Educational Resources > Eclipse FAQs

In this section you will find a few basic questions and their answers about the 2017 eclipse courtesy of NASA.

Eclipses occur due to the special coincidence of the moon and the Sun being the same angular size. The Sun is 400 times wider than the moon, but it is also 400 times farther away, so they coincidentally appear to be the same size in our sky. This is what allows us the phenomenal beauty of the total solar eclipse. (Note: You can give the audience the experience of the change in apparent size of an object close by and the same object farther away. They can use their hands to measure angular size.)
Because the geometry required for a total solar eclipse has nothing to do with local noon. It has to do with when the lunar shadow sweeps across your location during the time when the Sun is above the horizon. Even so, it is certainly possible for the Sun to be in full eclipse before it rises at your particular location.
Eclipses only occur if the Moon is located within 0.5 degrees of the plane of the ecliptic, on a line that passes through the center of the Sun and the Earth. The Moon travels along an orbit that is inclined by 5 degrees to the ecliptic plane, so there are only two opportunities each month when it passes through the plane of the ecliptic. These points are called the ascending and descending nodes. Eclipses of the Sun only occur if new moon occurs when the Moon is near of one of these nodes. A similar argument explains why lunar eclipses do not occur every full moon at the node opposite the Sun from the Earth.
Probably not. Because of liability issues, it is very unlikely that any school on the path of totality will allow their children to be outside viewing the eclipse, because no matter how many times children are told to not look at the bright sun, some will try to do so, and this will lead to safety and legal issues. Many parents are likely to take their children out of school to view this rare event at home, and under parental supervision. It will likely be counted as an unexcused absence because it is not health-related.
King Henry I of England, the son of William the Conqueror, died in 1133 CE. This event coincided with a total solar eclipse that lasted over four minutes on August 2 . Historian William of Malmesbury recounts this “hideous darkness agitated the hearts of men”. After  King Henry’s death, a struggle for the throne threw the kingdom into chaos and civil war.
Historians and astronomers believe that the eclipse that they failed to forecast occurred on October 22, 2134 B.C.E, making it the oldest solar eclipse ever recorded in human history. The Babylonian eclipse on May 3, 1375 BCE is the oldest recorded in the western world, and there is evidence that the Babylonians knew about the Saros Cycle (18 years 11 days) and could use it to predict the approximate years of eclipses.
Other than watch it with  your family and friends, you may want to create a time capsule, which you would open on April 8, 2024 when the next total solar eclipse occurs over the continental United States. You might want to write a letter to your older self and describe what you think you might be doing in 2024, or include some of your favorite items, or a copy of your daily newspaper.
The only requirement for a total solar eclipse is that the angular size of the sun has to match the angular size of some other object that passes in front of it. When the disk of the object is smaller than the sun, this is called a transit. It is also called an eclipse when the disk of the object is much larger than the sun, but in general this would not allow the corona to be viewed, which is how we define total solar eclipses viewed from Earth. When humans were rooted to the surface of Earth, this was only the case for the moon as the eclipsing object. But there are many known moons and asteroids across our solar system, and from a suitable vantage point near any of them, we can find a distance where again the angular size of the object matches that of the sun to form a total solar eclipse. There are so many different vantage points  to choose from that each case has to be specified. For example, eclipses need not be observed from the surfaces of a planet. In fact, Venus and the outer planets have inaccessible surfaces. Instead, we might consider standing on the surface of a planetary moon and waiting for another moon to pass in front of the sun. Given the myriad of planetary moon orbits, finding those instances where the angular sizes match is a significant computational challenge.  Jupiter frequently passes across the sun as viewed from its moons, but its diameter is huge compared to the sun.  There are 5 satellites capable of completely occulting the Sun: Amalthea, Io, Europa, Ganymede and Callisto.  All of the others are too small or too distant to be able to completely occult the Sun, so can only transit the Sun.

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