The Great Year or Platonic Year (Latin: annus platonicus) is a concept attributed to Plato. Plato in his dialogue Timaeus defined the "perfect year" as the return of the celestial bodies (planets) and the fixed stars (circle of the Same) to their original positions:
| “ | And so people are all but ignorant of the fact that time really is the wanderings of these bodies, bewilderingly numerous as they are and astonishingly variegated. It is none the less possible, however, to discern that the perfect number of time brings to completion the perfect year at that moment when the relative speeds of all eight periods have been completed together and, measured by the circle of the Same that moves uniformly, have achieved their consummation." | ” |
By extension, the term "Great Year" can also be used for any concept of eternal return in the world's mythologies or philosophies.
The Platonic year, based on the revolution of the planets and estimated by Macrobius as lasting 15,000 solar years.
Nearly two centuries after Plato, Hipparchus established the period of equinox precession, and the term "Great Year" also came to be applied to the period of that precession. The Platonic Year has in origin no connection with this concept (as the precession of the equinox was unknown to the public in Plato's time). caused by the slow gyration of the Earth's axis and discovered by the Greek astronomor Hipparchus:
| “ | Some time around the middle of the second century BC, the astronomer Hipparchus discovered that the fixed stars as a whole gradually shifted their position in relation to the annually determined locations of the Sun at the equinoxes and solstices... Otto Neugebauer argued that Hipparchus in fact believed that this was the maximum figure and that he also computed the true rate of one complete precession cycle at just under 26,000 years... | ” |
The confusion originates with the astronomer Ptolemy, who "adopted the larger, erroneous, figure, with the result that henceforth the two versions of the Great Year - the Platonic Great Year, defined by the planets, and the precessional, defined by the stars - were to be increasingly confused."
It has been claimed that Ptolemy committed scientific fraud by making up observations that would give the figure of 36,000 years even though the data available to him were good enough to get very near the true figure of 26,000.
"Some people called it the Yuga cycle, others called it the Grand cycle and others the Perfect Year...But the most common name found in use from ancient Europe to ancient China, was simply the Great Year".
Famous quotes containing the word year:
“And year by year our memory fades
From all the circle of the hills.”
—Alfred Tennyson (1809–1892)