The Calendar of Venus.

Progress, Volume IV, Issue 5, 1 March 1909, Page 153

The Calendar of Venus.

At the April meeting of the British Astronomical Association, Captain Grant read a very interesting paper on a subject which belongs to philosophy quite as much as to astronomy — the development t)f the idea of time and the evolution of the calendar from the most ancient epochs to the present day. Although the foundamental division of time, the day, appears to us intuitive, we must remember that in the arctic regions the marking of this division is by no means easy. During several successive months the sun is either always below or always above the horizon and the only method — a very uncertain one — of distinguishing between day and night is to observe the times of high and low tide. "We owe the months to the motions of the moon. To this day the Malays, Polynesian, and Australian aborigines reckon time exclusively by months and days. The greater unit of time, the year, characterised by the regular succession of the seasons, has presented the greatest difficulties to exact determination, partly because the seasons are not sharply distinguished in some regions, partly because of Sfche universal desire to establish among the year, month and day simple relations which find no support in the facts of astronomy. Mr. M. Maunder, in commenting on Captain Grant's paper, remarked that the innabitants of Venus, if there are any such, must find it extremely difficult to establish units of time. If Schiaparelli 's theory is correct, and Venus always turns the same face toward the sun, the planet has no day, and the lack of a moon deprives it of a month. Finally, it has no year, for its axis of rotation is perpendicular to the plane of its orbit and the latter is almost circular. The problem of the rotation of Venus is yet unsolved. Stefanik and Hansky include from their recent observations, made from the summit of Mount Blanc, that the planet rotates on its axis once in about 24 hours. This is the opinion that was generally held before the researches of Schiaparelli. Lowell, on the other hand, has brought forward fresh proof that Venus always presents the same face to the sun.