Tag: astrology

Astrology and Data Science

The discussion goes back some 6 years, when I’d first started setting up my data and management consultancy practice. Since I’d freshly quit my job to set up the said practice, I had plenty of time on my hands, and the wife suggested that I spend some of that time learning astrology.

Considering that I’ve never been remotely religious or superstitious, I found this suggestion preposterous (I had a funny upbringing in the matter of religion – my mother was insanely religious (including following a certain Baba), and my father was insanely rationalist, and I kept getting pulled in both directions).

Now, the wife has some (indirect) background in astrology. One of her aunts is an astrologer, and specialises in something called “prashNa shaastra“, where the prediction is made based on the time at which the client asks the astrologer a question. My wife believes this has resulted in largely correct predictions (though I suspect a strong dose of confirmation bias there), and (very strangely to me) seems to believe in the stuff.

“What’s the use of studying astrology if I don’t believe in it one bit”, I asked. “Astrology is very mathematical, and you are very good at mathematics. So you’ll enjoy it a lot”, she countered, sidestepping the question.

We went off into a long discussion on the origins of astrology, and how it resulted in early developments in astronomy (necessary in order to precisely determine the position of planets), and so on. The discussion got involved, and involved many digressions, as discussions of this sort might entail. And as you might expect with such discussions, my wife threw a curveball, “You know, you say you’re building a business based on data analysis. Isn’t data analysis just like astrology?”

I was stumped (ok I know I’m mixing metaphors here), and that had ended the discussion then.

Until I decided to bring it up recently. As it turns out, once again (after a brief hiatus when I decided I’ll do a job) I’m in process of setting up a data and management consulting business. The difference is this time I’m in London, and that “data science” is a thing (it wasn’t in 2011). And over the last year or so I’ve been kinda disappointed to see what goes on in the name of “data science” around me.

This XKCD cartoon (which I’ve shared here several times) encapsulates it very well. People literally “pour data into a machine learning system” and then “stir the pile” hoping for the results.

Source: https://xkcd.com/1838/

In the process of applying fairly complex “machine learning” algorithms, I’ve seen people not really bother about whether the analysis makes intuitive sense, or if there is “physical meaning” in what the analysis says, or if the correlations actually determine causation. It’s blind application of “run the data through a bunch of scikit learn models and accept the output”.

And this is exactly how astrology works. There are a bunch of predictor variables (position of different “planets” in various parts of the “sky”). There is the observed variable (whether some disaster happened or not, basically), which is nicely in binary format. And then some of our ancients did some data analysis on this, trying to identify combinations of predictors that predicted the output (unfortunately they didn’t have the power of statistics or computers, so in that sense the models were limited). And then they simply accepted the outputs, without challenging why it makes sense that the position of Jupiter at the time of wedding affects how your marriage will go.

So I brought up the topic of astrology and data science again recently, saying “OK after careful analysis I admit that astrology is the oldest form of data science”. “That’s not what I said”, the wife countered. “I said that data science is new age astrology, and not the other way round”.

It’s hard to argue with that!

The moving solstice

Today is “Makara Sankranti”. If the name doesn’t already strike you, “Makara” is the Sanskrit name for “Capricorn”. The Makara Sankranti is supposed to represent the Winter Solstice in the Northern Hemisphere, or the day when the Sun is directly over the Tropic of Capricorn.

However, we know that the winter solstice falls on the 21st or 22nd of December every year. Then why is it that the Indian version of the Winter Solstice falls on 15th of January?

I’m not sure if you remember, but a few years back, Makara Sankranti would usually fall on the 14th of January. After some back-and-forth movements, it has now settled on the 15th of January. You might have already noticed that this is unlike other Indian festivals such as Deepavali or Ganesh Chaturthi, whose dates according to the Gregorian calendar move every year (typically in a -11, -11, +19 cycle) over three years). This is because unlike Deepavali or Ganesh Chaturthi, which are observed according to the Lunar calendar, Makara Sankranti follows the solar calendar!

I recently read a book called “Solstice at Panipat”, about the third battle of Panipat in 1761 (my review is here). The Marathas went to battle four days after celebrating the Winter Solstice. The battle was fought on the 14th of January 1761, which means the solstice was observed that year on the 10th of January. So you see that the solstice, which is supposed to be observed on the 21/22 of December, was observed on 10th of January in 1761, and on the 15th of January in 2014.

This shows that there is an error in the Indian solar calendar. This error amounts to about 20 minutes a year, which means that the rate at which we are going, about 10000 years from now the Makara Sankranti (“Winter Solstice”) will fall in June, the middle of the summer!

That we know that the error in the Hindu solar calendar is 20 minutes a year allows us to calculate the last time the calendar was calibrated – we can date it to around 285 AD. Back in 285 AD, the calendar was calculated accurately, with the Winter Solstice falling on the actual Winter Solstice. After that, the calendar has drifted, and one can say, so has Indian science.

I’m informed, however, that this 20 minute error in the Hindu solar calendar is deliberate, and that this has been put in place for astrological reasons. Apparently, astrology follows a 26400 year cycle, and for that to bear out accurately, our solar calendar needs to have a 20 minute per year error! So for the last 1700 or so years, we have been using a calendar that is accurate for astrological calculations but not to seasons! Thankfully, the lunar calendar, which has been calibrated to the movement of stars, captures seasons more accurately!

I’ll end this post with a twitter conversation (I’m off twitter now, btw) where I learnt about this inaccuracy :

Update: The link to the tweet doesn’t show the entire thread. See that here.

Update: Here is a piece by astrophysicist Jayant Narlikar on the Makara Sankranti. Basically due to a change in the earth’s axis, our divisions of the night sky into 12 constellations are not stationary, and hence the date when the sun moves from “Dhanur” to “Makara” is no longer the solstice date.