El Paso herald. (El Paso, Tex.) 1901-1931, 1916-02-26
SUNS APPARENT PATH IN SKY.

complete circuit of the heavens The
length Of the day increases up to the
summer solstice, after which it begins
to decrease.
Now, by glancing at the diagram, you
viii observe that when the sun is at or
near one Of the solstices It's path, for
a time, is nearly parallel with the
equator. and the length Of the days,
which depends upon the suns declina-
tion. changes very slowly at such
times. But as the sun passes from,
say, the Winter sOlstice toward the
vernal equinox, its southern declinea-
tiOn begins to decrease more and more
rapidly and after crossing the equator
its northern declination also increases
rapidly but falls off as it nears the
Summer sOlstice. This explains the
irregular increase in the length OF the
days, or in the acceleration of the hour
of sunrise and the retardation Of that
Of sunset At the solistices the change
amounts TO only a few seconds a day.
Near the equinoXes this is increased
to minutes.
In calculating the hours for an al
manac it is necessary to consult tables
given in the American Ephemeris and
Nautical Almanac. The hours change
with the latitude, because the farther
north you are in summer the longer
the days viii be and the shorter the
nights until within the Arctic circle,
there is an endless day.
There are a number of other elements
affecting the measurements of time
which would require a treatise for their
full explanation. For instance. the
length of a day being defined as the
time taken by the earth to make one
turn on it's axis, we find that this is
not the same il measured by the sun
as IL is II measured by a star. The
true measure is that given by star.
because the stars are fixed in place, so
FAR away that the motion OF the earth
IN its annual revolution around the
sun produces no apparent change in
their places in the sky.
Consequently when any particular
star is observed to have come back
again to the meridian the earth must
nave made exactly one aXial rotation.
But the sun, being the center around
which the earth travels, seems to move
round against the background of the
SKY at the rate OF about one degree
every twentyfour hours, continually
sliding eastward, and since the earth's
rotation is from west to east IL must
make little more than one complete
turn each day in order TO bring the
sun again to the meridian.
Nearer Earth IL to sun the Faster it
Must Travel.
Set up a candle in the middle OF
room, ana walk around IL at distance;
you VIII see the candle apparently
advancing around the walls In the same
olrectlon IN which you are Walking
The result OF this apparent motion OF
the sun is that the solar day is nearly
four minutes longer than the sidereal,
or star, day.
Then, because the earth's orbit is
elliptical and not circular its distance
from the sun is continually changing,
and the nearer IL is the faster il trav-
els. This, together with other things,
causes an irregularity in the apparent
motion OF the sun which renders il i'm
possible for any clock to keep step
with 1t. For this reason astronomers
nave invented a Fictitious" sun, which
Is supposed to move at a perfectly
regular rate, thus furnishing the basis
OF what is called mean time" which
is the kind of time kept by ordinary
clocks. Four times in a year sun
time and clock time agree. The dates