In the early part of WWII, 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 SONAR or SOund and NAvigation Ranging.
The concept was simple. 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, the object it bounced against is far away. If it returns quickly, the object is close by. After sending out and measuring the return of sounds, you can, in theory, determine distances.
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 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 thirty-five years of man’s dedicated brilliance and the pressing needs of World War II to make it functional on the high seas. But ironically, this technology had 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. 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.
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 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 midflight 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. Griffin reports that one noted scientist approached him and his partner afterwards and “grabbed my colleague by the shoulder and shook him while complaining that we couldn’t possibly mean such an outrageous suggestion.”
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
But for bats in particular, it’s not that simple. 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 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 being amazed, but that is only the tip of the iceberg.
Why Isn’t the Bat Deaf?
By all rights, bats should not be able to use echolocation. Sound travels in waves. The further the wave travels, the more it spreads out and the weaker the sound is. The result is that when a bat sends out a sound, only a small fraction of it actually hits the target, and only a fraction of that sound is then sent back. The returning sound gets weaker as it travels, so the final echo that the bat hears is but a fraction of a fraction as loud as the sound that it emitted. To actually hear the sound that comes back, the bat must do two things: 1) It must emit a very, very loud sound and 2) It must have very acute hearing to then pick up the diluted sound.
To solve this problem, the little brown bat screeches at 120 decibels, the equivalent of a smoke alarm or a jet plane at take-off. Because the bat clicks in frequency above our hearing range, its immensely powerful sounds don’t keep us up at night. But as the bat is equipped with a highly sensitive ear, perfectly tuned to receive ultrasound, it is able to hear the returning echo.
That, however, is the problem. The bat’s very delicate ear is located less than an inch from its mouth — which is emitting those sounds. So with its immense and powerful screeches, it should make itself deaf. (Think of a smoke alarm going off an inch away from your ear, all day long.)
To solve this problem, the bat has a tampering mechanism. In the bat’s ear, as in the human ear, sound is transmitted from the eardrum by three tiny bones known as the hammer, the anvil, and the stirrup. Attached to the stirrup and the hammer is a muscle. Immediately before the bat screams, this muscle contracts, effectively freezing the bones and preventing them from transferring sound. As soon as the bat stops its scream, the muscle relaxes and again sound is transferred. The sequence of the muscle contracting and relaxing essentially turns the bat’s hearing on and off, on and off, between every chirp. A very clever solution, but the timing has to be flawless. On and off, on and off, in perfect marching order, ten times a second!
When Great isn’t Good Enough
But that’s not good enough. 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 you hand, 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 midflight, 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 two hundred clicks a second, which means that the muscle in its ear must keep pace, also turning on and off, on and off, two hundred times a second. A very delicate feat of timing.
Shooting Through a Propeller
In World War I, flight engineers were faced with a similar problem. They found that the most effective place to mount machine guns was on the wing of the plane. The propellers, however, were also mounted on the wing. If the guns were placed on the wing, they would shoot off the propellers. To solve this problem, the engineers timed the bullets with such precision that each bullet would fire precisely at the right moment so that it would shoot through air and not the blade of the propeller.
This is basically what the bat does. The shut-off mode on its hearing is so exquisitely timed that it turns on and off, keeping pace with the muscles in the larynx that create the click. To measure this, however, we can no longer use crude measurements like hundredth of seconds. Now we have to switch over to thousandths of seconds or milliseconds.
The way it works is that about six milliseconds before the larynx muscles begin the shout, the middle ear muscle contracts, shutting off incoming sound. This contraction lasts for 2-8 milliseconds and then relaxes. At this point, the ear is ready to receive the echo of an insect one meter away, which takes only six milliseconds to travel. Then the middle ear muscles again contract, and the larynx muscles create a shout. On and off, on and off – perfectly timed, like bullets shooting through a propeller, two hundred times a second. Pretty impressive stuff.
But that’s not the half of it.
For a bat to hunt, track, close in, and catch an insect, it needs to know size, range, and position of a prey’s flight. It needs to gauge distance, speed, and direction in midair. To do that, it seems that many species of bats make use of another recently discovered technology.
If you are standing on a street corner and an ambulance is approaching towards you, its siren sounds high-pitched, yet as it passes, the pitch seems to 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 the sound, the distance between the waves 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, the applications might. This is essentially the way that police detect speed. By aiming a radar beam (a form of light that also travels in waves) at a moving vehicle and measuring the frequency (or rate of light wave crests) 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 back will be higher. If it’s moving slowly, the frequency will be lower. Of course, the math is highly complex, and the calibration extremely sensitive, but it is now used in many applications.
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 speed, distance, and direction of a prey.
