Every year, we in India, celebrate Makar Sankranti in the middle of January. Sankranti is celebrated as the Indian New Year by those who follow the winter solstice based calendar. A solstice is the day when the axis of the earth is oriented directly away from the sun. These two days fall on December 22 (the winter solstice) and June 21 (summer solstice).
So how is it that Sankranti is celebrated in mid January? This has been happening because the Indian calendar is faulty as it does not consider the slow motion of the axis compared with the rest of the earth.
The earth is tilted on an axis. The tilt of the axis is 23.5 degrees. And so the latitudes of 23.5 degrees on either side of the equator mark the two extreme points where the sun can shine overhead- these are the tropics of Capricorn and Cancer. The sun shines overhead on these latitudes on June 21 and December 22 (the two solstices) and overhead the equator on two equinox days – March 21 and September 22.
One of these four days was generally taken as the beginning of a year and, hence, Makara Sankranti was taken on the winter solstice. The actual winter solstice and the day of Makara Sankranti are twenty-four days apart, which is a difference of almost a month. The earth can be considered as a tilted spinning top. The axis of the top also rotates but is slow compared to the spin of the top. This is because of the earth’s gravity acting on the tilted top. In case of the revolving earth, the gravitational force between the earth and the sun makes the earth’s axis rotate very slowly. In fact, it takes an astonishing 25, 800 years for the axis to complete one revolution. This scientific phenomenon is called the precession of the earth’s axis. On Equinox days, the sun shines equally on the two poles or on each hemisphere. After a year, by the time the earth comes back to the same position in its orbit- when the sun appears against the same stars in the sky- the axis would have moved to a different direction (due to its slower motion). This change in direction would not cause the Equinox. The actual Equinox would have occurred twenty minutes earlier. So these twenty minutes makes the year shorter and amounts to a difference of almost a day in 72 years. Further, since the length of the year adopted in traditional Indian calendars is another three minutes off the correct value, it jumps even faster and amounts to a day in a 60 years! So this present gap of twenty-four days has been accumulated in approximately 1450 years.Our illustrious astronomers of yore did, in fact, ponder over this discrepancy. Barahamihira (500 B.C) mentioned it in his ‘Brihat Samhita’ but suggested verification only after actual observations. Some others thought the precession to be oscillatory rather than cyclic. Hence, the shift would increase and decrease periodically. Much later, in 10th century A.D., Bhaskaracharya observed the correct shift but by that time, our calendar system had become so deeply rooted in the older methods that it was not changed. The Government of India set up a committee to reform our calendars in 1955 with the renowned physicist Meghnad Saha as its chairman. It recommended the Indian calendars to start on March 22 and the difference of old dates and new dates was brought down to six days. Thus, the Indian National Calendar was adopted in 1957 but it is hardly used anywhere, except maybe on the gazettes or broadcasts on A.I.R. Sadly, we are all blissfully unaware of this fallacy in our calendar system. With absolutely no debates and discussions on this issue, it seems very unlikely the calendars will be corrected in the near future.Nanda Kishore
(image courtesy: http://www.flickr.com/photos/y_i/376121027/)