Sunday, February 22, 2009

Wonder that is nature

You think you know the wonders of nature. They have ceased to amaze you. You greet every new bit of the working of nature with a "same old ... same old". Take for example the bat. Even the kids know that they use a radar (actually a sonar) to fly at night and detect prey. No big deal about it.

Sorry to break your bubble but you have not yet scratched the surface.

Here are some amazing facts ...

While cruising some bats emit an ultrasound pulse of about 10 per second. As soon as it detects a prey, the frequency increases to 200 pulses per second. This is done largely to conserve energy.

The intensity of any sound decays at square of the distance. This is because an emitted sound will spread out as if on the surface of a sphere. The echo again will spread out likewise. So the bats ears are extremely sensitive. It needs to pick up the very low intensity reflected back from its prey. However, to ensure that the reflected sound does not die down completely, the bat has to emit sound at a very high intensity. Imagine what happens when such loud intensity sound falls on super-sensitive ears. Instant deafness! The solution. When the bat emits a high intensity, high frequency sound the "microphone" (the three bones - hammer, anvil and stirrup, same as in human ears) is muffled - for that tiny fraction - by the surrounding muscles. So it is like switch on / switch off function.

Bats are known to use both Frequency Modulation and Doppler Shift to explore the world around.

Possibly the most difficult problem of all that bats face is the danger of inadvertent 'jamming' by the cries of other bats. Human experimenters have found it surprisingly difficult to put bats off their stride by playing loud artificial ultrasound at them.  ... Many species of bats roost in enormous aggregations, in caves that must be a deafening babel of ultrasound and echos, yet the bats can still fly rapidly about the cave, avoiding the walls and each other in total darkness. How does a bat keep track of of its own echoes, and avoid being misled by others? ... [E]ach bat might have its own private frequency, just like separate radio stations. To some extent this may happen, but it is by no means the whole story. ... It seems that bats may be using something that we could call 'strangeness filter'. ... The bat's brain relies upon the the assumption that the world portrayed by any one echo pulse will be either the same as the world portrayed by the previous pulses, or only slightly different.

Now I don't know about you, but I never thought beyond 'bats use radar to fly at night'.  Amazing isn't it?

[The American zoologist] Donald Griffin tells a story of what happened when he and his colleague Robert Galambos first reported to an astonished conference of zoologists in 1940 their new discovery of the facts of bat echolocation. One distinguished scientist was so indignantly incredulous that

he seized  Galambos by the shoulders and shook him while complaining that we could not have possibly mean such an outrageous suggestion. Radar and sonar were still higgly classified developments in military technology, and the notion that bats might do anything even remotely analogous to the latest triumphs of electronic engineering struck most people as not only implausible but emotionally repugnant.
The above information and extract is taken from The Blind Watchmaker by Richard Dawkins.

Hmmm.... So humans developed Radar technology independently and before they got to know about bats. That human brain can develop such technology and also find if something else in nature does something similar is in itself another marvel of nature, won't you say?

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