The Providence news. (Providence [R.I.]) 1891-1906, 1906-03-01

on the 2ist day OF March at Z a. m. the
sun crosses the equator from the south
side TO the north at the vernal equinox,
and real spring will he with us once more.
Twenty-one hundred years ago the sun
crossed at the first point OF the constella-
ton Aries but now II crosses 30 degrees
westward In the constellation Pisces. AS
tronomers still regard the first point of
Aries as the vernal equinox and allow for
the actual difference-3 degrees-in all
their calculations. This change in the
point OF the suns crossing the equator
has been going on for ages-in fact. ever
since the earth started upon Its career
and will continue ms long as the earth.
the sun and the moon last. While 1t
amounts TO only so seconds In n year. in
the course OF 26,00o years Il will make
a complete revolution of the earth.
This retrograde or backward movement
OF the equinoxes is called procession. and
was first discovered by Hipparchus. 13
years before the Christian era Newton
found 1t was caused by the sun and
moons attraction upon the earth at the
equator causing the earth TO tip just 30
seconds every year out OF a true axlal
revolution. This causes the earths axis
at the pole to move Tor "wobble') In a
circle having diameter OF about rs de-
grees (see map, and Is gradually moving
the axis OF the earth westward and away
from our present North Polar star. so
that we shall have TO find a new polar
star In the course OF few thousand
years
In about 6o00 years this will probably be
"a" Cepheus; then In 1900 years II will
be Vega In the constellation Dyra: I'm
1880 years, ~" Hercules In 2o.0oo years,
"a" Draco. and in 2s.ooo years the axis
will again point TO our present stellar
guide,
PATH OF THE NORTH STAR.
The real path OF the north pole in the
sky Ia not a true circle. but slightly
waving line, first on one side OF the circle
shown. then on the other; II Is caused
by the unequal attraction OF The moon at
the earths equator.
The sun is shown on our map at the
western horizon at p. m. on March q,
at the point in the constellation Pisces.
where IL crosses the equator at I a. IN.
on the morning OF that day. the change
in position being caused by the earth's
revolution for IL hours eastward, the sun,
really, not having changed its position on
the map one-half a degree I'm that time,
which, upon the scale here presented,
would not be one-eighth OF an inch.
The apparent revolution OF the stars
westward every night is caused by the
earths daily revolution eastward Day
and night are Of equal length-12 hours
over the whole earth on March 81
The stellar world presents for our ad-
mira tion this month it's most strikingly
beautiful considerations. as will be found
by reference 20 the map. Mercury will /
Join the planets Mars and Jupiter now
with US in the evening sky. and will be
found low I'm the west for a week or. ten
davs before and after the 18th inst, for
about an hour after sunset and close 10
where the sun went down.
THE BIG DIPPER
The Big Dlpper Is the one constellation
that every one I'm this latitude who looks
skyward probably can pick out at
glance. and is the key 20 the stars ana
that are visible to the max
ed eye In our northern hemisphere. From
night 20 night II seems 10 be slowly re-
volving around the north star with all It's
This Is caused bv the earth's
daily revolution eastward. The stars arc
hxed the earth moves; once this fact IL
made clear. the starry heavens becomes
an open book that all who will may read
The Big Dpper. the Little Dipper. our
Polar Star and the consultations Casio
pela Cepheus and Draco never pass from /
our view I'm this latitude. but as We VII |
den our sky view We hnd some constells-
tlons gradually. from night 10 night, dis
appearing on the western horizon. while |
others arc coming into view I'm the east |
This change Is going on AZ the rate or I
four minutes a day. the earth moving |
four minutes further east every day, which \
In the course OF n year amounts 10 a COM |
plete revolution OF the earth. during |
which All tine stars In our northern hsmis- 4
phere will have passed I'm review.
Moonlsss nights arc the best for star |
"a zing az the moons light dlns the glory /
of the stars. though "a has little effect /
apparently upon the planets. which arc /
much nearer the earth hy many billions 4
81 miles than any star In fact. the moon /
viii bs found helpful In locating the plan
cts as they all follow the same course /