A recent story on NPR was was from an astronomer discussing how earth’s axial precession (a slow wobble that takes 26,000 years) means that the constellations gradually shift each year, and that your astrological sun sign (Aries, Taurus, etc.) might not correspond with the actual constellation on the Zodiac. In other words, you could be labeled a Taurus (like my sister), even though your birthday does not fall on a day that the sun is in Taurus. Of course, every astrologer already knows this. Astrologers differentiate between the constellation of Taurus and the sign of Taurus- something the astronomer who wrote the article appears not to know.
Since there appears to be appear a chasmic divide between what astronomers think astrology is, and what it actually is, I thought I would take a moment to explain what astrology is, fundamentally. So what follows are just a few things that every scientist should know about astrology.
First, astrology is in essence the study of human behavior as it corresponds with celestial time. Astrologers do not study causality. The placement of a planet in a particular sign does not cause anything to happen, but it may correspond to a particular event. Does a clock hitting five make you leave work? While it happens that you do leave work at five, it’s not because of anything the clock did. Your action corresponds with the time, but is not caused by it.
Next, the ecliptic plane is an imaginary plane containing the earth’s orbit around the sun (see below). In the same image you can see that the celestial equator defines another imaginary plane. In fact, you can create an infinite number of planes emanating from earth going in different directions. But astrologers are interested in the ecliptic, because as you follow the ecliptic out into space you run into the zodiac belt.
The Zodiac belt is an imaginary belt that is used to contain the constellations that fall on the ecliptic plane. It is important to remember that the constellations only appear as they do from our perspective. If your were on Proxima Centauri (the nearest star to earth), the same stars would make very different constellations. If you look at the picture below, you will probably notice that the constellations are irregular in size. If astrology believed that a person born at a particular time of year was literally in a particular sign, then there would be a lot more people born in Pisces than in Aries, because the constellation of Pisces is so much bigger, but that’s not how astrologers divide up the zodiac belt. Instead, they divide the circular belt into twelve equal sections of 30 degrees. Thus each sign roughly corresponds to its actual constellation, and as a result of the precession (the wobble of the earth) it’s very rough indeed.
So why do they do it that way? Well, they don’t all do it that way. There are a lot of different astrologies out there. There is Vedic astrology, Chinese astrology, and the Mayans had their own version. While the 12 sections are divided differently, they do roughly correspond to the same constellations for no other reason than that it provides a visual landmark to frame your twelve signs around. Bear in mind that the discipline of astrology was created at a time with no computers or telescopes. The observable universe was the backdrop for what astrologers were interested in studying- the motion of bodies in our solar system.
Astrological signs are not nearly as definitive as you might believe. Or put another way: all Aries are not equal. If you are born on March 21st (like my son), you would be on the cusp of Pisces, and therefore you would share some traits with Pisces. If you were born on April 19th, you would be on the cusp of Taurus, and you would share some traits with Taurus. But if you were born on April 5th, you would be very Aries. In short, Aries is a spectrum. Western astrology might be very different if those points were set five degrees away from where they are now.
The “astro” in astrology and astronomy means “star”, but despite the name, astrologers are really interested in what’s happening in our solar system. The only star that counts (as far as the majority of astrologers are concerned) is the sun. All the other stars are nothing more than a backdrop, by which to measure the motion of planets, the moon and the sun (and for some asteroids).
A long time ago, all over the world people noticed that certain human behaviors corresponded with the positions of celestial bodies as observed along the zodiac belt. Some of this is pretty obvious. Every day, the earth revolves 360 degrees around its axis. The cycle of the 24 hour day is indisputably influential on human behavior. Similarly the orbit of the earth around the sun defines a human year. Yet again human activity is indisputably oriented around the orbit of the earth around the sun. When the days get shorter, some people experience SAD, and they don’t really recover until the days begin to get longer again.
