When put to the test, the predictive powers of Indian astrology simply don’t hold up


Nagesh Rajopadhyehttps://www.astrologyyesorno.com/
Dr. Nagesh Rajopadhye is an Astrology Researcher based in Pune, India. He was an astrologer himself at one time, but now he is a skeptic and critic of astrology. He holds a PhD in Physics, and after taking an early retirement from an MNC IT company he now devotes his time to the empirical testing of Indian astrology.

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In places such as India, astrology is an integral part of society. This may sound strange, but the vast majority of arranged marriages in India, which make up about 90% of all marriages, occur only after the matching of birth charts. There are other elements involved in this decision such as finance, education, etc, but astrological compatibility is the very first filter applied invariably in the selection process. Besides marriage, millions of Indians make numerous other important decisions, such as business and career choices on the basis of astrology, making India a major consumer of astrology. With a population of over 1.3 billion, the magnitude of astrological influence on Indian society can easily be estimated to be hundreds of millions of people, several billion dollars, millions of marriages every year and much more. 

Indian astrology, also called as Vedic astrology, is distinctly different from its western counterpart in many ways. Because the name ‘Vedic’ is based on ‘Vedas’ – the four religious Hindu scriptures – the general belief is that it is completely different to Western astrology, and more pious, as it was been told to ancient seers by god. For this reason, all the efforts made globally to refute astrology have not even created a single scratch on people’s beliefs in India.

Testing of Indian astrology in particular has many challenges, since it critically depends on birth time or the Moon’s planetary position, and no database of birth details is available to researchers if they wanted to undertake such a study. Additionally, there is no single authentic source of rules that can be relied upon for testing. To make things more complicated, there are many rules and diverse opinions about which planet or house is significant for what aspect of your life. If someone tries to disprove one set of rules, there is always another that remains to be disproved. It could be due to these reasons that there has not been any recent attempt made to test Indian astrology at scale, to the point that it will satisfy all believers.

A vedic astrology chart. Image from Wikimedia user Tomi Less [CC BY-SA 4.0]

It has now been nearly 12 years since astrology was put to the test in a double-blind study in Pune, India. It was India’s first publicly held test of Indian astrology and triggered a lot of discussions and ripples in society. In the test, astrologers in the state of Maharashtra, India  were given a random mix of astrological birth charts consisting of intellectually and developmentally disabled (hence after referred as IDD) as well as ‘intelligent’ people, while keeping their identity and details hidden. Then, they were asked to identify which birth charts belonged to IDD persons purely through astrological means. If astrology could tell a person’s intelligence from their birth-chart, it was expected that astrologers would have correctly classified at least 70 percent of the birth charts. However, results of the experiment showed that none of them could perform better than chance, that is, 50 percent.

In any double-blind experiment however, particularly when the outcome is negative, the astrology supporters get an opportunity to create an ambiguity by raising a question as to whether the results are due to the limitations of astrology, or the astrologers. Against this backdrop, we decided to undertake empirical testing of astrology principles, leveraging the same dataset which was used in the double-blind test.

Re-analysing the data

Two data sets with exactly opposite life patterns were created with sufficient sizes, one consisting of 338 birth-charts of ‘intelligent’ people (Group A) and the other consisting of 338 birth charts of IDD people (Group B). A few principles, which are given in the astrology textbooks as fundamental principles, were examined for each birth chart by applying them to all the planets or houses (as per applicability) and the results were compared amongst both the datasets.

Since these principles are the main focus of our experiment, let us explain them a bit more. If you have ever gone to an astrologer, typically he or she will take a look at your birth chart and mysteriously whisper to themselves something like: “Oh, Venus is in close conjugation with Saturn… sad.”. And you hold your breath till you get a chance to ask: “What does it mean?”. It is this principle that we are talking about. Here the underlying principle is “the conjugation, square or opposite of a planet with Saturn or Mars results in the negativity of planet and destructs the life effect for which the planet is significant”.

In our example, since Venus is negatively impacted by Saturn, astrology will predict an adverse effect for life events that are influenced by Venus, such as marriage. Since we have groups which are differentiated based on intelligence, if this astrological principle is true, we should see such conjugations occur in our IDD group (group B) with greater frequency for the planet(s) like Mercury and Moon which are usually related to intelligence.  

