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THE KINGS OF THE SEA<br />
IO3<br />
ter the mysterious one of June 30, 1954, that we will discuss later<br />
on in this book.<br />
The period of totality of the June 1973 ecHpse varied one full<br />
minute for every 36 km at the same latitude. If the eclipse took<br />
place over point A at noon, seeing it in point B a full hour later<br />
would mean that the distance east from A to B, if both these<br />
points are on the same latitude, was exactly 2,160, or 60 times 36<br />
kilometers. Now, eclipses are not a daily occurrence, so our ancestors<br />
had to find some other phenomenon of short duration<br />
that could be timed by simple means every day. Sunset and<br />
moonrise made possible for them to use the principle just explained<br />
and find more or less precisely how far away they had<br />
moved since they left home port or had passed some marker that<br />
was calculated for sunset and moonrise in their tables. Such astronomical<br />
tabulations written in cuneiform style have been<br />
found by the thousands on clay tablets in archaeological excavations<br />
in Mesopotamia. With the help of these timetables, ancient<br />
navigators could easily determine their longitude by using every<br />
2 minutes of sunset-moonrise difference for 15 longitude degrees<br />
of travel since the start of the voyage. If, for instance, the trip<br />
had started in Alexandria going west and the local sunsetmoonrise<br />
difference in the open sea was 54 minutes instead of 48<br />
minutes for the same day in Alexandria, the ship had to be as far<br />
west as the Canary Islands, 45 degrees west of Alexandria. When<br />
at the same time the astrolabe reading indicated a latitude of 28<br />
degrees, the captain would order the lookout on top of the mast<br />
and the helmsman to take extra precautions because these readings<br />
told him that his ship was in between the Canary Islands.<br />
If all this sounds complicated to the uninitiated, believe me it<br />
is not. Such checks and comparisons were entirely within the<br />
capabilities of our ancestors who figured even much more complicated<br />
movements of celestial bodies, like the cycles of conjunctions<br />
of Jupiter and Saturn and the precession of the equinoxes.<br />
The moon and the sun are exactly in line with our earth every<br />
346.62 days. This period is called the lunar year, or ecliptic year,<br />
because during this time one ecHpse of the sun can occur, followed<br />
by an eclipse of the moon 173.31 days later, when our<br />
planet passing between the sun and the moon throws its shadow
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