Earth’s Moon and the Sun: Characteristics, Movements, and Eclipses
The Moon
Basic Facts
- The Moon is Earth’s only natural satellite.
- It reflects sunlight.
- It orbits Earth in a spherical path.
- Its size is 1/49th that of Earth.
Surface Features
Lunar surface roughness is visible with telescopes and during solar eclipses, where prominences in the chromosphere appear as bumps.
Phases
Unlike the Sun, the Moon’s appearance varies from a fully illuminated disc to different levels of brightness.
Movements
Real Movements
- Rotation: The Moon rotates on its axis, taking approximately 27 Earth days.
- Revolution: The Moon orbits Earth at a speed of 300 km/sec, also moving with Earth around the Milky Way towards the star Vega.
Apparent Movements
These are due to Earth’s movements, including diurnal (daily) motion from Earth’s rotation and annual motion from Earth’s revolution around the Sun.
The Sun
Significance
The Sun is the primary source of life for Earth, providing essential energy.
Characteristics
- The Sun is a massive incandescent sphere, 1.3 million times larger than Earth.
- It is composed mainly of hydrogen, which converts to helium, releasing energy.
Structure
- Core: The central part with extremely high temperature and pressure.
- Photosphere: The visible surface, a bright layer emitting light.
- Sunspots: Dark areas caused by magnetic disturbances in the photosphere.
- Faculae: Bright regions often seen at the edges of the photosphere.
- Chromosphere: A pink/violet layer of gases, mainly hydrogen and helium.
- Corona: A halo extending millions of kilometers, with decreasing brightness.
Solar Phenomena
- Prominences: Eruptions of flammable vapors from the chromosphere.
Tides
Definition
Tides are periodic movements of sea water caused by the gravitational pull of the Moon and the Sun.
Types
- High Tides (Spring Tides): Occur during new and full moons.
- Low Tides (Neap Tides): Occur during the first and third quarter moons.
Tidal Phenomena
- Flow: The rising of sea water.
- High Tide: The maximum sea level during flow.
- Reflux: The falling of sea water.
- Low Tide: The minimum sea level during reflux.
Eclipses
Definition
Eclipses are temporary concealments of a celestial body by another.
Types
- Solar Eclipse: Occurs when the Moon passes between the Sun and Earth, when the Moon is in conjunction (new moon) and the orbital planes coincide.
- Lunar Eclipse: Occurs when Earth passes between the Sun and Moon, when the Moon is at opposition (full moon) and the orbital planes coincide.
Key Points
- The Sun is the solar system’s star, emitting light.
- Earth and the Moon receive and reflect sunlight.
- Earth orbits the Sun, and the Moon orbits Earth.