Page 183 - For Men of Understanding

RADAR
AND
THE BAT

Having such weak
sight as to be
considered "blind",
bats emit very high
frequency sound
waves called
ultrasound. These
sounds, which are
over 20,000 hertz
(cycles per second), are
inaudible to human beings. The sound waves
emitted by bats are reflected off birds in the
air, animals on the ground and other objects
that stand in the bat’s way. The bat
determines its direction and orientation
according to these reflected vibrations.
Radars work on the same principle.

THE CHICORY SEED
THE AEROPLANE AND THE PARACHUTE
AND THE CATFISH
The seeds of the wild chicory plant make
The flat shape of the catfish, which is a long trip floating in the air by means of
very effective hydrodynamically, has winds. The principle of parachutes is the
set a model for aeroplane design. same as that of this plant.
Today, flat-shaped models are
commonly used both in the THE MAPLE SEED
armaments industry and civil aviation. AND THE PROPELLER
For instance, the "Orient Express"
model by McDonald Douglas looks like The shape of the maple seed causes it to
a catfish. Twice as fast as sound, the rotate around itself very rapidly as it falls to the
flat shape of this new model keeps air ground. This shape inspired Sir George Cayley,
resistance during flight to a minimum. one of the first experts on aviation.

SUBMARINE AND THE NAUTILUS
When it wants to dive, the nautilus fills the little chambers in its
body with water. When it wants to surface, it pumps a special
gas it produces into these little cells and discharges the water.
The same type of chambers as those in
the nautilus are utilised in
submarines, where water taken
in is discharged via water
engines.