The Magdeburg
Hemishperes: In 1654 and again in 1657, Otto von Guericke
demonstrated the effects of air pressure, thereby prooving the
existance of the earth's atmosphere. source
The Magdeburg hemispheres
were a pair of large copper hemispheres precisely cast so that
their rims fit tightly together. When the rims were sealed with
grease and the air was pumped out, the resulting sphere contained
the world's first artificial vacuum. The Magdeburg hemispheres
were designed by German scientist Otto von Guericke in 1650 to
disprove Aristotle's famous supposition that 'Nature abhors a
vacuum'. To get the air out of the sphere, von Guericke also designed
the world's first vacuum pump, which consisted of a piston and
cylinder with one-way flap valves. To power the machine, several
people would turn a crank arm connected to the vacuum pump. The
pressure exerted on the spheres was so great that 16 horses were
unable to pull the two halves apart.