Moon in our solar system does not shine by its own light but in fact it is visible to us on earth because it reflects light from the sun, this phenomenon is known as moon’s Albedo. Albedo is basically the reflecting power of a surface and it is measured on a scale of 0 to 1; 0 means low reflection and 1 means high or low reflection. Our Moon’s average visual Albedo is 0.12 comparatively our earth has an average Albedo of 0.37. Moon’s Albedo varies from 0.07 as its darkest point and 0.24 as it’s lightest.
Moon orbits around the earth every 29.5 earth days and at all times half of the moon is lit by the sun. The other half of the moon is in darkness as it is facing away from the sun. We can see more and more of the lit side of the moon as it orbits around the earth. This process changes slowly and these changes are known as the phases of the moon.
When the moon is between the sun and the earth it is called the new moon and it rises and sets at the same time as the sun but it is not visible to us because the side being lit by sun cannot be seen from earth. Basically the Moon is not totally invisible to us at this point, because there is other light in the universe that it reflects, including the light the Earth itself reflects from the Sun to the Moon, but generally, a New Moon is very difficult for the naked eye to see.
One week after the new moon, first we see a slim crescent also known as the horned moon and then the moon looks like a half circle. This stage is known as the first quarter because the moon has completed one-quarter of its orbit around the earth. Half of the moon’s sunlight is visible from earth at this stage. This first quarter moon rises at noon and sets at midnight.
After a week when the moon grows out of the first quarter this process is called waxing. Now the moon has moved to a point where the earth is between the moon and the sun. We can now see the entire side of the moon lit by the sun. This full moon rises as the sun sets and sets as the sun rises. The Moon is said to be ‘gibbous’ when it is larger than a semi-circle, but not yet a full circle. One week after the full moon the moon again looks like a half circle and it is called the last quarter because the moon has completed the last quarter of its orbit around the earth. Now half of the moon’s sunlit side is again visible from earth.