Basically, the faster you push air around something, the less air that actually pushes the object. The air will flow around the object, and the object will lift into the air.. It's part of what keeps airplanes flying, too.
Anyway: Let's get to the levitating, already! ; )
In this Instructable, I'll show you how to use this principle to float a variety of objects, including 2-liter plastic soda bottles, soda cans, a screwdriver, a ping-pong ball, and your pet hamster! (Not really, but you could :P )
Step 1: What We'll Need:
We'll need something that can propel a lot of air, like a Blowdryer or a leaf blower. These don't have to be anything special, although you do get a little bit more power out of a gas-powered leaf blower.
Some open space if you're going to use a powerful blower, (I suppose you could use an electric leaf blower inside, though).
Something to levitate:
Table-tennis balls work well with the hair dryer, but other small, light things can work, too.
Using a leaf blower opens a lot more possibilities, like beach balls (these are the absolute best if you can find one ((or two!))), or two liter bottles, etc. (Anything without too many corners, and isn't too heavy. Think about how much a small apple weighs, and you have an idea of what we're looking for.)
Some ear protection for the youngsters is a good idea.
Step 2: Ready? Set? Go!
Now, Er....turn the blower on! Try and set it pointing straight up, (Another person is a great help here). Once you have it up, take an object and gently place it in the stream of air and let go carefully. Your object should be hovering in mid-air, with minimal wobble-age. Now let others marvel at your ability to levitate objects with magic!
Common problems are:
1. The object starts to hover and then falls away to the ground.
Solution: Get a lighter object, a rounder object, or a more powerful air blower. (Or just try again :P ). Also, make sure that the blower is fairly vertical, and listing too much off to one side.
That's really the only issue I've had so far, but if you find any, tell me and I'll update.
Step 3: Tips and Tricks
Try other objects, (like toilet paper :D ). You can put a roll on a dowel rod and hold it in front of the blower and stream the the toilet paper around, (It'll go about 30 feet into the air, if you're careful).
Try adding more than one object, and be amazed as they all hover in a line, and even "orbit" around each other.
A 2-liter bottle with a small amount of water in it for ballast will also work well.
Just experiment and have fun with it! I thought that extra exclamation points would make this Instructable sound a bit more cheerful!