Phases of the Moon

When we observe the sky daily for some days, we find that the moon changes its shape every day. It is called phases of the moon.

Phases of the moon occur because of following reasons:

• The moon is the non-luminous body and reflects the sunlight.
• The moon is revolving around the earth in its elliptical orbit.

When the moon forms an angle of 0⁰ from the plane of earth’s orbit, the whole dark part of the moon faces towards the earth and hence any part of the moon is not seen i.e. a new moon(m1). After 24 hours, when the moon forms an angle 12⁰ with the plane of its orbit, a little bright part of the moon faces towards the earth and a minimum part of the moon is seen bright. It is called waxing crescent (m2). When moon forms an angle of 90⁰, the bright part of the moon is seen in the form of the hemisphere which is called a first quarter (m3). When moon forms an angle of 168⁰, very little part of the moon remains in the dark which is called waxing gibbous (m4). When moon forms an angle of 180⁰ from the plane, the moon is seen completely round, which is called the full moon. When moon forms an angle of 192^o from the plane very little part is covered by the darkness and it is called waning gibbous (m6). When moon forms an angle of 270⁰, the moon is seen in the form of hemisphere again, which is called last quarter (m7). When moon forms an angle of 384⁰, very little part of the moon is seen in the sky and it is called waning crescent (m8). After completing an angle of 360⁰ by the moon in its orbit again, the new moon occurs.

Some interesting facts about the moon:

• The moon rises about 50 minutes late daily.
• The time of sunrise and moonrise is same on the new moon.
• On the full moon, the moon rises, at the time of the sunset.
• Moon rises at the mid-day on the first quarter.
• The moon rises at the midnight in the last quarter.
• The moon rises about 50 minutes after the sunrise on the waxing crescent.
• The moon rises about 50 minutes before the sunset on the waxing gibbous.