| 2401/
Fifteen percent of all gold consumed in the United States
is for teeth fillings and dental bridgework.
2402/ Finely divided
radioactive gold also has medical uses in the treatment of
arthritis.
2403/ Does the sixth
sense really exist? Possible magnetic field sensory organs
have been found in homing pigeons and in Monarch butterflies.
Both have tiny magnetic field-sensing materials in their bodies
that could be used for navigation. Millions of tiny compass-like
magnetite crystals occur in a pod next to the pigeon's skull;
in the butterfly the magnetite is distributed in the wings.
Now that magnetite has been found in these animals, it seems
likely that future research will discover its existence in
others.
2404/ Light rays traveling
from an object to the eye through the atmosphere are bent
up or down depending upon whether the density of air increases
upward or downward. The result can be a desert mirage, an
arctic mirage or the fata morgana which is a combination of
both types.
2405/ Desert mirages
result from the heating of air overlying a warm surface; the
hot sand. In a desert mirage objects appear to be lower than
they actually are. Also, the image is inverted top for bottom.
2406/ Just the opposite
happens in an arctic mirage because it results from the existence
of relatively cold air next to the ground surface. That cold
layer exists because the cold snow, ice or water surface extracts
heat from the air just above. In the arctic mirage a distant
object appears right way up but higher up than the actual
location.
2407/ At the turn of
the 20th century, over 100 years ago, the average American
consumed about 70 cubic feet of wood each year for fuel. For
easy thinking purposes, that is an amount roughly equivalent
to a 4 by 8 foot sheet of plywood just over two feet thick.
2408/ Over the years,
the per capita annual firewood usage has fallen drastically
down to about 3 cubic feet, roughly the equivalent of an inch-thick
sheet of plywood.
2409/ Even though the
number of people in the United States as a whole has grown
much since 1900 the total utilization of wood has dropped
from about 12 billion cubic feet in 1900 to 10 billion cubic
feet in 1976.
2410/ Birch sap contains
the sugars glucose and fructose, whereas maple sap contains
mostly sucrose.
2411/ A hundred United
States dollars laid side by side will cover an area one metre
square (just over a square yard). It takes about 8200 normally
worn bills to make a stack one metre high.
2412/ A stack of one
billion dollar bills will reach from the ground 120 kilometers
upward so that its top 20 kilometers would be immersed in
a normal aurora.
2413/ With a billion
dollar bills, one could lay down a band seventy bills wide
along the full length of the Alaska-Canada border from Demarcation
Point to Tongass.
2414/ With a lot of paste
and a billion dollars, one could paper over the outside of
the full length of the Trans-Alaska pipeline twice and still
have $140,000 left over for refreshments during coffee breaks.
2415/ There are probably
about 50,000 moose in Alaska, so with a billion dollars, one
could make a stack of bills beside each moose that would reach
at least as high as the moose's head.
2416/ If one sat down
to count a billion dollar bills and could count them at the
rate of one per second, every second of every day, it would
take more than thirty years to finish the task.
2417/ Rainbows are caused
by internal reflection and refraction of sunlight or moonlight
inside raindrops.Light entering a raindrop is bent by an amount
that depends upon the wavelength (colour) of the light. Each
raindrop acts as a tiny spherical prism. A rainbow is seen
whenever there are enough raindrops distributed properly with
respect to the viewer and the sun and there is not too much
absorption of the light in the rain. But rainbows are seen
only in specific directions relative to the direction of the
sun, directions that are determined by the number of reflections
within individual raindrops.
2418/ Every solid object
and every stretched wire has one or more resonant frequencies
at which it will vibrate easily. A person can make the tip
of a rather sizable tree oscillate by repeated pushing on
the tree trunk at just the right rate.
2419/ The United States
was officially made a metric country by Thomas Corwin Mendenhall.
In his position as Superintendent of Weights and Measures,
he issued the "Mendenhall order" in 1893 which set
the United States' standards of length and mass as the meter
and the kilogram.
2420/ The clenched fist
with extended thumb at arm's length is a useful device for
measuring vertical angles. If the base of the fist is placed
on the observer's horizon, the tip of the thumb will be 20
degrees above the horizon. By "walking" the clenched
fist up the sky 20 degrees at a time, a fairly accurate measure
of elevation can be made.
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