Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-10-07
RAD1uM AND SOLAR HEAT.
Latest Great Discovery Throws New
Light Upon Agesof the Earth.

rom the National Reviews
The discovery of radio activity makes it
necessary to reconsider our estimates OF
the time during which the earth can have
been fitted for the abode of living beings.
Consider first the suns heat. We know
that the sun is incandescent-that 1t Is
glowing white-hot body. 1t has been CIV
ing off heat for countless ages. Now. how
can this heat supply be kept up? Why does
the sun not cool down, owing to the loss OF
its primeval heat?
The most obvious answer would be that
this does happen. but that the cooling of so
large body Is too slow to be noticeable
even in very long periods of time. That
might seem at first sight to be a plausible
solution enough. But calculation conclu-
sively proves that 1t Is insufficient. The
heat which is stored up in white-hot body
would very soon be exhausted If 1t gave
out heat at anything like the rate that the
sun does.
The same reason prevents our supposing
that combustion can account for the out
put of solar heat.
Until lately the theory advanced by Won
Helmholtz has held the field. He showed
that IL the sun was assumed to be steadily
contracting to smaller dimensions. If, III
fact, the outer parts were assumed to be
falling down on the inner Ones enough
heat would be generated In the process to
account for the observed output for con-
siderable period The contraction which 1t
would be necessary to postuate Is too
small to be detected even by the most care
full observations on the SUMS diameter
which can be made
1t will readily be understood that calcu-
lations of this kind are affected by consid-
cradle sources of uncertainty; but when
due allowances have been made for these
1t seems impossible to admit that this
Of heat keen the SIlDDly for
more than, say, fifty million years. Indeed,
very high authority puts 1t lower than that.
Fifty million years Is a long time, judged
by human standards. But there are strong
reasons for regarding 1t as an insufficient
allowance. These are partly geological,
partly geological.
The earths surface is composed. In the
main, of stratified rocks, that is, of layers
of consolidated mud, deposited one on top
of the other. These layers extend to an
enormous thickness as we are able to see
when we examine cases where some of the
lowest ones have been brought to the sur
face by upheavel We can form some idea
of the gigantic period which the deposition
of these layers would take If we examine
cases where the process is now in opera
ton. The prevalent opinion Is that fifty
million years is quite an insufficient allow
ance of time. All but the very lowest or
the stratified rocks (and perhaps even the
very lOwesD contain fossils; thus 1t is GER
tain that the earths surface was fitted for
the abode of animal life at the time they
were deposited. In other words, its tenn
perature cannot have then been widely diff
ferent from what 1t now is, and the sun
must have been shining then with much tine
same brilliancy that 1t does now. so that
geological evidence seems to require a much
older age for the suns heat than 1t has
been possible to account for.
Zoology points in the same direction.
Consider the extraordinary complexity OF
structure of the bodies of the higher ami
mails, and especially Of. the human body;
consider further the fact that not the
slightest essential alteration of develop
ment of that structure has been observed
to take place during historical periods, and
1t will be admitted that no small allow
ance of time Is required for the Darwinian
process of natural selection, by which the
most complicated types of life are believed
to have been developed from the simplest.
Now that the development of heat by
radioactive change has been recognized 1T
is possible to understand how the suns
heat can have continued for much longer
periods than were formerly Ineligible. for
the present output of solar heat would be
toleraSly well accounted for If the sun con-
tanned much radium as pitchblende does.
The radium present at any one moment
would it is true, have only limited life;
1t is necessary to assume the constant evo-
luton of radium. or of some other radio
active element unknown to u.s.. as in pitch
biende and other similar minerals. A thou
sand million years heat without i'm
probability be thus accounted for.
The hypothesis that radioactive processes
are at work in the sun is not altogether
without confirmation, though have no
direct proof of it, for heium is abundant in
the sun; and helium is, so far as we
know, essentially product of radioactive
n