Motions of the Earth – Geography Notes PDF in English & Hindi for UPSC and Other Competitive Exams

Motions of the Earth: Motions are essential for the planet’s climate and seasons, as they affect the distribution of sunlight on Earth’s surface. The axial tilt, in particular, plays a crucial role in determining the length and intensity of daylight and the changing seasons throughout the year.

Motions of the Earth

The Earth experiences several motions as it orbits the Sun and rotates on its axis. These motions play a fundamental role in shaping the planet’s climate, day-night cycle, and seasons. The primary motions of the Earth are as follows:

1. Rotation:
• The Earth rotates or spins on its axis from west to east. This rotation is responsible for the day-night cycle.
• It takes approximately 23 hours, 56 minutes, and 4 seconds for the Earth to complete one full rotation, which is slightly less than 24 hours (a solar day). This shorter period is why we have leap years to account for the additional time.
2. Axial Tilt (Obliquity):
• The Earth’s axis is tilted at an angle of approximately 23.5 degrees concerning its orbital plane.
• This axial tilt is responsible for the changing seasons as the Earth orbits the Sun. When one hemisphere is tilted toward the Sun, it experiences summer, while the other hemisphere experiences winter.
3. Orbit around the Sun (Revolution):
• The Earth revolves around the Sun in an elliptical orbit. It takes approximately 365.25 days to complete one orbit.
• This orbital motion is responsible for the annual cycle of seasons. As the Earth orbits the Sun, the changing angle and intensity of sunlight lead to variations in temperature and weather.
4. Precession:
• The Earth’s axis experiences a slow, cyclic wobbling motion known as precession.
• Precession causes the orientation of the Earth’s axis to change over a period of approximately 26,000 years. As a result, the North Pole points to different North Stars during this cycle.
5. Axial Nutation:
• Axial nutation is a secondary, shorter-term wobbling of the Earth’s axis.
• It is caused by gravitational interactions between the Earth, the Moon, and the Sun.
• Axial nutation has an 18.6-year cycle and results in slight variations in the tilt of the Earth’s axis.
6. Orbital Variations (Milankovitch Cycles):
• Over very long time scales, the Earth’s orbit experiences variations in its shape (eccentricity), tilt (obliquity), and orientation (precession).
• These orbital variations, collectively known as Milankovitch cycles, are believed to influence the Earth’s climate and the timing of ice ages.