The ancient peoples of Babylon and Egypt have presented us with many valuable scientific and technical innovations. In the fields of arithmetic, geometry and astronomy they made major contributions and in the art of erecting barehanded buildings from huge stone blocks they are unsurpassed to this day. But as far as I know they did not get involved in the theory of gases, nor did they build machines to conquer the sky.
The history of the balloon starts with Greece, where Archimedes (287-212 B.C.) formulated the principles of sinking, rising and floating and Hero (20? A.D.) invented the plunger type water pump. In our own seventeenth century there was Torricelli (1608-1647), who demonstrated the phenomenon of a vacuum by upending a long glass tube filled with mercury and Von Guericke (1602-1686) who adapted Hero’s pump to pump air. In this way he could evacuate his famous Magdeburger Half Spheres and demonstrate the surprising force exerted by the pressure of the column of air above us.
One result of all these experiments with vacuum was that the idea that air had weight became generally accepted.
Magdeburger balls emptied of their inside air were somewhat lighter than air-filled ones. Giovanni Alfonso Borelli (1608-1679, see my previous post), Italian physiologist, mathematician and friend of Galileo, speculated that if one would make very light spheres, for instance out of very thin copper plate and draw all the air from their insides, they would float in the air according to the law of Archimedes. Unfortunately spheres formed out of very thin plate would not be able to withstand the atmospheric pressure from outside and would be flattened by it.
Undaunted by considerations like these the Jesuit father Lana de Terzi (1631-1687), who longed to go to heaven, made the same fatal flaw in his thinking. In his book ‘Prodromo Overo Saggio de Alcune’ of 1670 he describes a true ship of the air, an open gondola lifted by four copper spheres of almost 25 feet diameter that have no air inside. The ship is drawn forward by a span of twelve geese. De Lana was probably the first to be concerned that this invention, like all other man made instruments, could be misused for war. An airship such as this would make war even more brutal and horrifying than de Lana had experienced in his own lifetime. He therefore concluded that God would prevent the construction of this sort weapons. He certainly was he a naive optimist.
Of course his idea of the twelve geese was endearing. In flight it must have looked somewhat like the picture hereafter, which shows the Canadian Joseph Duff flying southward with a flock of cranes that have as much trust in their pilot as de Lana had in his god.