SUNSPOTS

Greymouth Evening Star, 18 April 1936, Page 8

SUNSPOTS

STRANGE EFFECTS ON EARTH

The constancy of the sun s behavioui tends to conceal the fundamental role of the sun in\ the life of the earth. As the. sun has risen and set eveiy day, without obvious changes, for innumerable centuries, philosophers have given it respectful salutation and then turned to the study of apparently moie changeable and interesting things. But a moment’s though shows that every change in the parent and support of the solar system should be reflected in corresponding changes in the events on earth (writes the scientific correspondent of the Manchester Guardian).

As the sun’s constancy is its most prominent quality, it follows that its variations are relatively not large. They could not be easily detected without refined instruments and methods of observation. Thus the most notable solar variation, the cycle in the number of sun-spots, was not discovered until 1843, by Schwabe. Since that date the occurrence of sun-spots has been carefully recorded, and fortuitous ancient records of outbursts of spots have /been studied. Europe became familiar with the existence of sun-spots when Galileo turned hi-s optic glass on the sun in 1610. They had been noted by the Chinese more than a thousand years earlier. After Schwabe's discovery that the number of sun-spots occurring within a given time reaches a maximum every eleventh year, efforts were made to discover whether this 11-year cycle appeared in any terrestrial phenomena. Almost immediately Sabine. Wolf and Gautier independently announced that such a cycle appeared in the strength of the earth's magnetic field. Interesting new evidence of the influence of the cycle on the electrical condition of the earth has been provided by wireless observations. About 1923 wireless amateurs in Europe found that American short-wave stations could be picked up. In the succeeding years wireless engineers found that transmission could be accomplished with shorter and shorter waves. They attributed this entirely to improvements in technique. Transmissions on waves as short as 13 metres were found effective about 1928. At this time the 8.8.C.’s Empire service was designed, and started with a wave of 49.6 metres. But after a few more years very short waves gradually became ineffective, and the wave-length had to be increased to 70 metres. Int 1934 70-90 metres had become the minimum wave-length for long distance transmissions. The period of 1922-23 included a cycle of spots from minimum to minimum. The maximum to minimum was about 1928, when longdistance short-wage" transmission was at its best. This was due to increased electrification of the upper atmosphere by the extra strength of the ultraviolet rays emitted by the sun during maximum sun-spot activity. This relation between sun-spots and wireless is now being systematically observed during the cycle 1933-34.

J COMPLEX RELATIONS. The relations between solar and meteorological phenomena have been authoritatively reviewed by Dr. C. E. P. Brooks. He writes that they are complex. For .instance, F. Baur found that the highest values of the total intensity of heat and light, emitted by the sun were not at those times when the number 'of sun-spots was largest. At. the same time, he found that severe winters in Berlin often occur near the times when sun-spot activity is at its greatest or smallest. Brooks himself was unable to discover any definite relation between the cycle and the distribution of barometric pressure over Europe. Jatho, Quayle, Eidson, and others have shown that there is definite relation between sun-spots and rainfall in various parts of the world. A. Septer found a close relation between the sun-spot cycle an dthunderstorms in Siberia. Brooks has continued this work, and finds that the annual frequency ,of thunderstorms over the world as a whole is related lo the cycle in the tropics and polar regions, but not in the temperate regions. It varies by about 11 per cent, during the cycle.

One of the most interesting pieces of evidence is provided by big trees in California and elsewhere. These may be many centuries old, and each year of age is recorded by a ring. It is found that the width of the rings increases and decreases in size over a range of about 11 years. The trees grow fastest when sun-spot activity is gieatest. This is probably due to increased rainfall and radiation, including light, heat and ultra-violet ravs. Douglass was able to trace a cycle in the rings of one tree for the years 1503 to 1910, and in two other trees I for the period from 1385 to 1503. .