Reference: AP1
Category: Atmospheric Pressure
Purpose: Shows the strength of atmospheric pressure.
Description: A repetition (on a less heroic scale) of Burgormaster Otto von Guericke's famous exmperiment at Magdeburg (about 1652). Two brass hemispheres which fit closely (aided by Vaseline). Space between them is evacuated by means of a rotary pump. Show that the whole contraption can be picked up by the handle on top of the upper hemisphere (despite its considerable weight). Open tap and point out that as the air rushes in the bottom hemisphere and heavy base will drop off. It usually doesn't for a bit, owing to the cohesion and adhesion of the Vaseline, but just after the class has stopped laughing, it falls of with a gratifying crash.
