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.


4 thoughts on “The moving solstice”

  1. Brilliant. One question though – You know Gavi Gangadhareshwara temple. They say on this day the sun’s rays falls directly on the idol through the “cleverly designed, spiritually occurring” space through the rock. How do you explain that, especially when the Sun is not aware of the astrological calendars and stuff?

    1. Good point! How old is this temple? And another thing – do we know if the sunlight filters through on the days just before and after Sankranti also?

  2. The 26,400 year cycle corresponds roughly with the period of precession of the equinoxes. This precession is causing the solstices (and seasons!) to move relative to the Gregorian calendar at (12 months)/(26000 years) = 0.0046 months/year, which is roughly 20 minutes/year, and is the cause of the deliberate error/correction you pointed out.

    So these two statements are incorrect:

    1. “we have been using a calendar that is accurate for astrological calculations but not to seasons!”

    2. “the lunar calendar, which has been calibrated to the movement of stars, captures seasons more accurately!”

    The Hindu solar calendar appears to be accurate for seasons too, because seasons also follow the 26400 year cycle. I don’t know if the makers of the calendar were aware of this precession–and it boggles my mind how they figured it out–but both the solar and astrological calendars appear to have long term corrections built in, and they are in sync with each other. The only problem is the zero error in the current date of the winter solstice, which will persist.

    Finally, you are correct that Makara Sankranti will fall in June in 10,000 years, but so will the winter solstice (roughly, and with the same zero error), so it’s all okay!

    1. Interesting! the problem with 26400 year cycles is that it is impossible to test whether seasons actually move with such cycles unless we do a cross-generational experiment. Are there any pieces of literature from say 2000 yaers back that talk give both the date and a description of the ewather? No other way, I think, to test this hypothesis.

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