Word: earthly
(lookup in dictionary)
(lookup stats)
Dates: during 1950-1959
Sort By: most recent first
(reverse)
After a few more moments on the evolutionary time scale, earth's restless social primate, man, can almost surely make himself felt throughout the system. Earth's life will no longer be confined to the earth. This startling development took place with explosive suddenness. Boys still in high school remember a time when sensible citizens considered space flight as impractical as hunting leprechauns. Only ten years ago the altitude record for rockets, 250 miles, was held a brilliant achievement. Only two years ago, the earth satellite, that humblest of space vehicles, seemed an almost impossible project...
...engine burns out, the rocket continues upward under the control of Newton's first law: . . . A body in motion continues to move at constant speed in a straight line unless acted upon by an unbalanced force. As it rises, it slows and curves because an unbalanced force, the earth's gravitation, keeps pulling at it in obedience to Newton's law of gravity: Each particle of matter attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them...
...fight free of the earth, the space navigator must reach a speed called escape velocity. Figured at the surface of the earth, this is 25,000 m.p.h. But rockets do not start suddenly. They accelerate gradually, keeping their speed fairly low while still in the atmosphere, then spurting quickly. If a rocket is moving 24,000 m.p.h. when it is 300 miles above the surface, it will escape from the earth's gravitation. When the Russian Lunik launchers, watching their bird with Doppler (speed-measuring) radios, saw it pass the critical speed, they knew it would never return...
Near the rim of the earth's gravitational pit is a much smaller pit belonging to the moon. An object shot away from the earth at 24,800 m.p.h. will reach the boundary, about 34,000 miles short of the moon, where the moon's pull is as strong as the earth's. If it reaches this point with a small velocity, it will fall on the moon. If it crosses the line at good speed, it will shoot past the moon, its course merely deflected. This is what happened to the Lunik...
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...