Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-11-12

hold that the ocean beds are permanent
features of the earths surface, protected
as they are from atmospheric erosion,
and have suffered no change in geological
time.
From the standpoint of quantity it
would have required shell of matter
covering all the ocean surface to depth
of thirly-fve miles to form a spherical
body the size of the moon. This depth
we may therefore take on this suppose
ton as the thickness of the crust of the
earth at that time. Since the average
depth of the ocean is about three miles,
this crust was floating on the earth s
liquid interior, immersed to a depth of
thirty-two miles. The density of this crust
as we find it in the moon Nhree and one
half gives us a not improbable value,
bearing out the supposition.
When first thrown off, the moon can
not have had its present shape, as the
attractive force of the earth would not
have permitted a spherical body of such
size to exist in its immediate vicinity.
1t possibly took the form of ring, more
or less irregular, surrounding the earth S
equator, and was probably composed of a
large number of separate bodies which,
as they receded, coalesced and eventually
took the present spherical shape.
Having now looked back into the past
as far as modern science can see, let us
turn in the opposite direction and learn
what the future has in store for us. Are
we going to lose our moon after all?
Apparently not, for the recession is lin
tied. The moon may continue to reCede
until it reaches a distance of three hun
dred and fifty thousand miles, or about
half as far again as it is now. It's month
will then last fifty of our present days.
Our day at that remote epoch will also
have increased and be fifty times as long
as it is at present. The earth and moon
will then constantly present the same
face to one another. The moon will
cease to rise and set, there will be one
point on the earths surface where the
moon will be always overhead, and people
living on the other side of the earth will
never see the moon at all. After that
the tides will cease to act, a permanent
condition will have been reached, and
no further change will be possible.
That this condition of affairs cannot
occur in many millions of years is obvious,
but is it not possible that in the mean
time other events may occur which will
modify or entirely change the order of
procedure? To this question science
gives a pretty distinct affirmative. The
moon will cease to reCede as soon as the
tides cease to exist, and the tides will
cease to exist as soon as the ocean dries
up, or freezes into one solid mass.
Whether in the future the ocean will dry
up, we cannot say, although it looks as
if it would, unless it first freezes solid.
The heat of our sun is maintained by a
steady contraction of its bulk, amounting
to an annual diminution of about two
hundred and fifty feet in its diameter.
The suns diameter is about a million
miles, and although this diminutiOn is
small, it is clear that it cannot go on
forever In short, before long, astronom-
ical1y speaking, the heat of the sun must
begin to diminish sensibly. Professor
Newcomb concludes that in five million
years it will be giving out less than half
its present supply of heat. Long before
that time our oceans will have frozen
| over, and soon after that occurs our
!