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I've gotten interested in physics recently due to the many educational channels on YouTube such as sixtysymbols and minutephysics. They talk about quarks sometimes, and I was wondering if there is anything smaller than a quark. I'm not at that stage in school yet, the smallest we have discussed in class have been neutrons, protons, and electrons, so I am just curious.

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marked as duplicate by Ben Crowell, Brandon Enright, Waffle's Crazy Peanut, Qmechanic Jun 17 '13 at 13:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Smallest in size? Since electrons and quarks are supposed to be point particles, they would be both the smallest particles. –  jinawee Jun 17 '13 at 1:09
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duplicate of physics.stackexchange.com/q/16048/4552 –  Ben Crowell Jun 17 '13 at 2:45
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possible duplicate of What is the smallest existing thing in theory and law? –  Brandon Enright Jun 17 '13 at 4:32

2 Answers 2

up vote 4 down vote accepted

All we know about the size of quarks is that they are smaller than the resolution of any measuring instrument we have been able to use. In other words, they have never been shown to have any size at all. Most physicists suspect that they are not actually points, but we don't know how small they are.

The same goes for electrons, by the way. (Protons and neutrons do have a known size, around $1\text{ fm}$ across.)

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From Wiki

In particle physics, an elementary particle or fundamental particle is a particle not known to have any substructure, thus it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. In the Standard Model of particle physics, the elementary particles include the fundamental fermions (including quarks, leptons, and their antiparticles), and the fundamental bosons (including gauge bosons and the Higgs boson). Although elementary particles are not made up of smaller particles, some of them may change to lighter particles (according to specific rules).

The elementary fermions (matter particles with half integer spin) are:

Quarks: up, down, charm, strange, top, bottom.

Leptons: electron, electron neutrino, muon, muon neutrino, tau, tau neutrino.

The elementary bosons (force carrying particles with integer spin ) are:

Gluon, W and Z, photon.

In what you said, the electron is a fundamental particle but the neutron and proton are not. The proton is composed of two up quarks and one down quark. The neutron has one up quark and two down quarks. Here are some links that will clear some of the basic questions about quarks (not to write a to long of an answer)

http://www.britannica.com/EBchecked/topic/486323/quark

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html

https://en.wikipedia.org/wiki/Quark

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