WHY COMET'S TAIL POINTS AWAY FROM THE SUN.

King Country Chronicle, Volume VI, Issue 458, 20 April 1912, Page 7

WHY COMET'S TAIL POINTS AWAY FROM THE SUN.

Because the tail increases in splen dour as the sun is approached, ant because it invariably points away from tho sun, no matter where th< comet may be in its orbit, it follows that some solar force, more powerful than gravitation, must drive matter from the head to form the tail. It is enly now that a satisfactory explanation Jias been found for this iiitomaly, An undreamed of force ha£ 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 know 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 ? Simply because light pressure acts not sc much on masses as on surfaces. Th: 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 reniains f.]ie aame, but the surface mns been increased. Divide each little bali again into onf thousand smaller balls. The resulting one million balls st.ill weigh one pound, but 1 lie surface has been snormously augmented. Carry this subdivision so far that leaden particles arc obtained r.iofsnm-in;; one twenty-thousandth of an inch in diameter. Each one of these particles if placed into interstellar space, will remain stationary because its weight (gravitation) will exactly counterbalance the, light pressure of the sun If subdivision be carried beyond that critical diameter, light pressure will wrench each particle from tho grip o solar gravitation and hurl it intc space.