Is it Astronomy, or Astrology?

We all have a basic understanding that Astronomy is a science that deals with space-related knowledge, and Astrology somehow predicts your future, but what is the real difference?  Should we take Astrology seriously? Let’s find out.

Definitions

What does the Google dictionary say?

as·tron·o·my

noun: astronomy

the branch of science that deals with celestial objects, space, and the physical universe as a whole.

as·trol·o·gy

noun: astrology

the study of the movements and relative positions of celestial bodies interpreted as having an influence on human affairs and the natural world.

So Astronomy is a science. Astronomy’s main goal is to understand the physics of the universe.  It uses testable hypotheses and the scientific method to make specific, verifiable predictions.

In contrast, Astrology is a belief that the positions of the stars and planets affect the way things occur on Earth and can predict future events.  Astrologers use mystical reasoning blended with mathematical techniques to make their predictions.

Astrology predates Astronomy

Astronomy as a pure science is relatively new, starting to come into its own with the invention of the telescope in the 17^th century.  Astrology has been around for thousands of years.  How might it have started?

One theory says that back in the cradle of civilization, the diet changed in sync with the rhythm of the seasons and the primitive agriculture of the time. 

Back then, they did not know about vitamin deficiency and certainly weren’t getting fresh produce from other countries all year long like us. 

Seasonal differences in diet, sunlight, and available nutrients affected expectant mothers, which might have had seasonal impacts on fetal brain development.

We know they used the timing of the constellations for planting and harvesting. Perhaps they thought they could detect differences in personalities for those born under specific constellations.

Astronomy and Astrology Diverge

Many of the most important early astronomers also practiced Astrology: Tycho Brahe, Johan Kepler, and Galileo Galilei.  By the time of Issac Newton, Astronomy was being treated as a separate discipline.

Astrology was widely accepted in medieval Europe.  It was used to predict the outcome of wars, explain natural disasters, and other earthly matters.

Is Astrology a Science?

Some may argue that Astrology is a science. It’s easy to test if Astrology meets the criteria to be classified as a science:

Does it try to explain the natural world? Yes

Does it use testable ideas? No

Does it modify hypotheses when presented with evidence that refutes its theory? No

Does it engage with the scientific community? No

Do its researchers behave scientifically? No

Is Astrology a science? No

Astrology predicts certain signs will command more respect and authority. That suggests  a certain sign should include leaders in politics and the military higher than chance would allow. This has been extensively studied and proven to be incorrect.

When Astrologers are presented with data that conflicts with their beliefs, it is ignored. An astrologer can go his entire career without ever publishing or presenting findings in any credible scientific meeting. 

Astronomers on the other hand routinely write and critique scientific papers and build upon the work of others to learn new things about the natural world.

Scientists don’t wait for others to do the research to support or contradict the ideas they propose.

Instead, they strive to test their ideas, try to come up with counterarguments and alternative hypotheses, and ultimately, give up ideas when warranted by the evidence.  Astrologers largely ignore evidence that contradicts its ideas.

The Zodiac

The word zodiac comes to us from the Greek word “zoion”, which means animal. Many of the constellations of the zodiac are described as animals.   Modern astronomers recognize the zodiac as chance visual groupings of stars, with no particular significance.

Astrologers claim the Sun spends about 30 days per month in each of 12 constellations.  Alas, not true.  The constellations have vastly different sizes, meaning the Sun actually spends 45 days a year in Virgo as an example, and just 7 in Scorpius. 

Then there is Ophiuchus.  My wife’s birthday is December 12, and on her birthday the Sun is really in the constellation of Ophiuchus, not Scorpius.  There are 13 constellations in the real zodiac.

Precession of Earth

If these problems weren’t enough, we have to consider precession.  The Earth wobbles on its axis like a top, once about every 26,000 years. The net effect is the Sun slowly drifts from one constellation to another over thousands of years.

What does this mean? Do you think you are an Aries, because the Sun is supposedly in your sign on the first day of spring? 

Sorry, on that date the Sun has drifted into Pisces in the 3000 years since Astrology was invented, so you are a Pisces.  According to Astrology I’m a Libra, but I’m really a Virgo.

Planet impact

Something I was always puzzled about is the impact of the position of planets on your horoscope. For example, Mercury and Jupiter are both treated the same by astrology, so it can’t be anything to do with the mass or distance of the planet. In fact Jupiter and Saturn have moons that are bigger than Mercury that you would think should have an equal impact.

Exoplanets?

We have discovered over 4000 exoplanets outside our solar system. Since we’ve determined planetary distance is no issue in Astrology, so shouldn’t they each be included?

Predictions in Astrology

Astrologers do use computers that accurately tell them the positions of the planets, but do not look through telescopes or learn about the physics of the stars like astronomers do. 

Rather than use science, Astrologers tend to focus on anecdotal evidence – stories that provide examples of astrology accuracy.

Here’s an example. The Astrological prediction: You should be careful driving, there’s a possibility of an accident. You may hear from an old friend who you haven’t heard from in a long time.

Astrology predictions tend to be vague.  Maybe you had a ‘close call’ on the road when someone swerved into your lane. Doesn’t that happen often and you don’t normally think about it?  

Don’t you get a call or email from a distant friend at least once a month?  Are these predictions really specific enough to be meaningful?

Predictions in Astronomy

In astronomy, a theory is proposed, then tested.  Only after the test outcomes match the theory is the proposal accepted.  And if ANY test of the theory fails, the theory is either rejected or modified.

Time Twins

There is an easy way to test Astrology, which has been done many times and always produces the same results.  Take 2 infants born seconds apart in adjacent rooms at the same hospital. Astrology says they will have exactly the same characters, future, and psychological profile.

Thousands of these ‘time twins’ have been tracked for decades.  Researchers studied occupation, marital status, personality, IQ levels, interest and ability in the arts, sports, music and scores of other characteristics. None of these time twins were similar in any way beyond random chance.

The Forer Effect

Psychologist Bertram Forer (1914 – 2000) gave a personality test to his students.  He then secretly threw away all their responses, and presented each student with their own ‘personalized’ evaluation that was in fact the same for all students.  The students rated the evaluations as 85% accurate – very good indeed!

The profile included many generic statements that apply to most people. For example, “At times you have serious doubts as to whether you made the right decision or did the right thing”, or “Some of your aspirations tend to be unrealistic”.

People tend to accept claims about themselves in proportion to their desire that the claims be true rather than in proportion to the real accuracy of the claims.  This test has been repeated dozens of times with different students in different environments, always with the same results.  Astrology predictions are very similar. 

You might also want to look up the Carlson Test, which proved that astrologers are unable to match people’s natal charts to their corresponding personality tests better than chance.

Summary

Astrology has been rejected by the scientific community as it has no explanatory power for describing the universe. Most predictions are either too generic to be useful “Today is a good day for shopping”, or are simply incorrect.


However…there are still many things that have not yet been fully explained by science (gravity, for example), and occasionally, uncanny predictions have been made by Astrologers that cannot be explained by scientists.  It’s those occasional ‘zingers’ that keep many people consulting their horoscopes.

One third of Americans still believe in Astrology.

References

1. Astrophotos of the twelve classical constellations of the Zodiac. (Licensed under the Creative Commons Attribution-Share Alike 4.0 International license.)