HW - 13) What is the line of nodes? Why is it important to...

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Lauren Collier 1/31/2011 Chapter 3 Questions 9) What is the difference between a sidereal month and a synodic month? Which is longer? Why? A sidereal month is the time that it takes the Moon to complete one full orbit around the Earth. A synodic month is the time that it takes for the Moon to complete one full cycle of phases. The synodic month is longer because the Earth is orbiting the Sun while the Moon is orbiting the Earth so the Moon has to travel a little more than 360 degrees. 11) What is the difference between the umbra and the penumbra of a shadow? The umbra of a shadow is the darkest region where no portion of the Sun's surface can be seen. In the penumbra of a shadow, a portion of the Sun's surface can be seen.
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Unformatted text preview: 13) What is the line of nodes? Why is it important to the subject of eclipses? The line of nodes are the points at which the Moon's orbit and Earth's orbit intersect. When the Moon is on the line of nodes, eclipses can occur. In order for eclipses to occur, the Earth and the Moon must be in line with one another. 20) How is an annular eclipse of the Sun different from a total eclipse of the Sun? What causes this difference? An annular eclipse of the Sun occurs when the Moon's umbra doesn't reach the Earth. This happens when the Moon is at its farthest distance from the Earth. During an annular eclipse, the Moon doesn't completely cover the Sun. During a total eclipse of the Sun, the Moon completely covers the Sun....
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