Hero could build devices which appeared to perform tasks either without human assistance or through divine intervention. It was the stage magic of its day, utilizing hidden machinery to make an audience stop in the street and look in awe at the show being put on by whichever god was worshipped in the temple where Hero had installed his device.
The illusion might begin even before worshippers entered the building, in the form of a machine he describes in Pneumatica:
Temple Doors opened by Fire on an Altar.
The construction of a small temple such that, on lighting a fire, the doors shall open spontaneously, and shut again when the fire is extinguished. Let the proposed temple stand on a pedestal, ABCD.
Hero of Alexandria, Pneumatica, machine 37
As the priest and congregation approached they would be faced with the huge, closed doors of the temple. Stepping forward, a priest would light a fire on an altar and, as though the god were pleased with the offering, the doors would swing open of their own accord, accompanied by a fanfare of trumpets. Behind the scenes, where only Hero and the priests ever went, a complex series of air- and water-filled tubes connected the altar to large bucket counterweights attached to the temple doors by pulleys. As the fire heated the air it expanded, forcing water in another tube into the buckets, which would then open the doors when there was enough water to weigh them down and set the pulley train in motion. When the fire was extinguished, the air in the pipes cooled and sucked the water back out of the buckets. As the weight in the buckets lessened, so the doors slowly closed under their own weight. It was all just advanced hydraulics, a subject first studied by another Alexandrian, Ctesibius, whose works Hero must have pored over in the library.
But the mechanical wonders had only begun. Inside temples it was very important for worshippers to purify themselves with holy water before any ritual. Selling this could of course be a useful additional income stream for a temple struggling against the competition, but collecting the money and dispensing the water was a time-consuming and frankly boring job, taking one of the priests away from his other duties. To ease this problem Hero invented a
Sacrificial Vessel which flows only when Money is introduced.
If into certain sacrificial vessels a coin of four drachms be thrown, water shall flow out and surround them. Let ABCD be a sacrificial vessel or treasure chest, having an opening in its mouth. . . .
Hero of Alexandria, Pneumatica, machine 21
Hero had invented the slot machine. On putting a silver four-drachma coin in the slot, a measured amount of holy water was dispensed—another little miracle for devotees. With ablutions complete, the acolyte could then proceed into the main sanctuary, where Hero could really allow his imagination to run riot with a series of miracle machines:
On an Apple being lifted, Hercules shoots a Dragon which then hisses . . .
The World represented in the Centre of the Universe . . .
A Fountain which trickles by the Action of the Sun’s Rays . . .
A Trumpet, in the hands of an Automaton, sounded by compressed Air . . .
Hero of Alexandria, Pneumatica, machines 40, 46, 47, 49
In one temple a steam boiler was used to create a jet of invisible steam on which a ball floated, apparently defying gravity. Hero also talks of a machine which allowed a group of mechanical songbirds to sing in a tree until a mechanical owl turned around to stare at them, at which point they fell silent in terror. And to complete the effect, in the temple gloom behind the miraculous machines, Hero’s moving statues blinked and waved like exotic extras in a Ray Harryhausen movie.
But these devices could also have a more practical use—and raise more money for the temple. Here was a chance for the great engineer to make the gods speak directly to their followers, and like any good show-man, he gave them what they wanted. Fortune-telling was a central part of many ancient classical religions, knowledge of the future, or a least a belief in having knowledge of the future, providing some bulwark against the fragility of life. Whole cities and states officially consulted the great oracles such as the Pythia at Delphi. The fabulously wealthy King Croesus of Lydia had many centuries before, according to Herodotus, asked the Pythia whether he should attack Persia. He had received a typically ambiguous response: “If you do, you will destroy a great empire” (Herodotus, The Histories, book 1). Heartened by this, he immediately attacked, only to discover that the empire the Pythia was referring to was his own.
Even Alexander had sought the oracle at Siwa to discover if his campaigns would be successful. This may seem like a piece of stage magic today, but the word of the Siwa oracle not only helped Alexander to resolve his course of action, but likely paved the way for his conquests. In the same way, not long after the Chaldean oracles of Babylon began predicting his doom, he did indeed die, and the same doleful prophesying had probably helped to oust Darius before that. Prophecies could be self-fulfilling. Enemies would attack a man marked out for bad luck. A man apparently blessed would be left alone. Oracles, to put it simply, worked, and many of all types and importance vied with each other. At the greatest, such as at Delphi and Siwa, kings themselves might send for answers, receiving back those cryptic messages from the god via a human intermediary, usually a priest or priestess absorbed in an ecstatic trance or under the influence of psychotropic drugs. Romans would seek answers in the entrails of sacrificed animals, as interpreted by their augurs.
Hero was interested in a somewhat more modest scale of fortune-telling, however, and one that could answer a large number of questions quickly and cheaply. So for all those worshippers who wished to know how a love affair might proceed or whether a business transaction would be profitable, he invented an omen machine. The omen machine had to fulfill several requirements. It had to give apparently clear answers, it had to make money for the temple, and, most important of all, it had to give the people the answers they wanted.