Are you a lark or an owl? Or put another way: are you a morning person or an evening person? Psychologists have actually studied human behavior as it corresponds with the time of day they were born, and no surprise (to astrologers) they found that people born in the morning score better on tests given in the morning, and the people born in the night scored better on the tests in the late afternoon.
https://www.dailymail.co.uk/sciencetech/article-4089536/Not-morning-person-born-night-s-not-old-wives-tale-s-scientific-proof-timing-birth-affects-like-wake-besides.html
Next, if you look at the cycles of the moon, you see that there is a similar (if more subtle) impact on human behavior. The menstrual cycle of woman tends to correspond with the waxing and waning of the moon, which takes about 29.5 days. What’s interesting about that is that it takes the moon 27.3 days to revolve around the earth. That’s because as the moon orbits the earth, the earth is orbiting the sun, and when the moon returns to the same place in its orbit, the sun is not in the same place relative to the moon. The female menstrual cycle is aligned not with the cycle of the actual orbit of the moon, but the observable cycle of the orbit of the moon (the waxing and waning). Also interesting is that while the timing of a woman’s cycle may be similar in length, women do not all have their periods on the same day. Of course, this cycle doesn’t just affect women, because fertility is important to men as well (biologically speaking).
While you may be willing to grant that the sun and the moon influence human behavior, it’s much easier to be skeptical about the role of the planets in human behavior. While we can observe the sun and the moon, many of us have no idea where Mars is right now. It takes Mars 687 days to orbit the sun, or about 1.88 years. Well, if you didn’t know about that cycle, you are unlikely to have observed if anything corresponds with that cycle. But astrologers have been observing that cycle for thousands of years, and they noticed that things did seem to correspond. Why that seems to be is tricky to answer.
First, astrologers are not researchers. They are not investigating why the orbit of Mars might influence human behavior. Astrologers pool their collective observations about human behaviors as it corresponds with the motion of celestial bodies. Two astrologers might not agree 100%, but they would likely agree on about 85% on the significance of a particular planetary placement. It's as discipline and not a science, and as such requires interpretation. While that is not very precise, it is still significant. It is this significance that matters to an astrologer- the causality, not so much. In short, astrologers don’t know why a planet might have influence, only that they have observed it. Of course, if you haven’t observed it, it might sound crazy.
Second, the people who do research- scientists- are reluctant to investigate for fear that they are buying into some folk superstition. I did a chart for a friend of mine who had a PhD in psychology. He found my information useful and helpful, but when I suggested the possibility of a study that would compare an astrological portrait and a psychological portrait of the same people, he shut that idea down saying, “I’m worried no one would take me seriously.” And he had an open mind about such things. Most scientists wouldn’t even go that far.
So for you skeptics out there, I posit two theories as to why astrology might hold some truths into human behavior.
The cultural explanation: people have been observing human behavior as it corresponds with the position of planets in our solar system since before recorded history. That’s a long time. They did it all over the world. That’s a lot of people. Whether it is fundamentally true, may be beside the point, because it has attained a level of cultural truth. It’s interesting to note that modern-day astrologers would define certain signs differently than astrologers would a thousand years ago. As the societies changed, the interpretations changed too.
Consider that Uranus wasn’t discovered until 1781. It was only then that astrologers began to integrate the planet into astrology. Uranus moves very slowly, so people with Uranus in a particular sign were all born in the same seven-year period, which is about half a generation. Neptune spends about 14 years in a particular sign, which corresponds with our concept of a generation. It might seem arbitrary to define a generation by its relation to a planet, but is it any more arbitrary than the way we do it today?
Gravitational dynamics: The orbits of the planets are not just affected by the gravity of the sun, but by each other as well. As a planet reaches the closest point in its orbit to another planet, there is a subtle pull or nudge these planets exert on each other. That might seem like a subtle effect on human life, but life on earth has evolved over 3.7 billion years. That’s a lot of nudges and pulls. In other words, a small effect if repeated over a long enough time can have a significant impact.
It may also be a combination of the two. We won’t know until we investigate. To dismiss something out of hand without having done any investigation of its underlying claims is unscientific. Astrology is admittedly unscientific, but it is is a discipline, and like other disciplines (English, History, the Humanities), it does have methodology. It is a pan-cultural and pan-historical phenomenon. While astrology shouldn't be expected to behave like a science, the sciences should be expected to do so. The idea that there is no place in academia to study such phenomena is absurd.