Sunday, December 01, 2013

The Forgotten Revolution by Lucio Russo

The history of science in the West, as those few of us who remember it goes, has the ancient Egyptians inventing some primitive technology, the ancient Greeks inventing math and science but scorning technology as not fit for truly noble thinkers, Romans who developed civil engineering and sanitation, and then a lot of barbarians who wrecked everything until math started being rediscovered and science and technology re-invented and went on to exceed anything mankind had ever seen before.

Name an ancient Greek scientist? Archimedes, Aristarchus, Aristotle, Ptolemy? (Aristotle does not really count, btw) Check the dates. That's quite a range of time.

It turns out that there's quite a bit missing, and some of what we know isn't quite true.

We tend to telescope everything from 1000BC to 400AD as "ancient," giving the illusion that everything happened more or less at once.

The Forgotten Revolution goes in depth to try to find out what happened: how high the Greek science and math rose, and why things starting falling apart.

The answer is very high indeed. Pick those famous "epicycles" that Ptolemy introduced to explain the motion of planets in the sky.

  • Ptolemy didn't invent them, some other Hellenists had done so centuries before. (He died in 168AD)
  • Hellenist math was constructive, and required straight-edge and compass. For anything not perfectly circular, epicycles were inevitable.
  • Look at this picture and tell me what you see. These are dates of astronomical measurements that went into the Almagest.

There's a nice spike at times close to Ptolemy, and a long list before--with a 2 century-long gap in the middle. Ptolemy wasn't developing something new, he was trying to retrieve something old. And since little details like known heliocentric theories were left out of the Almagest, it wasn't a thorough review.

Hint. Ptolemy was from the Imperial Roman era.

What sorts of things did the Hellenists have? Lenses, steam engines, gears and (one infers) metal screws, first principles shipbuilding design (so much for a disdain for technology), hydrostatics for pipe design, gigantic lighthouses (probably with a parabolic mirror--hard to be certain), timing of systolic and diastolic pulses of the blood, watermills, and of course differential gearing in the Antikythera mechanism. And mechanical puppets, and something that sounds like silent movies.


Russo is a physicist, and also versed in classical literature. This is rare. Most classicists don't know much math or science, and most scientists aren't familiar with old forms of Greek. So things like this slip by (p106)

The common idea is that Aristarchus was too far ahead of his time to have had a lasting influence on the course of science, and support for it is generally found in the accusation of impiety supposedly leveled against him because of his heliocentrism. The belief that Aristarchus was accused of impiety originates with the seventeen century philologist Gilles Menage who … changed a passage in Plutarch by amending an accusative into a nominative and vice versa.

Russo points out that planetaria were well known, and that Cicero's description of Archimedes' version is consistent with a heliocentric mechanism--not so much with a geocentric one. (Another advantage of having somebody with a technical background peering at the language details.)

More astronomy: Geminus (about 50BC) compiles a list of star positions and "warning the reader not to suppose it ("sphere of fixed stars") to have a physical existence, since the stars are at different distances from us." And "According to Pliny, Hipparchus (died 120BC) compiled his catalog of stars precisely so that later generations might deduce from it the displacements of stars and the possible existence of novae." (Talk about a long-term research program! Halley (1718 AD) recorded differences with Sirius, Arcturus, and Aldebaran.)

AristarchusEratosthenes famously measured the circumference of the Earth. From textual evidence and some references to the verticality of the sun in a band of about 200 miles, Russo strongly suspects that AristarchusEratosthenes (head of library of Alexandria too) had a team dig the famous well in a more accurate spot than merely a handy town, and went on to define his own version of the stadia, linked to the Earth's circumference. This suggests a little funding...

Technology, travel, engineering

How about military technology? The torsion catapult (about the middle of the 3rd century BC) was more powerful and faster to use than the trebuchet of western medieval times more than a millennium later. There's some evidence that a repeating catapult was used, and according to Philo of Byzantium, air piston catapults (thanks to Ctesibius, died 222BC).

