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If the earth had no atmosphere, would comets still be visible from its surface? Would meteors? |
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2 | |
Why do comets have tails only in the vicinity of the sun? Why do these tails always point away from the sun, even when the comet is receding from it? |
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3 | |
When a comet is close enough to the sun to be seen from the earth, stars are visible through both the comet's head and tail. What does this imply about the danger to the earth from a collision with a comet? |
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4 | |
The Perseid meteor shower appears early every August. Does this mean that the orbits of the meteoroids in the Perseid swarm all have periods of exactly 1 year? |
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5 | |
Over 90 percent of the meteorites found after a known fall are stony, yet most of the meteorites in museums are iron. Why do you think this is so? |
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6 | |
How do the orbits of comets compare in shape with the orbits of the planets? |
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7 | |
(a) How is it possible to distinguish the planets from the stars by observations with the unaided eye? (b) By observations with a telescope? |
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8 | |
Is the mass of the solar system concentrated in the sun or in the planets? |
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9 | |
Why do the planets shine? |
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10 | |
Which planet is the brightest? How does its brightness compare with that of the brightest star? Which planet is the second brightest? |
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11 | |
Why is Venus a brighter object in the sky than Mars? |
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12 | |
Which planets would you expect to show phases like those of the moon? |
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13 | |
Suppose you were on Mars and watched the earth with the help of a telescope. What changes would you see in the earth's appearance as it moves around the sun in its orbit? |
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14 | |
Why are Mercury and Venus always seen either around sunrise or around sunset? |
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15 | |
Which is the largest planet? The smallest? Which planet is nearest the sun? |
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16 | |
Mercury takes 59 of our days to turn completely on its axis, but the period of time between one sunrise and the next on Mercury is 176 of our days. What do you think is the reason for the difference? |
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17 | |
On which planets would a person weigh less than on the earth? On which planets would a person weigh more? |
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18 | |
Which planet resembles the earth most in size and mass? In surface conditions? |
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19 | |
Is there any evidence that planets other than the earth today have crusts that consist of huge moving plates? |
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20 | |
Venus is brighter when it appears as a crescent than when we can see its full disk. Why? |
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21 | |
About how much time elapses between sunrise and sunset on Mars? On Jupiter? |
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22 | |
Which planets have crusts of rock? |
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23 | |
Why is it very unlikely that there is life on Mercury? |
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24 | |
Why is the average temperature on Mars lower than that on the earth? Why is there a greater variation in Martian temperatures? |
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25 | |
Mars has surface features that seem to be the result of erosion by running water. Why does the presence of many meteoroid craters in some of these regions suggest that the running water disappeared there long ago? |
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26 | |
Saturn's satellite Titan has an atmosphere. Do any of the other planetary satellites also have atmospheres? |
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27 | |
(a) Which planets besides Saturn have rings? (b) What is the nature of these rings? |
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28 | |
Which planets, if any, have no satellites? |
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29 | |
What are thought to be the chief constituents of the giant planets Jupiter, Saturn, Uranus, and Neptune? |
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30 | |
What is believed to be the nature of the Great Red Spot on Jupiter? |
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31 | |
Distinguish between asteroids and meteoroids. |
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32 | |
We always see the same hemisphere of the moon. Why? |
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33 | |
What is wrong with the statement that the moon is more useful to us than the sun because the moon provides illumination at night when it is needed most? |
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34 | |
The moon rises in the east at midnight on a certain night. Can it appear as a full moon? |
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35 | |
Approximately how much time elapses between new moon and full moon? |
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36 | |
Eclipses of the sun and of the moon do not occur every month. Why not? |
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37 | |
If the moon were smaller than it is, would total eclipses of the sun still occur? Would total eclipses of the moon still occur? |
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38 | |
In what phase must the moon be at the time of a solar eclipse? At the time of a lunar eclipse? |
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39 | |
To what approximate length of time on the earth does the length of "day" at a given place on the moon correspond? The length of "night"? |
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40 | |
Is the moon the largest satellite in the solar system? The smallest? |
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41 | |
If the moon circled Jupiter in an orbit the same size as its present one around the earth, would its period of revolution be the same, shorter, or longer? Why? |
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42 | |
What has been the chief influence that shaped the lunar landscape during the past 3 billion years? |
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43 | |
The moon's maria are dark, relatively smooth regions conspicuous even to the naked eye. What is their nature? |
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44 | |
The moon's surface is about as irregular as that of the earth. What does this imply about temperatures in the moon's interior? |
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45 | |
Moonquakes are weaker and occur much less often than earthquakes. What do these facts imply about temperatures in the moon's interior? |
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46 | |
Why is it believed that the moon's interior is different in composition from the earth's interior? |
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47 | |
The densities of rocks on the moon's surface are about the same as the density of the moon as a whole. What does this observation suggest about the thermal history of the moon? |
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48 | |
Why is it believed that large-scale igneous activity ceased on the moon about 3 billion years ago? |
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