Which is astonishing. How advanced are their brains that they can detect the most minute changes in pitch? How sophisticated are their minds that they can process that new incoming information at the rate of two hundred times a second? But that’s not the half of it.
More than Just Speed
When a policeman stands at the side of a highway and clocks passing cars, he only needs to measure one thing — speed. If the blue sedan over there is travelling at fifty-five miles an hour, it’s not a problem. If it’s moving at eighty-five, it needs to be pulled over.
For a bat to navigate without sight, it must do something immensely more complex than simply 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 bug or a stick? 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. Then they 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 human mind.
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 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. When you shoot a basketball, a tremendous amount of computer power is being exerted to take visual, audio and sensory input and create a unified image. But many different systems in the brain all have to do their part to construct an image or we can’t see.
In 1910, for example, the surgeons Moreau and Le Prince wrote about their successful operation on an eight-year-old boy who had been blind since birth because of cataracts. Following the operation, they were anxious to discover how he could see.
When they removed the bandages from his physically perfect eyes, they waved a hand in front of the boy’s eyes and asked him what he saw. The boy replied meekly, “I don’t know.” He only saw a vague change in brightness; he did not know it was a moving hand. Not until he was allowed to touch the hand did he exclaim, “It’s moving!”
Without visual input during his early development, the boy had never developed the visual processing necessary for vision. The optical stage provides the raw message, but it is the interpretation of the brain that determines what can be seen.
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 two hundred times a second, so it “sees” the wings of a fly beating up and down. Of course, this is all without the bat thinking about it — the bat just sees.
If you aren’t moved yet by the astonishing wisdom that HASHEM has invested into bats, there is one last element that should wow you.
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?
The answer to this can be found in a powerful function of the human mind.
Imagine that you are at a kiddush in shul. The room is packed wall to wall with over two hundred people. Everyone is talking. Some in large groups, some in small ones. You can barely hear yourself think. After a few minutes, you meet someone you haven’t seen in a long time, and before you know it, you’re deeply engrossed in conversation. A few minutes pass when, suddenly, your attention is drawn to a discussion 20 feet away. And you can’t pull back. Why? Because you heard your name mentioned. “Hey, that’s me they’re talking about.”
Here is the question: There was such a din of noise all around, and you were focused on the person right in front of you. How did you suddenly hear your name?
The answer is auditory discrimination. While you were speaking to the person in front of you, you filtered out all the other conversations. The other sounds were entering your ears; your brain was lightly processing them but ignoring them. When your name was mentioned, an alarm went off. “That’s important! We need to pay attention.” And suddenly your focus was drawn to the conversation twenty feet away.
One of the most remarkable features of the mind is that it can process huge amounts of data and be selective as to what it focuses on, discriminating between what is applicable and pushing everything else to the background where it can be lightly monitored but not allowed to interfere with the conscious mind.
Our minds are constantly doing this.
As an example, I once gave my students an assignment. For two minutes, they were to write down any sound they heard. I held my stopwatch, said, “Go,” timed two minutes, and said, “Stop.” Then I asked them to describe what they heard. The list was impressive: people coughing, fluorescent light bulbs humming, a car in the street, the moving of a desk, footsteps down the hall, a pen scratching on paper. . . When we counted, we had a list of almost a hundred different noises from that two-minute period.
I was demonstrating that we are inundated by a constant stream of distractions — yet we are able to focus on certain sounds to the exclusion of others.
Not everyone has this ability to the same degree. Many children have difficulty in school because their auditory discrimination isn’t yet developed and they can’t filter out the distractions. Moishe may very well want to pay attention to the rebbe, but he is constantly being pulled away, first by the closing of the closet door, then by the bird singing on the tree, and then by the noise of the rebbe’s shoes. There is just too much sensory overload, and he can’t cut through all the static.
How Bats Zone In
Zoologists now believe that a similar type of mental filtering is what allows bats to focus on their cries to the exclusion of all the other bats in the cave.
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 sends out 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 large groups—very large groups. Some caves might house thousands of bats, some tens of thousands. One cave in West Virginia is home to a colony of approximately 125,000 individual small brown bats. But the Guinness Book of World Records counts the Monfort Bat Cave in Samal as the world’s largest colony; it is home to 1.8 million fruit bats.
What the means is that 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 like miniature spy planes, bristling with sophisticated instrumentation, their brains delicately tuned packages of miniaturized electronic wizardry, programmed with the necessary software to decode a world of echoes in real time.”
And just how big are those brains of theirs?
Well, a typical small brown bat weighs between a 1/16 and ½ ounce. But when it is born, it only weighs about 1/20th of an ounce, and it can fly at three weeks. At that point, its head is about the size of a pea. So how big is its brain? Not too big.
Why is this significant? The Rambam explains 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. By doing all this, you will come to see HASHEM, come to know HASHEM, and come to love HASHEM.