A centrifuge is any number of devices that spin at a high speed to press objects outward with centrifugal force. It is easy to see centrifugal force by performing a simple experiment. Fill a bucket half way full with water. A large tumbler will work as well, but it isn't as easy to use. Now you have a basic centrifuge.

Find a clear space where you won't hit anything or anyone with your centrifuge. With your arm at your side, quickly spin it in a circle, up over your head and back down to the ground. The centrifugal force created by spinning the bucket or tumbler will keep the water inside. This is a simple example of a centrifuge.

In a real centrifuge, the theory is the same. By spinning a container, whatever is inside is pressed toward the outside of the spin. The centrifuge can contain any number of things, from chemicals to blood to humans. The larger the centrifuge, the more you can spin with it.

NASA has a huge centrifuge, which it uses to expose astronauts to extreme forces. The outward force created by the monstrous centrifuge can be used to simulate the massive G-forces that an astronaut will experience during the take off of a space shuttle. NASA scientists use the centrifuge to test these forces on people in a controlled environment.

Smaller versions of this centrifuge operate in much the same way. Scientists use them to apply specific forces onto a subject in a controlled environment. In medical science, biology, and chemistry; this usually means putting liquids into test tubes, placing them in the centrifuge, and spinning it to apply force to the liquids.

This use of a centrifuge is valuable to scientists because the centrifuge separates liquids into layers based on their mass. More massive components of the liquid are pressed toward the outside of the centrifuge with more force, so they settle to the bottom of the test tube. Less massive components settle in layers higher up, with the least massive at the top. When a doctor or nurse uses a centrifuge on blood for example, the blood cells collect at the bottom while the blood plasma moves to the top.

By applying controlled forces in a confined space, a centrifuge can be a useful tool to many branches of science. From aerospace to chemistry to medicine, many scientists would find themselves unable to perform many important tasks without the use of a centrifuge.