The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1888-03-18
WHAT KEEPS THE sun HOT?
Prof Richard A. Proctor Examines the
Various Theories About the Question.
ter-The MeteOric Theory Insufficient
The True Theory of the Suns Heat.

Shakespeare makes Hamlet say, "DouDt tnat
the stars are fire." as one might say doubt tnas
two and two make four and elsewhere Shaks-
peare speaks of the also as fire, which as
suredly, were the stars fire. he would be, since ne
b one among the stars. But the sun IS not hre;
neitner are his feIlow-suns, che stars
The suns heat is not however. the product of
q process of combustion. 1t would be unfortu-
nate for the solar system were the suns heat SO
produced. since a mass equal to the sun of the
finest combustible material, and burning as
to give out, moment by moment, as much heat
"a the sun actually pours forth, would be en-
tirelv consumed in about 5000 years. period
which is but as a second compared with the past
duration. and probably with the future continu-
ance Of the suns emission.
There are. indeed, few problems OF greater in
terest, and few of greater difficulty than that
steady radiation of heat from the sun that has
gone on during millions of years in the past and
will. we trust, continue for millions Of years in
the future.
Let it be noticed at the outset that the suns
heat is not as many seem to imagine, a doubt
ful question, problem about which men OF
science are at issue. It has been supposed but
only by the ignorant, that the effects which are
commonly attributed to the suns heat are real
ly due to some kind of action in the earth, or
In her atmosphere, action started by the
suns rays, but actually their product.
suppose, indeed, that there few
among the paradoxes which perpex the
ignorant. Of which students of science hear
more, than about this one. have received
hundreds of communications on this subject
have been interrupted repeatedly, when lectur-
ing on the sun, 1 have been buttonho1ed in
hotels and railway cars to be told that if the
sun himself were the source of the heat which
seems 20 come from him. mountain rops
could be snow covered: the air would be hotter
rs we assembled in balloons, up mountain
slopes; and in other ways we should recognize
affects which are the reverse of those actually
noted
That objection from the SHOWS upon mount
ain tops is in particular favorite The
highest SUBMITS OF the Himalayas. for ex-
ample. more than 20, 900 feet nearer the sun
At midday than the valleys; yet. in the valleys
there is warmth, while the highest peaks
clothed in perennial SHOWS; what clearer proof
can there be that the heat is produced by the
air itself, not by the direct action of the suns
rays2 As a matter of fact however, this argu-
ment il wholly erroneous The notion that
there is cold at the mountain tops because the
mir is tenuous, and warmth at the lower Levels
because the air there is dens@r is simply mis-
take Rare air may be hot. dense air may be
cold, according the conditions under which
the rarity density has arisen. The air at
mountain tops 10 not cold because the air
ls rare, but because that air which is at the
ment rare, was dense not long before Given
mass Of dense air with room in which IL can ex-
band, and immediately cold results cold which
may become intense If the expansion and conse
quent rarifyipg of the air takes place freely;
and, on the other hand, though dense air-qua
dense-may be as cold ice, if rare air is
pressed into density it becomes hot under the
process. 1t is the expansion of dense air which
cools il, because it does work in expanding; the
contraction Of rare afr warns 1t. because the
contraction Is due to work done not by the
air but upon the air. and the expendi-
tnre of work upon it warns it. Thus
when air passes ND the sides of a mountain,
ito ~ de-
does work. and necessarily cools. even though il
be exposed to the direct rays OF a nearly vertical
gun On the contrary, when air is carried down
the sides of mountain 1t is exposed to inc rsas-
Ing pressures and thus is compressed and
warmed, even though at the lower levels it may
receive somewhst smaller supplies of heat than
at the higher. The wa ID of the air In one
position, and it's coolne another. argue in
reality nothing respecting the suns heat, which
In the OF dry air passes freely through
without apprecably affecting the temperature.
We find, accordingly, that surface, rock or
wood, or metal, exposed to the sun IS rays on
mountain top is as much warmed as similar
surface exposed where the air Is denser The
heat may not accumulate as fast because more
readily radiatsd, but il is received AS obviously.
A black bulb Thermometer shows greater heat
Mt a great height above the sea level than low
down; though the air is quite thin at that
height and the region around all snow-covered
The fact is that we have the of evil
aeuce of the suns heat that We have of the heat
of fire. We measure his heat By methods
As simple rs those by which the heat of fur
fine, by measurements Just such simple prin-
ciples. that the totality of heat emitted by the
sun has been measured by PouiIet by john
Herschel, by Secehi, and by others. 1t is of the
origin of this manifest heat the heat pervadlug
The suns Frame and rad1ated from the suns
surface into surrounding space that have now
to speak
have said that were the sun but mass Of
burning fuel. his supply of heat. at the present
rate of emission. would not have lasted more than
5000 years. There is, however. another way IN
which the suns heat may be conceived to be
emitted. He might not be like mass of burn
ing coal. but he might be like mass of glowing
iron. The difference between the coal and the
iron is that one ia undergoing a process of com
bustiou. the other is SIMPLY radiating heat al
ready communicated to it, and is not burning at
al. Tho coal burns away, and is changed into
another substance not suitable for combustion;
the iron glows with fiery heat, but remains all
She time iron. and is not consumed
Now the sun may be conceived to have been
heated in the remote past, and to have since
dated its heat into outer space a piece of glow
ing metal does. Were this so, the duration of
the suns emission of heat at his present rate
would depend somewhat the nature of the
substance which bad thus been heated. For
some substances give out more heat In cooling
by any given amount than do Others in the
technical way of speaking. their specific heat is
greater. OF all substances, water (most fortu-
nately for us) is that which has the greatest
specific heat Hence, If the suns had
originally been formed of water raised to
intense heat, the supply which the
could radate before he was wholly cooled,
would be greater than if he were made of any
other substance. But when inquire how
much heat the sun could emit were he thus
formed of the substance which would longest
maintain his heat-emission, find that it
would correspond to but about 5000 years sup
ply. at the suns present rate of emission 1T is
D mere chance that the duration in this case in
the in the preceding the case in which
supposed the sun To be but mass of burn
ing fuel, but the coincidence is worth noticing)
We have then give ali idea that thu suns
heat was originally produced by tho heating OF
immense mass of matter, which has since
gone cooling. andin such way that through
out the whole period the emission of heat has
been uniform
Another theory which for some time in
vogue. and which, though perfectly inadequate
10 explain the whole solar emission Of light an d
heat, yet relates to processes which doubtless
are actually ut work and have been at
work through long ages in the past, is what hes
been called the chemical theory, according