The National tribune. [volume] (Washington, D.C.) 1877-1917, 1895-08-29
TER FACTS OLE GRAVITY.

late personal and individual investigation that
he is pleased to put them forward
J.
THR FACTS OF GRAVITY.
When the writer first took up the study of
tides In the graded schools he refused TO accept
the lunar theory, for two reasons: First, he
cause he doubted the moons power over mat
sers of men; second, because he did not under
ttand, even if he ignored the first objection,
cow 1 could act in the opposite direction at the
lntpodes.
The remembrance of these difficulties sug-
gests the plan of discussion; and he VIII first
attempt TO show how it is quite possible for the
lunar mass to affect objects of the earth by
that infinite force OF gravity which operates
easily between the most distant planets
Although weight had always been known, it
was understood only upon the discovery OF
the law of gravtation. 1T is the measure of
gravity; which is condensed way of saying
that the weight OF an object is proportional to
the power gravity eXerts upon that object. and
that any modification in the source or applica-
ton of gravi8tion will produce correspond
ing change in weight distance being fixed
In other words if one-hslf of the earth
should suddenly be annihiiated we should as
suddenly find ourselves only half as heavy Or,
again. If two equal forces and Others were
exerted in opposite directions upon body, its
weight would be nothing; but il eXerted in the
same direction its weight would be doubled
distances in each case being equal.
Gravitation is that force which tends to bring
together any two objects which are separated.
Every object, from sun to "A micrOcoccus, has
q right to and does exert this inherent force, IN
proportion to its mass and inversely as the
square of the distances, upon every other
object.
LAW OF GRAvITATIoN.
The earth rises to meet the falling apple.
Two stones dropped from hight will be nearer
each other when they strike the ground than
when they started. Maskelyn, the English
astronomer, dropping pluinb!ine down the
side of q cliff on Mt. Schehallien, found the
mountain to draw the plummet fully IL" out
OF the vertical. Or. going beyond the narrow
limits OF earthly effects, We find Aicyone swing
ing the whole solar system into an orbit so vast
that we are rushing through space at the rate
of almost 1900 miles every day. And so tins
foree-always everywherc-is working out re-
suite from the incomprehensibly small TO the
iucomprehensibly great 1t is the mighty serv
ant of God, than which none is more certain
or more irresistihle.
The operations Of this force in terrestrial mat.
tiers had been matter of study to the imme-
date predecessors OF Newton. 1t remained
for that great Englishman to reduce them TO
q single law. aud that a universal one. lie
asked himself why this force which excrted
such power on the earth did not extend to
all creation He did an unusual thing,-he
stopped to think All the heavenly bodies
moved Somewhere they had acquired an ini-
tia motion. and would. as every body in motion
must 20 forward ia straight line forever,
unless interiered with 10y some external force.
(Newton's First Law of Motiou-The Law of
IDertiR.)
The fact then that the planets and satellites
did not move in straight lines, but in nearly
circular orbits. proved that they must be acted
upon by some external force. IL followed that
- f,.Aw-
about which the lesser one revoived. What was
the force that ruled worlds and preserved order
in the unversel
Newton thought 1t was gravity; and proved
il by showing that the moon falls toward the
earth according to the same law by winch an
apple falls, and that at the same time IL was
carried forward so far that the resultant mo-
tiOn was practically circular.
And so each revolving orb rushes on in its
endless course, hurried forward by these con-
Joined forces The earth holds the moon to her
orbit; aud the sun in turn cxerts the force that
keeps them both, with all the other eddying
worlds. wbirling about him. And he, finally,
with all his train, yields 10 the inyincible in
huence from the Peiadcs.
But If the sun pulls Neptune 1866 600 900
miles beyond tic reach Of his fiery arms, so
does Neptune pull the sun-though like the
ample and the earth, not with equal force
Earth pulls at the 50 aud filings thong about
every other planet and planetod Mercury.
Venus. Mars each asteroid, Jupiter, Saturn aud
Uranus are each pulling at one another.
Every meteor that flashes across the field OF
telescope adds it's slender thread TO the net
work. And so it goes until only the astrono-
mer aud mathematician can unravel the tan
gleG skein Of cross and opposing attractions.
But u can and Las been done. In 1921, 40
years alter the discovery Of Uranus. which was
then regarded as the outermOst planet, astron-
OmeTs began TO notice that il was disturbed in
its orbit as though some planet yet unknown,
body too far out TO be seen, was silently aud
perssteniy pulling at it.
They studied the yiedings Of Uranus to
this mysterious force and, finally, two men,
working Independently, calculated where in
the heavens the unseen planet could be found.
The strongest telescopes in existence were
turned aOft, and there marching serenely
forward like the trusty sentinel the ter
pickets, they beheldthe unnamed world Nep.
tune is lasting monument 10 the genius Of
Sir Isaac Newton.
And thus sec that each one of these
spheres is acting and reactiug upon every other,
not only perceptibly but practically consider
able. il is then, no longer possible 10 doubt
that the moon must exercise some graVitatinc
isfuence upon the earth-hoW much or how
little remains to be seen.
Ii this is clear, IL is our purpose next tc
show that the earth is in such condition thai
this influence, in whatever amount il comes
must be felt and appreciated.
III,