Bat Radar
It seems that millions of years ago, Mother Nature devised an ingenious way for bats
to find their way around in the dark. If the bat could make a special kind of sound
that most other creatures couldn't hear, then maybe they could use it to help them.
Well, what she figured out is that if the bat does generate this sound, then it could
listen for it if it bounced off of something. But, in order to hear the sound coming
back, the bat would also have to have very special hearing.
What finally worked out for the bats was this.
Most bats (or at least many, many bats) generate a very high pitched sound called an 'ultra-high frequency sound'. Say that someone sings a note. Then the note keeps getting higher and higher and higher. After a time, the note would be so high that people couldn't hear it, BUT IT WOULD STILL BE A SOUND. It is just a high sound that you can't hear.
Ok, so bats have this little thing in their heads, usually behind their noses, that makes these sounds. Most of the time, the bat's noses are shaped like little speakers, or little trumpets, so that they can send this sound out better. Then, in order to hear the sound that comes back, or echos back, they have big ears. If you'll notice, the little yellow baby bats here have really big noses, and really big ears. This echo that they hear when the sound comes back gives their technique it's name of 'echo-location'. When the sound that they send out hits the trees, ground, bushes, animals, insects, and other things around them, it bounces around in all different directions. But, the bats are able to tell the direction or angle that the echo is coming back from. This lets the bat know the direction that things are. Now, since sound travels very fast, the bat is also able to tell how long the sounds take to come back to them. So, now the bat knows where the echos are coming from AND how far away things are. Since sound travels very fast, this all happens almost instantly, and since the bats also are very, very fast they are able to know exactly where they are while they are flying without using their eyes.
If you look at the animation below very closely, you can see that it looks like the bat is spitting when the first sound goes out. This is when it's little organ in it's nose makes the sound. As the sound passes through the air, it hits the mouse and bounces off of it. When the sound bounces off of the mouse, some of it goes back to the bat. This sound that goes back to the bat is what tells it where the mouse is.
Interesting fact: Some of the bat's dinners got smart. There is a species of moth that has learned how bat radar works. So, instead of waiting to be eaten by the bat, the moth learned how to make the SAME sound as the bat. When the moth knows the bat is coming, it will make the same sound and the bat will get confused and ignore the moth. It will then go look or another dinner.
Putter's Bats
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pdenton@swbell.net
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