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Quark

physical science Maturity 7-9 Next article →

Quarks are tiny, fundamental building blocks of matter. They are elementary particles, which means they are not made of anything smaller.

Standard Model of Elementary Particles
Standard Model of Elementary Particles

Quarks join together to form larger groups called hadrons. The most stable hadrons are protons and neutrons. These particles make up the center of an atom, which is part of everything we see. Most matter in our universe is made of up quarks, down quarks, and electrons.

Quark masses as balls
Quark masses as balls

Because of a rule called color confinement, quarks are never found by themselves. They always stay inside hadrons or in special states like quark-gluon plasmas.

Quarks have several special properties that make them unique. They have mass, electric charge, and spin. They also have something called color charge.

This color charge causes them to feel the strong interaction, a force that pulls them together. Quarks are the only known particles that feel all four fundamental forces. These forces are electromagnetism, gravitation, the strong interaction, and the weak interaction. They also have electric charges that are not simple whole numbers. This makes them very different from many other particles in the Standard Model.

Scientists group quarks into six different types called flavors. These flavors are up, down, charm, strange, top, and bottom.

Quark weak interactions
Quark weak interactions

The up and down quarks are the lightest and most stable. Other quarks, like the charm or top, are much heavier. These heavy quarks undergo particle decay. This is a thing that happens where a heavy particle changes into a lighter one. Because they decay so fast, heavy quarks only appear during high-energy collisions. These collisions can happen in space from cosmic rays or inside particle accelerators on Earth.

People first thought of the quark model in 1964. Two physicists, Murray Gell-Mann and George Zweig, proposed it separately.

MurrayGellMannJI1
MurrayGellMannJI1

At first, some scientists were not sure if quarks were real physical objects. They thought quarks might just be a way to organize math. In 1968, experiments at the Stanford Linear Accelerator Center provided real evidence. These tests showed that protons actually contained tiny, point-like objects inside them.

George Zweig
George Zweig

Later, different teams found the other flavors. The top quark was the very last one discovered, found at Fermilab in 1995.

Understanding quarks helps us see how the universe is built. You can think of quarks like the smallest possible pieces of a Lego set. While you can see a Lego castle, you cannot see the tiny plastic bits that make it. Quarks are even smaller than that. They also have partners called antiquarks. An antiquark is like a mirror image of a quark. It has the same mass and spin, but its electric charge has the opposite sign.

QCDphasediagram
QCDphasediagram

Studying these tiny pieces helps scientists learn about the very beginning of our universe.

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🖼️ Images & Media (10)
File:Standard Model of Elementary Particles.svg
Standard Model of Elementary Particles.svg
File:MurrayGellMannJI1.jpg
MurrayGellMannJI1.jpg
File:George Zweig.jpg
George Zweig.jpg
File:Charmed-dia-w.png
Charmed-dia-w.png
File:Beta Negative Decay.svg
Beta Negative Decay.svg
File:Quark weak interactions.svg
Quark weak interactions.svg
File:Hadron colors.svg
Hadron colors.svg
File:Strong force charges.svg
Strong force charges.svg
File:Quark masses as balls.svg
Quark masses as balls.svg
File:QCDphasediagram.svg
QCDphasediagram.svg
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