Q. Why is solar and lunar eclipse not seen from all parts of the earth at the same time?

I think its because of the revolution of the earth but i am not sure. I want a more reliable answer.

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    $\begingroup$ What research have you done to try to figure this out? $\endgroup$ – HDE 226868 Jan 10 '16 at 17:01
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    $\begingroup$ It has to do with position. See picture: scienceblogs.com/startswithabang/files/2008/02/… The sun being bigger than the moon means the Moon's shadow grows smaller as it approaches the earth. The Earth is big enough to cast a shadow over the entire moon, but the Moon's shadow on the earth is quite small. About the size of a large state (ballpark) and it moves across the earth fairly quickly. $\endgroup$ – userLTK Jan 11 '16 at 6:47

Eclipses are a temporal alignment of the 3 bodies mentioned. Because those bodies are in constant relative motion -- and you have to be in the right location relative to that alignment to experience it (at least for solar eclipses) -- not everyone gets to see them.

In particular, to view a solar eclipse, you need to be somewhere "in line" with the line from 1) the center of the earth to 2) the moon to 3) the sun ... Of course, moon's shadow on the earth is not just a point on the earth but a circle, so you don't have to be precisely "in line", but close (within a few dozen miles, but you can do this computation yourself if you know the diameter of the earth, moon and sun). The circular shadow that crosses the surface of the earth moves in time (as the moon revolves around the earth and as the earth moves about the sun) so different places see it at different times. Finally, when the eclipse is over, it means that the moon's shadow has moved off the earth's surface and back out into space (where it is +99% of the time).

For lunar eclipses, you only have to be able to view the moon (at night and during the period of eclipse of course). That means if you can see the moon (about 1/2 the surface of the earth can see the moon at any time) you'll see the eclipse! This is because the entire earth is casting the shadow on the moon and when you can see the moon, by definition, you are on the side of the earth that is casting the shadow and hence in position to see that shadow transit the moon.

Again: all these effects are temporal since the earth/moon system is moving constantly (relative to the sun).

  • $\begingroup$ Yes, for a lunar eclipse you are looking at the Earth's shadow on the Moon. For a solar eclipse it is the Moon's shadow on the Earth - ie if you were on the Earth facing side of the Moon you could see the darkened patch caused by the Moon's shadow in much the same way as we can see it for a lunar eclipse. $\endgroup$ – adrianmcmenamin Jan 18 '16 at 21:22

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