Saturday, November 20, 2010

Astrology - Does it really work?

This is an article that I wrote during my early days of skepticism.


From the early days of civilization, humans have tried to make sense of the world around them. We have studied the skies and observed that planets and stars follow a predictable path. In fact, Astronomy was one the earliest sciences we had developed. Astrology was an offshoot of Astronomy of the old days. It was an attempt at mapping the predictability of paths of celestial
objects to predictability of life.

The objective of this article is to see how relevant Astrology is in today’s world. We have to ask ourselves “Does Astrology really work?”. It is an important question as a lot of people take decisions based on Astrology and this effects their lives as well as others lives. We will take a look at some of the basic tenets of Astrology and see how valid they are.

The Constellations

As observed from the Earth, the Sun traces on orbit around the Earth in the sky during the course of an year. This orbit is called the Ecliptic. The Moon and the other planets appear on or nearby to the ecliptic. It is nearly a circle and can be divided into twelve 30°arcs, making a total of 360°. Each part is named after a constellation that appears against the ecliptic. In Astrology, these twelve parts of the ecliptic are the basis for the Zodiac. Astrology claims that the fate of an individual can be told from the position of the Sun on the ecliptic at the time of the individual’s birth.

Apart from the Zodiac, Astrology also considers the Nakshatras. They are the stars in the constellations of the Zodiac over which the Moon passes by at the beginning of the day. On an average the Moon completes a revolution around the Earth every 27 days. As such there are 27 Nakshatras. Like the Zodiac, the Nakshatra at the time of a person’s birth is supposed to have an impact on his/her life.

Though Astrology states that life can be predicted based on the Zodiac and the Nakshatras, it doesn’t explain how the Sun’s or Moon’s position in the Sky actually affects life. The Sun has an obvious influence on Earth; it is the energy source for many processes and most life forms derive energy from the Sun. But Astrology doesn’t explain in what way the position of Sun determines an individuals life. It merely states what will happen. Many astrologers use terms like “cosmic energy” and “quantum disturbances” to explain Astrology, but the explanations are vague and are not quantifiable. A statement like “The Earth is big” may seem obvious, but it is vague. It doesn’t quantify “big” – big as compared to what? Is it bigger than the Moon? the Sun? Jupiter? If it is big, by what factor?

Astrology considers only those constellations which can be seen on the ecliptic. It ignores the other constellations. When seen from outside the Earth and outside of the plane of the ecliptic, the Earth itself passes through numerous constellations which are not on the ecliptic. If the combination of planet-constellation can have an effect on life, it is reasonable to assume that the Earth will have an greater or an equal effect, if not less. That Astrology does not consider this possibility suggests that at the time Astrology was being developed, Earth was thought to be stationary and all the other objects were moving around the Earth.

Planetary Influences

Astrology lists the following celestial objects, the Navagrahas, as having an influence on day-to-day life:

Astrological Name Astronomical Name
Surya Sun
Chandra Moon
Mangala Mars
Budha Mercury
Brihaspati Jupiter
Shukra Venus
Shani Saturn
Rahu North lunar node
Ketu South lunar node

Of the given nine Grahas, Rahu and Ketu are not celestial objects. They were believed to be demons who “ate” the Sun and the Moon causing Solar and Lunar eclipses. Today we know that eclipses happen at the lunar nodes. A lunar node is the point at which the Moon’s orbit crosses the ecliptic. For an eclipse to occur, the Sun, Earth and the Moon should lie in the same plane which can happen only when the Moon’s orbit intersects with the ecliptic. The rest of the Grahas are visible to the naked eye. As such astrology does not consider other objects of the Solar system which are not visible except with the aid of a telescope:
  • the remaining planets – Uranus and Neptune. Uranus’ mass is around 14 times that of the Earth and Neptune’s is around 17 times.
  • the sizeable moons of Jupiter and Saturn. For example, Jupiter' moons – Io, Ganymede and Callisto and Saturn’s moon Titan are larger than the Earth’s moon.
Name % of Moon’s Diameter % of Moon’s Mass
Io 105 120
Ganymede 150 200
Callisto 140 150
Titan 150 180
  • the Asteroid Belt between Mars and Jupiter. Four of the asteroids – Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea have diameters more than 400 km. Ceres, the largest asteroid, has a diameter of about 950 km and can be considered a dwarf planet (Moon’s diameter is around 3474 km).
  • the Kuiper belt which includes Pluto and extends outward from the orbit of Neptune for a distance of about 25 AU (1 Astronomical Unit = distance of Earth from the Sun = 149.60 × 106 km).
  • the comets which orbit the Sun outside the Kuiper Belt.

