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Astronomy Test One Review

Astronomy Test One Review - Astronomy Test One Review...

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Astronomy Test One Review Review and Discussion 1. How and why does a day measured by the Sun differ from a day measured by the stars? A day measured by the Sun differs from a day measured by the stars in that the time measure by the Sun is called solar day, which is longer (3.9min longer) than the day measured by stars, which is called a sidereal day. This is because the Earth has to rotate and the interval of time between two noons is slightly greater than the true rotation period. 2. How many times in your life have you orbited the Sun? However many years you have been living, as it takes one year to orbit the sun. 3. Why do we see different stars at different times of the year? Because the Earth revolves around the sun, and the stars are on an ecliptic. 4. Why are there seasons on Earth? Because of the tilt of Earth’s rotation axis relative to the ecliptic 5. What is precession, and what is its cause? Precession is is the change in direction of Earth’s axis over time (26,000 yrs). It’s causes the vernal equinox to drift slowly around the ecliptic. 6. If the sun always lights one complete hemisphere of the Moon, why do we see different phases of the Moon? We see different phases of the Moon because the Moon orbits Earth. 7. What causes a lunar eclipse? A solar eclipse? Why aren’t there lunar and solar eclipses every month? A lunar eclipse is caused when the sun and moon are in opposite directions as seen from Earth. A solar eclipse is caused when the sun and moon are in the same direction as seen from Earth. Neither occur every month because the moon’s orbit is slightly inclined to the plane of the ecliptic 8. Do you think an observer on another planet might see eclipses? Why or why not? No, because the planet would have to have its own moon line up with the Sun. 9. What is a parallax? Give an everyday example. A parallax is the displacement of a foreground object relative to the background as the observer’s location changes. For example, holding out a finger in front of an object and closing one eye, then the other.
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