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Difficulty: EasyEarth, Moon, and Sun Interactions

As the Moon orbits Earth over roughly 29.5 days, observers on Earth see changing amounts of its sunlit side. Arrange the following four primary lunar phases in chronological order, starting from the beginning of a lunar cycle.

  1. 1New Moon
  2. 2First Quarter
  3. 3Full Moon
  4. 4Third (Last) Quarter

Answer

The correct chronological sequence from the start of the lunar cycle is New Moon, followed by First Quarter, then Full Moon, and finally Third (Last) Quarter.
A complete lunar cycle begins with the New Moon, progresses through the waxing stages to the First Quarter, reaches the opposite side of Earth as a Full Moon, and then wanes through the Third Quarter before returning to a New Moon.

Step-by-Step Solution

1
Identify the phase that begins the lunar cycle.
The New Moon occurs at the start of the cycle (0 days0\text{ days}) when the Moon aligns between Earth and the Sun.
The synodic month is measured starting from conjunction (New Moon).
2
Track the progression of illuminated phases as the Moon orbits counter-clockwise around Earth.
The Moon waxes through crescent phases to reach the First Quarter at approximately 7.4 days7.4\text{ days}, reaches Full Moon at approximately 14.8 days14.8\text{ days}, and wanes to the Third Quarter at approximately 22.1 days22.1\text{ days}.
The Moon orbits Earth in a counter-clockwise direction (viewed from above the North Pole), progressing through waxing phases before waning phases.

Key Concept

Lunar phase progression throughout a synodic month
Estimated Time:45s
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Topics

Earth, Moon, and Sun Interactions

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