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THE RHODES CALCULATOR 95
Anything less won't do. And the sidereal year of 365.2564 days is
not much better. It takes 2,500 of these years representing
913,141 days. The gears of the computer would have to be too
big to be practical. But the Sothic year of the ancient Egyptians
fits like a glove for a small mechanical computer. It has 365.25
days, so we need only a gear ratio of 4:1 to obtain whole numbers
of days and years. Every four years of this Sirius, or Sothic,
calendar will give an exact number of days. The gears are small
and manageable. This simple and practical year of the Egyptian
priests makes many complicated astronomical cycles equally simple,
an advantage which modern astronomers with their ingrained
traditions have so far ignored. Use of the Sothic-year
cycle makes it easy to calculate all periods of revolution of all
planets, and all conjunctions, as well as aU phases of the moon.
The second important condition for a successful construction
of an astronomical calculator with gears is to find a simple relationship
between the cycles in full, whole days. The Mayan calendar
almost made it. So did the Sumerian calendar, which was
based on the Saros cycle of eighteen tropical years. The Greeks
used a calendar based on the Metonic cycle of nineteen tropical
years, and this system has no practical value for a gear computer
either, which proves that the Greeks were not so great mathematicians
after all and that whoever constructed the marvel of
Antikythera was a much stronger mind.
We are left with the ancient Egyptian calendar. It is the only
one that fulfills all the requirements, and it is the basis for the
Rhodes calculator. The seemingly complicated Egyptian calendar,
based on Sirius, the sun, and also the moon, actually works
like a charm. Every four years represent exactly 1,461 days
which in turn represent 49.474 synodical moon months. This last
number has to be multiplied only 19 times to give a number of
whole days—27,759—equal to 940 months, or 76 Sothic years,
which is the cycle of the Rhodes calculator!
It seems to me that the mechanism found on the Roman galley
reduced model of a much more complicated and
was a small,
refined machine that the Egyptian priests used to calculate all
the planetary movements in the solar system and more. But that
calculator has not been found yet.
When men decide to make a really serious effort to explore the