Iowa County democrat. [volume] (Mineral Point, Wis.) 1877-1938, 1915-04-22
HEAT OF our sun
To Measure It Is a Perplexing
Problem For Science.
NEWTON ONCE TRIED TO DO 1T

He Figured It at the Amazing Intensity
of 1865, 800 Degrees Centigrade, While
the Latest Estimates Place 1t at
About $500 Degrees.
How hot Is the sun? The question
has been answered in many different
ways, and it is by no means certain
that we have yet arrived at an even
approximately accurate answer. Yet
it would seem that, as the sun Is the
only source Of the earth'S heat, and
as we know the exact distance of the
sun, it ought to be easy to calculate
his heat. That is what Newton thought
in 1850 when, finding that thermom-
eter registered Is degrees @. in the
sun and 29.44 degrees G. in the shade.
and applying the law of the square Of
distance he announced that the suns
heat was 100000 degrees c.!
In 1887 Sir John Herschel and Pouil
let devised special instruments for
measuring the solar heat, but at the
very beginning disagreed on a funda
mental question. Pouillet wanted to
estimate that the eartb's atmosphere
cut off half the suns heat; Herschel
insisted that it cut off only one-third.
Herschel reached the conclusion that
the suns heat was two calories per
square centimeter per minute. Pouil-
let calculated it at 1.7633 calories per
square centimeter per minute. This
means that the suns rays falling YER
tically upon each square centimeter OF
the earth's surface would be sufficient
ly powerful. if it were not for their
absorption by our atmosphere, to raise
1858 grams OF water one degree Q.
per minute This number is what as
tronomers call the solar constant.
Pouillets figures, IL. were generally
accepted until recently. Forbes by ex
periments at the top and at the base
of high mountain calculated that 2.85
was the correct number. Wolfe made
it 2.54, and Crova asserted that it was
certainly superior to two calories per
square centimeter per minute.
The American Langley invented the
bolometer, by means of which be
measured the intensity of each ray by
the length of it's wave before entering
our atmosphere. Thus he proved that
the rays of shortest length are those
that are most absorbed. 1t is as If we
placed two red glasses between our
selves and the sun. one representing
the suns atmosphere and one repre-
senting our own
The Able Moreux. director of the
Bourges observatory. declares in an
article in Cosmos that if these two at
mOspheres were eliminated and we
could see the sun as be really is be
would appear to be il brilliant greenish
blue.
Langley's calculations placed the So
lar constant at about three. He proved
that scarcely 90 per cent Of the suns
rays penetrated to sea level
Other observers obtained other fig
ures, and at the beginning of this cen
fury the tendency was to return to
those announced by Herschel and
POuillet.
1t is certain that the earth intercepts
only about one two-billiOnth part OF
the actual heat of the sun. but II we
adopt Langleys figure. 3. we find that
the fraction of heat received would be
sufficient to melt annually a layer OF
ice 222.75 feet thick at the equator of
the earth. The average power receiv-
ed from the sun over the entire earth
is equal to 154.464.OOO kilogrammeters
a year, or one continuous horsepower
for every 1.72 square meters.
The greater part of this heat Is used
up in keeping the earth warm; but, ac-
cording to Helmholtz. about thou
sandth part of 1t is absorbed by ami
mails and vegeta bles and becomes an
abundant reserve of energy for the
human race.
If we accept the more recent figures.
which are the result of the calculations
of Messrs. Abbott, Fowle and Aldrich
at the Smithsonian institution in
Washington and call the solar constant
two calories per square centimeter per
minute. the results are scarcely less
striking.
If the total heat could be applied to
a block of ice at o degrees c. as thick
as the earth-8.OOO miles-this would
be entirely melted in a quarter Of an
hour. All the water thus obtained
would be turned to steam at 100 de-
grees c. 1T minutes later. the whole
operation from ice to steam having
taken only two hours and twelve min
uteS.
The most recent estimate OF the tenn
perature OF the suns surface Is be-
tween 5000 and 1000 degrees C.-New
York World.