Okay, maybe that title is a little misleading. It SEEMS like a gravity-defying, but it isn't. That's the awesome part of this science experiment.
What you need are two quarters and a nickel.
1. Make a nickel sandwich.
2. Hold the nickel sandwich with the fingertips of one hand.
3. Place the other hand 10 inches below.
4. Now let go of the lower quarter, still holding onto the top one.
What happened? Which coin ended up on top in your other hand? It wasn't the nickel, was it? Do it again. Same result, huh?
Why is that? The quarter is bigger. It's heavier. Shouldn't it just drop straight down, gravity pulling the heaviest object faster?
The reason the coins flip positions has more to do with your fingers dexterity, than gravity. Unbeknownst to you, when you release the bottom quarter, your fingers release one side before the other, causing the quarter to tip and the two coins to rotate.
This amazingly simply and truly astonishing trick comes from Vicki Cobb and Kathy Darling's book You Gotta Try This!