AS101ps2

# AS101ps2 - J.I AS101 Problem Set#2 15 What do we mean by...

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J.I. AS101 Problem Set #2 6/4/07 15. What do we mean by the apparent retrograde motion of the planets? Why was it difficult for  ancient astronomers to explain but easy for us to explain? The apparent retrograde motion of the planets is the observed movement of the planets in the sky as they pass a certain point they would appear to move backwards in their orbit. This data did not fit into the ancient astronomer’s model of an Earth centered system. Later other astronomers came up with the concept of epicycles to attempt to explain the retrograde movement. The epicycles were a clear method for recreating the movement. The issue was that the data did not exactly match up and still they could not accurately predict the motion of the planets. It is easier for modern astronomy to explain the motion after the onset of the sun centered system paired with the elliptical orbit all data fell into place and accurate predictions could be made. It is also technology that aids in this data. Being able to see through great zooms the phases of the planets as they passed the sun allows us to further confirm this concept. 34. The fact that we always see the same face of the Moon tell us that: (a) the Moon does not rotate.  (b) the Moon’s rotation period is the same as its orbital period. (c) the Moon looks the same on both  sides. (b) The Moon’s rotation period is the same as its orbital period. This is the only way this can be possible. The Moon’s rotation takes the same amount of time as the orbit, so every time it circles the earth it completes a rotation. You can picture a person facing the earth and taking a slow rotation while completing one walk around the earth. From the earth it appears that the person has always faced the earth. This is the same as the Moon with the Earth. It is also important to note that the Moon’s synchronous rotation is not perfect and that is why we are able to see approximately 59% of the moon’s surface over time even though only 50% is visible at any moment.

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39. View from the Moon. Assume you live on the Moon near the center of the face that looks toward  Earth.     a. Suppose you see a full Earth in your sky. What phase of the Moon would people on Earth see?  Explain.    b. Suppose people on Earth see a full moon. What phase would you see for Earth? Explain.    c. Suppose people on Earth see a waxing gibbous moon. What phase would you see for Earth?  Explain.    d. Suppose people on Earth are viewing a total lunar eclipse. What would you see from your home  on the Moon? Explain. (a) A full Earth would mean the people on Earth would see a new Moon. This is because
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AS101ps2 - J.I AS101 Problem Set#2 15 What do we mean by...

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