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THE ULTIMATE SONAR SYSTEM

By: Rabbi Ben Tzion Shafier



In 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 problem was 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 SONARor SOund NAvigation & Ranging.

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 youdiscover 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 detonate within 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.

Bats and Blue Whales

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. Somewith 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 shouldhave long ago taken over the earth. But they haven’t. They are kept in check largely by predators, a primary one being – bats.

A brown bat will eat up to half a pound of insects a day. 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 conference of zoologists by reporting that bats made use of 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 nowan 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. Theyneed to measure distances within fractions of fractions of inches. To do that, they have to measure responses within the slimmest slices of seconds.

The small brown bat does this by emitting clicks at varying rates. Its cruising rate is ten clicks a second. Because it uses ultrasound, the wavelengths are much shorter, and it can reliably calibrate fine distances, easily navigating amongst bushes and trees and in and out of caves. Naturally, the calibration needed to create the sounds and measure the returning echo would stun a mathematician and is well more advanced than anything man has yet to invent. But the bat doesn’t think much about it – he just clicks away and eats his dinner. If this alone were the level of sophistication of echolocation, it would be well worth our amazement, but that is only the tip of the iceberg.

Ten clicks a second is fine for navigating in and out of caves and amongst bushes and trees, but it would never suffice for the hunt. If you have ever tried to catch a housefly with youhand, you know that it’s extremely agile. When being chased by a bat, the fly performs aerial maneuvers that would leave the best stunt pilots jealous. Cut left. Cut right. Dip down. Now up. Stop. Turn.

Therefore, to actually catch an insect in mid-flight, the bat must increase the speed of its clicks considerably. In hunting mode, the little brown bat ramps up its rate to as much as 200 clicks a second! For a bat to hunt, track, close in, and catch an insect, it needs to know size, range, and the position of a prey’s flight. It needs to gauge distance, speed, and direction in midair. To do that, many species of bats make use of yet another recently discovered technology.

Doppler Effect

If you are standing on a street corner as an ambulance approaches you, its siren will sound high-pitched, yet as it passes, the pitch will seemingly drop. This phenomenon, known as the Doppler Effect, is caused by the manner in which sound waves travel. As a wave moves, it has a crest (top) and a trough (bottom). The distance between the crests determines the pitch. A higher note has a shorter distance between each crest. A lower note has a longer distance between each crest.

If you are moving towards the source of a sound, the distance between the wave crests will be shortened because you are moving into the oncoming waves. If you are moving away from the source, the distance between the wave crests will increase because you are moving away from the oncoming waves.

While the technicalities may not interest you, their applications might. This is essentially the way that police detect speed. By aiming a radar beam at a moving vehicle and measuring the frequency of the beam coming back, a policeman can accurately gauge the speed of the oncoming car. If the car is moving quickly towards the source of the radar, the frequency of the returning beam will be higher. If it’s moving slowly, the frequency will be lower.

This is how many bats maneuver. By constantly sending out streams of hoots, screeches, or chirps and measuring the change in pitch when the sound returns, they are able to track the speed, distance, and direction of a prey. Pretty astonishing, isn’t it? How advanced must their brains be that they can detect the most minute changes in pitch and process that new incominginformation at the rate of 200 times a second?

More Than Just Speed

For a bat to navigate without sight, it must do something immensely more complex than measuring speed. It needs to compute direction and movement. It needs to know density, composition,and texture. Is that a leaf or a fly’s wing? Is that a twig or a moth? It must also be able to make fine distinctions. Dry land and a lake might both be on the ground, but landing on each spells a very different consequence. The echolocation system is so accurate that bats can detect insects the size of gnats and objects as fine as a human hair. They then proceed to determine what it is, where it is, and what it’s doing. The question is: How do they do that?

The Reconstruction Of Sight

While the answer to this is not a hundred percent known, one theory is that the mind of the bat works in a similar way to the mind of the human. We normally think of our senses in simplistic terms. We see. We hear. We smell. We feel. We taste. But what’s actually going on is far more complex. Let’s take color as an example.

Light travels in waves similar to sound. The length of the wave determines the color. The color blue is light with a short wavelength. The color red is light with a long wavelength. If you were to approach the average person and ask, “Quick, what wavelength is the color purple? How about yellow? What about violet?” I doubt you’d get an accurate response. We see purple. We see yellow. And we see red.

But what actually happens is that light enters through the cornea, is focused by the lens, and then hits the retina in the back of the eye. The photoreceptor cones and rods convert the different wavelengths of light into distinct electrical impulses that travel along the optic nerve. These impulses are then sent to various parts of the brain for decoding and interpretation. Through a complex process that is still largely not understood, the mind then constructs what is almost a “computer model” of red, green, or yellow. We don’t actually see color. Our minds create something that we experience as color. For that reason, there is no universal red. What you perceive as red and what I perceive as red may
be different.

This same process happens with shapes, motion, and distance. The raw data is fed into the brain, sent to various nerve centers for analysis, and then a unified image is created.

What Bats See

The current theory is that bats “see” in a similar manner as we do. The echoes entering their ears are converted into raw data, and then their brains construct an image. They “see” an image brought to them by sound.

A bat can determine an object’s size, shape, direction, and motion because it creates a mental image of the object. It “sees a gnat.”
It can gauge landscape because it forms a topographic picture –
it “sees a rock ledge.” It can judge distance and motion because
it compares the image of the gnat against the image of the rock.

Those images are being constantly updated up to 200 times a second, so it “sees” the wings of a fly beatingup and down. Of course, this is all without the bat thinking about it – the bat just sees.

Why Aren’t They Distracted?

Brown bats typically live in colonies. Within a cave, there are many, many bats. So here is the question: if you have a hundred bats and all of them are echolocating any time they move, there should be a babel of bats’ cries bouncing of the cave walls in every direction. How does a bat not get utterly confused in the mayhem of thousands of conflicting messages?

Zoologists believe that bats are able to focus on their cries to the exclusion of all the other bats in the cave through ‘mental filtering.’ The theory is that each bat creates a unique sound and is able to distinguish between its cry and that of its neighbors. So when a bat sendsout a sound, it will zone in on its own voice coming back to the exclusion of any other sound. It hears the other bats, but its radar doesn’t get jammed because it ignores the other calls. It processes only those from its voice.

This is rather interesting because bats tend to live in very large groups. Some caves might house thousands of bats, some tens of thousands. The Monfort Bat Cave in Samal is home to over 1.8 million fruit bats!

These tiny bats are living in a cacophony of thousands and thousands of different cries bouncing all around. Their minds are so sophisticated that each one actively ignores the thousands of other cries and only focuses on its own.

In the words of a world-renowned scientist, “Bats are likeminiature spy planes, bristling with sophisticated instrumentation, and their brains delicately-tuned packages of miniaturized electronic wizardry, programmed with the necessary software to decode a world of echoes in real time.

Why Is This Significant?

The Rambamexplains that the most assured way to come to love Hashem is by studying nature. When a person looks out at the wonder and splendor of the physical world, he sees such beauty and wisdom that he begins to gain some sense of Hashem. If this is the creation, what does it tell me about the Creator? Look at this world. Study its enormity and complexity. Look at its harmonious systems, all integrated, all perfectly in balance. When you do, you will see the greatness of Hashem. Before long, not only will you come to know Him, but you will come to love Him.