As the moon circles the earth, the shape of the moon appears to change. a full moon appears as an entire circle in the sky. this happens when the

A Full Moon occurs when the Moon is on the opposite side of the Earth from the Sun.

Explanation:

Call the plane of the earth’s orbit around the sun horizontal. Then imagine a vertical plane thru the centers of the sun and the earth, that rotates as the earth moves around the sun. Once every 29.5 days or so the center of the moon passes thru that vertical plane, on the far side of the earth from the sun, and that moment is the full moon. The plane of the moon’s orbit is tilted enough that as it passes that point it usually misses the earth’s shadow.

they should be similar or the same

hypothesising or postulating