Originally Grahas were considered as deities who influence human life. Currently many astrologers try to explain the planetary influences in terms of “energy waves” which affects the human body. Again, as seen in the previous section, the explanations are vague. For example, they don’t explain effects of phenomenon like Sun spots. The Sun spot activity increases and decreases roughly following a eleven year cycle. When it is at the maximum, the Sun releases bursts of high energy radiation strong enough to disrupt radio communications on Earth. No where in Astrology is this phenomenon mentioned.

Astrology also ignores the the omnipresent force of Earth’s magnetism. It plays a vital role in deflecting charged particles emitted by the Sun away from the Earth. And the Earth’s magnetic field is not constant. There are local variations and during high Sun spot activity periods, it is severely deformed due to the increased flux of charged particles. Note that magnetic fields only deflect electric charges. They have no effect on electromagnetic waves.

Image Source: Wikimedia
Even if we were to ignore these phenomenon and still assert that energy of other planets and stars influence us, it is trivial to show that, in terms of the four fundamental forces of Nature – strong nuclear force, weak nuclear force, electromagnetism and gravity, objects on Earth itself can have more effect on energy fields than far away planets and stars. The strong and weak nuclear forces make sense only within an atom’s nucleus. Gravity decreases as the square of distance between objects. So if an object is brought very close to a human body, its gravity will outweigh the gravity of other celestial bodies. Like gravity, magnetic and electric fields also decrease as the square of distance. If there is any other kind of force which effects us as profoundly as Astrology claims that celestial objects effect us, it would be trivial to detect and measure such a force. So far, outside of the four fundamental forces, nothing else has been found.

Also, not enough importance is given to the Sun in Astrology. It accounts for 99.8% of the mass of the Solar system, produces about 3.83 × 1026 joules of energy per second (in comparison the Nagasaki atomic bomb produced a total energy of about 8.78 × 1013 joules), radiates in a wide range of the electromagnetic spectrum and ejects high energy charged particles. It has a much greater influence on Earth than any other object in the Solar system and when compared to it, the effects of other stars are minuscule. Even if we consider a billion stars as a whole, the effect of them is still small when compared to the Sun. The other stars are too far away to have a sizable effect.

Human Psychology

In 1948 a psychologist named Bertram R. Forer conducted an experiment with his students. He gave the students a questionnaire and said that based on the answers given, he will do a personality analysis for each student individually. After the students got their personality analysis, Forer asked them to rate how accurate the analysis was. On an average, the students rated it as being 85% accurate.

In reality what Forer did was, he gave all the students identical copies of the same analysis. The analysis itself was vague and described only general positive personal traits. This experiment shows that humans tend to believe persons in authoritative positions (the students trusted their professor to do an accurate analysis) and believe in good/encouraging things said about them. If a person were intially told that Astrology works by a trustworthy person, and if Astrology predicts some general matters about his/her life, the person may end up in believing that Astrology does work.

Also, humans tend to remember good things and try to forget bad experiences. So even if Astrology predicts a set events and only a few of them come true, the predictions about the events which did not come true are ignored. Only the events which came true will be remembered and it will bolster the belief that Astrology works. Note that Astrology never makes specific predictions. For example, it cannot say what a person will be doing on particular date and time, say, 10 years into the future. It can only make general predictions like “You are going through a rough patch. But after 6 months time, you will come across fortune”. The person may come out of the rough situation before 6 months. In that case, Astrology has failed. Something has happened before it was supposed to happen. But the person will only remember that Astrology predicted that his/her situation will get better and not the fact that the situation got better before the time as predicted by Astrology.

There is also another way in which Astrology may seem like it works. A person may subconsciously take decisions in such a manner that events predicted by Astrology come true. In fact, in double blind tests (the astrologer doesn’t know about the person whose fate is being predicted and the person doesn’t know what the astrologer has predicted), Astrology performs the same as guessing (accuracy rate of around 50%). But, as seen earlier, even if a few predictions come true, a person may believe that Astrology works.

A very important consequence of living life strictly according to Astrology is that it makes a person’s life easy to predict. For example, many people are named according to their birth Nakshatra. If Astrology deems that a person will succeed as an musician, then that person will persue a career in music. Important occasions in life – like starting a business are planned on days certified by Astrology as being good. Spouses are chosen based on horoscopes. Just by knowing a person’s date and time of birth, one can predict his/her name, occupation, spouse’s name and any other event which the person has performed based on Astrology.

