National Geographic : 1969 Jan
sound and light, radio and radar, heat and X-rays, magnetism and laser beams.t With fantastic versatility they pierce clouds and smoke, penetrate the earth, and scorn dark ness and camouflage. Some even see the unseeable, and take ghostly pictures of the past. Instruments Scan Earth and Space This revolutionary new technology (one might almost say black art) of remote sensing is providing scientists with all kinds of valua ble new information to feed their computers. It is a source of quite legitimate excitement today in many quarters, for it offers a verita ble cornucopia of benefits for the future of the human race. Remote sensing will help improve the food you eat, the water you drink, the air you breathe. It promises aid in averting famine, flood, fire. It may find new natural resources, as well as long-lost cities and buried treasure. Ultimately it may help determine whether man will be able to continue to live on his planet, the earth. Two major developments are spurring this revolution. One is the ability to place sensing instruments into orbit. In the past 11 years some 800 spacecraft have rocketed out from earth. They have, among other things, meas ured the powerful wind of particles blowing from the sun; explored the giant magnetic shield protecting the earth; taken the temper atures of Venus and Mars; and captured vir tually all the surface of the moon on film. They have also looked earthward. Photo graphs taken from Gemini and Apollo space craft and Nimbus, Tiros, and ATS satellites *See "How Bats Hunt With Sound," by J. J. G . McCue, NATIONAL GEOGRAPHIC, April 1961. tSee "The Laser's Bright Magic," by Thomas Meloy, NATIONAL GEOGRAPHIC, December 1966. WAVELENGTH IN METERS .000001 (.000039 INCH) ONE HUNDRED TRILLION ONE QUINTILLION TEN SEXTILLION FREQUENCY IN CYCLES PER SECOND in wavelengths and frequencies that he cannot see. Generated by matter's atomic and molecular ac tivity, radiation streams from every object in the universe in units of energy called photons. Remote sensors can span this entire spectral range. Radio telescopes gather "noise" from the depths of the universe, and radiometers detect natural micro- wave emissions of icebergs near sea lanes. Radar, bouncing pulses off the earth, yields topographic maps. Infrared sensors warn when volcanoes "run a fever," a prelude to eruptions. Satellites photo graph weather in visible light; X-rays give doctors and dentists inside information. Gamma rays striking scintillometers locate radioactive ores.