In 1900, the earliest known example of an astronomical computer (and quite possibly the first computer ever made) was discovered by sponge divers in a shipwreck off the coast of Antikythera, a Greek Island. Remarkably, this device, known as the Antikythera Mechanism, dates back to 80 BC, over 1,000 years before the next known gear-based astronomical device was created. The Antikythera Mechanism was able to track the solar system cycle with sophisticated gear ratios remarkably close to the Golden Ratio, which is used for astronomical calculations. While the model was used to display celestial bodies from an earthly perspective, it doesn’t necessarily favor a geocentric (with the earth as the center) or heliocentric (with the sun as the center) planetary arrangement.

The nature of the solar system’s center was of course quite a contentious topic. As early as 297 BC, Aristacrchos of Samos posited correctly that the solar system was heliocentric. Nevertheless, for nearly 2,000 years, a mix of prevailing scientific thought and stifling aristocratic consensus would see supporters of this theory persecuted for their beliefs.

At the time of the Antikythera Mechanism’s discovery, historians and scientists doubted the authenticity of the device. It seemed far more complex than what was known to be technologically capable in 80 BC. Regardless, the authenticity of the device was proven though analysis of fragments retrieved from the shipwreck as well as ancient texts corroborating the existence of similar devices. Additionally, CT scans show inscriptions within the device that can be accurately dated to this time period. (For more images of the Antikythera Mechanism, see the Interactive Relighting of the Antikythera Mechanism created by HP Labs.)

While it isn’t known exactly what purpose it had to ancient seafarers, the Antikythera Mechanism stands out for its technical sophistication relative to known developments at that ancient time.

More recently, additional light was shed on the ancient computer by Michael Wright, former curator at the Science Museum in London. In order to better understand its function, Wright created a working replica of the Antikythera Mechanism in his home outside of London. Through X-ray imaging techniques, Wright was able to extrapolate the correct arrangement of the mechanism’s (surviving) internal wheels as well as a display to show the 19-year Metonic Cycle, a system once used in Greek, Babylonian, and ancient Chinese calendars.