Nebraska advertiser., 1882-02-16

epoch which was crisi, in the history
Of our system. IL must have been at
least 50,000,000 years ago. 1t may
have been very much earlier. This
crisis was the interesting occasion
when the moon was born. The
length of the day was only a very few
hours. II we call il three hours
we shall not be far from the
truth. Perhaps you may think that If
we looked back TO a still earlier epoch,
the day would become still less, and
finally disappear altogether! This is,
| however, not the case. The day can
never have been much less than three
hours I'm the present order Of things.
| Everybody knows that the earth is not
sphere, but there is II protuberance at
the equator, so that, as our school-books
tell US, the earth Is shaped like an
orange. II is well known that this pro-
tuberance Is due to the rotation of the
earth on its axis, by which the equa-
torial parts bulge out by centrifugal
force. The quicker the earth rotates
the greater is the protubcrance. If,
however, the rate of rotation exceeds u
certain limit, the equatorial portions of
the earth could no longer cling togeth-
er. The attraction which unites them
would be overcome by centrifugal force,
and u general breakup would occur
IL can be shown that the rotation of the
earth when on the point of rupture cor
responds TO n length of the day some
where about the critical value of three
hours which we have already adopted.
II is therefore impossible for us to sup
pose a day much shorter than three
hours.
Let us leave the earth for n few min
utes and examine the past history of
the moon. We have seen the moon re-
volve around the earth i'm an ever
widening orbit, and consequently the
moon in ancient times must have been
nearer the earth than it is now. No
doubt the change is slow. There is not
much difference between the orbit of
the moon thousand years ago and the
orbit in which the moon is now NOV
ing. But when we rise to millions of
years the difference becomes very APP
preciable. Thirty or forty millions of
years ago the moon was much closer to
the earth than it is ut present, very pos
sibly the moon was then only half its
present distance. We must, however,
look still earlier, to certain epoch not
less than fifty millions of years ago.
At that epoch the moon must have been
so close to the earth that the two bodies
were almost touching Everybody
knows that the moon revolves now
around the earth in II period of twenty
seven days. The period depends upon
the distance between the earth and the
moon. In earlier times the month must
have been shorter than our present
month. Some millions of years ago the
moon completed its journey in week,
instead of taking twenty-eight days, rs
at present. Looking back earlier still,
we find the month has dwindled down
to Il day, then down to few hours,
until ut that wondrous epoch, when the
moon was almost touching the earth,
the moon spun around the earth once
every three hours
In those ancient times see our earth
to be noble globe, as it is at present.
Yet it is not partly covered with oceans
and partly clothed with verdure. The
primeval earth seems rather II fiery and
half-molton mass, where no organic life
can dwell. Instead of the atmosphere
which we now have, see dense mass of
vapors, in which, perhaps, all the
oceans of the earth are suspended as
clouds. see that the sun still rises
and sets to give the succession of day
and of night, but the day and the night
together only amount to three hours,
instead of twenty-four. Almost touch
ing the chaotic mass of the earth is Il
much smaller and equally chaotic body.
Around the earth see this small body
rapidly rotating. The two revolve to-
gether, rs if they were bound by invisi-
BILE bands. The smaller body is the
moon. - L0niOn Nature.