NOTES Topic 5. Earth Sun Moon 2024

Motions of Earth, Moon, and Sun

1. Earth's Movement

  • Rotation: Earth spins on its axis, west-to-east, once every 24 hours.

  • Revolution: Earth orbits around the Sun counterclockwise, completing one orbit in 365.25 days.

2. Earth's Rotation Details

  • Axis: An imaginary pole through Earth's center, tilted at 23.5°.

  • Rate of Rotation: 15° per hour.

3. Effects of Rotation Rate

  • Faster rotation results in shorter days.

  • Slower rotation results in longer days.

4. Apparent Motion of Celestial Objects

  • Apparent Motion: Caused by Earth's rotation; celestial objects appear to move from east to west at 15° per hour.

  • Examples include the daily rising of the Sun and the movement of the Moon and stars.

5. Earth's Revolution

  • Completes one revolution around the Sun annually, influencing seasonal changes.

  • Rate of Revolution: 1° per day.

  • Leap Year: Every 4 years, an extra day (February 29) compensates for the additional quarter day.

6. Seasonal Constellations

  • Different constellations are visible throughout the year, demonstrating Earth's revolution.

7. Definition of Constellations

  • Constellation: Pattern of stars named in ancient cultures.

  • Example: Orion, largest constellation, visible in winter.

8. Seasonal Changes

  • Seasons in the Northern Hemisphere:

    • Spring: March 21

    • Summer: June 21

    • Fall: September 23

    • Winter: December 21

  • Opposite in Southern Hemisphere.

9. Insolation and Seasons

  • Insolation: Energy from the Sun reaching Earth.

    • Angle of Insolation: Affects temperature; direct rays are strongest.

    • Lower angles result in cooler temperatures.

10. Impact of Earth's Axis

  • Earth's axis tilt and revolution around the Sun creates seasonal temperature variations.

  • Areas near the tropics receive direct rays seasonally.

11. Factors Influencing Tides

  • Tides: Cyclic rise and fall of sea levels caused by the Moon's and Sun's gravitational pull.

  • Two high tides and two low tides each day.

12. Types of Tides

  • Spring Tides: Occur during New and Full Moons; highest high tides.

  • Neap Tides: Occur during first and third quarter moons; lowest high tides.

13. Eclipses

  • Solar Eclipse: Occurs when the Moon lies between the Earth and the Sun (New Moon).

  • Lunar Eclipse: Occurs when the Earth is between the Sun and the Moon (Full Moon).

14. Moon's Revolution and Phases

  • The phases of the Moon are the visible shapes depending on its position relative to Earth and the Sun.

  • A complete cycle of phases takes about 29.5 days.

15. Tides and Lunar Influence

  • Moon's gravitational pull affects ocean tides significantly.

  • Tides cycle through approximately every 6 hours and 13 minutes.