White Bluffs spokesman. [volume] (White Bluffs, Wash.) 1907-1938, 1928-01-27
MOON RAISES HIGHER
TIDES THAN THE SUN
Distance Is Chief Factor in
Reducing Sols Pull.

-"Although the moon
Is the chief factor in creating tides,
the sun also makes itself felt notice
ably in piling up the oceans waters"
says bulletin from the Washington
headquarters Of the National Geo.
graphic society.
"But the sun is tremendously great.
er than the mOOn-mOre than 27,000,.
600 times as large; why does 1t play
subordinate part to the little moon
in tide production?
distance is one answer, but 1t is
not the whole answer. If the sun
were as close to the earth as the moon
is 1t would pull the earth and Its wa
tiers some 27,OOO,OOO times as hard as
the moon does. But since distance is
such great reducer of gravitation
the suns pull on the earth is roughly
only 1873 times that of the moon.
"But the question persists why does
the moon produce the higher tides
when the sun pulls on the earth 1873
times as strongly?
"The total pull of body on an.
other and it's tide-producing force are
not the same. The tide on the earth
results from the difference between
the pulls on the center of the earth
and on the near and far sides. These
are the pulls that tend to separate the
waters and the earth, and therefore
to pile the waters up. And 1t will be
seen on close thought that two weak
forces that are considerably different,
operating one on the earth and one on
the waters, can cause greater sepa-
ration than two very strong forces
that are nearly equal.
Weakened by Distance.
Light and gravitation act some
what alike in that each grows weaker
as the source of light or gravtational
pull is moved farther and farther
away, and that both grow weaker
very rapidly-in proportion to the
distance of the source multiplied by
itself. The differences in gravita-
tional pull on which tides depend can
be visualized, therefore, by an expert
ment with light.
'Turn on an electric desk light or
other single bulb and hold near it
sheet Of ordinary white paper. Hold
the paper with one edge toward the
| light and only two or three inches
away and turn 1t very slightly so that
the light shines along the sheet and
Eliminates it's whole surface. There
will be a noticeable difference be-
tween the brightness Of the light at
point near the close edge and at a
point near the far edge.
"Now hold the paper in the same
way at a distance of ten or twelve
feet from an even brighter light, or
hold it in the daytime at such dis
lance from a bright window. You
know that there is still difference
in the degree Of illumination of the
two sides, but 1t is so very tiny that
you cannot detect it.
"The two points on which the sun
pulls to make the near tide-the sur
face of the ocean nearest the moon
and the earth's center-are 1000 miles
| apart, and this 1000 miles is a tiny
fraction of the earth-sun distance,
little over four-one hundred thou
sandths. In the case of the moon this
same 1000 miles is relatively large
fraction Of the earth-moon distance
1866 one hundred thousandths.
"When all the values for distance
and mass are inserted in the rather
formidable equations for the pulls of
the moon at the center of the earth
and at the surface, and for the pulls
of the sun at these two points, 1t
works out that the difference in the
moons pulls are roughly 2A times the
difference in the suns pulls. The
moon, therefore, exerts 21A times the
tide-producing power exerted by the
| sun.
What Makes Highest Tides.
"Most of the time the sun and
moon are pulling in different drec-
lions. But twice each month they pull
in the same line. 1t Is then that our
coasts have their highest tides
Theoretically every star and planet
and satellite in the universe raises its
separate tide in our oceans. Actually
however, even Jupiter, the greatest
of our sister planets, is SO far away
and relatively so small, that it's infu-
ence cannot be detected. To all in.
tents, therefore, 1t may be said that
only the moon and the sun, our near.
est and our most powerful neighbors
in space, have a share in making the
earth's tides"