WHY COMET'S TAIL POINTS AWAY FROM THE SUN.

King Country Chronicle, Volume VII, Issue 568, 17 May 1913, Page 7

WHY COMET'S TAIL POINTS AWAY FROM THE SUN.

Because the tail increases in splen dour as the sun is approached, a n< because it invariably points away from the sun, no matter where th< comet may be in its orbit, it follow, that some solar force, more powerfu: than gravitation, must drive matter from the head to form the tail. It is only now that a satisfactory explanation has been found for this anomaly. An undreamed of force has been discovered. That force is nothing less than the pressure of light. It is rather startling to learn at thi:j late day that the sunbeams which play upon green grass; and blue water are actually pressing the earth. Yet that pressure has been so accurately measured that we kno-w now that the earth sustains a light load of no less than 150,000 tons. Why is it that we do not sea objects pushed intc space by the solar effulgence ? Simplj because light pressure acts not sc much on masses as on surfaces. The less thei mass and the greater the surface the more pronounced will be the effect of light pressure. Divide a ball of lead weighing one pound into one thousand little balls. The total weight remains the same, but the surface has been increased, Divide each little ball again into one thousand smaller balls. The resulting one million balls still weigh one pound, but the surface has been enormously augmented. Garry this subdivision so far that leaden particles are obtained measuring one twenty-thousandth of an inch in diameter. Bach, one of these pal tides if placed into interstellar space, will remain stationary because its weight (gravitation) will exactly counterbalance th« light pressure of the sun If subdivision be carried beyond thai critical diameter, light pressure will wrench each particle from tho grip o solar gravitation and hurl it intc space.