UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
How it Works
Ask a Question
Search Topics
Our Scientists
Science Links
Contact Information
I wonder how the solar eclipse started.
Question Date: 2017-09-11
Answer 1:

To envision haw a solar eclipse works it is best to first have an idea about the motions of the earth and moon in the solar system.

First off, the earth orbits the sun once every year. From above the North Pole of the earth, the earth moves on a counter clockwise orbit about the sun. The earth’s orbit around the sun is confined to a plane. This plane is called the ecliptic. If you envision a basketball (diameter =10 inches) as the sun, the earth is 0.1 inch and the earth travels in the plane defined by the center of the sun and Earth.

Now, the moon travels along with the earth in an orbit around the sun but while doing that, the moon also orbits the earth itself. So if you draw a simple picture you will see that there will be numerous times when the moon gets between the sun and the earth. That is we might expect each MONTH to have the moon come in front of the earth and block our view of the sun!

But wait, there is something I did not mention. The orbit of the moon around the earth is NOT in the same plane as the orbit of the earth around the sun. The moon is about 5 degrees out of the plane of the ecliptic. This means that instead of having a solar eclipse every month (how boring) we have them more infrequently only at those times when the moon is in front of the sun AND when the two orbital planes - the earth around the sun and the moon around the earth intersect.

In order to visualize this take two pieces of paper… partially tear one and insert the torn piece into the other non-torn piece. You will see that if one body, say Earth is confined to its orbit (the ecliptic) whereas the other is the orbit of the moon INCLINED with respect to the ecliptic, then there are restricted number of times when both the SUN, Earth and Moon are co linear!!! It is precisely these times when a solar eclipse can occur.

I hope this picture helps you visualize the situation:

Answer 2:

An eclipse happens when the moon gets between the earth and the sun. The moon orbits the earth in a plane, and the earth orbits the sun in a plane as well. These planes are not perfectly aligned with each-other, otherwise there would be a solar eclipse every time we have a new moon, and also a lunar eclipse with every full moon. The fact that the planes are tilted relative to each-other means that the moon only comes between the earth and sun occasionally, but when it does, it casts a shadow. People in the moon's shadow on the earth's surface will see a solar eclipse.

Answer 3:

The solar eclipse started after the moon started orbiting around the earth. The moon might have formed when some huge thing crashed into the earth, and rocks from the earth and the huge thing broke off into space and formed the moon, which orbits the earth. That big crash might have started the earth's spinning on its axis, too.

This website talks about those things; it's from NASA, the National Aeronautics and Space Administration:

Where did the Moon come from? here

Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use