O.K, why does the egg do what it does?

You would've seen the video clip of the egg, fire and milk bottle (if you haven't, check it out - it's awesome).
Anyway, let us explain what happens..

Once the egg is on top of the milk bottle, the fire goes out. Why? Because it uses all of the oxygen in the bottle and the egg is preventing any more getting in. Therefore, the air outside of the jar is stronger and heavier than the air in the jar. The air around the jar and egg is pushing down on the egg and pushes the egg into the jar. Very cool - try it at home (with adult supervision for the fire part)