Finally, one aspect which tremendously helps Astrology is that humans are credulous by nature. This is a trait which has some evolutionary advantages. If a person who is living in the wild, sees a yellow patch with black stripes in some distance with an unclear shape, the best survival strategy for that person is to assume that the yellow patch is a tiger, and run away from it. But if the person were to go near the yellow patch to investigate whether it really is a tiger or not, he may get killed if it is indeed a tiger. In the first case, where the person chooses to run away, there is no penalty for making a wrong decision where the yellow patch isn’t a tiger. But in the second case there can be a penalty – death. This kind of a selection pressure has caused Nature to make the human mind infer patterns even when there is little data. Sometimes, it is better to take a decision even if there is insufficient data, than to wait for more data. But there are cases where this process can be bad – where making the wrong decision has a penalty for all cases.

It is tempting to see a pattern between paths of celestial objects and life. The celestial objects must exist for a reason and that reason is to govern our lives. But there is no evidence that celestial objects influence human life in the way that Astrology says they do. The effects are not observable and cannot be verified. Even if the celestial objects influence life, Astrology uses insufficient data as we have seen in the previous sections. Either way, acting on insufficient/wrong data can be dangerous. For example, it may make a person choose a bad career option or create a false hope where there is none. Unlike the tiger case seen earlier, making the wrong decision here can have a penalty.


Astrology was based on our understanding of Nature around 2000-3000 years ago. Compared to today, that understanding was lacking in many areas. The best evidence for this is that Astrology does not consider celestial objects which are not visible to the naked eyes. Much of the apparent efficacy of Astrology can be explained in terms of human psychology. Under close scrutiny Astrology fails.


Anonymous said...

Astrology always works, it is the humans who fail it.

Indian astrology based on nakshatras and the likes, are to be trusted and followed thoroughly. It would give you the needed feeling of well-being, as well as guidance to how you are supposed to turn out to be. Every thing is set for you, if only you are willing to do your part. By selectively forgetting the unwanted, and reinforcing the predicted positives with your life experiences, you could make the astrology work well for you. If you are not willing to try, do not blame it our astrology.

Even if your personal traits do not turn out to be your liking or predicated by your horoscope, help is on the way, you have a recourse to get back to the grove by doing specific rituals.. And, you fail to take these simple remedial actions (or you do it incorrectly)! Who is to be blamed for your misfortune now..the astrologist or you yourselves?

You are on your own when you skip astrology, and do not expect it to help you. What is needed here is faith, a good deal of internalization, and resultant actions, in order to make our sure the sure science to work for/on you. Being blind to this, you try to blame your lack of success on us. How blind can you get?

Anonymous said...

"...Astrology uses insufficient data as we have seen in the previous sections."

Unfortunately your article does the same. Your conclusion is based on insufficient data, isnt it? You neither have understood the concept of "graha" or studied any of the works like brhat samhita, hora shastra or parashara shastra. First understand the originals, not translations - is "graha" really a "celestial body" ?

It would have been useful to study them and comment on them, rather than simply saying 'astrology is pseudo-science' and then cover it up with 'scientific skepticism'.

Lije said...


As I note at the beginning of the article, this was written during my early days of skepticism. If you ask me now, I'd say astrology is bullshit. There isn't even any need of going near grahas.

There are some rationalist associations in India which have open challenges for any astrologer to prove the efficacy of their predictions. You can prove that astrology is not bullshit by taking up one such challenge.

Anonymous said...

Hi Lije

If you ask me I am too not a believer of astrology but I must say that I am least impressed with the way you come across backing up your arguments about things you consider irrational in your opinion.

I have read the whole article and couldnt find any concrete "proof" provided against astrology...I was actually quite disappointed to say the least. I think the "burden of proof" rests with you this time. The arguments you put up at times come across as disgraceful especially when words such as "bullshit" are used on this formum...Sorry about the moan

Ganesh Sriram said...

Anonymous said (first comment above):

Astrology always works, it is the humans who fail it. ... You are on your own when you skip astrology ...

Wow! That's a creative explanation for the failure of astrology to predict! Imagine if science said the following:

Gravity always works, it is objects that fail it. ... You are on your own when you skip gravity ...

Wouldn't that be absurd? But science is too honest to make such statements.