The Rise and Fall of Alexandria (30 page)

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
Iliad:

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:

 
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

 
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:

 
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 Romans already had a source of cheap and plentiful labor in the form of slaves, and the Ptolemaic administration was particularly well suited to their use. If machines had replaced slaves, where would the slaves have gone? What would they do? No one wanted another Spartacus. For an elite whose wealth was based on land, such a device simply wasn’t in their interests.

And so Hero’s greatest invention was condemned to be no more than a party novelty, just another description of a marvelous mechanical engine in a book in the vast Alexandrian library. The Romans had no real
need
for his work, so their interest in the contents of the world’s greatest library lay not in the abstractions of Plato and Aristotle or in Hero’s experimental physics. They were interested in the construction of siege engines and artillery, in the laying out of roads and cities, in harvesting the vast resources of their new conquests. The mechanical delights of wine dispensers and Antikythera mechanisms had their place, but a machine that undermined the whole base of their society—slavery—certainly did not.