The Sun-Earth distance - 92,897,416 miles - is taken as a unit of measurement of inter-solar system space, and
is known as one Astronomical Unit. Its light requires 498.59 seconds, or about 8 1/3 minutes, to reach the
Earth. To travel the distance by an airplane at 300 miles per hour, would consume 35 years; to walk at 4 m.p.h.,
6300 y.
Hugh Rice, astronomer of the Hayden Planetarium of New York, says, "The Sun is the source of almost all the
power, heat and life on the Earth." Heat reaching the Earth amounts to 1.94 calories per minute, per square mile
of the Earth's surface. One caloric is the amount of heat required to raise one gram of water by one degree of
temperature.
In terms of power the Sun's radiation amounts to 1.51 h.p. per sq. yard of the Earth's surface, or 643,000 h.p.
per sq. mile. Were it not for loss by curvature and reflection it would amount to 4,690,000 h.p. per sq. mile, or
for the entire surface of the Earth, 127 plus twelve ciphers, or 127 trillions of horsepower - more than we could
possibly use. Actually our absorption amounts to from 0.34 to 0.38 h.p. per sq. yard, or the equivalent of a 60-
watt lamp in continuous operation. When it is recalled that the Earth as seen from the Sun is a point in the sky
apparently less than half as large as Venus when it is our brilliant evening star, and that this is the tiny object
which intercepts a total of 230 million-million horsepower of solar radiation, it becomes evident that the Sun
radiates an incomprehensible amount of energy. Indeed, we find that it radiates nearly 2,200,000,000 times as
much energy as that which lights and warms and gives life to our planet, and hundreds of millions of times as
much energy as is intercepted by all the planets, satellites, and planetoids combined.
Most of the Sun has a temperature of a million degrees. Its energy travels at the rate of 186,271 miles per
second. The Sun's heat would melt a block of ice the size of the Earth in 16.6 minutes; a block of iron of the
same size, in Less than 3 hours. Its heat for a year is equal to the burning of tons of coal amounting to 400 Plus
21 ciphers.
The Sun's Spectrum of visible light extends from 7700 Angstrom units on the red end, to 3600 Angstrom units
on the violet end. An Angstrom unit is one ten-millionth of a millimeter. A millimeter is 1/25th of an inch. A
wave of red light measures one 32-thousandths of an inch; of violet, one 64-thousandths. Hence the visible
Spectrum consists of one octave, although 40 octaves are known to Science. The ultra-violet band extends from
3600 to 1000 Angstrom units. However, the ozone in the Earth's atmosphere cuts out all rays shorter than 2900
A.U. Tanning is nature's way of protecting the body against an excess of ultra-violet radiation.
The light of the Sun is 465,000 times brighter than the Full Moon; 900,000,000 times brighter than Venus at its
brightest. In the Zenith this has been computed at 103,000 meter-candles. A meter-candle is the light received
from a candle at a distance of a meter.
According to the latest astronomical computations the Sun's proper motion in orbit is approx. 200 miles per
second; its apparent motion towards a point in the constellation Hercules is 12 miles per second.
Solar System Bodies: Moon.