Delaware tribune. [volume] (Wilmington, Del.) 1867-1877, 1874-09-24
Nswsen's Theery OF ravatasien.


What Sir Isaac Newton did WAS not to discover
gravitation, for every one who ever saw a stone
fall saw An effect OF that force. He only dis
covered that srAvitation extended into the coles
tial spaces. His first reasoning was this we
nee that I'll bodies ct the surface Of the earth
tend to fall toward its centre. This tendency 10
seen on the highest mountains A. we'll ut the
surface Of the ocean. How far does it extend
upward? Why should II not extend to the moon?
We know that the moon u revolving around the
earth, and without some force to keep it in it's
orbit around the earth it would fly on into
space, and We should soon lose sight OF it,
Why should not this force, by which tho moon
iB continually turned Aside from the line in
which It is moving and kept in path around the
fall to the ground2 10 answer these questions,
Newton began by calculating what force would
really be required to keep the moon in her
curved orbit around the earth, and comparing it
with the force which Caused bodies to fall to the
earth's service, with the view to learning wheth-
er the two forces were inversey A. the square
Of the distance from the earth's csntre. Now
allow me to state . circumstance which iuus-
trstes the exactness Of true scientific reasoning
in reaching these conclusions. In his first cal
culations Newton found that the two forces did
not correspond. Had he been any other than
man OF true science, fear he would have twist
ed something 30 ~ to make them correspond.
Instead Of doing 30 he laid his theory aside for
more accurate measurements Of the size. of the
earth than those accessible to him when he
made his calculations had been executed by the
French astronomers, and that these gave for the
size Of the earth in English miles quantity
much larger than that which he had used In
making his calculations. He now found that
when he based his computations on the true
magnitude Of the earth, the two forces OF the
stone toward the earth and the moon in its or
bit correspond exactly 70 the theory. We see
from this that Newton did not discover gravita-
ton ITSELF but only that it extended into celes-
tiAl spaces.
Not only does the moon move around the
earth, but all the planets around tile sun. II no
force acted on them. they would 20 forward in q
straight line forever, aud soon be lost in the ce-
lestial Spaces The very fact that they
move in curved orbits around the sun shows
that they must be acted upon by some force d.
exact observations that were made showed that
this force was at all times and in the case Of all
planets directed accurately toward the center
Of the sun. Knowing the relative distance OF
the various planets from the sun, it was easy to
calculate how strong this force must DO in the
case Of each and the result showed that in the
case Of each different planet its intensity was in-
versey - the planet s1distanoe from the sun. 1t
remained only to ahow whether tho elliptic orbit
in which each planet wAs known TO move around
the sun would be produced by = force inversely
~ the square Of the distance. This required .
mathematical investigation which the scientific
men Of that day found very difficult ;but New
ton at length succeeded in solving the problem
| in manner which left no doubt, 1t was now
proved that each and every planet wss hold in
its curved orbit by force acting directly toward
the sun, and being inversly as the square of the
distance Of the planet from it. Az this force
was to all appearance Of precisely the same nA-
ture with that which made the moon tend tow
ard the earth, it was quite reasonable to cali it
| gravitAtion. 1t differs from the force which
makes stone wall fall only in boing directed
towards the sun instead OF the EARTH From
''Some Talks Of an Astronomer in Harper's
Magazine for October.