The Celestial Cube

Extract

I. In the May number of the Gazette for 1943, Sir Percy Nunn contributed an excellent article on the celestial cylinder. He called it “an excursion intended to illustrate an application of elementary mathematics to astronomy” My experience has shown that, while many people are interested in the apparent motions of the heavenly bodies, few are prepared to make the necessary effort to obtain that degree of calculation in the subject, which makes it so much more fascinating. One of the main stumbling-blocks against attaining that precision, which Sir John Herschel so strongly emphasises in his Outlines of Astronomy, is the lack of knowledge of spherical trigonometry. The celestial cylinder and cube have been developed, therefore, in the endeavour to convert spherical into plane trigonometry. Mercator rendered signal service in transferring maps from the sphere to the plane. This movement has continued to such an extent that, in the intense concentration on the plane, children often lose sight of the spherical nature of the earth. They appreciate the beauties of the sky, they love to watch the relative positions of the constellations, but plane star maps are much more acceptable to them than spherical. Even with older students, attempts to introduce problems on the astronomical triangle are seriously hampered by a lack of knowledge of spherical trigonometry. To maintain their interest, one is obliged somehow to convert spherical trigonometry into plane trigonometry.