred by fitting mathematical equations derived from quantum mechanical solutions of differential equations.
A simplified description can be found here.
The most dominant extension of present day theories gives the "shape" of a closed string to elementary particles, i.e. fits them as excitations of one dimensional objects following a string theory, but the "point" is a good approximation since these strings have very small dimensions.
Please note that for clarity the standard model particles are shown as little balls, event though they are points at that level of magnification.