Thursday, January 20, 2011

Scientific Astrology

You may have heard about a story circulating around the internet about astrology being wrong. In short, an astronomer named Parke Kunkle talked to the Minneapolis/St. Paul Star-Tribune about how astrology’s dates bear little relation to actual positions of the constellations and that there is a 13th constellation that isn't included. It doesn’t seem like he intended it to be big news, but it made quite an impact on the internet all the same; doing a Google News search for "astrology" turns up hundreds of articles on the topic.

If you are like me and don’t pay any attention to astrology, this did come as a revelation: why wouldn’t a system with the prefix “astro-“ and using the names of constellations have to do with the positions of the stars?

The Sidereal Zodiac

There are actually two basic ways to ‘do’ astrology, sidereal (based on the stars) and tropical (based on the seasons). Sidereal astrology is based on the positions of the planets, the moon, and the sun in relation to the essentially constant background of distant stars and the constellations they form. The “sun sign” of sidereal astrology would be the constellation that the sun would appear to be in at your birth. According to astrology, the constellations that the other planets and the moon find themselves in could also have meaning.

Diagram showing the Earth, sun, the ecliptic, and the projected equator on the constellations.
(Image by Tau’olunga from Wikimedia Commons)

It just so happens that there are 12 major constellations along the ecliptic—the path that the sun (and, because they are all in roughly the same orbital plane, the planets and the moon) follows across the sky over the course of a year (red, in the diagram above): Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. When the Babylonians invented the system of astrology that we are most familiar with, they set the astrological calendar to start at the vernal equinox, when the sun was in Aries. They then divided the year into 12 equal segments named in the order of the constellations along the ecliptic so that the signs roughly corresponded to the constellation that the sun was appearing in. Although it should be noted that the constellations do not occupy equal portions along the ecliptic, meaning that each sign should theoretically last different lengths of time. The 13th constellation cited in the above controversy, Ophiuchus, also crosses the ecliptic (as defined by the internationally agreed upon constellation boundaries) but the major stars of the constellation are somewhat distant from the ecliptic (you can see this for yourself using the WorldWide Telescope), though it is possible that 12 was just a nice number that divided evenly into 360°.

The Tropical Zodiac

Originally, there was no distinction between a zodiac based on the background stars and one based on the vernal equinox. But there was a slight problem with basing it on the equinox: precession of the Earth’s axial tilt (see next section) causes the location of the sun during the vernal equinox (where the projection of the Earth’s equator crosses the ecliptic, at the arrow in the above diagram) to shift ‘backwards’ relative to the sun’s annual apparent motion. At this year’s vernal equinox, the sun will be located within the Pisces constellation, as it has been for many years, and will within the next ~100 years end up in Aquarius (and hence “Age of Aquarius”). The net result is that the entire astrological calendar is increasingly misaligned with the actual constellations. The tropical Babylonian system stuck with the vernal equinox, while other sidereal systems maintain the alignments to the constellations.

The location of the sun at vernal equinox at 1500 BCE (Aries), 500 BCE, and 150 CE (Pisces).
(Image by Dbachmann from Wikimedia Commons)


What’s causing this movement? The Earth of course is not spinning perpendicularly to its orbital plane; instead, it has a ~23.5° tilt, which is responsible for generating our seasons. But because the earth is not perfectly spherical (it bulges out at the equator), the gravitational interaction of the sun and moon with the Earth apply a torque (rotational force) to the earth. This force causes the axis to slowly shift around the perpendicular position, or precess (see diagram below). And because the direction of the tilt defines our seasons, this causes the stars to slowly shift along the ecliptic from year to year.

The earth's axis precesses around a circle.
(Image by NASA)

None of this is news to astrology "experts", but it certainly came as a surprise to casual followers of astrology, including the at least 25% of Americans believe in astrology (as of 2001). As I said before: Why wouldn't astrology be based on the constellations it claims it is?

What’s wrong with this whole picture?

So astrology claims that any person’s personality and even the future can be determined, or at least strongly influenced, by the positions and movements of celestial objects. Let’s pretend for a moment that positions of the heavenly orbs do, in fact, modify some undefined mystical cosmic energy flow that affects life on Earth. Alright. Why would this ‘energy flow’ divide into 12 distinct and evenly-spaced sectors along the ecliptic? Why would the characteristics of the ‘energy’ in a given sector have any relation to an imaginary figure in the stars based on human mythology? And if they are related, why wouldn’t the sections shift with the shift of the constellations? Add to that the fact that there is no clear reason why the birth date, especially in an age of induced and suppressed labor, and C-sections should so sharply divide one type of person from another if it falls on a border between signs. Now let’s stop the silliness of thinking that there is some vast cosmic energy flow, because there is no evidence that such a thing exists.

