A team of researchers from University College London and the Science and Technology in Archeology and Culture Research Center at the Cyprus Institute has solved an important piece of the puzzle that forms an ancient Greek astronomical calculator called the Antikythera mechanism.
Computer model of the display of the Antikythera mechanism: in the center, the dome of the Earth, the phase of the moon and its position in the zodiac – then rings for Mercury, Venus, true sun, Mars, Jupiter, Saturn and date, with small spheres and smaller marks for oppositions. Scale markers and index letters for the synodic cycles of the planets are inscribed on the planetary rings. Around these, the zodiac and the Egyptian calendar. The real sun ring has a ‘golden ball’ with ‘pointer’. When the moon and sun hands coincide, the lunar sphere is black for new moon; when the hands are on either side, the moon globe is white for full moon. The head of the dragon hand shows the ascending moon node; the tail is the descending node. Small triangles on the true sun ring, near the pointer, indicate wider and narrower eclipse boundaries. Eclipses are possible if the Dragon Hand is within these limits. When the moon pointer is in front of the dragon’s head, the moon is south of the node; after that it is located north of the node – vice versa for the descending node. A date hand is attached to a narrow date ring and shows the date in the Egyptian calendar. Image credit: Freeth et al., doi: 10.1038 / s41598-021-84310-w.
In 1900, a team of Greek sponge divers discovered a 2,050-year-old Roman shipwreck off the remote island of Antikythera in Greece.
The ship is believed to have transported looted treasures from the coast of Asia Minor to Rome, in support of a triumphal parade planned for Julius Caesar.
The divers found a rich collection of ancient artifacts from the wreck, including bronze and marble statues, jewelry, furniture, luxurious glassware, and a surprisingly complex device now known as the Antikythera Mechanism.
Built between 150 and 100 BCE, it was a bronze gear mechanical computer that used breakthrough technology to make astronomical predictions by mechanizing astronomical cycles and theories.
“It calculated the ecliptic longitudes of the moon, sun, and planets; the phase of the moon; the age of the moon; the synodic phases of the planets; the days excluded from the Metonic calendar; eclipses – possibilities, times, characteristics, years and seasons; the heliac rises and settings of prominent stars and constellations; and the Olympiad cycle – an ancient Greek astronomical compendium of dizzying ambition, ”said Professor Tony Freeth and colleagues from University College London.
Now split into 82 fragments, only a third of the original survives, including 30 corroded bronze gears.
Nonetheless, they are rich in millimeter-level evidence – with fine detail of mechanical components and thousands of tiny text characters buried in the fragments and unread for over 2,000 years.
The largest surviving fragment, fragment A, shows bearing, pillar and block features. Another fragment, Fragment D, has an inexplicable disc, a 63-tooth gear and a plate.
In previous research, scientists have revealed thousands of text characters hidden within the fragments using microfocus X-ray computed tomography.
Inscriptions on the back contain a description of the cosmos image, with the planets moving on rings and indicated with marker beads.
It was this display that Professor Freeth and co-authors attempted to reconstruct.
Inscriptions on the Antikythera Mechanism. (a) FRONT COVER: Planetary cycles, framed by design from fragment 3. FRONT COVER: Parapegma, above and below the Cosmos Display, indexed with the Zodiac Dial. BACK PLATE: month names on the Metonic calendar. Eclipse Features, Round Metonic Calendar and Saros Eclipse Prediction Dials – indexed to the latter. Eclipse glyphs indexed on the Saros dial. TAILGATE: User manual, including Cosmos description, calendar structure and moon-sun cycles. (b) Front Cover Inscription (FCI): composite X-ray CT of fragments G, 26 and 29 and other small fragments. The FCI describes synodic cycles of the planets and is divided for each planet into areas in the usual cosmological order (CCO). The numbers ΨΞΒ (462) in the Venus part and ΨMΒ (442) in the Saturn part are marked. (c) Back Cover Inscription (BCI): Composite X-ray CT of Fragments A and B. A User’s Guide: The top section is a description of the Cosmos front display with planets in the CCO; in red are the planet names as well as the word KOΣMOY – “of the cosmos.” Image credit: Freeth et al., doi: 10.1038 / s41598-021-84310-w.
“Ours is the first model to fit all the physical evidence and match the descriptions in the scientific inscriptions engraved on the Mechanism itself,” said Professor Freeth.
“The sun, moon and planets are displayed in an impressive feat of ancient Greek brilliance.”
Two critical numbers in the X-rays of the front of the Mechanism, 462 years and 442 years, accurately depict the cycles of Venus and Saturn, respectively.
When observed from Earth, the cycles of the planets sometimes reverse their movements against the stars.
Astronomers must track these variable cycles over long periods of time to predict their positions.
“Classical astronomy of the first millennium BCE originated in Babylon, but nothing in this astronomy suggested how the ancient Greeks found the very accurate 462-year cycle for Venus and 442-year cycle for Saturn,” said Aris Dacanalis, a Ph.D. . candidate in the Department of Mechanical Engineering at University College London.
Using an ancient Greek mathematical method described by the philosopher Parmenides, the team not only explained how the cycles for Venus and Saturn were derived, but also managed to restore the cycles of all other planets, where evidence was lacking .
“After much struggle, we managed to match the evidence in fragments A and D with a mechanism for Venus, which models exactly the 462-year planetary period relationship, with the 63-tooth gear playing a critical role,” said David Higgon, a Ph.D. candidate in the Department of Mechanical Engineering at University College London.
“We then created innovative mechanisms for all planets that would calculate the new advanced astronomical cycles and minimize the number of gears in the whole system so that they would fit in the tight spaces available,” said Professor Freeth.
“This is a significant theoretical advance in the way the cosmos was constructed in mechanism,” said Dr. Adam Wojcik, also from the Department of Mechanical Engineering at University College London.
“Now we have to prove its feasibility by making it with old techniques. A particular challenge will be the system of nested tubes carrying the astronomical output. “
The team’s results were published in the journal Scientific reports
T. Freeth et al2021. A model of the cosmos in the ancient Greek antikythera mechanism. Sci Rep 11, 5821; doi: 10.1038 / s41598-021-84310-w