What is a quark made of?

2,178 Views | 23 Replies | Last: 6 yr ago by fahraint
Martin Q. Blank
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Are they solid?
Woody2006
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Martin Q. Blank said:

Are they solid?
What do you mean by that in this context? Everything we typically consider to be a solid is mostly empty space anyways.
Martin Q. Blank
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That's true. The farther down we go, the more we discover matter is mostly nothing except for the newly discovered smaller thing. Does this happen ad infinitum?

Follow up question, the Big Bang theory posits that the universe was once an "infinite density" (according to wikipedia). What does that mean? Was that truly "solid"? Or was there empty space between particles?
Woody2006
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Martin Q. Blank said:

That's true. The farther down we go, the more we discover matter is mostly nothing except for the newly discovered smaller thing. Does this happen ad infinitum?

Follow up question, the Big Bang theory posits that the universe was once an "infinite density" (according to wikipedia). What does that mean? Was that truly "solid"? Or was there empty space between particles?
Good questions. I expect Astro or darg will correct me if I'm wrong, but the search for a truly fundamental particle continues. Here is a pretty interesting article on what we know so far: https://medium.com/starts-with-a-bang/ask-ethan-how-small-is-an-elementary-particle-2613f96b86e1#.kq3my1ngl

It's possible that many of the particles we know of are fundamental (by which I mean indivisible) including quarks, bosons, leptons and their anti-equivalents. String theory posits these particles are further divisible although we have yet to confirm this experimentally.

Your second question is interesting. A point of infinite density such as has been posited prior to the Big Bang would clearly not have space between particles. However, stating it this way is also incorrect because particles and fundamental forces did not yet exist prior to the Big Bang.
Martin Q. Blank
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1. What was the infinite density? A single "truly fundamental particle"?
2. "Truly fundamental particle" (by which you mean indivisible) is what I mean by "solid." Does such a thing exist? Wouldn't it also be of infinite density?
Woody2006
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Martin Q. Blank said:

1. What was the infinite density? A single "truly fundamental particle"?
2. "Truly fundamental particle" (by which you mean indivisible) is what I mean by "solid." Does such a thing exist? Wouldn't it also be of infinite density?
1) I do not believe we know the answer to this question. What happened "before" the Big Bang may forever be beyond our ability to prove.

2) There is disagreement within the scientific community about this subject. I think most believe that there are truly indivisible particles, but it could be that we simply cannot reach energies high enough to experimentally observe them. I'm not certain about this point, but I believe you would have to reach infinite energy levels to achieve infinite density.
Rusty Aha
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Martin Q. Blank said:

Are they solid?

Dad-O-Lot
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Martin Q. Blank
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Woody2006 said:

Martin Q. Blank said:

1. What was the infinite density? A single "truly fundamental particle"?
2. "Truly fundamental particle" (by which you mean indivisible) is what I mean by "solid." Does such a thing exist? Wouldn't it also be of infinite density?
1) I do not believe we know the answer to this question. What happened "before" the Big Bang may forever be beyond our ability to prove.

2) There is disagreement within the scientific community about this subject. I think most believe that there are truly indivisible particles, but it could be that we simply cannot reach energies high enough to experimentally observe them. I'm not certain about this point, but I believe you would have to reach infinite energy levels to achieve infinite density.
I think you're right that it would boil down to "belief." One side says we've made it to the bottom. The other side says we haven't, but simply don't have the means. The limits of science I guess.
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Woody2006
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AstroAg17 said:

Do you have a source that says string theory hypothesizes that quarks can be broken down into smaller things? You may be right, but I thought quarks were just string states and were therefore as fundamental as the strings.
No, I'm sure I misstated something along the way. Our current understanding of quarks is that they are fundamental. I'm not going to preclude the possibility that our current understanding is wrong, however.
Woody2006
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Martin Q. Blank said:

Woody2006 said:

Martin Q. Blank said:

1. What was the infinite density? A single "truly fundamental particle"?
2. "Truly fundamental particle" (by which you mean indivisible) is what I mean by "solid." Does such a thing exist? Wouldn't it also be of infinite density?
1) I do not believe we know the answer to this question. What happened "before" the Big Bang may forever be beyond our ability to prove.

2) There is disagreement within the scientific community about this subject. I think most believe that there are truly indivisible particles, but it could be that we simply cannot reach energies high enough to experimentally observe them. I'm not certain about this point, but I believe you would have to reach infinite energy levels to achieve infinite density.
I think you're right that it would boil down to "belief." One side says we've made it to the bottom. The other side says we haven't, but simply don't have the means. The limits of science I guess.
I'm not sure I agree with this statement. I don't know of anyone saying we've figured it all out. There are way too many open questions.