Travel? Pytheas (late 4'th century BC) traveled direct to India from the Gulf of Aden--no sticking solely to the coastline; that's high seas navigation. He also got far enough north that the sun stayed up all summer, and even saw the polar pack ice. Herodotus preserves (and disdains) a report suggesting a circumnavigation of Africa.

Civil engineering? Canals, a blossoming of irrigation methods used from that day to this, aqueducts, and so on. Remember the Roman aqueduct system?

Vitruvius' regard for the role of applied science is the greatest of any Latin author. He enumerates the fields of knowledge required by a good architect … writing, drawing, geometry, arithmetic, history, philosophy, music, medicine, law, and astronomy. But consider the ensuing explanation of the uses of this knowledge: astronomy is regarded as necessary, in essence, for determining the four points of the compass, and geometry for understanding the uses of squares and levels….

Vitruvius' work represents the highest level achieved by a Roman technical treatise. As for the rest, Frontinus, the author of the main Latin work on aqueducts, systematically mixes up the flow rate of a pipe with its cross section, thus ignoring, in particular, the role of the slope. The high technological level of Roman aqueducts seems hard to reconcile with such incompetence, but we should not forget that Frontinus was not an engineer but the bureaucrat in charge of Rome's water supply, … whereas the actual designers, builders and maintainers of the aqueducts were slaves, who of course were not in a position to write books.

In the same way we find that, for all productive activities with technological content, Rome had to import either finished goods or workers from the East.


The installation of the Pharos was considered so useful that other pharoi were erected at every important port of the Hellenized Mediterranean. But Greek sources contain no overall description or a single technological detail relative to the Pharos, even though it was regarded in its own time as one of the seven wonders of the world. This confirms how reticent our sources are about technological products, in a case where the product itself is not in doubt. Because the only extant descriptions of the Pharos are by Arab historians, who visited it long after it had ceased to function, we know very little of its technology. Yet some conjectures can be made on the basis of its purpose and contemporary knowledge. First, we can imagine that the reflector consisted, as it would today, of a parabolic mirror, all the more so because the relevant theory arose precisely around the time of the construction of the Pharos.

At this point Russo starts to stretch things a bit for my tastes--but maybe he is right:

It should be stressed that modern steam engines are not at all, as is often implicitly assumed, an invention independent of the Hellenist engines; there is a continuous line of descent. Heron's expositions were studied carefully by Leonardo da Vinci, among others.

Apparently Leonardo drew pictures based on the old books, including a picture or so that aren't found in any of the known old books. Heron (1st century AD) seems to have been a compiler rather than a scientist or engineer himself. The dioptera Heron describes used small screws, but Heron's description of how to make screws only works well for big ones, and in his Automata he never uses gears in the descriptions at all, only friction devices. But gears would have worked better in some cases, and we know that centuries before there were precision gears.

This implies that by Heron's time there had been a significant technology loss. There was still a lot to see. Heron says that an early automatic play "merely showed, by way of motion, a face with blinking eyes. … Heron also says that with "still" automata, one can either show a character in motion, or a character appearing and disappearing."

There is some suggestion of the use of acids in mining, and we know they had pumps to raise water 30 meters out of an underground mine; some of the hardware is still there.


Apparently Galen was not the pinnacle of "ancient" medicine. Herophilus, for example, had "a water "stopwatch" built that could be adjusted for the age of the patient." He described some mental illnesses, studied the circulatory system (with terms still used), studied the eye with great care, discovered the nerves (sensory and motor both!), and "For some diseases, such as the cholera, it is recorded that Herophilus handed down no treatment: this is perhaps the best proof of how serious he was in his medicine."

Science as such

Russo goes to considerable pains to define a scientific attitude as abstracting details from reality to create models of more or less validity--and making clear that the models are not the reality. It seems fairly clear that this attitude was gone by Imperial Roman times. He argues for its presence in Hellenist times. This is a little tricky, since most of the Hellenist scientist are known only by later references; not much is left.

