Have you ever heard about quarks? Quarks are tiny particles which are building blocks for our world.
Of course there are other particles which are important ingredients of our world, but quarks are certainly
some of the most important blocks.
There are six different kinds (or flavors, as scientists like to call them) of quarks. You can see them illustrated
on the left. However, in your room you'll probably find only two kinds of quarks; the up quark and the down quark.
Matter in our world is built up only of up and down quarks and several other particles. So how do we know that there are
six flavors of quarks? Particle scientists enjoy spending their time building enormous machines which are
able to accelerate different particles to extremly fast speeds. They smash high energy particles together in
specially designed rooms. When two high energy charged particles collide with each other, new particles can be created.
By observing the tracks that the particles leave, particle scientists can find out which particle left
the track using a few laws and calculations. By smashing particles they were able to create and
identify the charm, stange, bottom and top
quark. Maybe someday they'll be able to find even more quarks.
How can you tell whether a particle is a quark or not? Quarks have special properties. The most important property
is that you never find a quark on its own. Quarks are always confined in groups of two or three. You can think of
the force that keeps the quarks together as being like a bungy rope. When the bungy jumper jumps
off the tower, the energy in the rope will get bigger as she gets closer to the ground. Until, at some point,
the energy will be so high she goes right back up again, even though gravitation is still pulling her down.
The force that keeps the quarks together (it is called the color force) is very similar.
In the animation on the left you can shoot energy (photons) onto a tightly bound
quark. When there's a whole lot of energy in the field created by the color force, the quark will break away,
the same way a bungy rope will break if it's not strong enough to hold the jumper. Out of the excess energy
created when the quark breaks free, two new quarks are created. So even though the quark broke free of its original
brothers, it still isn't alone.