Cheatsheet: The Earth-Sun-Moon System

1. Earth's Structure and Characteristics

1.1 Earth's Shape and Size

1.2 Earth's Rotation

1.3 Earth's Revolution

2. The Sun

2.1 Sun's Characteristics

2.2 Sun's Structure

2.3 Sun's Features

• Sunspots: Dark, cooler areas on photosphere caused by magnetic activity
• Solar Flares: Sudden bursts of energy from Sun's surface
• Prominences: Loops of gas that extend from Sun's surface
• Solar Wind: Stream of charged particles flowing from Sun

3. The Moon

3.1 Moon's Characteristics

3.2 Moon's Motion

3.3 Moon's Surface Features

4. Moon Phases

4.1 Phase Cycle

4.2 Phase Facts

• Complete phase cycle takes 29.5 days (lunar month)
• Phases caused by changing positions of Moon relative to Earth and Sun
• Moon does not produce light; reflects sunlight
• Waxing means growing; waning means shrinking
• Same phases occur in same order every month

5. Eclipses

5.1 Solar Eclipse

5.1.1 Types of Solar Eclipses

• Total Solar Eclipse: Moon completely blocks Sun; see corona
• Partial Solar Eclipse: Moon blocks only part of Sun
• Annular Solar Eclipse: Moon too far to completely cover Sun; ring of sunlight visible

5.2 Lunar Eclipse

5.2.1 Types of Lunar Eclipses

• Total Lunar Eclipse: Moon passes completely into Earth's umbra
• Partial Lunar Eclipse: Only part of Moon enters Earth's umbra
• Penumbral Lunar Eclipse: Moon passes through Earth's penumbra only (hard to see)

5.3 Eclipse Frequency

• Eclipses do not occur every month because Moon's orbit is tilted 5 degrees
• Solar and lunar eclipses can only occur when Moon crosses the ecliptic plane
• 2 to 5 solar eclipses occur each year somewhere on Earth
• Total solar eclipses are rare at any given location
• Lunar eclipses are visible from entire night side of Earth

6. Tides

6.1 Tide Basics

6.2 Causes of Tides

• Moon's gravity pulls on Earth's water, creating bulge on side facing Moon
• Inertia creates second bulge on opposite side of Earth
• Sun's gravity also affects tides but has less effect than Moon (Sun is farther away)
• As Earth rotates, locations pass through bulges, experiencing high and low tides

6.3 Types of Tides

7. Seasons

7.1 Cause of Seasons

• Earth's axis is tilted 23.5 degrees from vertical
• Axis always points toward North Star (Polaris)
• As Earth revolves, different hemispheres tilt toward or away from Sun
• Seasons are caused by tilt, NOT distance from Sun

7.2 Effects of Tilt

7.3 Key Positions in Earth's Orbit

7.4 Solstice and Equinox Details

• Solstice: Sun reaches highest or lowest point in sky at noon
• Equinox: Sun is directly overhead at equator at noon; day and night are 12 hours each
• Tropic of Cancer (23.5°N): Sun directly overhead at summer solstice
• Tropic of Capricorn (23.5°S): Sun directly overhead at winter solstice
• Arctic Circle (66.5°N) and Antarctic Circle (66.5°S): Experience 24 hours of daylight or darkness on solstices

8. Day and Night

8.1 Cause of Day and Night

• Earth rotates on its axis once every 24 hours
• Side facing Sun experiences day (receives sunlight)
• Side facing away from Sun experiences night (in shadow)
• Rotation from west to east makes Sun appear to rise in east and set in west

8.2 Time Zones

• Earth divided into 24 time zones (one for each hour)
• Each zone covers 15 degrees of longitude (360° ÷ 24 hours)
• Time is earlier to the west and later to the east
• International Date Line: located at 180° longitude; crossing changes calendar date

9. Earth-Moon-Sun Interactions Summary

9.1 Key Relationships