I’ve read examples of the vast amount of space within an atom. For instance, if we could increase the size of an atomic nucleus to that of a billiard ball and place it on the 50 yard line of football field, the electron would be like a fly buzzing around the outer perimeter of the surrounding parking lot. (Bill Bryson I think that was)
My question is, is there a similar sense of emptiness within the proton or neutron? Are the up and down quarks within the nucleons separated by similar expanses? Or are they much closer?
I am only an armchair physicist but I can tell you the popular view of the atom is completely wrong. It is not a group of little particles buzzing around the nucleus like planets around a star. Instead, quantum mechanics dictates that the particles are probability distributions that tell where the particle might be at that time. In that sense, there is no empty space. They are everywhere and nowhere at once.
I can’t tell you how this translates into empty versus non-empty space but I am pretty sure that the whole answer is counter-intuitive.
Basically, the question doesn’t even make sense. What we call a proton or neutron is sufficiently unlike a classical object that most of the things we’d like to use to describe them don’t even apply.
Is there any better (and readily visualized) way to describe them?
Ever read Jabberwocky? That’s about the level of understanding we’re capable of.
Mathematically, I think we have some very workable and experimentally-verified models. Translating those models into English (or any natural language) is very difficult, because the language fights you every step of the way. Humans simply don’t live in the kind of quantum world subatomic particles exist in, so our languages aren’t evolved do describe it.
Well, there’s this gang called the Pros…
'Cause Shagnasty’s description, while a physicist might nod in agreement, ain’t much help to the laity.
OMG! Is this from Welcome Back Kotter?!?!?
Actually, I do understand this and Shagnasty’s response. I know it’s not like the Neils Bohr model that so often gets miscontrued as reality, and I know that my question is insufficient, but such is the nature of reality at that level. So I realize that any answer given is going to be riddled with “ifs”, “ands”, or “buts”, and will likely end with a phrase like, “but it’s really nothing like that at all.” Nevertheless, I was hoping someone would give it a shot.
As far as I can tell, we’re only now beginning to suspect that “point” particles are anything but point masses.
If (super)string theory is true, it has a lot of implications for the “geometry” of elementary particles.
I did find this rather tentative article that describes experiments to explore the structure of the proton.
Here’s another one that talks about the internal structure of the proton.
Don’t forget the Elected Ones. 
As others have stated, the conceptual model of atoms as resembling planetary systems or being made of “stuff” is badly misleading. Although we went into greater detail in [thread=299054]Why can’t my hand go through my desk? (physics question)[/thread], the essential answer is that particles exist as fields about a central focus, and the likelyhood of interaction–say, a neutron being captured–is determined by a cross-sectional “area” of probability; in other words, particles are best represented as big clouds in which the actual locus of action appears instanteously. There is no physical lump of stuff that makes up the particle, not even a point. Or, as Chronos says in [post=5771301]this post[/post], “It’s just not true that 99% of matter is empty space. It’s all space, and none of it is empty.”
Quarks do not exist as independant particles under normal conditions, owing to the phenomenon of confinement. Attempts to isolate quarks (by splitting subatomic particles) result in hadronization, or the spontaneous generation of quark/antiquark pairs to prevent fractionalization of charge. Quarks exist in a state seperate from hadrons only in a state of matter known as a quagma or quark-gluon plasma. These conditions only existed naturally in the first few fractions of a second after the Big Bang, and while the quarks are considered deconfined under such conditions they still aren’t seperable as distinct entites. So thinking of bayrons like protons and neutrons as being made of a collection of quarks is erroneous.
The truth is, as valuable as the Standard Model for particle physics is in our current use, there is almost certainly a better explaination which will dispense with the particle model in favor of some other other concept which addresses the nature of the underlying plenum from which “particles” are formed; i.e. it’ll tell us what these supposed particles are actually made of, be it superstrings, twistors, tears of Og, or whatever. The point is, don’t get too attached to the idea of tiny colored billiard balls swinging around in space like a Star Trek backdrop; it’ll keep you from making the correct intuitive understanding of what is going on, insofar as it is possible to understand particle physics at all.
Here’s an article on nuclear forces by SDSAB Karen, and [post=5779100]here[/post]'s a post I made in the above-mentioned thread explaining electromagnetic interaction which some readers seemed to find amusnig if not wholy informative.
Stranger