The many misconceptions in the science of the ancient Greeks become apparent during the Copernican Revolution. In several ways though, ancient Greek science was more advanced than usually acknowledged. For example, Over 200 years before the birth of Christ the Greek scholar Eratosthenes calculated the circumference of the Earth to be 25,000, just 99 miles more than the actual figure, 24, 901 miles. Although Eratosthenes made mistakes in his calculations, these mistakes cancelled each other out to produce a very accurate result. Several decades later, another Greek scientist, Posidonius, believing Eratosthenes to be wrong, calculated the circumference to be 18,000 miles (this figure Columbus would use when planing the voyage that resulted with the European discovery of the New World). Posidonius was from Rhodes, where the Antikythera mechanism is thought to originate.

Article by Derek J. de Solla Price

From June 1959 Scientific American p.60-7

Slide 1:

In 1901 corroded bronze relics were found in a shipwreck discovered off the island of Antikythera near Greece. For years the significance of the find went unnoticed until 1959 when Dr. Derek De Solla Price of Yale University published a paper in Scientific American.

Slide 2:

At first the three pieces of corroded bronze seem unremarkable, except for a similarity to modern clockwork. As for its purpose, archeologists were as mystified as the sponge divers who discovered it.

Slide 3:

Gear teeth around the large main plate are plainly visible, even through the corrosion. At first, it was thought to be some sort of astrolabe. Years of research, however, would reveal a far more complicated device.

Slide 4:

X-ray photographs reveal sliding, circular plates marked with scales of measurement. Scientists have dated the construction of the mechanism to around 87 BC. The shipwreck occurred circa 76 BC.

Slide 5:

Closer examination by Price revealed it to be a complicated mechanical device comprised of 32 gears, including a differential gear; technology thought not to have existed before 13^th century Europe.

Slide 6:

The mechanism, as it originally appeared, was set in a wooden rectangular box slightly larger than an 81/2 by 11 sheet of paper. A cover was hinged to the front and back and a handle on the side turned the gearworks. Directions were inscribed on every available surface.

Slide 7:

Inside the front cover, fixed on top the main driving gear wheel, is a single large, circular dial with two scales. A fixed scale names the signs of the Zodiac and a second movable slip ring shows the months of the year.

Slide 8:

Here we can see a view of the gearing system from the front. The handle that turned the gears is on the top right. The large main gear, shown here in red, turned in a clockwise direction.

Slide 9:

On the back are two dials. The top dial has four slip rings and is thought to have indicated the positions, and the times, of the rising and setting of the five planets known to the Greeks. The lower dial has three slip rings and seems to indicate lunar phases as well as the times when the moon rises and sets. There is also a smaller "subsidiary" dial, comparable to the "seconds" dial of an analog stopwatch.

Slide 10:

When the handle was turned all 32 gears, including a differential gear, turned. Arms, like those of a modern clock, would turn…as well as the eight slip rings.

Slide 11:

Once the operator set the position of the Sun or Moon on the front plate, the Antikythera Mechanism would automatically adjust all the dials providing solar, lunar and planetary data for the corresponding time indicated by the user. The mechanism is thought to have been accurate to 1 part in 40,000.

Slide 12:

How useful was the mechanism? The teeth of the gears were triangular, rather than the more reliable square shape in modern use. It was constructed of a low-grade tin bronze and was repaired twice; indicating that the device was frequently used.

Back View. Wood case replaced by Plexiglas to reveal gearing system.

Slide 13:

If not lost to the dark ages, such a device, had it been applied to other technological areas, could have accelerated the pace of human invention more than 1,000 years ahead of where we are today.

http://www.math.sunysb.edu/~tony/whatsnew/column/antikytheraI-0400/kyth5.html