If the moon is completing the rotation of the earth every month shouldn’t eclipse be a monthly phenomenon
In: 1
The moon’s orbit is tilted with respect to the Earth and the Sun. This means that most of the time, when the Moon is between the Earth and the Sun, or the Earth is between the Moon and the Sun, the moon is actually “above” or “below” when viewed from the side, which means the shadow is also “above” or “below,” and thus there’s no eclipse. [This video might help explain it.](https://www.youtube.com/watch?v=v9TM-67pRDA)
It has to do with the tilt of the Earth’s axis. The moon is actually slightly tilted relative to Earth’s orbit around the sun. So, when it passes between us and the sun, sometimes it will cover up most of the sun (a total eclipse), and sometimes only a little bit of it (a partial eclipse). And sometimes we’ll be on the far side of the moon from where it passes in front of the sun and won’t see anything (a no-eclipse). And how does that happen Why doesn’t it always align itself in such a way that there is an eclipse once every month Good questions! The reason for this has to do with some details about how gravity works. It turns out that if you have two objects orbiting each other, they tend to line up so that one body never passes right through another body’s shadow. So, since both Earth and Moon are orbiting around each other, they will stable orbits so that neither ever crosses into each others’ shadows while they are doing their orbits around each other. But because they’re also orbiting around different things at different speeds [Earth goes faster as it’s bigger], this alignment is not exactly
Lunar eclipses are reasonably rare becauase the moon must pass through opposition while also on the node between lunar and terrestrial orbits. Solar eclipses are more frequent, but most are only visible from polar regions.
The earth moves around the sun in a nearly circular orbit. You can imagine a circular flat plate that extends from the sun with the earth running around its perimeter.
The moon moves around the earth in a similar fashion and you can imagine a similar plate extending from the earth.
The KEY point is that those 2 plates are not coincident because the orbit of the moon is at an angle to the orbit of the earth. (NOT related to the tilt of the earth’s axis btw).
Eclipses only happen when all 3 bodies are in a straight line (in 3D). In most cases when the moon is full (i.e. in a straight line in 2D) it lies above or below the shadow of the earth (which will be on the ‘plate’ delineating the earth’s orbit)
It should also be noted that by the geometry of the sizes of the bodies and their orbits the shadow of the earth at the distance of the moon is not very much bigger than the moon itself. That is why a) Lunar eclipses don’t last long, and b) why partial eclipses are much more common than total.
The same applies for when the moon is between the earth and sun – creating a solar eclipse.
Latest Answers