Our Astronomical Column

Abstract

THE DRAYSON PARADOX.—A pamphlet by Mr. A. H. Barley on “The Drayson Problem “shows that this curious paradox has still a considerable vogue. It had its origin solely in the somewhat loose language of certain text-books which described the motion of the pole of the equator as circular, the pole of the ecliptic being in the centre. This description would be correct if only the solar and lunar precessions were concerned, but planetary perturbations cause the plane of the ecliptic (and hence its pole) to shift, thus causing a variation in the radius of the circle. Drayson, without carefully studying the evidence for the shifting ecliptic, asserted that it was really fixed among the stars, and that the centre of the north pole's motion was 6° away from the ecliptic pole, thus bringing about a very large change in the obliquity, which he supposed to be near its minimum at present. It would reach 350 at its maximum, when Drayson considered an Ice-age would occur. Dray-son's supporters slur over the fact that all the planetary orbit planes are changing, owing to mutual perturbations, theory and observation being in good agreement. Further, they claim to account for stellar proper motions by their revised precessions, omitting apparently to note that motions due to a mere change in the earth's axis would affect all the stars in the same region of space alike, whereas the actual motions differ from star to star, as can readily be verified from stellar photographs. If the Draysonians would study the full collection of modern observations of sun, planets, and stars, instead of wresting a few isolated observations to suit their preconceived views, they would soon be convinced that their hypothesis is not consistent with the facts, but that the ecliptic is actually shifting through an angle of some 47 per century.