A temple equipped with one of these devices would not, of course, expose its mechanism. As a suppliant walked into the gloom of the temple’s interior he would see just a mechanical bird and a large wheel. After paying a suitable fee he could ask the god a simple yes-or-no question and turn the wheel, and the bird would either sing or not—the god had spoken.
Singing gave one answer, not singing another, and the priests could choose which was the more appropriate. Inside the mechanism an air pump forced air through a pipe to make the birdsong effect when the wheel was turned. A simple cog attached to the inside of the mechanism could then be disengaged, perhaps by a priest, to silence the bird if the other answer was required.
Hero’s machines could also be found in the theaters Alexandrians attended for recreation. Theater was a very big part of life in Alexandria and throughout the ancient Mediterranean world. It was not only where you got to see the latest plays but also a place to be seen. It was the place where politics happened, where great speeches were made, where factions were formed and broken. It had even been the site of Julius Caesar’s assassination. In the first century AD all the world really was a stage.
For the wealthy survivors from the old Ptolemaic regime and the new Roman administrators, putting on a big production was a good way to get noticed and hence a good way to make a name for yourself. But standards were high and the Alexandrian audience expected a lot. Just as in our modern city theaters, people wanted more than just brilliant dialogue and acting—they wanted spectacle, effects, something to transport them into the world of the play. Hero himself describes various forms of rotating backdrop for scene changes, flying galleries where gods and heroes could be winched into the air, and even thunder and lightning machines. But Hero wanted to take his audience a step further.
To achieve this he invented a piece of stage machinery with a unique ability to wheel itself on- and offstage of its own accord at a preset time. Even older sources mention such self-propelling devices, although in an entirely mythical context, such as the god Hephaestus’s magical tripods, mentioned in Homer’s Ilia
d:
Thetis of the Silver Feet made her way to the palace of Hephaestus, which the god of the Crooked Feet had built, with his own hands, of imperishable bronze. It shines like a star and stands out among the houses of the gods. She found Hephaestus hard at work and sweating as he bustled about at the bellow in his forge. He was making a set of twenty tripods to stand round the walls of his well-built hall. He had fitted golden wheels to all their legs so that they could run by themselves to a meeting of the gods and amaze the company by running home again.
Homer, Iliad, book 18
Hero determined to make the myth a reality. The inside of Hero’s automatic scenery was, in effect, a giant egg timer. As a huge hopper of sand emptied onto a platform, the weight pulled a cord wound around the axle, pushing the scenery forward. When the cord was fully unwound the scenery stopped—hopefully on the right part of the stage. Sand now continued to pour from one container to the other, marking out a set period of time, and at its conclusion, a lever switched and the scenery trundled back offstage again. Today modern theaters use similar computer-controlled “trucks” to move scenery, but unlike modern versions, Hero’s had a problem. Once the machine was put into action there was no way to control it. If the actors spoke too slowly or fast, or if there was some interruption of the play, then the scenery might arrive or leave at the wrong time. A great speech might be rudely interrupted by the untimely departure of the street scene or leafy grove in which it was set. So Hero came up with a solution to this as well—automate the entire play, doing away with human actors altogether.
Attempts at creating robotic theaters had also, perhaps surprisingly, been tried before, notably in the late third century BC by Philo of Byzantium, who was himself an imitator of the Alexandrian Ctesibius. Although Philo’s book on automatons is lost, Hero tells us that he proposed mechanical theaters powered by a simple weight on a rope. Unfortunately, this required that the theater be perched on the edge of a cliff for the duration of the action. During these long drops the weights tended to speed up too much, making the final scene more dramatic than intended as wooden actors, scenery, and theater all suddenly hurtled over the cliff edge.
Hero now proposed a much more complex system, and to demonstrate it he chose a play so complicated that it was almost impossible for human theatrical companies to put on. Nauplius is a classic Greek tale of tragedy and bloody revenge set just after the Trojan War and centers on King Nauplius, whose son has been stoned to death by Ajax after being falsely accused of treason. Nauplius wants revenge and calls on the goddess Athena to help.
Hero takes up the story:
At the beginning the curtains open, then in the picture there appear twelve figures . . . who are repairing the ship and moving it forward to be launched into the sea. These figures move themselves busily: one is sawing, the others are hammering, while yet others work with drills. And there is a great noise, as of the sound of actual working.
Hero of Alexandria, On Automata
The curtains then close and open again on another ship being launched. The scene then changes again and now there is a seascape with the one ship following the next. For some extra color Hero adds, “Often dolphins swim along with them, which quickly dive into the sea, then become visible, just as they really do. Then the sea becomes stormy” (Hero of Alexandria, On Automata).
When the curtains open again the ships have gone and we see old King Nauplius, standing next to Athena, who is holding a burning torch. The curtains then close again and open one final time, where Hero tells us
there appears the shipwreck of Ajax’s boat, and Ajax swimming. A machine raises Athena above the stage out of view; thunder crashes, and a bolt of lightning falls directly from above the stage onto Ajax, who is made to disappear. And in this way the story comes to its conclusion.
