The Moon's illuminated appearance changes over the month as it orbits Earth. What is this cycle called?

The Moon's illuminated appearance changes over the month as it orbits Earth. What is this cycle called?

• A. Lunar phases
• B. Tidal locking
• C. Eclipses
• D. Phase

Answer: (A)

Lunar phases describe the Moon's changing illuminated appearance as it orbits Earth. As the Moon moves around us, the Sun lights different portions of its surface that we can see, creating a sequence from new moon through crescents, first quarter, gibbous, full moon, and back to new moon. The full cycle takes about 29.5 days, the synodic month, because it depends on the relative positions of the Sun, Moon, and Earth. This is different from tidal locking, which is about the Moon always showing the same face to Earth, and from eclipses, which are temporary events when the Sun, Moon, and Earth align. The word phase can refer to one stage in the cycle, but the repeating progression as a whole is called the lunar phases.

Lunar phases describe the Moon's changing illuminated appearance as it orbits Earth. As the Moon moves around us, the Sun lights different portions of its surface that we can see, creating a sequence from new moon through crescents, first quarter, gibbous, full moon, and back to new moon. The full cycle takes about 29.5 days, the synodic month, because it depends on the relative positions of the Sun, Moon, and Earth. This is different from tidal locking, which is about the Moon always showing the same face to Earth, and from eclipses, which are temporary events when the Sun, Moon, and Earth align. The word phase can refer to one stage in the cycle, but the repeating progression as a whole is called the lunar phases.