Community Magazine August 2017

86 COMMUNITY MAGAZINE I n the early part of World War II, the Allied forces faced a major obstacle getting supplies across the ocean. While they had sufficient transport ships and plenty of battleships to defend them, their convoys were at the mercy of the German U-boats. These submarines would wait for a ship to pass overhead and torpedo at will. The problemwas detecting something that couldn’t be seen – something submerged hundreds of feet under water. Teams of scientists were called on find a solution. One suggestion was to use a then-undeveloped technology called SONAR or SO und NA vigation & R anging. If you stand at the top of a mountain and shout “hello,” the sound bounces against the next mountain and comes back in the form of an echo. Sound travels at a specific speed. If the returning echo takes a long time to arrive, it’s because the object it bounced against is far away. If it returns quickly, you can be assured the object is close by. All of this means that, in theory, by sending out and measuring the return of sounds, distances can be determined. The idea was to mount an instrument on the bottom of the ship that would emit sounds. The sound would travel until it hit something solid and then bounce back. In water, sound travels at close to 5,000 feet a second. If a U-boat was underneath, the signal would return in about a 20th of a second. If there was nothing under the ship but ocean bottom, the sound would only return after a delay. The theory was simple. The application wasn’t. What do you do once you discover a U-boat? At the time, the way to fight submarines was to drop a depth charge. A depth charge is a pressure sensitive bomb, set to explode when it sinks to a given depth. To be effective, the charge had to detonatewithin ten to twenty feet of the submarine. So the calibration of the sonar had to be measured by hundredths of seconds – a great technical challenge. SONAR was first introduced in 1906. It took almost 35 years of man’s dedicated brilliance to make it functional on the high seas. But ironically, this technology has been around for a lot longer than most people realize. RABBI BEN TZION SHAFIER Bats If you go outdoors on a summer’s night, you will see an untold number of insects. Big ones and little ones. Some that crawl and some that fly. Some with two wings and some with four. Some with eight legs and some with a hundred. It is now estimated that there are over 1.5 million species of insects in existence. Because they are so hardy and because they reproduce at such rapid rates, insects should have long ago taken over the earth. But they haven’t. They are kept in check largely by predators, a primary one being – bats. A brownbat will eat up tohalf apoundof insects aday. Considering the weight of a mosquito, that’s a lot of bugs to eat (about 1,000 or so). Bats, however, face a problem. While many are not blind, most hunt at night when there is little or no light to guide them. The small brown bat is a good example. These bats spend most of their lives in deep caves and yet manage to navigate and in mid-flight consume all types of flying insects. For many years, how they found their prey and avoided obstacles in complete darkness was a mystery. In 1940, Donald Griffin, a distinguished scientist, astonished a conferenceof zoologists by reporting that batsmadeuseof something he called, “ echolocation .” He and his colleague, Robert Galambos, claimed that by emitting chirps and then measuring the speed of the returning echoes, bats were able to navigate in complete darkness. The reaction of the assembled experts was less than favorable. To the assembled learned men, it seemed preposterous that a primitive bat could make use of cutting edge technology that was just then being discovered by man. Nevertheless, it is now an accepted fact that bats, blue whales, bottle-nosed dolphins, and many other animals navigate by using SONAR. There’s More Here Than What’s Hidden From The Eye We must remember: Bats don’t track objects the size of school buses. They catch flies. They need to measure distances within fractions of fractions of inches. To do that, they have to measure responses within the slimmest slices of seconds. THE ULTIMATE SONAR SYSTEM