The Moon and Its Phases

Vocabulary

• Satellite: An object that orbits another.

• Collide: To crash into.

• Habitable: Capable of supporting life.

• Orbit: A repeating path that one object in space follows around another.

Formation of the Moon

• Formation Time: The moon formed approximately 4.5 billion years ago due to a collision between a rock and Earth.

• Process: A fragment of Earth broke off and, along with other orbiting debris, melted and cooled to form the moon.

• Impact of Rocks: The moon’s surface was bombarded by rocks for about 500 million years, creating craters.

• Observation: Craters are visible through binoculars or telescopes, indicating the lack of erosion due to absence of atmosphere.

• Appearance: The moon appears as a white circle in the night sky and has dark areas known as "seas", formed by ancient lava flows.

Characteristics of the Moon

• Size Comparison: The moon is about 1/4 the size of Earth with a diameter of 2,149 miles (3,475 kilometers).

• Environment: Lacks an atmosphere, weather, or oceans, making it uninhabitable for humans.

• Temperature Extremes:

  • Daytime: Average of 253°F (123°C)

  • Nighttime: Drops to -387°F (-233°C)
    (Perspective: Water boils at 212°F and freezes below 32°F).

• Gravity: The moon's gravity is approximately 1/6 that of Earth, making it difficult for humans to walk without assistance.

• Oxygen Requirements: Humans cannot breathe on the moon due to the lack of atmosphere; special devices would be needed to supply oxygen.

Orbit and Effects on Earth

• Natural Satellite: The moon is Earth’s only satellite and orbits while rotating, keeping the same face towards Earth.

• Tidal Effects: Tides are influenced mostly by the moon due to gravitational pull, particularly having a significant impact despite the sun’s larger size.

• Tidal Variations: High tides occur on the side of the Earth facing the moon and also on the opposite side.

• Light at Night: The moon reflects sunlight, providing illumination during the night. Without the moon, nights would be much darker and the Earth’s rotation would be less stable.

Lunar Cycle and Phases

• Lunar Cycle: The moon undergoes a cycle of phases taking about 29.5 days from one New Moon to the next

• Phases Definition: Phases are determined by how much of the illuminated side of the moon is visible from Earth.

Moon Phases

1. New Moon: Not visible from Earth; rises at sunrise, sets at sunset.

2. Waxing Crescent: Increasing light; crescent shape visible in the west.

3. First Quarter: Half of the moon is visible (25% of the cycle completed); rises at noon, sets at midnight.

4. Waxing Gibbous: Majority of moon is illuminated; visible for most of the night.

5. Full Moon: Entire face visible; rises at sunset, sets at sunrise, halfway through the lunar cycle.

6. Waning Gibbous: Light decreasing; shape similar to Waxing Gibbous.

7. Last Quarter: Opposite half is lit; rises at midnight, sets at noon.

8. Waning Crescent: Decreasing crescent shape until the new moon phase begins again.

Visual Observation and Timing

• Each phase appears to last about three days to the naked eye. Scientists can pinpoint exact moments for phases like the full moon.

• The transition from full moon to waning gibbous shows a gradual decrease in size.