Dendera zodiac: does the planet pattern really point to 50 BC?

The question

The round zodiac from the temple of Hathor at Dendera, in Egypt, shows the five naked-eye planets beside zodiac signs. Scholars disagree about which carved figure is which planet, and each reading gives a different date.

Aubourg (1995) read the planets as drawn where they last stood still and reached June to August 50 BC, adding that such a match would not come round again for at least a thousand years. Park and Eccles (2012) argue for early spring, 2 BC to AD 2. Fomenko and Nosovskiy reach the morning of 20 March AD 1185.

Is the 50 BC match distinctive, or would a random alternative do as well? This tests the planet pattern only, not the eclipse symbols or the temple's date from other evidence.

The test

Paul asked an AI model (Claude) to run this on public data. It computed where the five planets stood on every day from 3000 BC to AD 1500 (1,643,625 days, Julian calendar) using the Swiss Ephemeris, and checked itself by reproducing the two eclipses Aubourg links to the ceiling: 7 March 51 BC and 25 September 52 BC.

Each reading was scored as the sky on one day or, following Aubourg's argument, as where each planet last stood still before turning back. Signs were 30 degrees wide, fixed either to the seasons ("tropical") or to the stars ("sidereal"). Matching days less than two years apart count as one episode. The fair comparison was the real sky on a random day, widened to the same number of signs per planet, over 2,000 draws.

The plan was written before scoring. A reading counted as "distinctive" only if its episode count was among the rarest tenth of those patterns and no more than 20% of them also matched somewhere in 200 BC to AD 100, the era of the temple's construction (a window the study chose).

What came out

Two readings cannot be a one-day sky: Aubourg's and Neugebauer and Parker's put Mercury and Venus almost opposite each other, yet those planets are never more than about 75 degrees apart. Neugebauer and Parker's set is exactly the classical "exaltations", a symbolic scheme. It matches on no day at all and claims no planetary date.

Aubourg's match is real and falls at the end of his published range, but only with his second choice for Mercury (Leo or Virgo). It begins on 13 August 50 BC, when Mercury stops in Virgo, and ends on 15 August, when Venus stops there. By the seasons the pattern occurs only in 1199 BC, 964 to 963 BC and 50 BC, and never between 50 BC and AD 1500, which fits his claim.

Is it distinctive? Partly. By the seasons it has 3 episodes where random patterns typically have 7, rarer than about 94% of them. But about 40% of equally loose real-sky patterns also match somewhere in 200 BC to AD 100, against the 20% allowed. By the plan's rule it is not distinctive, and nor is any other reading at its author's date. (Aubourg's first-choice reading passes both numbers by the seasons, but its one match is 964 to 963 BC.)

So the planets agree with a first-century BC date already known from the temple, but cannot alone show that the zodiac records 50 BC rather than another year of that era. Aubourg's (with his alternatives), Park and Eccles's and Fomenko's readings each match at their own author's date, which each can do because each chooses which figure is which planet.

What this does not show

It does not show that 50 BC is wrong, only that the planets alone cannot prove it. The limits:

• Equal 30 degree signs were used; the ceiling shows constellation figures, and Fomenko uses unequal ones.
• "Last standstills" is this study's reading of Aubourg's method. He compared a table of events spread over January 51 to August 50 BC, which is looser.
• "Between X and Y" was scored as either sign, and a narrower rule was not run. Visibility and backward motion were not scored.
• The readings reached the study through a web summariser (Neugebauer and Parker's via Park and Eccles) and are still to be checked against the printed papers, so this page is marked provisional.

Where it goes in the books

This is Book 6, The Sky Remembers: Chapter 10, "The Ceiling They Blew Out", with the full account in the Interlude, "The Machine Checks the Sky".

Check the 50 BC match with any ephemeris. Aubourg's signs, with his alternatives, are Mercury in Cancer, Leo or Virgo; Venus in Aquarius or Pisces; Mars in Capricorn or Aquarius; Jupiter in Gemini, Cancer or Leo; Saturn in Virgo or Libra. The latest standstills before 14 August 50 BC were Mercury on 13 August 50 BC at 157.7 degrees, Venus on 23 February 51 BC at 303 degrees, Mars on 19 June 50 BC at 297 degrees, Jupiter on 12 March 50 BC at 102 degrees and Saturn on 12 June 50 BC at 185 degrees, all as tropical longitudes.