El Paso herald. (El Paso, Tex.) 1901-1931, 1910-11-03

teresting. The earth must cast a Shad-
ow. and if this shadow falls on any
solid bodies, we will become aware Of
it? How. then, about the solid par
ticles in our atmosphere, the dust
specks? We can see these when a ray
of sunlight shines across a darkened
room The dust is carried many miles
up into the atmosphere. and the beam
of the electric searchlight across the
night sky makes it plainly visible
The dust is generally least after
heavy rain. If it were not for the
dust and water vapor in the atmos-
phere, darkness would settle down on
the earth very quickly after sunset
twilight would be very short Twilight
is caused by the reflection of the suns
light from the cold particles of our
atmosphere, and is ordinarily supposed
to be lost until the sun has sunk Is
degrees below the horizon. And II
the sunset cOlors and twilight arc make
the dust in the. atmosphere visible, why
cannot we see the earth's shadow? We
can see it, if we only try and observe
it. On a clear evening shortly after
sunset one can see the colorS of gold
and pink also in the east. AS the min
utes pass. these colors gradually fade
and are pushed up from the horizon
by blush gray darkness If one has
a good view of the eastern horizon, he
will see this grayish color gradually
rising up from the horizon in the form
of an arc of a circle AS the time
goes by, this arc mounts higher and
higher. The highest point of this arc
is exactly opposite the point where the
sun sets. This is the shadow of the
earth on the sky which appears as
the shadow bow. BY imperceptible de-
h. 14-~I,& e.
the shadow bow rises higher, the Colds
and pinks above become less pro-
nounced. the shadow bow fades into
the darkening sgy. and night comes
on. Thus can We realize that the
earth casts a shadow.
The Eclipse.
AS everyone knows, the earth moves
in her orbit about the sun in the
ecliptic $50 called because eclipses oc-
cur only when the moon is near it, !
If the moon moved in her orbit also |
in the ecliptic, there would be two |
eclipses each and every month. At |
the time of new moon, our satellite |
would come between us and the sun, !
and there would result an eclipse OF /
the sun. A fortnight later, the moon |
would pass into the shadow cast by the !
earth and a lunar eclipse would take |
place. But the moons orbit is not in /
the ecliptic. but is inclined to it by a !
small angle, little more than five
degrees. To have an eclipse of the /
moon our satellite must pass into the
earth's shadow, or in other words, the
moon and sun must be on opposite
sides Of the earth the moon rising
at sunset and the moon full. Since the
earth and sun are in the plane of the
ecliptic, the earth's shadow is like
wise In this plane. and an eclipse of the
moon can occur only when the moon is
near the echptic-or expressed In tech
meal terms-near her node. If the
full moon, she will pass through the
cepter of the earth's shadow, and a
centre of the earth's shadow, and a
long total eclipse will result. The far
Their the moon is from the ecliptic at
the time of full moon, the shorter will
be the duration of totaIity Evidently
1t is easy to calculate at what dis
lance 1t is possible for the moon to be
from the node of her orbit and still
have an eclipse take place. Since the !
motion of the moon is well known to
the astronomer. it is possible for him
to calculate many years in advance the
time of which an eclipse of the sun !
or moon will take place. In re- !
markable German book by Oppolzer, !
there Is given the elements of all the |
eclipses which occur for the next $50 |
years, and by a glance at a map one
can tell where to travel in order to
see any eclipse of the sun during that |
interval. Not only can the astrono-
ner by his calculations see into the
future in such remarkable way but
he can look back into the dim and
misty past and this same both tells !
when and where all eclipses have ia
ken place during the past 80 centuries,
to the date 1907 B. c.
The accuracy of astronomic predic-
ton in the case of Halleys comet
caused all to wonder at the exactness
Of the grand old science of ASTRONOMY.
but ecliDses can be foretold with a
precision far greater.
Moon Overtakes Earth.
Since the moon moves in her orbit
In an easterly direction, it overtakes |
the shadow of the earth and a darken-
ing appears first On the eastern edge |
Of the moon. The appearance of the !
moon as 1t crosses through the shad-