18# Echolocation

In the early part of World War II the allies faced a major obstacle.  Any ship that the allies would try to send across the ocean were subject to the U-boats, the German submarines that sank merchant ships, sank battleships on a regular basis.  And to deal with this, the allieds had to come up with a solution.  Some scientists very cleverly suggest a concept called sonar.  Sonar sends sound waves into the ocean and then measures the time it takes to come back.  If you send a sound wave into the ocean and it goes straight to the bottom it’ll take a rather long time to come back.  If it hits something along the way it’ll come back much more quickly and by carefully monitoring the speed of the echo returning scientists had devised a method to detect things under water.  Obviously it was very crude and obviously it needed quite a bit of refinement but in fact it began the concept of sonar and eventually later radar, which came after it.

In 1940, a very interesting thing happened.  There was presentation made by a zoologist to a group of scientists and he basically offered the following theory.  For years scientists could not understand how bats could navigate at night.  After all, it’s dark.  Many bats spend their lives in caves and so this zoologist along with one of his colleagues presented to a very distinguished group of scientists a theory that they called echolocation.  Basically Donald Griffin presented the concept that the bat emits a sound and then listens to the returning echo and through that process is able to determine where things were.  Now he describes that as — when he presented this theory in 1940 to this learning group of scientists the reaction was not warm.  He described that one fellow walked over to a colleague of his, grabbed him by the shirt collar and said, “How could you possibly mean something like this.  That’s absurd.  It took man so many years to even think of this idea of sonar, that’s ridiculous.”

However, as ridiculous as it may have sounded then it’s now an accepted fact.  Blue whales, dolphins, bats — navigate by echolocation.  But it’s very, very interesting to note that the bat uses it to such a refined degree that it’s almost mind-boggling.  You see, the way the bat will tell where something is, is by sending out an echo and listening for what comes back.  The bat is very, very busy.  We live in a world replete with insects.  If you go out on a summer’s night you’ll see some insects with two wings, some with four.  You’ll see many, many types.  Scientists now tell us that there are about 1.4 million species of insects and by all rights insects should have long ago overrun the Earth.  The reason why insects don’t overrun the Earth is because they have natural predators, namely one of which is the brown bat.

The brown bat — which is a very small, little bat — will go out at night and will hunt and with its echo location will find a mosquito, find a housefly, and eat them one after another after another.  The average brown bat each night will eat around half a pound of insects.  If you study the weight of a mosquito you realize that it’s quite a number of insects, about 1,000 that it will eat in a nightly foray.  But here’s the amazing part.  All of this is done in pitch black and all of it is done with sound going out and coming back.  But how does it do it?  How does it measure?  How does it tell?  It has to tell whether what’s in front of it is a twig or a fly, has to tell whether it’s moving closer or further, has to tell it’s density.  It has to be able to get a whole mental picture of that object so it knows whether it’s a leaf or a fly or a bird or whatever.

So what the brown bat does is it emits a sound and very, very carefully detects what’s coming back.  To emit the sound it has to scream very loud because any sound that you send out and you’re getting a reflection back is going to be greatly diminished.  The brown bat lets out a series of chirps when it’s flying at kind of just regular modulated mode, about 10 chirps a second and it sends these at a very, very loud decibel rate.  It sends it out at about 120 decibels rate, that’s the equivalent of something like a jet plane taking off.  It sends out a very louds scream.  Now it’s above the human hearings so we’re not troubled by it but it sends out these very loud screams and even though it gets back only a part of it is reflected back it has such acute, sensitive hearing that it’s able to determine the wingspan, the size, the density, the placement of what’s in front of it — sends out the 10 beats a second, listens for it back, and is able to get a report.

Now, here’s the interesting thing about the brown bat.  The distance between it’s mouth and its ear is about 1 inch.  Now if it’s screaming out at a very loud rate so that the reflected sound will come back and it has very acute hearings here’s the problem: the brown bat should be deaf after one night flying.  Imagine you were to take a smoke alarm and put it next to your ear and listen to that all night long.  When it screams out at 120 decibels it’s screaming at a very loud rate so that the reflected sound will come back accurately.  It’s hearing is very, very acute so it’s able to listen very carefully.  It should make itself deaf in no time at all.  However, the reason why it doesn’t make itself deaf is because there is a muscle that dampens the hearing of the bat.  You see, the anvil, the hammer, and the stirrup in the bat’s ear similar to the human ear transfer — those bones transfer the sound to the brain.  Right before it’s about to screech a muscle tamps down that bone so when it screams it’s effectively deaf.  It doesn’t hear it.

