Energy and machines in Antiquity (Part II)

Mechanical Devices

It is seldom possible to determine exactly when a particular mechanical
device was discovered or invented, but in general the chronological development
was as follows.

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The principle of the lever was certainly known as early as the Upper Paleolithic Age, when it was employed in such composite tools as the spear-thrower; at the same time the concept of rotary power is evident in the use of the bow drill. The lever, the inclined plane or wedge, and the cylindrical roller were all used to great advantage by the Egyptians in the construction of their pyramids at the beginning of the Bronze Age.
The lever was later to be applied to other devices, such as the beam-press of the classical period.

With the invention of the pulley came two important advantages: the ability to change the direction of a force, and the multiplying of the available power. The pulley, together with its attendant devices such as the windlass, is not mentioned in literature until the fourth century B.C.E., but it was certainly used much earlier: even the Egyptians had discovered the usefulness of changing the direction of a force by passing a rope over a fixed horizontal bar, but it remained for the Greeks to devise a pulley system that increased mechanical advantage as well; and we credit the Greek scientist Archimedes with the invention of the compound pulley.

We are told, perhaps with some justification, that it was Archimedes, too, who, in the Hellenistic period (late third century B.C.E.), applied the concept of the screw (really just an inclined plane wrapped around a shaft) to practical uses like the raising of water and crushing of olives. He is also credited with the invention of the toothed gear, a revolutionary device that could change the direction of power and increase or decrease
the speed of movement.

It was in part thanks to this device that in the Hellenistic and Roman periods the water wheel was used both as a lifting device and to power other kinds of machines like mills and (at the end of the ancient world) even saws. It was the Hellenistic Greeks, too, who invented the water pump with automatic inlet and outlet valves. Still, it remained for humans and animals to power most of the machines of antiquity: animal-powered mills, for example, are always more common than their water-powered cousins.

Perhaps the single most remarkable example of the ancients’ skill in designing machines based on these basic mechanical principles is the now-famous Antikythera mechanism. Just over a hundred years ago, sponge fishermen working in the waters off an islet near the Greek island of Kythera discovered an ancient shipwreck, and hauled up from it
(among other things) an encrusted mass of bronze. This unprepossessing discovery was to prove to be a late-Hellenistic instrument that, through an intricate system of gears and dials, allowed complex calculations of data apparently related to the solar and lunar calendars. Understandably, this bit of ancient high technology is often identified as the primitive ancestor of our modern computer. This is a bit of a simplification, since the gears of the mechanism bear a greater relationship to Renaissance mechanical astrolabes and clockworks than to the binary system on which our computers are based. But the device remains one of the most intriguing and advanced applications of mechanical theory in antiquity.

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