Vol 12, No 1
Does the Solar System contain a tenth planet? This is not one of those deeply philosophical questions like "Where do flies go in winter?" which have puzzled mankind since time immemorial, rather it is a question which it has only become sensible to ask within the lifetimes of some of our readers (Harry Edwards for instance). An article by Nigel Henbest in the November 30 edition of New Scientist indicates that the answer is probably "No", but to find out why we ever thought it might be "Yes", we need to cover some of the history of planetary discovery. Importantly, we need to ask what, if anything, the answer would mean for astrology?
Astronomy in History
As long as history has been recorded, and almost certainly for a lot longer than that, humans have been aware of the existence of the six planets that we know as Mercury, Venus, Earth, Mars, Jupiter and Saturn. Admittedly, for most of that time, most people thought that the Moon and the Sun were also planets, but did not recognise Earth as being one. There is no record of when these planets were found to be different from the stars, but it is obvious that anyone studying the night sky would notice that some `stars’ do not stay within the same relationships, night after night. Our word `planet’, for these peripatetic `stars’ comes from the Greek word for `wanderer’. Nor do we know in what order they were discovered, but it is likely that it was Venus, Mars, Jupiter, Saturn and Mercury, because that is how conspicuously they appear in the night sky. We do know that Earth was first recognised as a planet by the Greeks circa 500 BC, though this information appears to have been discounted for two millennia and then it only became common knowledge after 1543, when the Polish monk, Nicolaus Copernicus, proposed a heliocentric universe. This theory argued against the geocentric model which had been widely accepted for thousands of years and which had been formalised fifteen hundred years before Copernicus by the great Alexandrian astronomer Ptolemy. The heliocentric system had been held to be an inalienable truth by various systems of mystical thought (including the Christian church) for most of that time.
Copernicus’ idea came to be accepted because it worked better and made fewer untested assumptions than did Ptolemy’s system, which required increasingly obscure artificial fixes in order to accord with more accurate observations.
Further theoretical and observational refinements were added to the Copernican model by the Dane, Tycho Brahe (who had an artificial nose), and his German assistant, Johannes Kepler. In 1610, telescopic observations by the Italian, Galileo Galilei, provided the evidence that finally confirmed the theory. Most importantly, Galileo observed that Venus showed phases like the Moon and certain of these could be explained only if Venus orbited the Sun in an inferior position to the Earth. No amount of tinkering with the Ptolemaic system could account for this fact.
Time running out for Astrology
Until the advent of all this scientific discovery, astrology, now known to be the illegitimate step sister of astronomy, had been having a field day, or more precisely, a few field millennia. It is moot whether astronomy or astrology came first, though the proponents of the latter usually claim that the scientific discipline is a descendant of their art. On the other hand, and more logically, it can be argued that observation must have preceded prediction, so astronomy should be considered as the senior study.
Certainly it is reasonable to assume that an original purpose for studying heavenly phenomena was to determine the arrival of the seasons, vital information when our species first took up agriculture. It is logical to infer that, once the idea of predicting seasonal changes had been accepted, and shown to be reasonably accurate, then the idea that these heavenly bodies could exert some influence on human affairs, particularly those of important individuals,would appear to be a logical next step. Here we can see the genesis of the dichotomy which still characterises the division between the two studies. There undoubtedly is a relationship between the appearance of the stellar patterns and the seasons, but where astronomy has come to recognise this association as coincidental, astrology has always falsely postulated a causal connection.
Not that it really matters which came first, as most astronomers, from Ptolemy up until Kepler, dabbled in astrology and who can blame them? Generally, until the 16th century, the two studies were intertwined and while there probably wasn’t much of a living to be made in straight astronomy, at least astrology had the potential, as it still does, to raise a few units of currency for its practitioners and to keep them from starvation. In any case astrology had the arguably useful cultural aspect of making predictions which, while not necessarily very accurate, were likely to be as good as any other predictions available at that time. Astrology, in common with other methods of divination and prediction, then, as now, couched its claims in generalities and obscure jargon and no doubt scored its greatest triumphs by means of post facto validation. The new methods of science were, however, spelling the death knell for astrology as a serious study and the age of astronomy as a separate and powerful discipline was about to dawn.
