Is Astrology Based on Science or Pseudoscience?

Is astrology scientifically accurate? Or just pseudoscience? - graphic of symbols of the zodiac

For thousands of years, people across multiple cultures have looked to the stars to predict events on earth. But is there actually any substance behind astrology? The short answer is no, but let’s talk about that a little more.

Western 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 we can see in the night sky that (very loosely) resemble certain shapes. I call them made up because the stars involved don’t actually have any relationship to each other; they just look like they do from where we are Because they’re so far away, they’d have to do a whole lot of moving around before their relative positions would start to look any different from where we’re standing.

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 500 years ago; the light from that point in time hasn’t reached us yet. It could also have been swallowed up by a black hole, but we’re still seeing older light. 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?

The illusion of causality is a type of cognitive bias that involves seeing cause and effect relationships where they don’t actually exist. Just because things look like they have a cause-and-effect relationship is not evidence that such a relationship exists. One way of poking holes in this illusion is to look for some kind of reasonable mechanism that would account for the presumed relationship.

It 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? Science always seeks 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 the question of “how”. The explanations may sound fancy, but they have no actual substance.

Sometimes, it’s difficult to ascertain the exact mechanism for a phenomenon. Still, 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, involve explanations that fly in the face of established scientific principles.

Leaving science aside for a moment, though, how arrogantly self-referential is it to think that all of these massive celestial bodies would give a crap about earth even if they did have the ability to give a crap? To anthropomorphize Mercury, why would it give a rat’s ass what’s going on in your world just because a visual illusion makes you see retrograde motion? Mercury has been around a hell of a lot longer than humans have, so why, in the astronomical nanosecond that’s passed since telephones were invented, would Mercury have decided hey, it would be fun to interfere with that nonsense?

Confirmation bias

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. It also means we 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 the many different things that happened to you during the day. You’re not so likely to think of all the things 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.

Similarly, take the general descriptions of the zodiac signs. Let’s say 3 out of 10 descriptors were a good fit, and you thought wow, that’s so me! As for the other 7, that’s easy enough to brush off, because hey, it’s not going to get everything right, but look at those 3 that are bang-on!

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 believe them.

If reading your horoscope is amusing or prompts you to do some self-reflection, then hey, why not? If you’re looking for predictive value, though, a magic 8-ball is probably just as good.


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30 thoughts on “Is Astrology Based on Science or Pseudoscience?”

  1. From a very early age I figured it out. I don’t like to share my birthday. I didn’t like to share my birthday with another girl in my class. I didn’t like her that much because she shared my birthday. Therefore she couldn’t have had all the traits that I had. I saw that every day in class. Bye bye astrology! You managed to understand the houses? That is just weird stuff. Now, I need to refill my aromalamp with lavender because all of this is throwing me out of my balance. Imagine that for a Leo with the ascendant in Scorpio!

  2. I don’t understand astrology at all and certainly don’t read my horoscope. I’ve read some in the past and they don’t make much sense. I agree with the confirmation bias where “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.”

    There’s only twelve star signs so billions of people are going to have the same characteristics, emotions and “events” occurring each day?

  3. I think it’s a bunch of bushwah, always have and yet – the personality descriptors always seem to be spot on (taking into account sun sign, moon sign and ascendant.) So I don’t know what that’s about. As a predictive tool – no, just, no.

  4. I like astrology, but do admit that much of it is very vague and full of loose interpretation, similar to tarot reading. I do not like the daily predictions type of astrology, but I do like reading about the various signs/planets and their correlations.

    1. So funny… I did a WP search for ‘Pisces’ and one of my posts came up, followed by this one.

      I read astrology stuff and NASA stuff. It’s all interesting. I agree that astrology has no scientific basis. One of the things that occurred to me is that a LOT of people believe in it, so that gives it some ‘power’. Like a prayer group can affect people.

      Have you ever heard of or read the 100th Monkey Effect? It’s pretty cool.

      At the end of the day, astrology is fun. Anything that leads to self reflection is good IMO. And basing decisions on a roll of the dice or astrology is chancey.

      1. I agree, fun and self-reflection are good things. I would hope that most people would recognize that it has no scientific basis, but then again, there are people out there that think the earth is flat…

  5. Well, I am entertaining myself by reading random blogs and commenting on whatever interests me. Now, importantly, I am working on a Magic Modernization Project ( and it is essential to put into perspective the obsoleteness of “old” or “traditional” magical approaches and theories in order to modernize and rationalize magic to empower the children of the 21st century and beyond. From a scientific standpoint astrology, numerology, tarot, alchemy and so on have no factual basis: they only seem to work for reasons more psychological than real. So, finally ashleyleia, I intend to write a wicked post about astrology in particular, and your blog inspired me!

  6. I haven’t really studied too much astrology, although I did study and practice palmistry a lot.
    I find your post very well written. The scientific perspective from NASA is well integrated. My study and experience of mind science for 28 years tells me that it isn’t planets etc which effect us. We choose our destiny. The planets, as the lines of the hand provide a correlatory probabilities of circumstances. Our choices at any time remain.
    however, that is only my opinion. Not etched in stone.
    I really find your blog informative. worth a follow.

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