Solar & Lunar Eclipse_sadiq_fdk

Solar & Lunar Eclipse LUNAR ECLIPSES The earth, lit by the sun, casts a long, conical shadow in space. At any point within that cone the light of the sun is wholly obscured. Surrounding the shadow cone, also called the umbra, is an area of partial shadow called the penumbra. The approximate mean length of the umbra is 1,379,200 km (857,000 mi); at a distance of 384,600 km (239,000 mi), the mean distance of the moon from the earth, it has a diameter of about 9170 km (about 5700 mi). A total lunar eclipse occurs when the moon passes completely into the umbra. If it moves directly through the center, it is obscured for about 2 hours. If it does not pass through the center, the period of totality is less and may last for only an instant if the moon travels through the very edge of the umbra. A partial lunar eclipse occurs when only a part of the moon enters the umbra and is obscured. The extent of a partial eclipse can range from near totality, when most of the moon is obscured, to a slight or minor eclipse, when only a small portion of the earth’s shadow is seen on the passing moon. Historically, the view of the earth’s circular shadow advancing across the face of the moon was the first indication of the shape of the earth.

. SOLAR ECLIPSES The length of the moon’s umbra varies from 367,000 to 379,800 km (228,000 to 236,000 mi), and the distance between the earth and the moon varies from 357,300 to 407,100 km (222,000 to 253,000 mi). Total solar eclipses occur when the moon’s umbra reaches the earth. The diameter of the umbra is never greater than 268.7 km (167 mi) where it touches the surface of the earth, so that the area in which a total solar eclipse is visible is never wider than that and is usually considerably narrower. The width of the penumbra shadow, or the area of partial eclipse on the surface of the earth, is about 4828 km (about 3000 mi). At certain times when the moon passes between the earth and the sun,

its shadow does not reach the earth. At such times an annular eclipse occurs in which an annulus or bright ring of the solar disk appears around the black disk of the moon. The shadow of the moon moves across the surface of the earth in an easterly direction. Because the earth is also rotating eastward, the speed of the moon shadow across the earth is equal to the speed of the moon traveling along its orbit, minus the speed of the earth’s rotation. The speed of the shadow at the equator is about 1706 km/h (about 1060 mph); near the poles, where the speed of rotation is virtually zero, it is about 3380 km/h (about 2100 mph). The path of a total solar eclipse and the time of totality can be calculated from the size of the moon’s shadow and from its speed. The maximum duration of a total solar eclipse is about 7.5 minutes, but these are rare, occurring only once in several thousand years. A total eclipse is usually visible for about 3 minutes from a point in the center of the path of totality.

Topic:- Solar & Lunar eclipse • Class :- 7th • Prepared by :- Harwinder singh • Computer faculty • G. S. S. S. Jand Sahib. • Faridkot. •