Naming the Planets
We owe the names of the five `classical’ planets to the Romans who named them after their gods who, in their turn, owe many of their characteristics to the equivalent Greek gods. Mercury was the messenger of the gods (Greek - Hermes); Venus the goddess of love (Aphrodite); Mars the god of war (Ares); Jupiter the supreme god (Zeus) and Saturn, an Italian agricultural god, was later linked with the Greek Kronos, the god of time, who was, among other things, Jupiter’s old dad.
There is no reason to suppose that the Romans saw the planets as the actual gods whose names they bore; they were merely one of many manifestations of these superior beings. Polytheistic religions have a tendency to ascribe distinct individual (and all too human) personality traits to their gods (monotheists seem to prefer schizoid deities) and this was certainly the case with the Greeks and Romans. Nevertheless, astrologers ascribe influences to the planets which were in fact part of the characteristics attributed to the Roman (or Greek) gods. Those whose lives are allegedly influenced or controlled by Jupiter are described as jovial, while the terms mercurial, venereal, martial and saturnine, also part of the astrologer’s stock in trade, can be traced to the personalities of their respective classical gods. Interesting as this excursion into classical mythology might be, we must return to the scientific exploration of the Solar System which put the writing on the wall for astrology and other magical systems of thought.
The Age of the Observer
Galileo, using his telescope, discovered the first new extraterrestrial objects (apart from comets and meteoroids) seen since prehistoric times. These were not new planets, but four satellites of Jupiter later named, following the classical tradition, Io, Callisto, Europa and Ganymede. The first three were named for women seduced by Jupiter (who was not only jovial, but a prize lecher), and the latter for a young man, made an immortal and the gods’ cup bearer by Jupiter. In the Greek version, he also was seduced, but the Romans tended to be a bit wowserish about this sort of thing and it is rarely mentioned. Astrologers at the time may have been interested but their modern successors do not seem to regard these new bodies as having any great significance, which is odd considering the importance they attach to our own moon.
Galileo’s discoveries were not so much critical in the scientific explanation of how the solar system worked, as they were vital in changing the mode of European thought. Until this stage of our history it was obvious that the Earth, and by extension us human beings, was the centre about which everything revolved. The Earth, including all of its imperfections that we were forced to acknowledge, was seen as man’s domain, while the heavens, perfect and unchanging, were God’s domain, though it is important to remember that they revolved about our centre. This very cosy cosmology, which says more about human conceit than it does about God’s plan, was obviously incorrect when it was shown that there were celestial objects actually revolving around another planet.
Information such as this undermined the authority of the conservative bureaucrats of the Christian church who persecuted Galileo, though not being a group to hold a grudge, they finally forgave him for being right. (The fact that the forgiveness took the best part of four centuries can be attributed to the slowness of the mills of God.) But it was not only the church whose perspective was overturned by the advent of a scientific world view, it was equally a blow to other forms of magical thinking, including astrology, which went into a decline for centuries. Astrology could not accommodate itself to the scientific view, holding steadfastly to the idea of the geocentric universe and to the notion that the sun and moon were planets, as it has ever since.
The advent of the telescope and the new world view led to further 17th Century exploration of the Solar System with the discovery of the rings and five satellites of Saturn. Saturn’s retinue of satellites were given the names of individuals associated with that deity and again astrologers did not take much account of these bodies.
The publication by Isaac Newton of his Principia Mathematica in 1687 put the study of the Universe onto a more solid theoretical footing and this, coupled with the discoveries made by many gifted amateur observers, greatly increased the sum of human knowledge.
With all this observation going on it was almost inevitable that other planets, if they existed, would be found. Yet it was not until 1781, almost a century after the publication of the Principia, that the next planet was discovered.
