The star. (Reynoldsville, Pa.) 1892-1946, 1908-07-08
The Soap Bubble and Its Secrets.
BY WILLIAM S. sIReE, N. b.

is free from drafts, the bubble WI.
be a perfect one. and will teach us
the principles that underlie the maxi
ing of sphere. This perfect form.
however, is seen only when the bub-
BILE floats. When resting upon the
goblet. it appear; very much like an
orange-that is. an oblate spheroid,
the true shape of the earth.
Putting 1t into the simplest lam
guage, the form of bubble is due
to the holding together of the soap
solution. to the outward pushing of
the air within and the resistance Of
the film.
If the air in the room is moderately
cool the bubble will float like tiny
balloon. The mouth and lungs at all
times having temperature of nearly
100 degrees, the air blown into the
toy bubbles is warmer and conse-
quently lighter than the air which
surrounds them; therefore they float,
and 1t is their lightness and grace that,
with their beauty, give them such a
charm. AS soon as the air within the
bubble cools 1t slowly sinks till 1t
reaches the floor. and the jar of its
contact usually ruptures the film.
The extreme thinness of the bubble
is indeed wonderful 1t is estimated
that the film in some places is only
one 3,000,000th of an inch in thick
ness. Probably few of us can con-
ceive of such thinness. Let me ex-
press 1t In another way. The Old and
New Testament contain some 3,000,-
900 letters. Now one 5000, ,000th is
such part of an inch as the first let
ter of the Bible is part of the sum
of all its letters.
The bubble, however, is not of
equal thickness at all points, and 1t is
for this reason that 1t has the various
colors. For instance, wherever the
film is orange red it measures about
three 1000, ,000ths of an inch, and at
point where lemon yellow is prom
inent about twenty 1,000,00Oths of
an inch. Perhaps you wonder why
the colors change from one part of
the soap bubble to another. This is
because the film of the soap bubble
evaporates and grows thinner, but
unequally so at different portions. A
greenish blue with pale rose red
spot near 1t Indicates an extreme
thinness, and at such point the film
is ready to give way at the least jar
You will be glad to know the source
OF the beautiful colors. Every one is
delighted with them, even If not in
terested by the explanation of their
origin. We may say that they come
from the light. Light gives color to
all objects, but not exactly as it does
to the soap bubble. White light from
the sun can be broken into the seven
colors which we have seen in the rain
bow. In that instance the raindrops
separate 1t into its parts. A glass
prism will do the same, as you may
prove by looking through a glass pen
dant from hanging lamp.
When the light reaches the surface
of the soap bubble a part is reflected
from it, and we see images on its sur
face as if it were a curved mirror.
Another portion of the light, how
ever, enters the film and is separated
so that a part Of the seven colors are
thrown into the bubble, and we can
see them at various portions of the
opposite surface. Another part OF
the light, after being broken by the
film, is reflected by its inner surface
back to our eyes, so that we see col
ors at the point where the light en-
ters.-Christia Advocate.