The Antikythera Mechanism
In 1900, sponge divers discovered the wreck of a Roman cargo ship in 149 feet of water off the Greek island of Antikythera. Among the treasures retrieved from the vessel was a heavily encrusted object that appeared at first to be a rock with a gear embedded in it. Later researchers used x-ray and gamma-ray imaging to determine that the object was a brass orrery, a highly sophisticated mechanical model of the solar system showing the movements of the five known planets, plus the sun and moon. Dating from the second century BCE, the hand-operated device could be used to determine the position of the planets against the Zodiac at any given time, as well as to predict lunar and solar eclipses. An interdisciplinary research team at University College London has recently built a digital replica of the device.
The Antikythera Mechanism, as it came to be called, displayed a level of technical complexity that was previously unknown in the ancient world. Nothing comparable would be seen until the development of astronomical clocks in 14th-century Europe. There is speculation that Archimedes himself may have constructed the original, since he alone was believed to possess the knowledge and technical skills to do so. The achievement was all the more impressive in that it was based entirely on astronomical observations using the naked eye (the first telescope would not be invented until 1608). Dozens of meshing brass gears were responsible for the complex interplay of sun, moon and planets, including the 462-year cycle for Venus and the 442-year cycle for Saturn. The device was able to take into account the variable speed of the moon in its orbit and the apparent reversal of the planets in their orbits as seen from the earth.
We think of the Antikythera Mechanism as a model of the solar system as it was known in antiquity. But technically speaking, it was built not on direct observation of the sun, moon and planets but on a mathematical model developed by the fifth-century Greek philosopher, Parmenides. Indeed, it was Parmenides’ method for calculating the planetary cycles that enabled researchers from University College London to reconstruct the device from the fragments found in the sunken Roman-era cargo vessel.
The device was the first mechanical construct of a scientific theory. It achieved a remarkable degree of accuracy, predicting solar and lunar eclipses decades in advance. And yet the mathematical model on which it was based was wrong. In keeping with the astronomical theories of classical antiquity, the model assumed that the sun and planets revolved around the earth. For purposes of calculating their relative positions, however, it was largely irrelevant whether the earth or the sun stood at the center of the solar system.
“The map is not the territory,” the mathematician Alfred Korzybski reminds us. This is why all scientific theories are at best provisional — true only until a better “map” comes along. Aristotle believed the stars and planets were mounted like jewels in concentric spheres that surrounded the earth.· Astronomers puzzled for a thousand years over why their observations failed to conform to the geometric perfection of Aristotle’s universe. Copernicus solved part of the puzzle by placing the sun rather than the earth at the center of the cosmos, but he was thrown off by the lingering notion that the heavenly bodies moved in circular orbits. Kepler eventually figured out that their orbits were elliptical.
Isaac Newton first conceived of the “clockwork” universe (although he never called it such), with celestial objects moving through three-dimensional space according to fixed laws of motion. Einstein’s special theory of relativity overturned many of Isaac Newton’s cherished assumptions about time and space, including the belief that the universe was pervaded by an invisible and undetectable substance called aether that was needed to transmit light through space. His laws of motion survived, but three-dimensional space has given way to a four-dimensional time-space continuum in which time was infinitely elastic and space was curved.
As far as we have come in our understanding of the universe since the Greeks built the Antikythera Mechanism, we would do well to remember that the map is still not the territory. Einstein once quipped that he would feel sorry for God if experimental evidence had not confirmed his general theory of relativity, since the theory was correct. It was. Yet Einstein would soon find himself fighting a rearguard action against quantum physics, which governed the behavior of elementary particles. It turned out the building blocks of matter did not conform to fixed laws but to probabilities. This famously caused Einstein to grumble, “God does not play dice.” To which Neils Bohr, one of the pioneers of quantum mechanics, replied, “Einstein, stop telling God what to do.”
The basic framework of the universe might appear to be of small consequence to those of us who are not in the business of forecasting eclipses or landing rockets on Mars. But each of us has internalized a cognitive map that enables us to navigate the everyday world in which we live. Our most basic concepts about reality --· of time and space, self and other -- are learned at our mother's knee.· These are not phenomena of nature but constructs of the mind. Once internalized, these basic concepts about the world and our place in it are largely transparent to us. We may think we are still capable of perceiving the world as it actually presents itself to us, but the pristine sensations that greeted us as newborns are irretrievably lost. As the philosopher Owen Barfield has noted that “the perceptual world comes over its horizon already organized.”·
Our internal mapping system is centered in a part of the brain called the hippocampus, which not only processes memories of events, names and faces but also handles “spatial” memories that tell us where things are and where we have been. These work together to form a complete picture of the world, with everything in its place and properly labeled. They enable us to answer when our name is called, keep a dentist appointment six months from now and find our way to the bathroom in the dark.
We imagine that we live in the world, not realizing the extent to which the world we live in is actually the world that lives in us. This becomes especially apparent when the wiring in our brains is scrambled by dementia, as happened with my mother. Then we discover that the bedrock of time and space is actually built on the sands of memory. We eventually become as helpless as newborns, lost in a strange world where it is impossible to get our bearings because we have also lost the map.