The Hanoverian born British astronomer William Herschel was not the first to see this new planet; it had already been catalogued by several others as a star, but he receives the credit for the discovery. Herschel himself was looking for stars not planets, and first reported his sighting as a comet, however, he later determined it to be a new planet. Herschel at first named it for his patron George III though, fortunately, wiser heads prevailed and the established practice of naming celestial objects after figures from classical mythology was adhered to, resulting in the planet being officially designated Uranus.
Uranus, Greek god of the sky, was the father of Kronos (Saturn), and was later castrated by him (unpleasant sods, these Olympians). Herschel also discovered two satellites of Uranus and two new satellites of Saturn. Shortly after this, at the beginning of the 19th century, several new bodies were discovered which, while they directly orbited the sun, were designated as asteroids. Named Ceres, Pallas, Juno and Vesta, these bodies, and thousands of others, revolve around the sun between the orbits of Mars and Jupiter, in the so-called Asteroid Belt and are generally considered by astrologers to be insignificant, for reasons best known to themselves.
Enter the Theoreticians
Science was now getting into its stride; the effect of gravitational interaction was becoming well understood, leading to concern among mathematicians that Uranus was not following the orbit that theory predicted for it. John Couch Adams in England and Urbain Leverrier in France calculated that another planet must be orbiting further out than Uranus, whose gravitational interaction would account for the discrepancies in its orbit. Adams and Leverrier knew nothing of each other’s work and each was relying on observations by various observers, using telescopes with varying degrees of resolution and computing without the aid of computers. When this is considered, together with the fact that the mass, the orbit and the position of this hypothetical planet were unknown, then its discovery by the German astronomer Galle in 1846, following Leverrier’s directions, was a truly remarkable demonstration of the power of scientific prediction. This planet, Neptune, was less than 1¯ of arc from Leverrier’s predicted position and less than 1.5¯ from that of Adams.
Neptune was named for the Roman god of water, who was linked to the Greek god of the sea, Poseidon.
The foregoing shows how the scientific approach was developing.
Observations led to certain conclusions being drawn - Uranus was a planet. Further observations led to refinements in the theory and further conclusions were drawn - there should be another planet because its effect could be shown. Careful calculations indicated where the planet should be; and there it was.
It should not be thought, however, that all scientific investigations brought immediate or successful results. Leverrier noticed discrepancies in the orbit of Mercury and proposed an inner planet, which he tentatively named Vulcan, whose gravitational attraction could explain the perceived errors. There were even several claimed sightings of this hypothetical planet, though they finally amounted to nothing.
The mystery of the variations in Mercury’s orbit were not finally resolved until Einstein, in the early part of the 20th century, proposed his General Theory of Relativity which predicted just such an orbital discrepancy. This was confirmed when Arthur Eddington’s observations in 1919 provided the first empirical proof of Einstein’s theory. An amusing, though probably apocryphal, sidelight to this story concerns a question put to Eddington, that he was one of only three people who understood relativity. Eddington is alleged to have paused for some time and when his questioner put the question again, replied "I am trying to think who the third might be".
Nor did later investigations of Neptune’s orbit exactly confirm the predictions of Leverrier and Adams. In this context, it should be remembered that Neptune has not yet completed one full orbit since its discovery in 1846 and will not do so until 2011.
The crowded Solar System
The story of planetary discovery does not end with Neptune, as it soon became obvious that its orbit and mass was insufficient to account for the perturbations in the orbit of Uranus. Many astronomers took up the search for a transneptunian planet, prominent among whom was the American Percival Lowell, who set up his own observatory in Arizona and dedicated the remainder of his life to the search. It was the use of astronomical photography which finally led, some years after Lowell’s death, to the final success of this venture. In 1930, his assistant Clyde Tombaugh, after exhaustively (and probably exhaustingly) searching thousands of photographic negatives, found a new planet, which was named Pluto after the god of the underworld. The selection of the name, from among many possible gods, was specifically to honour Lowell, the first two letters of Pluto being Percival Lowell’s initials. Pluto has a highly elliptical orbit, at a high angle to the ecliptic plane (17¯ compared with Mercury at 7¯ and all the other planets which are within 2¯), and for most of its orbit it is the most distant known object in the solar system. At the moment, however, its orbit lies closer to the sun than that of Neptune, as it does for about 20 years of its 240 year span.
