Vishnupurana 2.8.p8

2.8.p8

When the sun goes to Pushkara Dwipa, a thirtieth part of the circumference of the globe, his course is equal in time to one Muhurtta; and whirling round like the circumference of the wheel of a potter he alternately spreads day and night on the surface of the earth. At the beginning of his northern course the sun passes to Capricornus, thence to Aquarias, thence to Pisces, successively passing from one sign of the Zodiac to another. After he has gone through them the sun gets at the vernal equinox when he makes the day and night of equal duration. From then the length of the night decreases and the day grows longer until the sun reaches the end of Gemini when he follows a different course and entering Cancer begins his declension to the south. The sun moves quickly on his southern course like the circumference of a potter's wheel revolving respectively. He glides along his course with the velocity of the wind and traverses a great distance in a short time. In twelve Muhurttas it goes through thirteen lunar asterisms and a half during the day, and during the night, it goes through the same distance only in eighteen Muhurttas. As the centre of the potter's wheel revolves more slowly than the circumference so the sun in his northern course revolves with less rapidity and passes over a less space of the earth in a longer time, until at the end of his northern route the day is again eighteen Muhurttas long and the night twelve the sun passing through them by day and night respectively in those periods. As the lump of the clay on the centre of the potter's wheel revolves most slowly, so the polar star, which is the centre of the Zodiacal wheel, moves very slowly and always remains in the centre like the clay. The relative length of the day or night is dependant upon the greater or less motion with which the sun revolves through the degrees between the two points of horizon. During the midday when his diurnal course is quickest his nocturnal is slowest and when he moves quickly by night he moves slowly by day. The length of his journey in both the cases is the same; for during the day and night he travels through all the signs of the Zodiac or six by night and six by day. The length and shortness of the day are measured by the extent of the signs; and the duration of day and night is measured by the period which the sun takes to pass through them. When he declines towards the north the sun moves quickest by night and slowest by day and when he declines towards the south the case is thoroughly the reverse.