The minute the scream stops the muscle lifts so it’s able to hear the echo and you’ll hear that coordination — scream, stop, scream, stop, muscle on, muscle off, muscle on, muscle off — as it flies around.  Now, that’s very impressive when it’s emitting sounds at about the clip of 10 beats a second.  But when it actually has to hunt down a house fly ten beats a second is nowhere near fast enough.  If you ever try to catch a fly with your hand you notice it does maneuvers, it cuts left, cuts right — very, very difficult.  When a bat is after a housefly, that housefly is doing all of those maneuvers.  Ten beats a second is way too slow.  When it actually hones in on the insect it picks the pace up to about 200 beats a second and that means that coordination is so exact, so precise — 200 times a second it’s screaming, the muscle tamps, then it stops so it can listen — back and forth, back and forth.  And it’s so perfectly coordinated that it’s hard to imagine.

In World War I, scientists were given a similar challenge.  Those planes in those days were propeller planes and basically the pilots explained that the most effective place to put the machine guns were right on the wings.  Well, the problem was on the wings were also the propellers.  So, if the pilot would shoot his guns he’s shoot off his propellers.  So the scientists had to coordinate the timing such that each time the propeller moved that’s when the bullet would penetrate.  When the next blade of the propeller would come the bullet would be there and they timed it to that coordination.  The little brown bat has that coordination with its screaming and it shutting its hearing off, screaming and shutting its hearing off — putting it back on, putting it back off and then is able to interpret that sound, create the image in its brain in total darkness.  But that’s not yet the most astonishing part about the brown bat’s ability to hear.

If you’ve ever stood in a room with a lot of people.  Imagine you’re in a room with 200 people, some you know, some you don’t know and you might be in conversation right here with somebody and suddenly something catches your attention.  You hear your name.  Isn’t that strange?  There could be 200 people speaking, a tremendous amount of conversation, words, discussions went back and forth but the minute that you heard your name suddenly you were able to discern it and hear it.  Now how is that possible?  You couldn’t possibly process all that information.  You couldn’t possibly listen.  Scientists now explain to us that the subconscious mind does a tremendous service for us.  It filters out unnecessary information.

For instance, if you were to stop and listen you would hear constant distractions.  There might be a truck down the street.  There might be the noise of a coworker, there might be various things but your mind filters that out so that you can focus on the discussion or focus on what you want to.  But the rest of that information is being processed by your subconscious mind.  When you’re in conversation with that one person all of the 100s of other conversations are being processed.  They’re there and you’re not aware of them but when something is greatly troubling, all of a sudden — my name — you’ll focus in on it because your subconscious is processing all that information yet allowing your conscious mind to be focused until it’s alerted you that it’s time to switch your conscious mind to some place else.

Now this ability to concentrate is tremendously significant tool.  Often time little children don’t have it tot the same degree.  Attention deficit disorder is a manifestation of the lack of that executive function but here’s the point — the human mind is able to filter out many distractions so that it can focus on what it should.  Well, here’s the interesting observation — bats talk to one another.  So when one bat speaks to the other bat the other bat hears it and they can converse back and forth.  Yet astonishingly a bat is able to navigate in a cave.  Now imagine you have a brown bat in a cave and it sends out a sound.  It gets a bounce back.  Well, there’s another bat next to it that sends out a sound and it gets a bounce back.  And there’s another brown bat that sends out its sound and it gets a bounce.  So this cave is a bunch of echoes back and forth, back and forth, back and forth.  How does a brown bat not get lost?  How does it not get confused with other people’s screams, other people’s screeches?  How does it manage to find its own screech?

The answer is it was given a filter mechanism.  It hears all the other screeches, in fact, if it’s necessary to communicate with another bat it will focus on it, but when it’s not it filters it out and only focuses on its own echo coming off the wall.  Now, if this is not astonishing, let’s just focus on the fact that bats live in very large colonies.  Often as many as a million bats will be in a cave.  Echoes and echoes and screaming and screaming and yet the bat is able to filter out every other sound, hear only its echo, be able to determine size, dimensions, thickness with it — able to interpret it all at 10 beats a second, 200 beats a second.  It’s ear always shutting off, shutting off the muscles and listening.  And when you study the wisdom that’s replete in this creation you should step back and say this is astonishing.  If this is the creation what does it tell me about my creator?  And by studying the wisdom in the creation you begin to get an eye glimpse as to the capacity, the greatness of our creator.

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