Solar Eclipses

Both the Earth and the Moon have elliptical (or squished) orbits. The Sun-Earth orbit has an eccentricity (or variation from circularity) of approximately 1.67 %, and the Moon-Earth orbit has an eccentricity of 5.49%. As a result, sometime the Moon is too far away to cast an umbral shadow. In such cases, viewers experience an annular eclipse. In this case, when the Moon is fully over the Sun, there is still a ring of the Sun, or annulus, showing.In this animation, we generate solar eclipses by varying the Sun-Earth and Moon-Earth distances. The yellow slider varies the Sun-Earth distance, and the other slider varies the Moon-Earth distance. For the Sun slider, the A and P refer to the aphelion and perihelion of the Earth's orbit around the Sun. For the Moon slider, the A and P refer to the apogee and perigee of the Moon's orbit around the Earth. The "D sub s" counter gives the Sun-Earth distance, and the "D sub m" counter gives the Moon-Earth distance. The "D sub u" counter gives the diameter of the umbral shadow cast (if any), and the "D sub p" counter gives the diameter of the penumbral shadow cast. All distances are in km. The "T sub u" counter gives the time of totality (total blockage of the Sun's light for a viewer in the umbral shadow), and the "T sub p" gives the time in minutes of partial blockage of the Sun's light in the penumbral shadow. All times are in minutes.When you play with this animation, see what scenarios create annular solar eclipses, and which create total solar eclipses. What is the longest time of totality that you can create? Does this make sense? Also, use the "D sub u" and "T sub u" counters to determine the speed of the umbral shadow across the face of the Earth.

If you would like to see an animation of a solar eclipse from the perspective of outer space, as represented by the image to the left, click here to download the animation. You will need the program VLC Media Player, or similar, to view it.