For thousands of years, people across multiple cultures throughout the world have looked to the stars to predict events on earth. But is there actually any substance behind astrology?
The current system used in Western countries is based on the work of the Greek scholar Ptolemy in the 2nd century CE. The twelve signs of the zodiac represent 12 constellations that the sun moves through as the year progresses. These star signs, also known as sun signs, are divided into earth, air, water, and fire elements. Each of these is associated with certain characteristics.
There are also seven “planets” that are said to have an influence on the human psyche. Each of the planets “rules” one or two of the star signs. The term planet is used rather loosely, though; classically the planets include the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. Modern additions include the dwarf planets Pluto and Ceres.
Then you’ve got your angles (ascendant, descendant, midheaven, and imum coeli), your 12 houses (divided along the ecliptic plane and further divided into four hemispheres), and your aspects (relative angles between pairs of planets). If you have a yod aspect, made up of two quincunxes joined by a sextile, you are restless and unstable. And if you think I was making those words up, you would be wrong.
Then you have American astrologer Marc Edmund Jones, who has identified some relative patterns of the planets, including bucket, seesaw, locomotive, and splash.
Is it starting to seem a bit out there yet?
Constellations and Astronomy
The zodiac is based on 12 constellations in the night sky. So what exactly is a constellation? Essentially, constellations are made up based on patterns viewed in the night sky that (very loosely) resemble certain shapes. The reason I call them made up is that the stars involved don’t actually have any relationship to each other whatsoever; they just look like they do from where we’re situated.
Constellations are arbitrary
Let’s take Pisces. The stars that make up Pisces vary widely in their distance from earth, ranging from 106 to 680 light-years away. A light-year is the distance that light travels in one year, which is around 9.46 trillion kilometres. The nearest star to our own sun is 4.24 light-years away. For all we know, one of the further stars in Pisces may have exploded in a supernova five hundred years ago, and the light from that event hasn’t reached us yet. After all, the light that we see shining in a certain place in the sky was emitted by the star 680 years ago (to use the furthest star in Pisces as an example).
So, how is it that the position of the sun in relation to an assortment of stars hundreds of light-years away, that we can only see as they existed hundreds of years ago, that have no relationship to one another, supposed to affect a person who happens to be born on a certain day?
What would the mechanism be?
It also seems highly implausible that any of the “planets” could affect someone’s personality just by their position in relation to the earth or each other. How exactly would this happen? A hallmark of science is always seeking to know how and why – what’s the mechanism by which something happens, and why does it happen the way it does? Pseudoscience tends to either minimize or obfuscate any “hows” it comes up with, so the explanations may sound fancy but have no actual substance.
Sometimes it’s difficult to ascertain the exact mechanism for a phenomenon, but there should at least be some ideas that are consistent with already established scientific principles. Yet the fundamentals of astrology have been scientifically tested and have failed with flying colours. Any of the proposed mechanisms for astrology to work, such as gravity or electromagnetism, fly in the face of established scientific principles.
Confirmation bias is a type of cognitive bias, a shortcut that the brain takes to avoid having to think about things more than necessary. It means that we tend to pay the most attention to things that confirm what we already believe, and filter out things that are contrary to our beliefs.
So first you start with your daily horoscope, which will always be fairly vague. At the end of the day, you consider all of the many different things that happened to you during the day. You’re not so likely to think of all of the different things that happened that had nothing to do with the horoscope prediction; instead, you’ll focus on the events that confirm your belief in the predictive power of daily horoscopes.
Tests have been done to see if people would rate a newspaper horoscope for their own sign as any more accurate than another horoscope that was actually for a different sign. There was no difference; both the “correct” and “incorrect” signs were rated as equally accurate.
What NASA has to say
According to NASA, the way the sun lines up with the constellations in the present day doesn’t actually match the traditional zodiac. A blog post by NASA states:
Astronomy is the scientific study of everything in outer space. Astronomers and other scientists know that stars many light years away have no effect on the ordinary activities of humans on Earth.
Astrology is something else. It’s not science. No one has shown that astrology can be used to predict the future or describe what people are like based on their birth dates.
Given that NASA has some of the best and brightest, if they’re saying the universe doesn’t work the way astrologers say it does, I’m inclined to go with NASA.
If reading your horoscope is amusing or prompts you to do some self-reflection, then hey, why not, but if you’re looking for predictive value, a magic 8-ball is probably just as good.
- NASA: Constellations and the calendar
- Wikipedia: Astrology
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