The Republican. [volume] (Oakland, Md.) 1877-current, 1891-09-18
EARTH VIEWED FRONTS NOON.
Abou= Sixteen Times as Big as the Sun and
Blue.

10 CNlNChI lIdI " d lunar OOSCIhCI
Che disk of earth appears to be equal tc
about sixteen areas of the solar disk.
The solar disk, as seen from earth, is
on an average equal to the lunar disk
seen from the same point, for, in
! solar eclipse, the disk of the moon
covers the sun in a total event of that
character, while it fails to cover the sun
! in an annular eclipse. Therefore, the
apparent sizes of these bodies must
average about equal in size to terres-
trial observer. Again, the solar disk
will appear to the lunar observer just
| equal to what it seems to be when seen
| from earth, because the distance from
the san to the moon averages equal to
the distance from the sun to earth.
| Furthermore, the diameter of earth is
equal to about four lunar diameters,
and of course the areas of their disks
vary as the square of their radii, and
| TINS makes the terrestrial disk about
| equal to sixteen lunar disks, and, of
course, if the lunar disk is equal to the
solar disk at given distance, then the
terrestrial disk will seem to be about
sixteen times as great at the same
| distance.
This enormous disk of earth must be
| blue in color to the lunar observer, be-
cause earth's atmosphere is blue. and
all things seen through il seem blue
Even intcrstellar space seems blue
through this medium, and the unillumi-
mated parts Of the moon can not be dis
tinguished from the space that abuts it.
Bright, direct and reflected light is not
affected appreciably by its passage
through our atmosphere; therefore,
stars, moonlight and distant illumina.
tons are not noticeably blue from that
| cause.
1t may be well to examine sunlight
to see why it is not made blue in transit,
and as the moonlight is sunlight reflect.
ed the explanation will do for both, and
i'll fact, for all. TO the terrestrial oh.
server of the sun there is visible an illu.
minated cone, the apex of which is in his
eye and the base on the solar disk Re.
ducing this cone to dimensions that the
mind can grasp, we will adopt Il scale
of 5000, 900 of miles to the inch and i'm,
aglne or construct a conc ten feet high
whose base is one-half an inch in diam
eter. Now, if the mathematical point
or apex of this cone be blue, five ten.
millionthS of one inch thick, which is
the proportion roughly, considering the
atmosphere to be forty miles high, it
will be seen why sunlight 50 easily
OvercOmes the color of air If, how
ever, we construct a cone to Illustrate
the view OF the earth to lunar OBJ
server we must, to a height of ten feet,
have base of two inches diameter,
with blue coat on that base one-six-
tieth of an inch thick Ga very thick card
is about that thicknesS). Here the base
of the cone is blue instead of the fine
point, and every ray travels through
the whole thickness of the atmosphere of
earth twice. The whole terrestrial disk
covered by its blue envelope is seen at
once, and if, as we know to be true,
the air colors distant objects blue to the
observer on earth it must color earth
blue to a lunar eye.
do not forget that when the earth
is full to the moon there may be a
white spot or spots where the direct
solar rays are reflected to the moon, but
that spot can not equal the apparent
area of the solar disk, or rather one-six-
teenth part of the apparent terrestrial
disk.
OF course, when the moon is eclipsed
to earth. the effect of the lunar observer
would be solar eclipse. Then the blue
air should be visible around the edge of
earth slightly like that seen about the
moon in some cases of total eclipse and
known as the corona. At such times
the aurora should family illuminate the
dark side of earth and perhaps slightly
be reflected on the eclipsed satellite.
If we consider aurora borealis and its
data. comparing it and them to nebula
and comets tails, we must believe that
earth has on the side opposite the sun a
valuable streaming appendage of bright
luminous effect. Authorities, after diff
fering infinitely in results, now declare
that they are ignorant of the height to
which this phenomenon reaches. Hum
boldt says ten degrees, which means
any height according to the distance.
The same aurora has been seen from
the polar localities to fourteen degrees
north. No one knows their height, be-
cause our atmosphere may shut out
great part of distant effect. and moon
light and twilight probably ncutralize
the higher effects of all observers The
only question is: Does the lunar OBJ
server see a tail streaming after
earth? And considering the clearness
that the tails of comets exhibit one hun
dred millions of miles distant and visi-
BILE nebula unknown millions of miles
in space, l assert that aurora borealis
should be and is bright and beautiful
trail after our great mothers glorious
garment.
There are many colored stars and
| planets Mars is red, Venus is white.
Many stars are blue; in one group all
| are blue.-N. y. Times.
| Thought She Had Been Neglected.
"What an enjoyable concert that was