National Geographic : 1969 Jan
SCOTTPOLARRESEARCHINSTITUTE traces a profile of Antarctica's Nimrod Glacier (diagram at left). British scientists from the Scott Polar Research Institute flew over the glacier in a U. S. Navy plane in late 1967, beam ing down radio signals. The echoes, flashing on an oscilloscope and recorded by a slowly grind ing camera, show both the flat surface and irregular bottom of the ice-the upper edges of the two white bands. Riding on sea and rock, the great glacier reaches a thickness of 3,000 feet. If there is an unknown chamber, muons traversing it on their way through the pyra mid will lose less energy than if they passed entirely through tons of limestone. The exis tence-or absence-of the secret room can thus be confirmed, Dr. Alvarez believes, by computer analysis of many months of muon counts. This somewhat bizarre example of remote sensing, if it succeeds, may produce one of the great discoveries of archeology-an unrifled tomb of a major king of ancient Egypt, one far more important than Tutankhamun. MAGNETISM Magnetometers have long been in use for hunting submarines and for ore and petroleum exploration.* GRAVITY One gravity meter, used for finding salt domes where petroleum may be plentiful, is made entirely of quartz, including its spring; it is so sensitive that its readings change when it is lifted from floor to table. EARTH VIBRATIONS Seismometers, de tecting some 10,000 earth tremors a day, help geologists improve prediction methods. SOUND Mark Twain's riverboat captains used to blast their whistles in the dark and fog and listen for the echoes to locate bluffs. Sonar has for years employed essentially the same technique under water, sending out pulsed sound waves and recording echoes from the bottom or from objects in the water. Sonar signals sent vertically can penetrate not only water but dozens of feet of mud be fore bouncing back. Thus they can even lo cate buried shipwrecks or submerged cities. Sonar was used in the search for both the *See "The Canadian North, Emerging Giant," by David S. Boyer, NATIONAL GEOGRAPHIC, July 1968. infrared sensor developed by U. S. Forest Service scientists. The device registers hot spots on a screen for instant recording on Polaroid film. On the mosaic second from left, a forest road is plotted for fire fighters. Use of IR for fire mapping and detection has saved an estimated $13,000,000 in timber since 1965, and another $1,500,000 in fire-fighting cost.