Hero of Alexandria, On Automata
To automate this entire play was a task of breathtaking ambition, but Hero went on to describe exactly how it could be done. The central power for all movements came as before from a hopper into which sand poured, the weight of sand pulling on a rope tied around a drum. As the rope was pulled down, the drum turned, providing the power. But rather than just having the drum slowly unwind in one direction, Hero “programmed” it by placing pegs on the drum’s surface; thus the rope could be wound around in one direction until it reached a peg, then looped around the peg to run in the other, making the drum reverse. With the pegs placed correctly, the drum could be made to perform a complex series of turns and reverses, each one timed to provide the power for one of the scenes. So when his automatic theater opened its curtains, its audience witnessed the closest thing to a modern movie anyone would see before the invention of the magic lantern in the seventeenth century.
Nor were Hero’s devices restricted to the temple and theater. For the novelty-loving Roman with enough money to spare, Hero also devised mechanical toys for the home. Parties were just as important a part of ancient life as they are today, and then, just as now, it was customary to bring with you something to drink to help break the ice. In Hero’s world, that something would probably be wine, and it presented a problem that has remained unchanged for centuries: As host, how do you make sure your guest doesn’t bring cheap wine and then just drink your expensive stuff? Or from the guest’s point of view, how do you make sure that other people don’t drink all the good stuff you were kind enough to bring, leaving you with the dregs? For any party thrower, these were real questions, and Hero had a mechanical answer for them in his Pneumatica:
A Vessel containing different Wines, any one of which may be liberated by placing a certain Weight in a Cup.
If several kinds of wine be poured into a vessel by its mouth, any one of them may be drawn out through the same pipe: so that, if several persons have poured in the several wines, each one may receive his own according to the proportion poured in by him.
Hero of Alexandria, Pneumatica, machine 32
This was in effect a more elaborate version of the holy water dispenser. Inside the wine jar were three compartments into which each of three guests poured his or her wine. These were all connected to a single outlet which was controlled by a valve. The valve had three open positions, one for each wine, and each weight would set it to one of these. When your guest poured his wine into the top, you handed him the weight that corresponded to the compartment he had filled. When he wanted a drink, he just placed his weight on the dispenser; that action set the valve to his position, and his own wine was then dispensed.
But while Hero’s inventions were mechanically ahead of their time, they represent something of a conundrum. Although his work undoubtedly was of practical use to temple priests and he also describes civic projects such as the construction of a fire engine, the vast majority of his work was simply of novelty value. For the Alexandrians of his day, Hero was not a mechanical genius but just another in a long line of toy makers, a gadgeteer. It was this attitude that would lead people to overlook perhaps his greatest invention, one that would eventually change the world forever.
Tucked away in his surviving notes lie his plans for an aeliopile. He describes this novelty toy as two copper tubes soldered to the top of a sealed metal container. These passed through two metal sleeves leading into each side of a copper sphere that could rotate between them. From the sphere emerged two outlets facing opposite each other. When water was boiled in the lower sealed compartment, steam would shoot out of the outlets, making the ball spin around, to the delight of the audience. And they should have been delighted and amazed. Spinning at around 1,500 rpm, this was the fastest man-made rotating object in the ancient world.
But it was much more than that. It was the first use of jet power. And more amazing still, it was, of course, a prototype steam engine. Had Hero combined this toy with the piston—something his fellow Alexandrian Ctesibius had invented some three hundred years before—he could have created a working steam engine; but tellingly, he didn’t.
To Hero, all these technologies,
so similar to those which take pride of place in our modern society, were simply curiosities—the descendants of the first items collected by the museum to help lecturers explain natural philosophy. Of course, even if Hero couldn’t see the value of his toys, others could read about them. His extraordinary books continued to fill the shelves of the library: the Metrica on measurement of surfaces, the Stereometrica on measuring in 3-D, the Mechanica on how to move weights with the least effort, the Automata on how to build robots, the Pneumatica on devices worked by compressed air, the Dioptra on taking measurements at a distance, the Catoptrica on curved mirrors. Some of them made their way to Greece and Rome, but even there no one realized the potential of these ingenious devices.
There were fundamental problems with his aeliopile design that certainly didn’t help. The main problem with it was its efficiency, or lack thereof. To allow the ball to spin freely the joints had to be made quite loose, but if the joints were loose then a lot of the steam escaped through them. Then there was the problem of fuel. In the Roman world the boiler would have to be powered by wood, and that would have to be collected by someone—probably a slave. So if the useful energy gained from burning the wood to make the steam to turn the ball was less than the energy used by the slave to collect the wood, then the efficacy of the device would be lost and the slave might as well be told to do the work himself.
But it’s not just efficiency that worked against Hero’s steam engine. Those very slaves who would be needed to collect the fuel were themselves an obstacle to there ever being a Roman industrial revolution. The main use of steam engines during our industrial revolution was for producing cheap and readily available power. Hiring people to do jobs by hand was expensive, and it was sometimes difficult to get skilled people when you needed them. Steam engines could work day and night without rest, they were always available, and they were very strong.
The Rise and Fall of Alexandria Page 23
