The Solar System, Earth Movements & Moon Phases

The Solar System is gravitationally bound to a central medium-sized yellow star called the SUN. • The Sun: - Accounts for over 99.8% of the total mass of the solar system. - Composed mainly of Hydrogen (~74%) and Helium (~24%) undergoing nuclear fusion at its core, releasing immense heat and light. • The Eight Planets in Order from the Sun: 1. Mercury: Smallest planet, closest to the Sun, extreme temperature swings, no atmosphere. 2. Venus: "Earth's twin" in size; hottest planet due to a runaway greenhouse effect from dense CO₂ atmosphere. 3. Earth: The only known planet supporting life, with liquid water oceans and a protective nitrogen-oxygen atmosphere. 4. Mars: The "Red Planet", rich in iron oxide dust, with thin atmosphere and polar ice caps. [Asteroid Belt: Thousands of rocky fragments orbiting between Mars and Jupiter] 5. Jupiter: Largest planet in the solar system, gas giant, famous for the Great Red Spot storm. 6. Saturn: Second largest gas giant, distinguished by spectacular, bright rings of ice and rock particles. 7. Uranus: Ice giant, pale cyan color due to atmospheric methane, rotates on its side. 8. Neptune: Outermost planet, intense blue ice giant with the fastest supersonic winds. • Mnemonic: "**M**y **V**ery **E**ducated **M**other **J**ust **S**erved **U**s **N**oodles" (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune). • Note on Pluto: Reclassified by the International Astronomical Union (IAU) in 2006 as a "Dwarf Planet".

The Earth undergoes two distinct, simultaneous celestial movements: • 1. Earth's Rotation: - Definition: The spinning of the Earth on its imaginary axis, which is tilted at an angle of 23.5° from the perpendicular. - Direction: Rotates from WEST to EAST (anticlockwise when viewed from above the North Pole). - Period: Takes 24 hours (1 solar day) to complete one full 360° turn. - Effects of Rotation: 1. Causes DAY and NIGHT: The side facing the Sun receives light (day), while the side facing away is in darkness (night). 2. Causes the apparent daily movement of the Sun, Moon, and stars rising in the East and setting in the West. 3. Deflection of winds and ocean currents (Coriolis Effect). • 2. Earth's Revolution: - Definition: The movement of the Earth in an elliptical orbit around the Sun. - Period: Takes 365¼ days (1 year). Every four years, the four ¼ days accumulate to form 1 extra day (366 days), creating a LEAP YEAR with 29 days in February. - Effects of Revolution: 1. Causes the FOUR SEASONS (Spring, Summer, Autumn, Winter in temperate zones; Wet and Dry seasons in tropical Ghana), because the Earth's axis remains tilted at 23.5° in the same direction throughout its orbit. 2. Varying lengths of day and night at different latitudes during the year. 3. Changes in the altitude of the midday Sun at different times of the year.

• The Moon and Its Phases: - The Moon is the Earth's only natural satellite. It does not produce its own light; it reflects sunlight. - It orbits the Earth every 29.5 days (lunar month). As it moves, the portion of illuminated surface visible from Earth changes, producing the PHASES OF THE MOON: New Moon → Waxing Crescent → First Quarter → Waxing Gibbous → Full Moon → Waning Gibbous → Last Quarter → Waning Crescent. • Eclipses: An eclipse occurs when one celestial body moves into the shadow cast by another, due to the straight-line propagation of light. 1. Solar Eclipse (Eclipse of the Sun): - Spatial Alignment: Sun → MOON → Earth (The Moon is directly between the Sun and Earth). - Occurs during a NEW MOON in daytime. - The Moon casts its shadow onto the Earth. People in the dark inner shadow (UMBRA) experience a Total Solar Eclipse; people in the lighter outer shadow (PENUMBRA) experience a Partial Solar Eclipse. 2. Lunar Eclipse (Eclipse of the Moon): - Spatial Alignment: Sun → EARTH → Moon (The Earth is directly between the Sun and the Moon). - Occurs during a FULL MOON at night. - The Earth blocks sunlight from striking the Moon, casting the Earth's shadow on the lunar surface. The Moon appears reddish-brown ("Blood Moon") due to light refracted through Earth's atmosphere.