The story becomes even more interesting when we look at the non-planets which have been discovered in the past two centuries. There are now more than 3,450 named asteroids, mostly lying within the Asteroid Belt, although some have highly eccentric orbits, including a number known as the Apollo Group (rather chillingly described as `earth grazers’ and a large one and several smaller ones of which came very close to the Earth in 1991), two groups of Trojan asteroids which share Jupiter’s orbit , leading and lagging the planet by 60¯, and the recently discovered Chiron whose highly elliptical orbit lies between those of Saturn and Uranus. Curiously, the only one of these that seems to mean anything to astrologers is the last, and it is sometimes calculated in horoscopes. This is curious because, while it is far from being the largest asteroid, it is certainly the most distant yet discovered.
Failures of Astrology
While the science of astronomy was making its great discoveries, what of astrology? As it happens, nothing much was occurring on that front. Three new planets had been discovered which had never been known during the heyday of astrology and, following tradition, they were assigned the names of classical gods. The astrologers were thus forced to delve into classical history to discover the attributes of those gods so as to find out what the new planets meant. Now there are a few obvious things wrong with this approach. At least the ancient planets had had a long association with the gods whose names they bore, and it could be argued that somewhere in the mists of antiquity there had been some connection between the gods, the planets and human affairs (remembering that there was still a good deal of mystical thinking around in the 18th and 19th centuries). But here we had planets whose names had been arbitrarily assigned and which had never been associated with those gods by the ancients, who did not even know of their existence. Nor did their discoverers regard these finds as representing the relevant gods. Indeed, the name of Pluto was selected purely to honour one of its discoverers. So the characteristics the planets were supposed to confer had no precedent in history, nor in the manner of their naming. It was all purely a matter of whim. Nonetheless, the characteristics of the gods concerned were those that the astrologers chose.
The second fatal flaw in the astrologers’ case lies in the central claim made for their art, that of prediction. Traditionally astronomy had been merely an observational science while astrology made predictions. Now it had been shown that astronomy had a powerful predictive ability and where was astrology? It could logically be assumed that astrologers should have noticed that some human characteristics were not accounted for by the known planets and they should have suspected, not only that other planets existed, but approximately where they were located. Astrologers make great play of the importance of the angles subtended by planets, yet it was not an astrologer who pointed the observers’ telescopes in the right direction - that was left to the mathematicians.
Moreover, if the planets have an influence, the length of time taken by the new planets to complete an orbit should present substantial evidence for this. Uranus spends seven years in each sign, Neptune almost 14 years and Pluto more than 20. Indeed Pluto has only completed one quarter of an orbit since its discovery. This offers a huge base population of individuals upon whom the influence of Pluto can be measured very accurately, with whole populations of people showing distinctively Plutonian attributes, changing every 20 years. This is calculable and should pose no problem to any astrologer, yet no such measure of long period personality changes in large populations has been made and no serious claim has been advanced that there is a consistent 20 year cycle in personal characteristics.
Then there is the question of the asteroids and satellites. Several satellites are larger than the planets Pluto and Mercury and certainly they are much closer to us than Pluto is. Also consider Ceres, the largest asteroid, which circles the sun at about 2.5 AU (Astronomical Units: the radius of Earth’s orbit = 1 AU), while Pluto’s average orbit is 39 AU and it is only approximately 3 times the diameter of Ceres, yet Pluto is important and Ceres is not. Why? Furthermore, there is the fact that, while the earliest noted asteroids continued the tradition of being named after figures from classical mythology, obviously such names would soon be used up, so that now asteroids are named after anyone or thing, from the name or home town of the discoverer to anything else that takes their fancy.