Russo also complains that a reliance on "homogeneity" undermines science, but another word for that in context is "dimensional analysis." Things like x^2+x^3 were allegedly not dealt with by Greek mathematicians (not clear that this is true, BTW). If x is a distance, the expression as it stands does not seem to make any sense. Given how important constructive techniques were for the Greeks (They didn't have computers, OK? And you can try mapping the measurements from a small construction to a big one by hand, but I'll bet you make mistakes.), it isn't too surprising that these wouldn't have been high priority.

Did Newton base his work on gravitation on old Greek manuscripts? That seems likely to Russo and extremely unlikely to me. Some extraordinarily muddled Roman descriptions of Greek astronomy have triangles emanating from the Sun to move the planets. This, to Russo, looks a lot like Newton's geometric explanation of step-by-step motions of the planets under the Sun's gravitation, and Russo's explanation of how the language could have been garbled is quite plausible. However, untangling that rubbish is harder than figuring it out in the first place, and I think Newton's work was independent.

Newton acknowledges his debt in optics to the Archbishop de Dominis, who used Greek terminology and borrowed from Arabs.

It seems that the development of optics was plagued by amazing bad luck: The "Ancients" knew how to make good lenses but did not know what to make of them and kept them as baubles, later intellectuals--not just Leonardo and Fracastoro, but also Roger Bacon and Gosseteste centuries earlier--knew many uses for them, yet could not build them and had never seen such things. Some medieval manuscripts even show astronomers looking at the sky through long tubes; the incongruity has been addressed by postulating that these were empty sighting-tubes!

Consider that Bacon, in the fifth book of the Opus maius, waxed enthusiastic about the Ancient's ability to enlarge small objects and to bring faraway ones close, using appropriate configurations of lenses and mirrors

What happened?

Disasters piled on limited knowledge pools seems the likely culprit. Quite a bit of this is my interpretation of his data. He doesn't devote as much time as I'd like to seeing what went wrong.

Thebes had the death penalty for spying on their shipyards. No technology spread if they could help it. I don't know if I'm reading between the lines, but the complete absence of details about lighthouse construction sounds as though it was better for your health not to be too specific.

If you have many small pools of knowledge trading finished goods, if not the technology proper, with a big pool of talent at Alexandria, you can keep developing sciences and skills and reverse engineering things for quite a while provided there's peace.

There wasn't. Rome was expanding. Archimedes was killed by a Roman soldier, and Syracuse wasn't the last place; the Romans kept on.

Euergetes II (Ptolemy VIII) perhaps decided that the Romans would like him better if he moved against Greeks, so he persecuted the Greek population of Alexandria--including the ones from the library. Almost nobody was left, and some of the survivors from the library seem to have headed East far out of Roman reach; some suggest all the way to India.

Do I need to say more? Even if the books survive, explaining what exactly what the most advanced treatises mean demands some humans who still understand. Lose continuity, and the most advanced material is now unreadable--or if readable, not understood. Tell me what the average news reporter would make of the phrase fiber bundle, and compare it to the link. And any complicated technology demands the work of different kinds of experts. Lose any of them, and you can't repair it anymore.

So the Roman predilection for encyclopedic works rather than deep analysis makes sense--they don't understand the hard stuff. Nobody did anymore. And you can only coast so long on an encyclopedia, especially when it get corrupted and larded with superstition.

Can it happen again?

Of course. The barbarians are always with us, both outside and inside. We spread our knowledge far more widely today, so the catastrophe would have to be much greater to hit it all, but the same problem of transmission of the hard details remains. Don't count on Wikipedia being there after a disaster; think in terms of what books the local library kept from the great starving seventy years ago when the burners went through.

1 comment:

Loooop said...

"Aristarchus famously measured the circumference of the Earth. From textual…"

Eratosthenes, not Aristarchus.

"…strongly suspects that Aristarchus (head of library of Alexandria too) had…"

Eratosthenes, not Aristarchus.