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What holds matter together?

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photo: CERN
Electromagnetic force is responsible for the spiral motion of these particles. Click on the image above for an activity involving the electromagnetic force.

If everything from people to planets is made of tiny subatomic particles, why don't they fall apart and crumble into piles of particles? What holds all this stuff together?

Particles "stick" together by interacting with one another in complex ways. More specifically, they exert what we call forces on each other.

What is a force? Let's take this example. You may have heard of gravity. Gravity is the force that all objects with mass exert upon one another, pulling the objects closer together. It causes a ball thrown into the air to fall to the earth, and the planets to orbit the sun.

The tiny particles that make up matter, such as atoms and subatomic particles, also exert forces on one another. These forces are not gravity, but special forces that only these particles use.

There are several kinds of forces that particles can exert on one another. These forces can cause one particle to attract, repel, or even destroy another particle. For example, one kind of subatomic force, known as the strong force, binds quarks together to make protons, neutrons, and other particles.

Battling Ships

These battling ships illustrate how force carrier particles work. Two ships exchange cannon fire, and recoil from one another when they are hit. The ships here "pass" cannonballs that transmit a repulsive force. Similarly, subatomic particles may pass force carrier particles and repel one another .

So how exactly does a particle exert a force on another particle? It's not a magical thing. Rather, a force involves one particle passing something to the other particle. This "something" is actually another kind of particle, known as a force carrier particle. In the example of the strong force, quarks pass particles called gluons that make them stick together.


The Heart of the Matter



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