EARTH’S DIAMETER

Greymouth Evening Star, 19 June 1926, Page 7

EARTH’S DIAMETER

CHANGES EVERY CENTURY

Tfie earth clumges its diameter about once a century, and, as a consequence, its speed of .rotation. This statement was made at a recent meeting of the American National Academy of Science by Dr. Ernest AV. Brown of Yale University. Dr. Brown, who is an authority on the motions of the moon, reached his conclusions from a study of the lunar body. For a long time it has been known that the moon does not stick to schedule. At times it seems to be moving too last, and at other times too slow. The late Dr. Simon Newcombe first suggested that the moon might be on schedule and the earth at fault; apparent changes in the mtoon’s motions resulting from changes in the earth’s speed of rotation. Dr. Brown announced that his recent analysis of records of the moon’s motions, made for the last 175 years by American and European astronomers, leads him to believe that the earth’s speed is variable. He said mathematical analysis indicates that the change in the earth’s speed of rotation could result only from an expansion or contraction of the earth as a whole. This mass variation, however, is too small to measure by ordinary means. If the’change takes place throughout the earth, it is a change of about five inches in diameter, Dr. Brown said. If, however; it occurs only in the earth’s upper crust, then it must be a change of about 12 feet. In the hundred years before 1795, the earth had its minimum diameter. In the next few years, however, it expanded to its maximum diameter which it maintained until 1898, when it contracted again to the minimum. At present, it has its minimum diameter. The earth has its slow speed when at maximum diameter, and its fast speed at minimum diameters,-observa-tions’indicate. The earth, therefore, is rotating in its high speed at the’present time. Changes in the earth’s size may have a bearing on the frequency of earthquakes. ’The moon is also peculiar, Dr. Brown said. It is lop-sided. The lower half of the moon is heavier than the upper half and, consequently, is more contracted. As a result, the moon bulges at the top, an expanded surface making up for a smaller mass.