Many of us are fascinated by lava lamps, how the cool blobs float up and down and around the tank, bouncing off each other and melting into the pool at the bottom. The lava lamp is truly an amazing invention - but how does it work?

So you know Whyville is about science, although that fact is sometimes pretty cleverly disguised as fun. Well lava lamps operate using stuff you learn in science class, and perhaps in the future, you can learn in Whyville.

(Most of you older kids probably already know this, though.)

But for those of you who don't know. . .

Density = Mass/Volume.

Density is basically how tight the molecules are packed into a certain space. The more molecules are packed in there, the heavier the thing becomes.

So with lava lamps, there are two substances of different density.

The cool looking bubbles you see in there are actually wax. Yes, wax. The other substance is a liquid made of stuff that can vary with each different lava lamp.

Now before we go any further, there is one more thing you must understand.

When molecules heat up, they vibrate. The higher the temperature, the more they shake. And when they shake, they need room to shake. So automatically, all the molecules move away from each other, and the entire mass of the object expands, thereby decreasing the density!

Remember, density is how closely the molecules are packed together.

So when the wax at the bottom of the lamp heats up, it's density becomes less than the liquid above it, so it floats up to the top.

At the top, it cools down, thus increasing the density, making it sink to the bottom again.

And this is how those fascinating tanks of globs and color work.

This just goes to show that science is heavily involved in any type of fun. Video games, slip-n-slides, bikes, soccer, and just about anything.

This is RoseOfRed, going to replace the bulb on her lava lamp.