It's not that it boils down to belief. When we don't know something we don't have to fill that hole with "belief". It's ok to just say we don't know.
Martin Q. Blank
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You said "I think most believe..."
Solo Tetherball Champ
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Dad-O-Lot said:


I knew there was a Star Trek reference to be made, but I couldn't put my finger on it.

Blue Star to you, sir.
Woody2006
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Martin Q. Blank said:

You said "I think most believe..."
Believe was the wrong word there. Replace it with the word "expect" and I think my statement is more accurate.
Martin Q. Blank
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Faith is the assurance of things hoped for, the conviction of things not seen.
Woody2006
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Martin Q. Blank said:

Faith is the assurance of things hoped for, the conviction of things not seen.
Faith and expectation are not the same thing.
Star Wars Memes Only
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I think Woody and Astro have done a good job here. I want to add a few comments of my own:

1.) How do we know atoms aren't fundamental? There are a few lines of reasoning that can lead us to this conclusion. For example, atoms are electrically neutral, but they scatter light at certain frequencies. We can ask ourselves why would this be, and see where this leads. But the real confirmation is through scattering experiments. By bombing metallic plates with alpha radiation and recording how the alpha particles scattered, scientists were able to mathematically deduce that the positive charge was accumulated in a tiny region within the atom. A similar procedure revealed the quarks within the protons and neutrons. Studying these kind of interactions lead to the standard model, which is the most cutting-edge theory we have in physics right now. It has been incredibly successful at low energies. We have theoretical predictions that match with experimental results 10,000,000,000 times more precisely than what would be needed to be considered a good match in other fields. There are some mathematical reasons to think that quarks are fundamental (from a certain point of view -- ST would supersede this if correct, but not overwrite this -- if it is correct particles would be analogues of phonons, which would render the question of composition meaningless). But the truth is, nobody knows for sure if there is something else more fundamental. The LHC is probing this, and other questions right now.

2.) The word "solid" describes a bulk property of matter. Asking if a quark is solid is a meaningless question in the same way as asking if a single methane molecule is biological.

3.) As Astro pointed out, before a certain point in time when the universe was exceedingly small (though not "infinitely small") we don't know what happened. To answer those questions we need a quantum theory of gravity, and we don't have a definitive one yet. We can ask what general relativity says happens before that point in time, but at that point you're doing mathematics, not physics.
Star Wars Memes Only
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So Cern has announced the discovery of five new particles today. They're not fundamental particles, and are still made of quarks, but I thought this was tangentially related enough to my previous post to post it here.

Here's the link: http://home.cern/about/updates/2017/03/lhcb-observes-exceptionally-large-group-particles
TexAgs91
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Quarks are strings, according to string theory...
http://www.nuclecu.unam.mx/~alberto/physics/string.html

Quote:

The essential idea behind string theory is this: all of the different 'fundamental ' particles of the Standard Model are really just different manifestations of one basic object: a string. How can that be? Well, we would ordinarily picture an electron, for instance, as a point with no internal structure. A point cannot do anything but move. But, if string theory is correct, then under an extremely powerful 'microscope' we would realize that the electron is not really a point, but a tiny loop of string. A string can do something aside from moving--- it can oscillate in different ways. If it oscillates a certain way, then from a distance, unable to tell it is really a string, we see an electron. But if it oscillates some other way, well, then we call it a photon, or a quark, or a ... you get the idea.

So what's a string?

TexAgs91
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Here's another interesting pov... Quarks, strings etc are not fundamental building blocks. Their conserved quantities (mass in MeV, spin, baryon number etc) are the fundamental objects. Particles can change from one kind to another but the conserved quantities never change.
Star Wars Memes Only
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Seems like an odd position to take for a few reasons.

1.) Those numbers by themselves are meaningless. They only make sense as a conglomerate, at which point you're referring to something that's larger than any individual quantum number, which we simply call a particle.

2.) The quantum properties you've listed are subject to fluctuation, and only the expectation value of those number is conserved. You can have cases, such as with spin, where the expectation value of a quantum number will never match the measured quantum property. It seems odd to define something as physically real when it's never physically measured.

3.) The reason we might say something like, "a string is the fundamental building block," or, "a quark is the fundamental building block," tells you some additional information aside from just the relevant quantum numbers. It also tells you how these fundamental particles behave, which is very different. So in addition to my above two points, I think saying it this way carries additional information as well.
fahraint
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