The Columbia herald. [volume] (Columbia, Tenn.) 18??-1935, 1891-06-12
THE EARTH'S ORBIT.
How Kepler Discovered That the Planets
Move In ElIipses.

|
Move in ElIipses.
kepler was the first astronomer to dis
cover the form of the orbits Of the plan.
cts and the laws governing their motion
around the sun. He soon found that
the earth and the other planets did not
move in circles, but In ellipses. An
ellipse is an oval figure, bounded by a
regular curve and corresponding to an
oblique projection Of a circle, or an OBJ
lique section of conc. 1t is plain that
there is no point in an ellipse, which is
equally distant from all points of the
circumference, as the center of circle
Is. But mathematics shows this figure
TO have two points, which are palled fppi
iplural of fQcus) the sum of whose dis:
tances from any point of the boundary
curve line, always equals the major
axis, or longer diameter of the ellipse.
Keplor discovered, by much laboriops
calculations, that the orbit of Zach
planet is an ellipse having tho sun in
one focus Kepler discovered this
law; it was left to Newton to find
its reason In the laws of motion.
Newton's great primary discovery
was the law of grayitatioD, but he
did not merely rest with showing that
the planetary motions could be OK
plsined by that lew. but further solved
the inverse problem. and determined
what kind Of molten that law required
He found that the orbit of o body HaQV..
Ing about o central mass under the law
OF gFavitatioL Is not of Reoessity circle,
nor an ellipse OF certain proportions
But 1t must be comic section, and
whether 1t is a circle, an ellipse, paro-
bola, or hyperbola. depends upon cir
cumstances- The first law of motion,
as shown by Newton, is that body set
In motion and acted upon by no outside
force, will move forward forever In a
straight line. The second is that when
q moving body is acted upon by any
force its deviation from the straight
line motion will be in the direction of
the acting force and proportional to 1t.
Newton argued that two forcas we're act
ing on the heavenly bodies. tangential
force carrying them forward In straight
line, and o central force drawing them
to the center of our great solar system,
the sum- Two forces acting upon a body
at the Same time, ono in the line of It's
motion and the other directly across tho
line of its motion, will give resultant
curvilinear motion. This can be demon
strated by any simple natural object, as
q ball and a string. Mathematics can
demonstrate. with absolute accuracy |
the rate of motion produced by these |
forces and the form of orbit |
through which they will carry body.
A calculation from tho laws which Kep- |
ler had deduced from observation Of the |
planetary motions, enabled Newton to |
chOyU haf fhn ~ fof
on each planet directly as to its mass
and inversedly as the square of its mean
distance He further showed that if the
planets are acted upon by force direct
ly in the line of the sun, the radius VOC
tor Of each body, that is, the line con-
Meeting the body with the central force,
will sweep over equal areas in equal
times, which is Kepler's second law.
The determination of the form of orbit
that would be described. in these con-
ditions, was one involving difficult
calculations, but Newton
succeeded in showing, by rigid demon,
itration, that this orbit would be an ell
ipse, with the sun in one of its foci. II
must not DO forgotten that the discovery
II Newton was not only of a force draw.
ng the falling apple to the earth and
'no ear6n bOWaru Ine sun, Out also OF |
by which, In direct pro
'ortion TO mass, the earth draws the sun
md tho apple, the earth. Thus by action
md reaction, as we'll as by opposing
orces the entire created universe is
lept in equipoise and holds its harmoni.
us movement through the boundless
ealms of space.-Chicago Inter Ocean.
Hadn't Any of the Symptoms.
Fair Entertainer Ito young operator)
What side of the markets. that the
vay to put it?-are you on this week, d
Ir. Brokaw?
Young Operator lat the other end Of
ne sofa II am what they call Fbear,'i
[iss KAionea liz
Fair Observation-Disclosures You-you
on't aet the isaat BIT In the world like :
bear. nt. HtekAR.-ChicATn TFibaAa g