holds matter together?
Do and Notice
Electromagnetic force is responsible for the spiral
motion of these particles. Click on the image above
for an activity involving the electromagnetic force.
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
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 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.