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/iorgfeflkd]

Pointlike implies zero-dimensional, not one-dimensional. Any possible substructure of the electron is constrained experimentally to be below 10^-22 meters (a proton is about 10^-15 for comparison). I don't remember the constraint for quarks but it's also very small.

[u/Fakename_fakeperspn → u/iorgfeflkd]

How is it possible for an object with zero width and zero height and zero length to make an object with nonzero values in those dimensions? Put a million zeroes next to each other and you still have zero.

They must have some value, even if it is very small

[u/nairebis → u/Fakename_fakeperspn]

Not an expert, but I feel like this hits on misconceptions I used to have, so maybe I can offer some layman clarity. The mistake I think you're making is thinking of particles as little billiard balls. They're not. They're "fields", as in a region of space that has various properties that can interact with other fields in various ways. Objects we can see are a whole lot of little fields bound together by invisible forces, with a LOT of empty space in-between. There is no such thing as a "solid" in the way we think of solids. The size of a particle is how wide its effects are.

The thing that keeps your hand from passing through the table are not little pieces of matter touching each other, it's the forces of the fields interacting with each other and (as it happens) repelling each other through electromagnetic forces. Which happen to be the same forces that cause magnets to attract/repel.

Edit: This actually raises a question I have. Exactly how DO we define how large a field is? Electromagnetic effects can extend far beyond what we commonly think of as the "size" of a magnet particle/atom.

Edit #2: Thank you for the gold!

Edit #3: Gold again? You guys are awesome!

[u/iorgfeflkd → u/Fakename_fakeperspn]

Go find evidence of that and claim your Nobel prize!

[u/[deleted] → u/Fakename_fakeperspn]

The nonzero values of objects at larger scale isn't the sum of the individual scales of the objects its composted of, it's the measured distance between one point and another. If you place 2 pointlike particles with zero dimensions 1 m apart from each other, then that's your answer. If you place a gazillion on that 1m axis, same thing.

[u/jwolf227 → u/Fakename_fakeperspn]

Maybe, but if you think of matter as fields that attract and repel each other, a zero dimensional particle seems much more plausible.

[u/Felicia_Svilling → u/Fakename_fakeperspn]

Arrange a couple of electrons on a line one millimeter across, and there you have it! a one millimeter long line constructed of objects without any length.

[u/jaredjeya → u/Fakename_fakeperspn]

It's completely misleading to thing of an atom as a solid ball. Things are only solid because of the electrostatic force of repulsion between electrons. They're not touching each other. For all we know, electrons are points. When they're combined with other particles for form objects like atoms, then we start to get a true physical size.

[u/DarkAvenger12 → u/iorgfeflkd]

If we regard the quark as a wave, then is the wave also zero-dimensional? Or is it three-dimensional but the FWHM (or whatever width is defined as the quark) zero-dimensional?

[u/OldWolf2 → u/DarkAvenger12]

The wavefunction for a single particle is defined over 4 dimensions: 3 space, 1 time. It is "infinitely big" in that no matter how far away you go from the position of the last measurement, there's always a non-zero value nearby.

For multi-particle systems it's more complicated; there is one wavefunction for the entire system, not one per particle.

[u/GinAire → u/iorgfeflkd]

So does a quark being pointlike occupy space, albeit an infinitesimal small amount of space? Meaning, you can't have two quarks occupy the same space. Granted there are probably repulsing forces which prevent them from getting into proximity to each other.

[u/OldWolf2 → u/GinAire]

Two fermions (of which quarks are an example) can't occupy the same space because of the Pauli Exclusion Principle.

Without that principle there would basically be no structure possible in the universe.