The river press. [volume] (Fort Benton, Mont.) 1880-current, 1909-05-19
THE EARTH'S MOTIONS

| IHt tARIH'S MUIlUNy
How We Are Whiriing Aroune
and Through Space.
THE INFLUENCE OF THE SUN,
Without lts Attraction That, Draws tn,
World Toward Il In an EIiiptieaI
Course Our Globe Would Wander on
Forever In a Straight Line.
There r those who think much OF
moving from n point to another of
the earth-travel they call it-and vet
pay little heed to tie wonderful jour.
ney Of the earth itself. Many. again,
go to seek a climate while the hurry.
Ing earth is bringing to them one eli.
mate after another in endless success.
sion. Those who have not hitherto
taken much notice Of the earth's prog.
ress-who have not, 30 to speak, looked
out OF their carriage window as they
are whirled along-might ind a new
interest In doing 30. Look, for exam.
pie, at the apparent size Of the sun.
Casual observation shows that it ap.
pears larger in the winter heavens.
And exact measurements tell us that
1t Is largest on Jan. 1 and smallest on
July 2. The size Of the SUN thus marks
the earth's nearest approach and
| greatest distance from the sun. Accu-
rate astronomical measurement Of the
suns diameter might even determine
the day Of the year, for the daily vari-
alton in the apparent size Of the sun is
some nine-1ftieths Of a second Of an
gular measurement. And astronomers
profess to Measure the second decimal
Of seconds.
There are three ways In which we
are journeying with the earth. There
Is. first, the daily revolution, which car.
ries us through a complete circle in
twenty-four hours at a rate varying
from rather more than a thousand
miles an hour at the equator to moth
ing at the poles, where no one, by the
way. has ever been. Then We are trav-
cling around the sur once a year at
the rate of eighteen miles a second.
Thirdly, we are journeying through
stellar space, for n Of the most re-
markable facts which modern astron-
omy has brought to light is that our
solar system, the sur with all its plan.
cts, is on a journey toward the con-
stellation Lyra at the rate Of ten miles
a second.
AS we sit in a train and are whirled
along 1t sometimes appears as If the
scenery were flying. past us rather
than we past it. So the daily revolu-
ton Of the earth-a thousand miles an
hour at the equator-makes the sun
rise and set. and our yearly Journey
makes the sun apparently travel
through the consultations of the 20.
diac. If we move round any stationary
object on the earth we see it with a
constantly changing background-now
a windmill. now a cottage, now a
wood, now g. church, etc. So as we
travel round the u we see it with an
ever changing background Of stars
now those of Aries, now of Taurus,
now Of Gemini, and so on. The posi-
ton Of the sun among the stars marks
the stages of the earth's annual jour-
ney. And as the earth arrives at diff
ferent points of its orbit the times Of
the risings Of certain stars vary. These
indications Of the earth's progress
have been taken as marks of the sea-
sons. Thus when Sirius rose with the
sun 1t was known that the dog days
had begun. Early astronomers watch
ed carefully for the rising Of the dog
star. The Egyptian astronomers look
ed for the helical rising Of Sothis to
proclaim the new year.
1t is the earth's yearly journey round
the sun which enables us to determine
the distances of the stars. The method
is precisely that adopted by surveyors
for determining the position of objects
on earth. The direction of the object
whose distance Is to be found is OBJ
served from two points a known dis.
lance apart. The rest is mere calcula-
ton. In the ease of the stars the direc-
lions r observed from two extreme
points in the. earth's orbit instead Of
from the two ends of a base line. The
process Is called triangulation when
applied to earth measurements, and
everybody understands what it means.
When applied to the stars it is called
parallax and remains a mystery to
most people. Such Is the obscuring
power Of a word.
The "litt1e more" and the little less"
Of Browning are forcibly illustrated In
the direction Of the earth's journey
round the sun. An elliptic course DIFF
fering very little from a circle, COM
bined with a tilt Of the axis, gives us
the seasons. But IL this difference and
tilt did not exist there would be no
seasons and one climate would rule
the year. If, again. the course were
more elliptic. then for the hemisDhere