Can a glass of water defy gravity?

Science and magic are closely linked. so in fact you could use this experiment also as a magic trick on a children's birthday party. If you have seen it for the first time it is really unexpected.

Materials you need for this experiment:

glass of water	The glass of water is the key for your experiment
cardboard or stiff paper	The cardboard/paper has to be big enough to easily cover the glass of water. If there is only the slightest hole in the cover, the trick will not work
big bowl	This is just if the experiment doesn't work to keep the water from flowing all over your place.

How to do the experiment:

	Fill most of the glas with water and put the carboard on top of the glass. It has a better effect, if you fill the glas not to the top so that you could easily see the liquid level.
	Take the bottom of the glass in one hand and the softly press the cardboard with the other hand on the top of the glas.
	Turn everything around, so that the cardboard is at the bottom end with the liquid on top of it. Be sure that the cardboard is really horizontal. If you hold it askew, the cardboard can slip sideways and all the water will spill out (so always do the experiment over a bowl until you get enough practice to get it working every time!).
	If the Cardboard is horizontally, you can remove your hand from the cardboard and the air pressure will take over the role of your hand.

If you have enough experience that the experiment works every time, you could also try to modify it. How much liquid do you need? Is it sufficient if you just wetten the rim of the glass to make sure that you have an airtight seal? Does it also work with more flexible materials like plastic foil? If you use it as a magic trick it might be usefull to put some color into the water so that the audience can see it better.

Have fun experimenting!