Astrology as practiced simply has no validity. I would hope that this whole internet firestorm will make more people realize just how inane the whole idea is. But I don't hold out much hope for that.

What’s a budding young astrologist to do?

My advice to someone who truly believes that the movement of the planets, moon, and sun affects life on Earth is this:

  1. Throw out everything you think you know about astrology and start from scratch. That mythological baggage is holding you back.
  2. Collect copious amounts of information about the personalities and birth dates and locations of anyone and everyone—you’ll need a *lot* of data from all age groups over an extended period of time. Make sure you get a statistical cross-section of the population, preferably world-wide, though a single country would do to start.
  3. Recording national and world events, crime statistics, and the like would also be useful, going back as far into history as you can.
  4. Run an analysis of all of your data against the measured (or predicted, if necessary) positions and movements of all of the planets, the moon, and the sun. If you’re looking for energy-flow stuff, you’ll need to control for mundane sun and moon effects. And you’ll also want to control for people who strongly believe in current astrology, as that could bias your findings.
  5. Examine any strong correlations that result. Rigorously verify that the strong correlations can’t be accounted for by other unrelated activity.
  6. Take your new correlations and see if they hold up in the future.
  7. Congratulations! You now have a scientifically-rigorous astrology, and probably have some hints as to what could be causing the correlations, because that would lead to new physics. So congratulations on the Nobel Prize as well!

Is there a kernel of truth?

In fact, there may well be some small truth to the tropical zodiac’s sun sign. Gestation and infancy are important formational times in any person’s development, and it would not be so surprising that these processes could be impacted by the changes in the environment caused by the seasons.

The most direct effect of time of year, and the one most constant from one year to the next at a given latitude, is the amount of light in the day. In fact, a study published in Nature Neuroscience this month by Ciarleglio et al. demonstrated that the initial photoperiod (length of daylight during a day) that newborn mice are exposed to ‘imprints’ their circadian rhythm, which is controlled by a group of neurons in the brain called the suprachiasmatic nuclei, and that this imprinting affects the later ability of the mice to adapt to changes in the length of daylight. However, as the authors note, they only examined the mice after seven weeks, and can’t make the conclusion that it necessarily lasts for the entire life of the organism. It is hard to say how altering the circadian rhythm might impact other aspects of behavior. And of course not everything found to be true in mice holds true for humans, but the circadian rhythm system is fairly well conserved (that is, it hasn’t changed all that much) over evolution, so it is fairly likely that the same thing happens for us.

However, even if a person’s personality is affected by the seasonal conditions into which they are born, people at different latitudes (and especially those on opposite sides of the equator!) would experience very different conditions from each other, and you can be assured that the effects the seasons have on personality have absolutely nothing to do with the constellations in the sky, and they certainly can’t predict the future.

Unless otherwise noted, the information for this post was obtained from Wikipedia information that was properly cited to an external source.


  1. Remind me to never place an ad for you in the Indian matrimonials.

  2. Cosmic energy? Who ever said that cosmic energy was the cause of astrological type effects? Surely, the movements of the planets relates to the small gravitational effects upon the billions of tiny neurons in our brains.

  3. I think that the quantum effect seen when the manipulation of atomic particles effects other atomic particles that are seperated by thousands of miles, show that there is an underlying field.

  4. Anonymous:

    "Cosmic energy" is my placeholder for whatever it is that they think is trasmitting effects from the celestial bodies to us. Gravity of the other planets is far too weak to have any substantial effect on us, even the gravity of the sun over the course of the year isn't different enough to have a substantial effect.

    As far as quantum mechanics, that isn't really what's going on. It isn't that there's some instant communication from one to the other saying "Hey, I'm A, so you must be B!", its that they originated as a fully linked system in which they are either (A and B) or (B and A), and it just so happens that if we determine that one is A, we know that the other is B.

  5. Its not too long ago since radio waves or electricity were 'discovered' by mankind. Before their discovery a person may have been labelled as a quack if that person believed in such phenomena.

    Just because the human species hasn't discovered something doesn't mean it doesn't exist. Try considering the vastness of time and space and how infinitely small we are and how puny our brains are in relation to the whole cosmos.

    Maybe let this teach you some humility about what we do or do not know.

  6. Those people would still be quacks. Even if someone was lucky enough to guess more or less correctly, that does not validate all their other, and anyone's other, not-(yet)-proven beliefs.

  7. Some people can prove to themselves by an inner type of science that things that modern science has not yet proven do exist. They use their own bodies and meditation as their scientific process.

    So throughout history people have seen energy and other aspects of creation that modern science has not proven yet. It does not make them quacks. It just means that we generally do not use a lot of our latent abilities.

