Word: moone
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Dates: during 1950-1959
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Solar Orbit. The earth and moon, whirling around each other, are not alone in space. They also orbit around the sun, and so do the other planets. A gravity chart of the solar system shows an enormously deep pit, the sun's, with much smaller pits in its slope, one for each planet. When a spaceship has climbed out of the earth's gravitational pit, it is still deep in the sun's pit. This does not mean that it will fall into the sun. Besides the comparatively small speed contributed by its own engine, it also...
...successful launching. Mars never comes closer to the earth than 34.5 million miles, Venus never closer than 25 million miles. To cover these great distances, it takes more time (146 days to Venus, 260 days to Mars), but only slightly more speed than is needed to go to the moon, which is only 230,000 miles away. This is because space between the planets is comparatively smooth. It is only slightly affected by planetary gravitation, and the great pull of the sun is countered by the orbital speed that a spaceship inherits from its home planet...
Controversial Moon. The moon is an exception. It is so close that it shows a wealth of detail that astronomers have studied for centuries. They have also argued bitterly over many questions presented by its serene face, e.g.: Are the ring-shaped craters the result of volcanic activity or meteor impacts...
Dutch-born Astronomer Gerard Kuiper (rhymes with hyper), head of the University of Chicago's Yerkes and McDonald observatories, thinks the moon was formed at the same time as the earth (5½ billion years ago), but at first it revolved only about 20,000 miles from the earth's surface. Beyond it were a lot of smaller satellites arranged in a disk somewhat like the rings of modern Saturn...
This situation did not last. When the earth acquired oceans, the great tides aroused in them by the nearby moon made the earth rotate more slowly. This made the moon spiral outward. As it moved, it crashed into the lesser satellites, each of them blasting an impact pit in its surface. The bigger pits punched through the moon's crust and were filled with lava from the molten interior. The biggest satellite of all, about 100 miles in diameter, hit the present site of the lunar plain called Mare Imbrium-the right eye of the "man in the moon...