The moon revolves around the earth in a plane slightly inclined (5 degrees) to the earth's orbit. Eclipses occur when sun, moon, and earth are aligned in a straight line.
When the moon is in between the earth and the sun we get to see the dark side of the moon called the new moon.
However due to the inclination of the moon's plane with respect to the earth, the moon does not block the sun's light every time it passes between the earth and sun. When the new moon occurs close to the sun, the sun's light is partially obscured resulting in a partial solar eclipse. On rare occasions, the moon directly moves between the sun and the earth blocking the sun's light from reaching the earth thus producing a total solar eclipse. On such occasions the sun, moon and the earth are in the same plane (and in a straight line).
Similarly, when the moon is on the opposite side of the earth from the sun we get to see a full moon.
At certain times the moon passes directly through the centre of the earth's shadow called the umbra. This results in the earth completely blocking the moon from the sun. The net result of this alignment is the total eclipse of the moon otherwise known as the total lunar eclipse. When the moon just grazes the earth's shadow passing within the penumbra we see the moon eclipsed only slightly.
This is partial lunar eclipse. Since the moon is not directly aligned with the earth and sun, the earth's shadow rarely falls on the moon. The inclination of the moon's plane with respect to the earth's orbit thus does not result in a total solar and total lunar eclipse every 28 days.
Published in The Hindu on June 27, 2002.
When the moon is in between the earth and the sun we get to see the dark side of the moon called the new moon.
However due to the inclination of the moon's plane with respect to the earth, the moon does not block the sun's light every time it passes between the earth and sun. When the new moon occurs close to the sun, the sun's light is partially obscured resulting in a partial solar eclipse. On rare occasions, the moon directly moves between the sun and the earth blocking the sun's light from reaching the earth thus producing a total solar eclipse. On such occasions the sun, moon and the earth are in the same plane (and in a straight line).
Similarly, when the moon is on the opposite side of the earth from the sun we get to see a full moon.
At certain times the moon passes directly through the centre of the earth's shadow called the umbra. This results in the earth completely blocking the moon from the sun. The net result of this alignment is the total eclipse of the moon otherwise known as the total lunar eclipse. When the moon just grazes the earth's shadow passing within the penumbra we see the moon eclipsed only slightly.
This is partial lunar eclipse. Since the moon is not directly aligned with the earth and sun, the earth's shadow rarely falls on the moon. The inclination of the moon's plane with respect to the earth's orbit thus does not result in a total solar and total lunar eclipse every 28 days.
Published in The Hindu on June 27, 2002.
