The L'Anse sentinel. (L'Anse, L.S., Mich.) 18??-current, 1890-10-11
Why THE SKY. is BLUE.
Various Prominent Heavenly Tints Ana
1yEsd-Wby Stars Twinkle.


"You have all noticed said the pro-
lessor, according to the Cincinnati
TlDies-Star, ''that when we look away
from the sun into the clondless sky. tho
heavens appear blue; when. however,
we look In the direction of the sun,
especially when. after sunset. we look
toward the western horizon. the color
Is a yellowisb red. With the spectro-
scope'it can be shown that the white
light from the sun is produced by a
mingling OF different colorcd rays. In
deed. this can be shown by means of
any triangular prism. say one of tho
pendants of a chandelier. One OF
these placed in the path of beam of
light will project on screen band
OF seven colors--rcd. orange. yellow.
green. light blue. dark blue and violet.
Understanding this we can readily see
how tie effect Is blue when piece Of
blue glass is interposcd or red when
red glass is used. All but the blue and
red rays respectively are absorbed;
these, however. pass through freely,
and we say that the body is blue or
red, when really the color is not a
property of the glass in any true sense
but of the sunlight. What has this to
do with the sky colors? l will now
show you. Dissolve n little white
CASTLE soap in Il tumbler of water, so IA
to make the water slightly turbid.
Place black screen behind the
tumbler and hold the whole so that the
sunlight must be reflected from the
liquid before it can reach your eye.
Tho lio,,id will .nnoor hIna JI,1I -
next in direct line toward the sun and
it appears yellowish red. Now. these
are the exact appearances of the sky.
Sky light is refractcd light. The water
particles in the atmosphere, like the
particles of soap in the water refract
blue light; while the background of
darkness surrounding the earth re-
places the black screen. The atmos-
pbere. like the solution Of soap and
water. transmits yellow and red rays,
but slightly refracted, while the blue,
being II weak color, is refracted too
low 10 be seen; hence when we look
toward the source of light in the even
ing or morning the sky is of a yellowish
red color. This effect is more pro-
nounce,l then than during the day, be-
cause when the sun is near the horizon
the rays travel n greater distance in
the. air in order to reach the earth than
when directly above us. Consequent
ly the blue rays are moro thoroughly
refracted.
The atmosphere has many effects in
modifying the appearance OF the sky
and the heavenly bodies. Look at
Venus over there near the western
horizon and just below the crescent
moon. which has come into plain view
while we have bccntalking ION account
of the deepening darkness). Its real
distance from the horizon is not rs
great us it appears. for the rays of
light which it reflects to us and which
it receives from the sun are bent down
ward when they pass into our mir.
perhaps fifty miles from the carth's
surface.
las the effect is the same rs that
which would be produced were there
no atmosphere. by rays proceeding
from higher star. we locate tho body
In more elevated position than the
one which it actually occupies. Put
dime on the bottom of a pail filed with
water and you have like conditions
with similar effect. If you place
your hand where you think that you
see the coin you will not touch it, but
a spot perhaps IN inch above the true
bottom. Again, do you notice how
steadily Venus shines? Ifyou are here
an hour later. when the stars are all
out, you will observe that all those
near the horizon, the others to similar
extent. are merrly twinkling. This
appearance, made familiar to all of us
by the old nursery rhyme, Twinkle,
twinkle, little STAR Is not noticeable in
the case of any planet except Mercury.
and has been Il subject of much study
on the part of scientific men; it now
generally believed that 1t arises from
the Unequal bending of the rays Ut
light as they pass through aerial cur
rents of different temperatures and
densities. The facts seem to support
this theory, for where the air is the
densest-near the horizon-the effect
is most noticeable. where it is the
rarest-in our zenith--it is less marked.
This twinkling produces another
illusion. When we look ut the heavens
on II clear winters night the first i'm
preston on our mind is that we see an
almost infinite number Of stars. In
truth seldom can an ordinary eye dis
Germ more than 1000 at once. If you
should observe the sky nightly for
whole year there would DO presented
to your view only about 5000. But IL
you take q telescope rs Sir William
Herschell did, and point it toward that
portion of the milky way which looks
the whitest and the m;lkiest, you will
see more than GOO. 600 stars pass across
the field of your instrument every fifteen
minutes"