Name: Star Systems and Types of Galaxies
Uploaded: 2019-07-19
Duration: 12 min 50 s
Description: Astronomers classify galaxies into three major categories: elliptical, spiral and irregular. Let's watch this video to know more about it.

Question

Why does the moon keep on changing its shape? Describe its various phases.

Accepted Answer

The moon will complete its rotation on its axis in $27$ days. It takes approximately the same time to revolve around the earth. During this process, the face of the moon that is visible from earth gets illuminated by the sunlight. The portion of the moon that gets illuminated keeps on changing due to its rotation. Therefore, the shapes of the moon are varied.

The various phases of the moon are as follows:

New moon: At this position, the moon is approximately in line between the earth and the sun. We see no moon in this position as we are looking at the dark side of the moon.

Increasing phase:

Waxing crescent: At this phase, a thin part (less than half) of the illuminated moon becomes visible.
Waxing gibbous: At this phase, most part (more than half) of the illuminated moon becomes visible.

Full moon: In this phase, the earth is in between the sun and the moon, due to which the full moon gets visible from earth.

Decreasing phase:

Waning gibbous: During this phase, the illumination region starts decreasing, and this phase represents the illuminated part which is lesser than the full moon but greater than the semicircle.
Waning crescent: During this phase, the region of illumination decreases further and only a thin portion of moon gets left with illumination.

Note: When moon forms a $90$ degrees with the sun and the earth, we see exactly half the moon.

Why does the moon keep on changing its shape? Describe its various phases.

Important Questions on Stars and the Solar System

Learn and Prepare for any exam you want !