  8. You are welcome to keep believing that. But "inner science" is not science. There are very many problems that come from trying to interpret subjective single experiences. (See my most recent post on anecdotes for an example).

    Evidence that cannot be accessed by anyone else is not evidence at all.

    I assume you also believe the misconception that we only use 10% of our brains?

  9. There are also many problems with seemingly objective modern science. On closer examination it is not so objective. Many things that are proven today are disproved tomorrow - I.e the goalposts keep shifting.

    Evidence which has been experienced by individuals through mediation has been experienced by many others in the same way. In fact different traditions who lived on different continents came up with the same conclusions time and time again. So what is accessed by this method is accessible to others.

    Don't get me wrong, I think the modern scientific method has a lot of value but I certainly don't accept it as the only way to knowledge.

    And what is truth if it does not relate to personal experience? I would rather eat honey than read a dissertation on it...

  10. All that common experience proves is that there is a common mechanism because we all have very similar brains. The experiences of meditation do not have to have any basis in a reality outside of the brain.

    Everyone can experience an optical illusion. That doesn't mean the illusion is anything but an illusion. Science necessarily rejects subjective experiences as evidence because we easily and demonstrably fall prey to illusions.

    Nothing is stopping you from eating honey. But if you want to say something about honey other than just "it tastes good", such as nutritional or health benefits, you need those dissertations.

  11. Nicholas, a lot of what the modern scientific method puts forward is itself subjective with countless 'theories' being put forward. These theories change from year to year.

    If the common 'illusion' of many meditators of the highest degree has been the reality of love at the centre of all of creation based on their 'similar brain types' then this so called illusion is doing more for humanity than any modern scientific discovery.

    Having an inner scientific realisation of this type and magnitude leads one to treat all human beings and all of nature and creation in an intimate and sacred way thus being life promoting and highly rational.

    Scurrying around trying to put everything in boxes from an external scientific point of view without taking cognisance of personal inner reality leads to the what the world is now experiencing - brink of nuclear war / destruction of natural environment / creation of foods and building practices which are unhealthier than previous non-scientific generations and much more.

    This is ultimately highly irrational behaviour which stems from an un-sacred view of life which itself stems from rejection of the inner personal journey.

    I take it from your statements that modern science would necessarily reject the reality of love as it is based upon personal experience and cannot be proven? Either this or it would theorise something about survival instinct being it's basis etc.

    But Nicholas I believe that although you are a modern scientific adherent you will probably end up loving somebody in your life and ultimately realising that it is not to be 'necessarily rejected' because it is based upon personal experience. I would guess that at some point in your life you may realise that it is in fact the only really important thing in life.

    And before you say it, morality comes from love. Morality without love is simply a set of rules...

    I am not saying that modern science has not given a lot of positive information and discoveries to mankind Nicholas. But i am saying that this is secondary to the more important inward personal journey.

  12. You don't really get it. Subjective human experiences exist. No one is denying that, least of all me. The point is that they these experiences cannot be extrapolated beyond the subjective realm of the human mind.

    Meditation and such experiences clearly do affect people. But there is no need for us to assume that the effects are based on anything beyond the human brain.

    Metaphysics-types love to harp on love, but never mention hate, which is every bit as much a human emotion. Nuclear war and all the rest are as much born out of human emotion as good works are. The 'scientific view' wouldn't lead to anything good or bad on its own except more knowledge.

    As for science changing, you are exaggerating the scale and magnitude of changes, and when the evidence changes we have to integrate it. It's a process of refinement to determine how things are really working. This is not a weakness as you would have it, but a strength. Let's say everyone lived in Kansas and thought that all land was flat. Then if we all took a trip west and saw there were mountains, we would update our information. That's how science works: start from what we can be sure of and build out piece by piece as we discover things. The only ideas about the world which can avoid this process are ones that cannot be objectively verified.

    And no, modern science would not reject the reality of love or any emotion. What it would reject are claims that the subjective experiences are informative about the world *outside* the realm of the human mind.

    I suggest you check your prejudices--"modern scientific adherents" are not the emotionless robots you seem to be suggesting we are. We just recognize the proper role for subjective human experiences and try to keep them out of the objective collection of information we are working to accumulate.

  13. Nicholas,

    I am not saying love is an emotion, I am saying it is the creative force behind all objective reality.

    Hate is an effect of not knowing your true nature as love.

    However this objective reality can only be proven to oneself through the experiential path of mediation.

    There will come a point when people begin to realise that what goes on inside is related to what goes on outside and as such inner and outer science will become one.

    The modern scientific method as it stands is incapable of understanding this reality because it externalises and compartmentalises everything.

    Because of this it is rejecting the reality of love and is actually anti-life because of this.

    I am not being prejudiced, I am just being clear.

    Thank you