MYSTERY OF RADIO WAVES

Hawera Star, Volume LIV, 9 March 1935, Page 11

MYSTERY OF RADIO WAVES

Speed of Travel Now Found to be Variable

gCIENCE started the new year with a new, first-class mystery on its hands, as amazing and disconcerting ! as a discovery that half the time two. and two make eight instead! of four, states the New York Times. Yne mystery lies in the discovery thac! radio l waves apparently take twice as long to cross the Atlantic Ocean at some times as at others. Heretofore scientists have been assuming radio i waves always travelled at the same*' speed—the speed of light, which is 186,000 miles per second. Hr Harlan T. Stetson told the American Association for the Advancement of Science, however ,t'hat he had found that sometimes they travel at only half this speed, about 93,000 miles a second. Dr Stetson says that may be ac-! counted for by studies which “indicate that the nearer the propagation! path (of the radio waves) lies to the earth’s north magnetic pole, the greater is the retardation of the velocity of the wave. Since the velocity m the electromagnetic' wave depends upon the electronic density of the medium, it is believed that conditions in the ionosphere are seriously modi fied by the electromagnetic field of the earth.” He has found signals from Rugby, England, to Annapolis, vary greatly in speed, while those from Bordeaux, France, to Annapolife do not vary. This variation in speed mixes up scientists on three things which they had been thinking they were, sure of. The first is the speed at which radio waves travel. Thinking this speed was as unchangeable and dependable a» iiiiiiiiiiiiiiiiiiiimiiiiiiiiimiiiiiiiimitTiiiiiiiiiiiiiMmiciiiiiiiiii miiiiniiiiifiiiuiiiiiiiimimimiiiiititiiiiiuiiiiiiiiiiimiiiiiiiitiii

the length of a foot rule, scientists had been using it as a measuring rod Tor long distances. Now they find tha„ in effect the foot rule is sometimes j two feet long instead of one foot, j The second mix-up., which is a result jof the first ,is that the exact longitude or east-and-west position of any point on the earth’s surface is now less certain than before. Because it , was believed the travel-speed of radio i waves was unvarying, scientists had ; been using the time of travel of the. waVes (between two points a» >ihe most accurate possible means of measuring their distance east and west of each other.; But now, with the most. accurate yardstick shown to be of changing I length, the world finds its measurej ments of how wide the Atlantic Ocean ! is, and just what- the longitude of i New York City is, as uncertain as before’the invention of radio. The third mix-up comes in a worldwide experiment which scientists have been making to try to determine whether the continents are drifting, as some people believe. Assuming radio signals always travel with the same speed, scientists in 1926 all oyer the world measured the time taken by radio signals to travel from points on some continents to points on others. Then in 1933 they repeated the measurements. It was thought that if the time of travel of the signals varied between the two years, it would be evidence the continents had moved apart. But if the time of travel of the signals themselves varies ,the measurements are worthless. iiiaiiiiiiiiiiiiiiiiimiiiiiiiiiiiiiimiiiiiitiiiiitifttciiiiiiiiamiiifii- • iiaaiiaaaaaiaaaaaiaaaia air»»«a taitaaiaiaiaitaaaieiinai*