SPIN AND PRECESSION | English
Channel: Arvind Gupta
Date: 28/09/2015

Here you see a propeller on a stick kept in a glass. The propeller spins on its axis but also goes round-and-round creating a large cone. This wobble is called Precession. To understand it you need a pointed wooden stick, a plastic propeller and a glass. The propeller is a stiff plastic disc with 16 cuts. The cuts are twisted to make fan blades. Press fit the pointed stick in the propeller. Place the stick and propeller in the glass. The lower end of the stick will rest on the base rim of the glass at an inclination. On placing the model under a ceiling fan the propeller will spin and also go round-and-round in circles. This is called Precession. Precession is the change in the rotational axis of a rotating body.
Precession is also the wobble of the earth which makes the POLES shift their positions over a period of 26,000 years. Precession is caused by the gravitational pull of the sun and moon on Earth. Hipparchus first discovered this phenomenon in 130 BC. Today’s Pole Star is in Polaris, but in 3000 BC the celestial pole star coincided with the star Thuban (in the constellation of Draco).

This work is supported by IUCAA(www.iucaa.ernet.in) and TATA Trust (www.tata.com/aboutus/sub_index/Tata-trusts)

Credits:,Ashok Rupner, Manish Jain, Shivaji Mane, Jyoti Hiremath, Arvind Gupta, Vidula Mhaiskar TATA Trust: Education is one of the key focus areas for Tata Trusts, aiming towards enabling access of quality education to the underprivileged population in India. To facilitate quality in teaching and learning of Science education through workshops, capacity building and resource creation, Tata Trusts have been supporting Muktangan Vigyan Shodhika (MVS), IUCAA's Children’s Science Centre, since inception. To know more about other initiatives of Tata Trusts, please visit www.tatatrusts.org