单选题 Nowadays the scattering of galaxies and the astounding abundance of stars are forcing those who ponder such matters to a further adjustment of their concept of the place and function of a man in the material universe.
In the history of the 1 human mind, with its increasing knowledge of the surrounding 2 , there must have been a time when the philosophers of the 3 tribes began to realize that the world was not simply centered on a man himself. The geocentric concept, which accepted a universe centered on the earth, then became common 4 .
The second adjustment in the understanding of a man"s 5 to the physical universe was not generally acceptable 6 the sixteenth century. Copernican revolution soundly 7 the heliocentric concept—the theory of a universe 8 on the sun. A man is a stubborn adherent to official dogma; 9 , however, he accepted the sun as the center.
Then, forty years ago, came the need for a third adjustment. This 10 has deeply exploded a man"s pride and 11 , for it has carried with it the knowledge of the 12 number of galaxies.
The galactocentric universe 13 puts the earth and its life near the 14 of one great galaxy in a universe of millions of galaxies. A man becomes peripheral among the billions of stars of his own Milky Way; and, according to the revelations of paleontology and geochemistry, he is 15 and apparently transient in the 16 of cosmic time.
The downgrading of the earth and sun and the elevation of the galaxies is not the end of this 17 of scientific pilgrims through philosophic fields. The need for another 18 adjustment now 19 —not wholly unexpected by scientists, 20 wholly the result of one or two scientific revelations.
Our new problem concerns the spread of life throughout the universe. As unsolicited spokesmen for all the earthly organisms of land, sea, and air, we ask the thrilling question: are we alone?