At some stage, there must have been an opera buff among the discoverers as we have Turandot, Zerlina, Pamina, Senta, Kundry, Norma, Violetta, Aida and Carmen all discovered at around the same time. Then scientists got a run with Einstein, Darwin, Herschel, Adams and Leverrier among many others as well as such disparate individuals as Tolkein, Tchaikovsky, Mark Twain and Mr Spock similarly honoured, not to mention places such as Kansas, Antarctica, Coonabarabran and Kiev.
The distinction between asteroids (not a particularly appropriate name, suggesting an affinity with stars) and planets is purely an arbitrary one, based on size. Asteroids are more accurately referred to as minor planets, and why shouldn’t they? Like planets, they revolve around the sun, some have satellites (the asteroid Pallas has one) and some do not, and it could be said that Pluto has a lot more in common with Ceres than it does with Jupiter. Oddly enough some comets, Halley being the most obvious, are regarded as important by astrologers despite their being far more ephemeral than asteroids.
The question of why asteroids and satellites are not taken into account in the casting of a horoscope has never been satisfactorily answered by astrologers . The usual answers given are long on hyperbole and short on logic, yet the real answer is glaringly obvious. The inclusion of the positions and the angular relationships of thousands of asteroids and satellites would make the casting of horoscopes extraordinarily complicated (imagine a problem with almost 4,000 variables). Moreover, the research required to discover the personality traits of the thousands of individuals named would daunt even the most dedicated astrologer. Yet the question remains and it demands an answer from the astrologers.
If the influence of the most numerous bodies can be safely discounted, then so too can the influence of the planets. After all, logic dictates that if planets influence our lives, then so should everything else in the Solar System. Indeed, this failure to include all the influences is sufficient reason to dismiss astrology as nothing more than superstitious twaddle.
It is also fair to ask that if our personality traits can be equated with those of Saturn or Venus, then why shouldn’t they be also linked with Karl Marx, Shakespeare or Carl Sagan (all asteroids)? I leave it to the reader’s imagination to determine what influence asteroids No 1703 and 1763 should have. They are named Barry and Williams respectively.
At last, we can return to the question we asked at the beginning, "Is there a tenth planet?". Nigel Henbest strongly suggests the answer is "No". Our reasons for believing that it might exist were the fact that Neptune alone was not enough to account for the deviations in Uranus’ orbit, that Neptune itself also deviated and that Pluto was certainly not massive enough to make so much difference. Since the Voyager missions, we now know that the perceived discrepancies in Neptune’s orbit were largely caused by miscalculations due to insufficient data. It now appears that the same might also apply to Uranus, based on inaccuracies in historical observations. Astronomers have modelled planets in various orbits to account for the perceived variations in Uranus’ orbit and have concluded where such planets should lie.
Extensive scanning of the relevant parts of the sky, using both Earthbound optical telescopes and the IRAS infrared satellite, have been without success. As a result, the consensus among astronomers is now moving away from a tenth planet and it will be surprising if one is found. Pluto may then indeed be the furthermost major body of the Solar System. As to what that will mean for astrology, the answer must be, "Not a thing". The evidence shows us that astrology is a study with precisely no predictive ability; it is committed to beliefs rooted in ancient mythology which have long been shown to be baseless; its fundamental tenets are arbitrarily derived and owe nothing to reason, logic or evidence; it is a study completely devoid of theoretical underpinning and it gives us no reason at all to think that it even might be a valid study.
History recorded the beginning of the end for astrology when human beings began to understand how the universe actually worked. It traced the decline of astrology over the succeeding centuries as human knowledge increased, yet it shows a curious upsurge at the very time when the gains in our knowledge of the workings of nature are at the highest level in history. Astrology should be long dead and buried, yet it still has many adherents. Why this is so is a question beyond the scope of this article and can only be answered by those who study the strange workings of the human mind.
Of only one thing can we be certain; the answer will never be found in the stars.
Copyright © 1996-2001 Australian Skeptics Inc. - Journal Articles - Vol. 12, Nº 1