In order to make our experiment we needed two plastic bottles of
1´5 liters. In the first place, we perforated a hole of 1 cm in
the corks of the two bottles. Soon we filled one of the bottles
with water until approximately three fourth parts and if united
the two bottles by the corks. In order to unite the two bottles
insulating tape can be used. Is very important a good union
between the bottle. When the bottle with water is on the empty
bottle it is observed that the water does not fall easily to the
inferior bottle, but if we give a circular movement to the
superior bottle is generated an eddy and the water falls easily.
When placing the bottle in the superior part, water does not
fall by the little compressibility of the air locked up in the
inferior bottle that does not leave space to the water that
falls. When the eddy is generated when moving the superior
bottle, it is put in communication the air that is in both
bottles and the water of the superior bottle falls easily in to
the inferior bottle.