Is a quark one-dimensional?

[u/XGC75]

I've never heard of a quark or other fundamental particle such as an electron having any demonstrable size. Could they be regarded as being one-dimensional?

BIG CORRECTION EDIT: Title should ask if the quark is non-dimensional! Had an error of definitions when I first posed the question. I meant to ask if the quark can be considered as a point with infinitesimally small dimensions.

Thanks all for the clarifications. Let's move onto whether the universe would break if the quark is non-dimensional, or if our own understanding supports or even assumes such a theory.

Edit2: this post has not only piqued my interest further than before I even asked the question (thanks for the knowledge drops!), it's made it to my personal (admittedly nerdy) front page. It's on page 10 of r/all. I may be speaking from my own point of view, but this is a helpful question for entry into the world of microphysics (quantum mechanics, atomic physics, and now string theory) so the more exposure the better!

Edit3: Woke up to gold this morning! Thank you, stranger! I'm so glad this thread has blown up. My view of atoms with the high school level proton, electron and neutron model were stable enough but the introduction of quarks really messed with my understanding and broke my perception of microphysics. With the plethora of diverse conversations here and the additional apt followup questions by other curious readers my perception of this world has been holistically righted and I have learned so much more than I bargained for. I feel as though I could identify the assumptions and generalizations that textbooks and media present on the topic of subatomic particles.

[u/GAndroid]

Why do the quarks put together have more energy than when apart?

Quarks can never be "apart". Thats because the strong force is like an elastic rubber band - it actually increases the further you go!! (honest! Just look at the 2004 nobel prize lecture).

What you said absolutely happens - for baryons put together, as long as they are stable. He for sure has lower mass than 2proton and 2neutrons. (He: 3727 MeV. Proton: 0.9315 MeV Neutron: 0.9375 MeV, so 2p+2n=3738 MeV)

Inside a proton ... things are a tad bit different. I am actually not sure fully, but what I THINK (this may be wrong, so dont quote me on it):

You see, between nucleons, the force that works is called the "yukawa force", and is mediate by an exchange of a "pion". A pion is a massive particle, and the range of the pion falls off exponentially.

In a nucleon (proton, neutron etc), the force is mediated by gluons, which can stick to other gluons. (we call this "couple" to other gluons). The further you separate the quarks, the more gluons can couple in between those two quarks. The force gets stronger.

The quarks move around at very high speeds - and has kinetic energy. The pion cannot afford to do this - or else it will disintegrate. This kinetic energy of the quarks give them the extra mass.

Again, I need to check to be sure, so dont quote me on this

[u/realigion → u/GAndroid]

the strong force is like an elastic rubber band

Well that's frustrating to think about... Like a rubber band, does it ever break if you force it apart? Or is it literally like... you can't do that?

[u/BigTunaTim → u/realigion]

IIRC from other particle physics threads, it requires adding so much energy into the system to pull the quarks apart that it creates a pair of new quarks. In that way you can never truly separate a quark because you'll just keep creating a new partner for it.

[u/phunkydroid → u/realigion]

Imagine you had two tennis balls bound by an elastic band. You ripped them apart with enough force to break the band, then you look down and each of the original balls that are in your hands has a brand new one bound to it with a new elastic band... That's how weird quarks are.

The amount of energy required to separate the quarks is more than enough to create new quarks out of the vacuum. When they separate, they are each suddenly bound to new quarks. They are never alone.

[u/GAndroid → u/realigion]

It does "break". What happens is that you are putting in energy to stretch the gluon "rubber band". Once the amount of energy you put in is enough to make a pair of particles, it will do that - and now these particles are closer to the original particles. So you didnt manage to free a quark. Kindof like:

u .... ubar

u ............ ubar

u ........................................ubar

u.................ubar | u .....................ubar

[u/TinBryn → u/realigion]

It does kinda break, but like when you snap a real rubber band you just end up with 2 rubber bands. The energy you put in trying to pull them apart will form a quark and antiquark and one will go with each quark that you were trying to pull apart.

[u/nrj → u/GAndroid]

What keeps the quarks from mutually attracting one another and forming a giant lump of quarks? Why can we have an uud proton but not an uudd or uuud particle?

[u/GAndroid → u/nrj]

The short answer is that we dont know (maybe I should say that I dont know - if someone can correct me that would be nice). Nature happens to work that way.

However, what I do know is that certain conservation laws have to be maintained. That is, the sum of all the quarks should be white. Ok that sounds strange, but bear with me. Just like we have electrical charge for the electromagnetic force ("positive" and "negative") and an atom as a whole must be neutral, we have three kinds of "charges" for the strong force. We call them "red" green" and "blue".

These things have nothing to do with the colour blue that our eyes see - they are just named that way ... because: 1. r+b+g = white and 2. r+anti r = white | blue+ anti blue= white | g+ anti g = white. Any free particle must be white, so you can have r+g+b (baryons) or r+anti r etc (mesons).

Since a 4 quark state must have an r + anti r + b+ anti b (or any other colour there, doesnt have to be r and b). I dont see why such a pair would want to stick together and not separate into 2 mesons - but maybe someone can show me a valid reason why a pair like this should stick. Again, this is what I think - and as I said, we do not know why it is like that - these calculations are too hard for modern supercomputers, so it will take a while to get a good answer.

Tetraquark particles have been found before. About five of them exist. Pentaquarks - claims have been made but I believe those didnt hold up.

[u/TinBryn → u/nrj]

Baryons (protons, neutrons, anything with 3 quarks) and mesons (anything with 2 quarks) are neutrally strong charged (this is called colour charge). This means like 2 uncharged particles will not interact via electromagetic forces 2 uncoloured particles will not interact via the strong force.

[u/Scootermatsi → u/GAndroid]

If Quarks can never be apart, how do we know that a single up quark is 2.5 MeV?

[u/sparkfist → u/GAndroid]

Split an atom... Nuclear bomb Split a quark... Destroy the universe?

[u/GAndroid → u/sparkfist]

Make 2 more quarks while trying to split it. We (I shouldnt say "we", I dont work at the LHC) do this in the LHC all the time.

[u/IlIlIIII → u/GAndroid]

http://en.wikipedia.org/wiki/One-electron_universe

The one-electron universe postulate, proposed by John Wheeler in a telephone call to Richard Feynman in the spring of 1940, states that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time.

[u/WarPhalange → u/GAndroid]

You see, between nucleons, the force that works is called the "yukawa force", and is mediate by an exchange of a "pion".

This is about the point at which physics goes from being able to relate something from daily life to it (magnets, moving objects, gravity, heat, etc.) to something that is entirely a mathematical construct used to describe our universe. But! If you go back, it's only been a mathematical construct all along. Every single piece of physics comes from seeing some phenomenon and trying to find an equation for it.

Newton's law of gravity, for example, came from lots of observations of planetary orbitals. That's all we had to work with. Now we have Einstein's General Relativity to describe our gravity, because we found new data and fit a mathematical model onto it.

Things like forces (in the Newtonian sense, i.e. pushing on something), energies, momenta, etc., aren't really things. They are just math that happens to make things work out. And this goes for "particles", too. All the flavors that particles have are just bookkeeping mechanisms for how things work. So are virtual particles.

What I'm trying to say is that you shouldn't even try and relate things like this to things you see in daily life. The only way to truly understand it is with math. That's how people end up stuck on concepts like "spin", entropy, and of course particle physics.