Makar Sankranti, celebrated generally around January 14-15 has been gradually shifting over the years due to the rotation of the earth, says the director of the Nehru Planetarium, N Ratnasree.
Talking to the Hindustan Times, Ratnasree said Makar Sankranti unlike several other festivals like Holi, Diwali is celebrated on a fixed date because unlike other festivals — which are determined by specific phase and position of the moon against the background of distant stars —Makar Sankranti is determined purely by the position of the sun against the background of the zodiacal constellations.
Makar Sankranti is supposed to signal the entry of the sun into the Makar Rasi or the zodiacal constellation of Capricorn. Its date, therefore, seems fixed within our calendars, she added.
Although Makar Sankranti is related to the Uttarayana or the beginning of the northward movement of the sun, the dates of these two events have been drifting apart, she said.
It is quite likely that sometime in the past Makar Sankranti had started as a winter solstice festival, Ratnasree added.
“If we look at the position of the sun against the background of the zodiacal constellations around 600-400 BC, we find the sun entered Capricorn exactly as winter solstice set in. In fact, this must have been the time the tropics got their names,” Ratnasree said.
The nomenclature for the tropics must have taken place around 600-400 BC, when the sun was in the constellation of Cancer at summer solstice and the constellation of Capricorn at winter solstice, she added.
“The drifting apart of Makar Sankranti from Winter Solstice comes about due to the precession of the axis of rotation of the Earth. The Earth spins around its axis once a day. Just like a top, however, the axis of rotation of the Earth itself precesses, but, very, very slowly, completing a full rotation once in about 26,000 years resulting in the current separation between the winter solstice and the Makar Sankranti,” Ratnasree said.
“With time, this precession will ensure that the separation will end in a divorce –– a few thousand years later, Makar Sankranti would take place in summer, diametrically opposite to the Uttarayana” the director said.