I N S I D E T H I S I S S U E

Astronomy and Astrologyby Roy Swanson, Mississauga Centre (swanee@direct.com)1. IntroductionOver the last several centuries, there has been a lot ofconfusion about the relation between astronomy andastrology. In this article, I will describe some observationsconcerning this interesting juxtaposition of human knowledgeand creativity.Any article that has the temerity to discuss astronomywith astrology is going to encounter a lot of reader preconceptions,so I will go very carefully. These preconceptions arise becausemost people have strong feelings toward this meeting of worlds.Let me start by affirming that I have positive views for bothsides.I might begin with a legal case I ran into when I was a lawstudent. In the British casebooks there was, some sixty yearsago, a case where a young lady was suing a gentleman forseduction using dishonest means. Apparently, in Brighton, ayoung man was dating a young lady who incautiously mentionedthat she firmly believed in astrology. He held back the fact thathe wrote the local newspaper’s astrology column. As one mightexpect, he inserted the admonition to “throw caution to thewinds” at just the right time, with predictable consequences.My point with this vignette is to underscore the mostimportant aspect of astrology, that it is akin to religion for somepeople, and one does not pontificate in this area lightly withoutincurring the wrath of many readers.To balance things, let me mention another vignette. I waswalking along an ocean beach once with a person who was veryskeptical of astrology, and he emphasized the impossibility, tohis mind, of action at a distance. He seemed to be ratherknowledgeable about tides, so I got him to agree about theinfluence of the Moon on the Earth’s surface water. Then Imentioned the unusually high and low tides, and he had toagree that the Sun’s position could be considered the cause ofthese extra large swings in the magnitude of the tides. I thenventured the opinion that perhaps humans, who are to a largeproportion made of water, might somehow be affected as well.He said that a car driving near you has much more gravitationaleffect than distant bodies. I pointed out that more than gravityis implied by the believers in astrology — think of “the musicof the spheres.” We will return to another effect of the Sun,Moon, and planets shortly.2. Precession and OphiuchusOne of the strong tenets of astrology is that the exact positionsof heavenly bodies of the Solar System with respect to the celestialbackground significantly influence your destiny and portentousinferences are made on that basis. Thus if you state in a horoscopethat the position of a heavenly body at a given significant time,such as at birth, provides an indication of what lies ahead inyour destiny, the mere divulgence of the position lends anauthenticity to what is then surmised. In The Mikado, Poo-Bahcalls this strategy the addition of “...corroborative detail, intendedto give...verisimilitude to an otherwise...unconvincing narrative.”(Gilbert & Sullivan 1885)As an amateur astronomer, I find that there are two mainpoints about these two disciplines that require discussion: theprecession of the Earth’s axis of rotation, and the existence ofa thirteenth constellation in the zodiac.2.1 PrecessionFirst I want to begin with the Earth’s dynamics in the SolarSystem. It is very much like a spinning top, with extra mass atthe equator. The spin axis is tilted 23.5 degrees to the plane ofthe ecliptic. Now a spinning top will gyrate, or “precess,” unlessit is perfectly homogeneous and not affected by nearby objects.Since the Earth has an equatorial bulge, and has large gravitationallyinteracting bodies like the Moon and Sun relatively nearby, itsaxis wanders around in a circle. If there were a pencil stickingout of the top, it would point to different positions at differenttimes, moving smoothly around, and repeating the cycle aftera lot of spins.The Earth precesses in a 25,800-year cycle. The northernextension of its axis is presently pointing very near Polaris, butthe axis is always moving, and one day in the future, it will nolonger be pointing near Polaris. The Starry Night Pro softwarepackage has a very interesting subroutine that shows thewandering of the celestial pole over this 25,800-year period. TheRight Ascension (RA) of all the stars shifts due to precession,but the plane of the ecliptic does not change. Without applyinga correction, key times in the seasons on Earth would change.Two thousand years ago, the spring equinox occurred when thecelestial equator intersected the zodiac in the constellationAries (first point of Aries). Our calendar is very deliberatelyaltered with leap years, and earlier, even more drastic measures,to make sure that the spring equinox stays relatively put. At thepresent time, this important first seasonal point occurs withthe celestial equator intersecting the zodiac near the Circlet inPisces.This process means that the positions of the Sun andplanets as observed from the Earth are not time-invariant, asastrology assumes, but are really (slowly but continuously) time-204JRASC October / octobre 2006