Solar & Lunar Eclipses

Are the Sun & Moon the same size?

Are the Sun & Moon the same size? The sun is 400x larger (diameter) than the moon The moon is 400x closer to Earth than the sun This ratio is what enables total solar eclipses This fluke of nature enables total eclipses of the sun to occur. Based on the size and distance comparisons of the sun & moon, the moon seems to fit exactly inside the sun during a total eclipse. They seem, from Earth that they are the same size!

Shadows & Light Umbral shadow – Darkest part Penumbral shadow – Lighter part Umbral Shadow blocks all sunlight and is a slender cone shape. Penumbral shadow is a lighter, funnel shape that partially blocks sunlight. The shadows are created by the Moon and are cast upon the Earth.

Total Solar Eclipses About 2-4 per year on average Rare to see Can occur during a New Moon phase Only the outermost part of the Sun (Corona) is visible at totality Umbral shadow 8/21/17 – Total eclipse over North America (Oregon to Georgia) You need to be in the umbral shadow the moon is casting on Earth to see the total eclipse. The shadow can travel over 1/3rd of the Earth’s surface Total eclipses can last up to 8 minutes but are usually shorter.

Total Solar Eclipse

Partial Solar Eclipses 35% of all solar eclipses are partial More prevalent due to less reliance on Sun/Moon size & distance ratio Can occur during a New Moon phase Varying amounts of Sun will be seen Penumbral shadow A partial solar eclipse occurs when only the penumbra (the partial shadow) passes over you. In these cases, a part of the sun always remains in view during the eclipse. How much of the sun remains in view depends on the specific circumstances. Usually the penumbra gives just a glancing blow to our planet over the polar regions; in such cases, places far away from the poles but still within the zone of the penumbra might not see much more than a small scallop of the sun hidden by the moon. In a different scenario, those who are positioned within a couple of thousand miles of the path of a total eclipse will see a partial eclipse. The closer you are to the path of totality, the greater the solar obscuration. If, for instance, you are positioned just outside of the path of the total eclipse, you will see the sun wane to a narrow crescent, then thicken up again as the shadow passes by.

Partial Solar Eclipse From May 2012

Total Lunar Eclipses Can occur during a Full Moon phase Moon passes through Earth’s umbral shadow Partial eclipses will be seen on either side of totality Everyone on the night side of Earth can see Lunar eclipses Earth’s full (umbral) shadow falls on the moon. The moon won’t completely disappear, but it will be cast in an eerie darkness that makes it easy to miss if you were not looking for the eclipse. Some sunlight passing through Earth’s atmosphere is scattered and refracted, or bent, and refocused on the moon, giving it a dim glow even during totality.

Partial Lunar Eclipses Can occur during Full Moon phase Moon passes through Earth’s penumbral shadow Everyone on the night side of Earth can see Lunar eclipses

Draw the Solar eclipse

Draw the Lunar eclipse

Why don’t eclipses happen every month? Moon is on a 50 inclined plane (tilted orbit) compared to Earth Shadows of Moon & Earth typically miss each other Only perfect or near perfect alignments create the eclipses If the sun, Earth and moon were truly lined up perfect, this would be the case. But the reality is that they're not lined up. The moon is actually on an inclined plane to the Earth. Imagine the solar system is a flat disk, like a DVD. This is the plane of the ecliptic, and all of the planets are arranged in that disk. But the moon is on another disk, which is inclined at an angle of 5.14 degrees. So, if you follow the orbit of the moon as it goes around the Earth, sometimes it's above the plane of the ecliptic and sometimes it's below. So the shadow cast by the moon misses the Earth, or the shadow cast by the Earth misses the moon.

Moon orbit around Earth