WHY THE SKY IS BLUE

Hokitika Guardian, 6 December 1923, Page 1

WHY THE SKY IS BLUE

George I'. Sieges, 11. 5 c., writing in the Daily Mail says that the blue colour of the sky is a matter that has given scienti-Is lar more trouble than is generally known, for hundreds of years tin- explanation et the blueness

was in dispute, and < veil the modern solution I' -omewliat complicated. Tito opinion which is very commonly held, that the blueness of the skv is just due to the nature of the atmosphere which reflects the blue rays of light and lets the other colours pass, is very

largely erroneous

Among the early scientists, Leonardo da Vinci put forward the interesting theory that the blue is in reality a speckled mixture of white light from the atmosphere with the black of space. In this connection one may refer to the llhie Andalusian fowl, which is a cross between a black and a while, the two colours being blended m the feathers to produce a blue e fleet.

Sir Isaac Newton believed that ill® blue wax produced by the interference ol rays reflected from the front and rear surfaces ol water drops, 111 the same way as colours are produced in -cap hubbies. This theory held ground mr 1 10 years. Then if was discovered that such droplets as .Newton required would cause tin; heavenly bodies to appear magnified, and to get over this difliciilty hollow droplets were invented. Finally, it was found that sky light is partially polarised (vibrations in one direction instead of in all direction--), and this discovery laid Newton's theory open to attack from tlie mathematicians, who proved that the observed angle of polarisation did not agree with what should lie produced by reflection from water. Tim modern theory is that the blue colour is produced by ••.scattering” of light, a process which is more difficult to understand than the name indicates.

Under the influence of sunlight the molecules ol I lie air and oilier particles

siu h as dust moles give out a light of their own. Physicists have shown ‘hat: when the pariieles in a medium through weieh light passes are verv

•nuili the light produced in this manner is of short ware-length or belonging to the blue end of the spectrum. The that rises freshly from the end of a cigar is blue from this same cause, and so also is that from a cigarette, l>m during inhalation the smoke particles become agglutinated together and on exhalation t.bov arc

too large r.> nr.xlm-e tlie him- light •Inis the exhaled smoke is ustuili white.

V" .--.lien talk about a smoker being up in the clouds, and it is rather curious to lit id that Micro is a link in science F-iuv.-i; smoke and the blue