Page 237 - Lokmanya Tilak Samagra (khand 2)

24 SAMAGRA TJLAK- 2 • THE ARCTIC HOME

This causes the seasons to occur at diffeient points in the earth's
orbit during this great cycle. Thus if the winter in the northern
hemisphere occurred when the earth was at P at one time, some
time after it will occur at p and the succeeding points in the
orbit until the end of the cycle, when it will again occur at P.
The same will be the case in regard to summer at the point A
and equinoxes at Q and Q'. In the diagram the dotted lines qq'
and pa represent the new positions which the line QQ' and PA
will assume if they revolve in the way stated above. It must
also be noted that though the winter in the northern hemisphere
may occur when the earth is at p instead of at P, owing to the
aforesaid motion of its axis, yet the orbit of the earth and the
points of perihelion and aphelion are relatively fixed and unchang-
eable. Therefore, if the winter in the northern hemisphere occurs
at p, the earth's distance from the sun at the point will be greater
than when the earth was at P. Similarly, in the course of the
cycle above mentioned, the winter in the northern hemisphere
will once occur at A, and the distance of the earth from the sun
will then be the longest. Now there is a vast difference between
a winter occurring when the earth is at P and a winter occurr-
ing when it is at A. In the first case, the point P being nearest
to the sun, the severity of the winter will be greatly modified
by the nearness of the sun. But at A the sun is farthest removed
from the earth, and the winter, when the earth is at A, will be
naturally very severe; and during the cycle the winter must once
occur at A. The length of the cycle is 25,868 years, and ordi-
narily speaking half of this period must elapse before the occurr-
ence of winter is transferred from the earth's position at P to its
position at A. But it ·is found that the points P and A have a
small motion of their own in the direction opposite to that in
which the line of equinoxes QQ' or the winter point p moves
along the orbit. The above cycle of 25,868 years is, therefore,
reduced to 20,984, or in routid number 21,000 years. Thus
if the winter in one hemisphere occurs when the earth is at P,
the point nearest to the sun in the orbit, it will occur in the same
hemisphere at A after a lapse of 10;500 years. It may be here
mentioned that in about 1250 A. D., the winter in the northern
hemisphere occurred when the earth in its orbit was at P, and
that in about 11,750 A. D. the earth will be again at A, that is,
at its longest distance from the sun at the winter time, giving