# I What is a realistic image of quarks?

#### ZapperZ

Staff Emeritus
2018 Award
From the above physics, I conclude that quarks are not spherical balls. Then I ask, If quarks are not spherical balls, why is it that they are commonly drawn as spherical balls? Is that a bad question?
Because a cow from a very far distance looks like a sphere.

Zz.

#### A.T.

If quarks are not spherical balls, why is it that they are commonly drawn as spherical balls?
How would you draw them instead?

#### BvU

Homework Helper
I was first !
How would you represent a point ?
Didn't get a reply, though . . .

#### DaveC426913

Gold Member
From the above physics, I conclude that quarks are not spherical balls. Then I ask, If quarks are not spherical balls, why is it that they are commonly drawn as spherical balls? Is that a bad question?
The spherical shape represents the strength of its properties. Because the properties are symmetrical about a point; they are the same in all directions.

Look at these two representations of the same molecule:

The top one renders a sphere at the distance of some large value of charge (so the spheres actually intersect).
The top one renders a sphere at the distance of some small value of charge (so the spheres do not intersect).

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#### DaveC426913

Gold Member
This is what we actually observe when we look a subatomic particle.

We detect the value of a property of interest at a given distance.
It happens that that value is often the same at the same distance from the centre no matter what direction.

How might you represent the above particle?

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#### Zeynel

This is what we actually observe when we look a subatomic particle. [...] How might you represent the above particle?
I don’t understand this graphic. When you say “how might you represent the above particle” do you refer to the point particle at the center of the field or do you call the spherical field of charge a “particle”?

Also “quarks are never directly observed or found in isolation”. So, the “point particle” at the center cannot be a quark. Is this correct?

#### BvU

Homework Helper
By reading the accompanying text. And a textbook on physics.

#### DaveC426913

Gold Member
I don’t understand this graphic. When you say “how might you represent the above particle” do you refer to the point particle at the center of the field or do you call the spherical field of charge a “particle”?
It would be impossible to try to represent zero-dimensional particles in a video Since you would not be able to see them, you would have to artificially inflate their size.

So the next best thing to do is to represent what is essentially an "operating radius".

Also “quarks are never directly observed or found in isolation”. So, the “point particle” at the center cannot be a quark. Is this correct?
Well, it was not meant to be a picture of a quark "in the wild".

But you're right - it isn't really mean to be a quark at all; I'm generalizing how to represent the properties of a subatomic particle.

Well, you could ask the artist...

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#### Zeynel

It may be worth noting that is was a very basic visual representation, and there are other things which were not shown in the picture, for instance that quarks exchange gluons with each other, and quarks have fractional charges.
I found this video that shows the gluons too (also as spheres).

There were some comments here that the CERN video was "visual candy" and should not be taking seriously, but the video I linked was more technical and very informative and I think it reflects the current understanding. So it's a puzzle why physicists know that quarks are not spheres (in the same video he describes quarks as ripples in the quark field) but insist on representing quarks as spherical particles. Any insights?

#### DennisN

So it's a puzzle why physicists know that quarks are not spheres (in the same video he describes quarks as ripples in the quark field) but insist on representing quarks as spherical particles. Any insights?
Yes. We are venturing into quantum field theory, which is far beyond this subforum we are in which is general physics.

Quantum field theory is the most modern and advanced theory of these things, and I'm not very familiar with it.
To the best of my knowledge, according to quantum field theory, all elementary particles have an associated field throughout space. And it is these fields that are fundamental, not the particles; particles can be thought of (note I say thought of, not seen as ) as excitations (or "ripples", or "vibrations") in the fields.
Here is a crash course, or rather, a basic introduction to it by professor David Kaplan (the video is actually about the Higgs boson, but he briefly describes the quantum fields too).

#### BvU

Homework Helper
Lovely video (in #49). A level deeper than the original one in this thread.
insist on representing quarks as spherical particles
Not all the time : if there is a gluon nearby it morphs into a nike-like swoosh

that makes me feel giddy for a split sec . And a gluon that looks like a pessarium will probably also not be 'realistic'

I think they did a good job visually supporting the spoken text with representing the unvisualizable. Moving balls are so much more bearable that rippling blobs of colour (nice colours, though).

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#### Zeynel

It may be worth noting that is was a very basic visual representation, and there are other things which were not shown in the picture, for instance that quarks exchange gluons with eachother, and quarks have fractional charges.
I found a picture showing gluons as springs. Do gluons obey Hook's law?

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Staff Emeritus
2018 Award

#### Nugatory

Mentor
Oh dear. This is never going to end, is it?

Zz.
Yes, it will end.
In fact, it just did - this thread is closed.

"What is a realistic image of quarks?"

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