Phases of the Moon

The correct answer is option 'A', which states that the change in the size of the moon when viewed from Earth is called the phases of the moon. The moon goes through a continuous cycle of changing appearances, which are known as its phases. These phases are a result of the relative positions of the sun, Earth, and moon.

Explanation:
The moon does not emit light of its own, but rather reflects sunlight. As the moon orbits around the Earth, the amount of the moon's surface that is illuminated by the sun changes, leading to the different phases of the moon.

The Phases of the Moon:
1. New Moon: During a new moon, the moon is positioned between the Earth and the sun, with the side of the moon that is illuminated facing away from Earth. As a result, the moon appears dark or completely invisible.

2. Waxing Crescent: After the new moon, a small sliver of the moon becomes visible. This is known as the waxing crescent phase. The illuminated portion of the moon increases gradually.

3. First Quarter: During the first quarter phase, half of the moon's surface that faces Earth is illuminated. It appears as a half-circle shape.

4. Waxing Gibbous: Following the first quarter, the illuminated portion of the moon continues to grow. The waxing gibbous phase refers to the increasing illumination of the moon's surface.

5. Full Moon: A full moon occurs when the Earth is positioned between the sun and the moon, with the sun fully illuminating the side of the moon facing Earth. The moon appears as a complete circle during this phase.

6. Waning Gibbous: After the full moon, the illuminated portion of the moon gradually decreases. This phase is known as the waning gibbous.

7. Third Quarter: During the third quarter phase, half of the moon's surface that faces Earth is illuminated, resembling a half-circle shape.

8. Waning Crescent: The final phase before the new moon is the waning crescent. Only a small sliver of the moon is illuminated, and it continues to decrease until it reaches the new moon phase again.

Conclusion:
The change in the size of the moon when viewed from Earth is not due to any physical alteration in the moon's size but is a result of the varying amount of the moon's illuminated surface that is visible to us. This cyclical change in appearance is known as the phases of the moon.