SSC GD 2026 PYQ — Question 31

Correct Answer:

Gravitational pull of the Sun and Moon

Explanation:

The precession of the Earth's axis is primarily caused by the gravitational pull of the Sun and the Moon acting on the Earth's equatorial bulge. Because Earth is not a perfect sphere and bulges slightly at the equator, the gravitational forces exerted by the Sun and the Moon create a torque that causes the Earth's rotational axis to wobble or trace out a conical shape over a long period (known as the Great Year or precession cycle, taking roughly 25,772 years).

Key Points:

The phenomenon is formally referred to as the axial precession or the precession of the equinoxes.

Hipparchus of Nicaea is credited with the discovery of the precession of the equinoxes in ancient Greece.

This gradual shift causes the position of the celestial poles to change slowly over millennia.

Important Questions and Answers:

Question: Approximately how many years does it take for Earth to complete one full cycle of axial precession?

Answer: About 25,772 years.

Question: Who discovered the precession of the equinoxes?

Answer: Hipparchus.