Since there are diverse opinions among astrologers about which planet(s) is important for intelligence, we tested this principle by applying it to each of the planets in turn. The idea was that no matter which planet is important for intelligence, if this principle is true, we would see a significant difference for at least one or more planets. Likewise, we tested six other fundamental principles, to see if they showed the negative astrological influence of a planet with more frequency in Group B. These six principles covered traditional Indian astrological beliefs such as a planet in cruel Nakshatra, a planet in a debilitated or enemy zodiac sign, a planet in the 6th, 8th, or 12th house, etc. create negativity in birth chart and lead to adverse effects in life. We also tested the two most fundamental principles for the houses of birth charts which deal with the presence of destructive planets inside or opposite to the house. The astrologers can debate all they want on which house exactly is significant for predicting intelligence, but as we decided to test all twelve of them individually, if astrology has any predictive powers, at least one of them should show up in the results.

We processed birth-charts via a computer program, and counted the number of cases in the dataset that complied with the above mentioned astrological principles. The program could process hundreds of birth charts in one go, and passed the data to our statistical module. We used the Chi-square test and the Two sample T-test to confirm if the differences observed between two groups in each case was significant enough to prove the principle was valid. We decided to consider the principle as valid if the difference between the two groups was greater than 10 per cent. This was a very generous test for an astrological principle to pass through, against the expectation that if an astrological principle was true, it should ideally show a difference of at least 40% or more between the two groups, given that astrology is so widely used in India for predicting critical life decisions.

We were extremely curious about the results, just as much as you must be at this point. Interestingly, we found that for all the principles we tested there was no significant difference between the two groups, for any of the nine planets. This means that none of the six principles we tested – that planets could have a negative impact on our lives – were shown to have any empirical validity. The same was true for the two negative principles of the houses we tested. None of the 12 houses showed any significant difference in compliance, so regardless of which house is meant to be most important for intelligence, none of them were astrologically more negative. 

Planet Saturn as imaged by NASA's Hubble Space Telescope on July 4, 2020. Image was processed and auroras added by Pablo C. Budassi [CC BY-SA 4.0]

Our results also showed that what was true for negative astrological principles was also true for positive principles, such as the prediction of beneficial outcomes. By definition, these positive principles are the opposites of negative principles. For instance, if a conjugation of Saturn and Mars is meant to have a negative effect, a conjugation of Jupiter and Venus is meant to have a beneficial outcome. If such positive principles were true, they should have shown more benefit for Group A (Intelligent) than for Group B – but that was not what our test found. We are currently in the process of publishing a research paper with more details.

Although we cannot claim to have tested the full scope of astrology, the above results are of paramount importance. This is because the principles involved are so basic that they are invariably and extensively used in everyday practice of astrology. This poses a direct question as to the accuracy of predictions made using them.

Usually, astrologers apply all the principles they think are important, and take a judgement on the overall negativity or positivity involved in the birth chart for making a prediction. To emulate this, we compared the total negativity associated with each planet and the house. Total negativity has been measured in terms of how many negative rules are complied with in total by a given planet or house. From an astrological point of view, one would expect a greater number of negative rules concerning intelligence to be complied with on an average in Group B, the IDD group. However, we found no statistically-significant difference between the two datasets in terms of the total negativity for any of the 10 planets, nor for any of the 12 houses, in spite the groups being differentiated on intelligence level.

As part of our testing, in total we tested 34 entities (all planets, Ascendant, houses, and lords of houses) and 68 parameters (considering negativity and positivity for each entity) but none of them differed beyond 10% between both groups, which shows the actual veracity of Indian astrology. Despite this extensive testing, there will always be arguments about what has not been done and about which additional rules should have been tested. While more principles can always be tested, there should be a logical explanation as to why none of the 68 parameters of our comprehensive test could show any difference, when they would be expected to be substantially different from an astrological perspective.

Our results explain why in the double-blind test of 2008 the astrologers could not hit a better success rate than 50%. In our view, though astrologers have their own sets of rules they use for predictions, they are mostly made on the basis of the fundamental principles tested in our experiment. These principles, in reality, do not act as a differentiator themselves, nor do they produce a differential negativity when they are summed up together – hence no one could achieve a success rate better than random chance.  It was thus the limitation of astrology, and not of the astrologers, that they could not succeed.


This work has been done together with Mr. Prakash Ghatpande, from Pune, India. We thank Dr. Jayant Narlikar for the discussions and guidance he provided for this research. His inputs have added a great value to the paper. We are also grateful to him for having been the architect of the double-blind experiment carried out in 2008 which forms the basis of our test. The late Dr. Narendra Dabholkar and the late Dr. Sudhakar Kunte were also part of this double-blind experiment and we express our sincere gratitude for their contributions. We are grateful to the volunteers of ANS who collected the birth details of several hundred students over a period of a few months.

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