Babylonian Planetary Astronomy 7
A sexagesimal number system (i.e., a system based on the number 60)
was used. Positions are reported, for example, as 28, 55, 57, 58, with each
succeeding unit representing so many sixtieths of the preceding unit—thus
28 degrees, 55 minutes, 57 seconds, and so forth. Decimal and sexagesimal
systems, as well as others, were used concurrently in Mesopotamia. ( The sexa-
gesimal system is more cumbersome than the decimal system, but we still
divide our hours into 60 minutes and our minutes into 60 seconds.)
The fi rst column of the table lists the months, starting with month XII of the
year 133
B.C. Following this are months I through XII for the year 132 B.C.
The second column lists how far the Sun moves in each month. During
month I, the Sun moves 28 degrees, 37 minutes, 57 seconds, and
58
/60 second
(line 2, column 2). Add this movement to the position of the Sun at the end of
the previous month (line 1, column 3), and the result is the position of the Sun
at the end of month I (line 2, column 3).
The third column gives the position of the Sun. It is obtained by adding to
the initial position the amount of motion during the month, listed in the second
column. For example, adding the top line of the third column and the second
line of the second column produces the second line in the third column—after
subtracting 30 degrees and listing the position 30 degrees ahead in the next
segment of the zodiac.
The fourth column is the house of the zodiac in which the Sun resides
that month. Each house of the zodiac occupies 30 degrees, one-twelfth of the
360 degrees of a complete circle.
The table shows a decrease of 18 minutes in the distance traveled by the Sun
from one month to the next for months I and II of this particular year (132
B.C. ).
Babylonian Ephemeris for the Position of the Sun in the Years 133–132 B.C.
XII 28,55,57,58 22, 8,18,16 Aries
I 28,37,57,58 20,46,16,14 Taurus
II 28,19,57,58 19, 6,14,12 Gemini
III 28,19,21,22 17,25,35,34 Cancer
IV 28,37,21,22 16, 2,56,56 Leo
V 28,55,21,22 14,58,18,18 Virgo
VI 29,13,21,22 14,11,39,40 Libra
VII 29,31,21,22 13,42, 1, 2 Scorpio
VIII 29,49,21,22 13,32,22,24 Sagittarius
IX 29,56,36,38 13,28,59, 2 Capricorn
X 29,38,36,38 13, 7,35,40 Aquarius
XI 29,20,36,38 12,28,12,18 Pices
XII 29, 2,36,38 11,30,48,56 Aries
Source: Otto Neugebauer, Exact Sciences in Antiquity, 2nd. ed. (Providence, Rhode Island:
Brown University Press, 1957; New York: Dover Publications, 1969), p. 110