Ocean waves off the coast of Mexico
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copyright 2002 University Corporation for Atmospheric Research

What is a Fluid?

When you hear the word Fluid you might think of a liquid like water or juice - something that you can stir up with a spoon. That's right - all liquids are fluids. But did you know that gases like air are fluids too?

If you can stir something up with a spoon or blow it through a straw, it's a fluid. Actually, all liquids and gases are fluids. In space and inside stars there's another kind of fluid called a plasma. Plasma makes up stars.

Most of the universe is made of fluid! All of these things are fluids: oatmeal, jello, milk, blood, rain, the Earth's atmosphere, oceans, giant gas planets like Jupiter, stars like the Sun, and huge clouds of gas and dust in space. Can you think of others?

Last modified November 2, 2005 by Jennifer Bergman.

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