Extraterrestrial Civilizations by Isaac Asimov

of humanity.
    On October 30, 1938, for instance, nearly forty years after
War of the Worlds
was published, Orson Welles (1915–), only twenty-three years old at the time, produced a radio dramatization of the story. He chose to bring the story up to date, and had the Martians land in New Jersey rather than in Great Britain. He told the events in as realistic a fashion as possible, with authentic-sounding news bulletins, eye-witness reports, and so on.
    Anyone who had turned the program on at the start would have been informed that it was fiction, but some weren’t listening closely enough and others turned it on after the start and were transfixed at the events that were apparently taking place—especially those who were near the sites of the reported landings.
    A surprising number of people did not pause to question whether it was at all likely that there was an invasion of Martians, or whether there were even Martians at all. They took it for granted that Martians existed and had arrived to conquer Earth and were succeeding. Hundreds got into their automobiles and fled in terror. Like the Moon Hoax of just a century before, it was a remarkable example of how ready people were to accept the notion of extraterrestrial intelligence.
    Though Lowell and his theories concerning the Martian canals were successful with the general public, professional astronomers were extremely doubtful. At least the large majority were.
    A number insisted that though they looked at Mars carefully, they never saw any canals, and they were not soothed by Lowell’s lofty assurance that their eyes and telescopes just weren’t good enough. The American astronomer Asaph Hall (1829–1907), whose eyes had been good enough in 1877 to discover the tiny Martian satellites, never saw a canal.
    One American astronomer, Edward Emerson Barnard (1857–1923), was a particularly keen observer. In fact, he is often cited as the astronomer with the sharpest eyes on record. In 1892, he discovered a small fifth satellite of Jupiter, one that was so small, and so close to the brightness of Jupiter itself, that to see it required eyes of almost superhuman keenness; yet Barnard insisted that no matter how carefully he observed Mars, he could never see any canals. He said flatly that he thought it was all an optical illusion; that small, irregular patches of darkness were made into straight lines by eyes straining to see objects at the very edge of vision.
    This notion was taken up by others. An English astronomer, Edward Walter Maunder (1851–1928), even put it to the test in 1913. He set up circles within which he put smudgy irregular spots and then placed schoolchildren at distances from which they could just barely see what was inside the circles. He asked them to draw what they saw, and they drew straight lines such as those Schiaparelli had drawn of the Martian canals.
    Meanwhile, astronomers continued to study the habitability of Mars. As the twentieth century advanced, instruments were devised that could detect and measure tiny quantities of heat. If these heat detectors were placed at the focus of a telescope and the light fromMars were allowed to fall upon it, the temperature of Mars could be deduced.
    This was first done in 1926 by two American astronomers, William Weber Coblentz (1873–1962) and Carl Otto Lampland (1873–1951). From such measurements, it seemed that at the Martian equator the temperature would rise above the melting point of ice at times. In fact, it was even possible for the equatorial temperatures to rise as high as 25° C (77° F) on rare occasions.
    The temperature dropped sharply during the night, however. There was no way of following the temperature at night, for the night side of Mars was always on the side away from Earth. However, the temperature of the early morning could be taken at the western edge of the Martian globe where the surface of the planet was just emerging from night and into the dawn. After twelve and a