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This is the fifth in a series of articles by retired science teacher Dan Slais to help Parkland residents prepare for the April 8 solar eclipse that will be visible in southeast Missouri. – Editor
An eclipse is a blocking of light when one heavenly body moves into the shadow of another heavenly body. Both the Sun and the Moon can get caught in shadows and disappear from view of the Earth.
A lunar eclipse occurs in the full moon phase when the Moon is in alignment with the Earth-Sun plane. The shadow of the earth crosses the Moon, creating three types of eclipses. The umbra portion of the earth’s shadow is where the direct or umbra shadow of the sunlight is blocked. This umbra will produce a total lunar eclipse if the whole Moon is in the umbra.
If only part of the Moon is in the umbra shadow, then it will be a partial lunar eclipse. The penumbra shadow is not the direct shadow, and only some of the light is blocked. Most of the time, the penumbral eclipse is faint and not noticeable.
Solar eclipses occur when the Moon is in the New Moon phase or between the Earth and the Sun. The Moon has to be in alignment with the Sun-Earth plane. Often, the alignment will place both the solar and lunar eclipse two weeks from each other. This spring, a penumbral lunar eclipse will happen on March 25, two weeks ahead of the total eclipse on April 8.
Both a total or partial eclipse of the Moon is all reflected light of the Sun and presents no danger to the eyes.
There are also more eclipses on the way in 2024. Some of the world will see a partial lunar eclipse on Sept. 18, which will precede another annular solar eclipse on Oct. 2. The path of the solar eclipse goes across the Pacific NE to SW and crosses South America, southern Chile, and Argentina.
There are three types of solar eclipses. A partial solar eclipse is when one sees only part of the Sun blocked out. A total solar eclipse is when the whole Sun is covered, like what will be seen in April, and the third type is called an annular eclipse. It happens when the Moon is at apogee — its farthest distance from Earth, according to Kepler’s Laws — and produces a smaller shadow that fits inside the Sun and cannot produce totality. This is the “ring of fire” eclipse like the one seen in the United States on Oct. 14.