Guericke · Magdeburg hemispheres
Can nothing be stronger than sixteen horses?
That time, that place
Guericke was the mayor of Magdeburg, the man who led its rebuilding after the Thirty Years' War left it in ashes. In the same years he built a pump for removing air.
Why this question
To people then, air was barely a thing at all. That it has weight, that it presses from every side — neither claim carried any felt reality. Torricelli's tube circulated among scholars.
What Guericke did was not argue. He looked for something anyone could watch and be astonished by.
What was found
He made two copper hemispheres, set their rims together, and pumped the air out. Nothing glued them, nothing latched them. They were simply placed together.
Then he harnessed eight horses to each side and had them pull in opposite directions. Sixteen horses pulled, and the hemispheres did not come apart.
This was in front of the emperor and assembled princes. In one stroke they understood how hard the air they had taken for nothing presses from every direction.
Air was as good as nothing
Copper hemispheres that sixteen horses could not separate
The demonstration is an early instance of science acquiring a public stage