Astrology and Science - the Zodiac

translation from French by L. Blake Finley, M.A. ABD-2

1)  Zodiac of signs or zodiac of constellations? -- Francis Santoni

2) Report on a lecture presented at a conference of the French Astronomical Society -- M. François Biraud


1)    Zodiac of signs or zodiac of constellations?

Main points :

 As general schema, astrologers distinguish 3 cycles: 

    Hypotheses that critical astronomers would like to see employed by astrologers are marginally relevant to astrology.

 Francis Santoni



2)  Report on a lecture presented at a conference of the French Astronomical Society

Extracts from a lecture by M. François Biraud, Meudon Observatory Astronomer, and Director of Research at the CNRS (French National Center for Scientific Research)

presented 14 October 1998 in Paris to the French Astronomical Society

 The following summary is based on notes taken at the conference.

Astrology claims to delineate the relationships between the positions of celestial objects and human events.  And how is an astrological chart set up?

The Sun, the Moon, and the planets are defined by their longitude along the ecliptic, measured from the Vernal Point or "Gamma".  This longitude ranges from 0° to 360°.  A chart therefore requires locating the planets in terms of their dirunal movement: the "Ascendant" and "Descendant" correspond to the intersections of the ecliptic with the horizon at the place of birth, while the "Midheaven" corresponds to the intersection between the ecliptic and the meridian of the location.  Thereafter, some further divide the zodiacal circle into "houses".  Thus, few people possess the same chart, just as there are 4.5 babies born per second on our planet, yet all at different locations.

The problem of births occurring north of the Polar Circle

It has been purported that those born north of the Polar Circle can have no birthchart due to irregularities of house divisions at those latitudes, but this is not the case.  The astrological chart remains valid regardless of questions of division of house systems.  One can clearly determine the Ascendant, Descendant, and Midheaven, except in very rare cases.  What changes in the case of these polar births is that there is no rising or setting of the Sun near solstice periods, and thus calculating house divisions can be problematic.

The problem of dividing the ecliptic into 12 equal segments: the 30° signs

The method is to calculate longitude in equal 30° segments ("signs") from the Vernal Point.  The zodiac of 12 signs is thus functional for locating celestial objects.

The problem of the precession of the equinoxes

There is an angle of 23.5° between the Earth's axial pole and that of the ecliptic.  However, the Gamma point moves due to the precession of the equinoxes.  For astrologers, the Sun is at any given time located in a zodical sign defined by this Gamma point.  Ptolemy wrote long ago that the sign is not defined by its associated constellation.  It is therefore not accurate to use this argument against astrology.  The Sun appears in 13 constellations during the annual period, while there are only 12 corresponding 30° segments covering the same 360° circle.  One might note that certain of these segments are named in accord with their sequence in the annual cycle; for example, Libra, meaning "balance" corresponds with the period when days and nights are of equal length.

In sum, the only views one can reasonably advocate in opposition to astrology should be proven convincingly with statistical evidence... and for those one should remain in strict accord with scientific method, with identification of method prior to the experiment, and publication of all the results.  Under such conditions, there are no results at the moment which are considered convincing.


To further investigate the views of the speaker (in French) on the Paris Observatory's website:



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