El Paso herald. (El Paso, Tex.) 1901-1931, 1911-01-28


asked, What is meant when Il
- daytime a clock says u o'clock p
about go out Of every hundred would
answer that at exactly at that hour the
sun is on the meridian and it is noon
But the sun is not on the meridian
each day when the clock is at u
Nearly every one has a friend who
owns a valuable watch that keeps ex-
cellent time, and many a time this
friend. on being asked the exact time
has looked at his watch with a great
deal of pride. and has told the hours,
at the same time remarking, This
watch regulates the sun" If the
watch keeps as poor time as does the
sun. It should be sent to q watch
maker. for the sun is a wretched1y
bad timekeeper. Il sometimes is as
much as a quarter Of an hour fast
and at another season It may be an
equal amount slow. In fact, II may
be said that clock Of extreme pre-
cision, such as the astronomers use.
is never exactly at II when the sun is
on the meridian.
Earth Gives Us Our Time.
But, it will be asked, eff the sun
does not give US our time, what then
does?" As everyone knows, the rota-
ton of the earth on its axle is our
luton marking a day. AS the earth
rotates, It carries our meridian around
with it, and as the meridian crosses
through the heavenly bodies in sue
cession they are said to transit" The
interval of time between two success
i've transits Of the same celestial body
across the meridian is called a day.
If the body considered is a star, we
have what IS known TO the astronomer
as a star day, or sidereal day.
The stars are fixed, the earth ro-
tates uniformly on its axis, and as q
result the sidereaI days for all stars
are of equal length. But which star
shall be chosen as the most important
in the heavens so that time shall be
reckoned from it? Intsead of select
ing a star, the astronomers have picked
upon the VernaI equinox, the intersec-
ton in the sky Of the equator and
eclipt1c. When II is on the meridian
the astronomers clock says Oh. ON.
Q. 0s, the beginning OF the sidereal
day, whose hours run from Oh. to
24h- In a great observatory, the po-
sitions Of the stars are recorded in
time kept by such a sidereal clock, and
sidereal time is Of great Importance
TO the astronomer.
Movements of the Sun.
earth about the sun, the sun appears
TO move continuously eastward among
the stars, completing a journey once in
q year. The sun moves In what is
called the "ecliptic," and it's motion is
from west to east among the stars.
This apparent annual motion of the
sun has very important consequences.
Let US consider those only that refer
TO time. Imagine the sun and a star
on the meridian together at noon on a
certain day. One complete revolution
Of the earth on its axis would bring
the earth's meridian back to the star
and a sidereal day would have elapsed
In this interval OF time, the sun has
apparently moved eastwards among
the stars, and If is necessary for the
earth to rotate a little farther on its
axis to overtake the sun, bring 1t on
the meridian, and complete the solar
day. Hence sidereal days are each
shorter than solar days.
AS the sun completes its journey in
a year II crosses the meridian one
time less in a year han does q star,
and with respect to he sun, the stars
gain one revolution and hence IN
year there are 1917 SOLAR days, but
1864 sidereal days. Consequently, it
IS readily seen that in II months a
sidereal clock will gain a day or "a
hours on a solar clock. Twenty-four
hours per year means two hours per
month, or nearly four minutes a day,
a second every six minutes.
Sidereal time keeps track of the mo-
lions of the stars (Which is its sole
purpose), and hence is seen that each