The Brandon news. (Brandon, Miss.) 1892-1961, 1910-04-28
HOW THE OLD EARTH MAKES AN
EXTRA REVOLUTION.
In s6s Days ID Turns Upon its Axis 500
Times-Why Watches And Sun Dials
Do not Keep the Same Pro-
cesnion

/ ceSSion.
1t is fact not generally known that
:, owing to the difference between solar and
sidereal time, the earth rotates upon Its
axis once more often than there are days
in the year. The earth performs one
complete revolution upon its axis in % :s6:-
400 of solar time
This is called "sideral day." because
in that time the stars appear to complete
one revolution around the earth.
But, as the earth advances almost de-
gree eastward in its orbit, in the time
] that it turns eastward around its axis, it
is easy to understand that just one rotation
never brings the same meridian around
from the sun to the sun again; SO that
the earth requires as much more than once
complete rotation upon its axis to com
plete "solar day" as it has gone for
ward in that time.
1t will be obvious, therefore, that in
every natural, or solar day, the earth
performs one complete rotation upon its
axis and that the 365th part of another
rotation Consequently, in upon its axis
and the 365th part upon its axis; and as
every rotation of the earth upon its axis
completes a "sidereal day" there
must be 900 sidereal days in year.
APPLIES TO OTHER PLANETS.
The same consideration will apply to
our neighbor worlds of the solar system,
and since the rotation of any planet upon
its axis is the length of a sidereal day
at that planet, the number of sidereal
days will always exceed the number of
solar days by one, let that number be what
it may, one rotation being always lost in
the course of an annual revolution.
This difference between the solar and
sidereal days may be illustrated by re-
ferring to a watch or clock. When both
hands set out together, at IL o'clock for in
stance, the minute hand must travel more
than the whole circle before it will over
take the hour hand, that is before they will
again come into conjunction.
As the star-sphere turns a little more
than once around in twenty-four hours,
if we observe the heavens night after
night, at the same time, we shall notice
precisely the same kind of change as when
we look at the heavens hour after hour on
the same night. If we look at the stars
at 10 o'clock on any night and note their
position, and we again note the position
| of the stars at II o'clock on the same
night; then, afterward we examine the
stars night after night at 10 o'clock, we
! shall find that at the end of about fifteen
days they have at this hour the same Po-
sition that they had on the first night at
II o'clock-that is, they have advanced
by just one hours motion. In month
or thereabouts they will be found to have
advanced by two hours motion.
AN EXTRA REVOLUTION.
In a year they advance by twenty-four
hours motion-that is, by one complete
rotation-so that they have resumed their
| original positions, and this fact explains
why, in the course of year, the star-sphere
/ Gin reality the earth) turns around once
oftener than there are days in the year,
of goo times While during the year the
sun rises 365 times, star rises 900 times.
The latter will therefore during the year
have risen at every hour of the day and
night.
structive article on "How to Learn the
Stars" says: 'The amount by which
the stars have advanced each night on the
position they held at the same hour on the
preceding night is by no means so small
as is, perhaps, commonly imagined. This
may be easily tested. Let there be an up
! right of any sort few yards to the north
of the observers station, and let him no
tice the exact hour when a star lat a
| fair height above the horizon) appears
from behind the edge of the upright At
this hour on the next night he will find
that, as seen from the same station, the
star IS about two moons breadths past
the upright's edge. The observer should
look through fixed tube placed in the
same position on each night
LENGTH OF DAY.
The rotation of the earth determines
the length of the day, and may be re-
garded as one of the most important ele-
ments in astronomical science. 1t serves
as a universal measure of time, and
forms the standard of comparison for the