SUN-SPOTS.

Wairarapa Age, Volume XXXII, Issue 3102, 27 January 1909, Page 4

SUN-SPOTS.

The fact has long been recognised that the sup. is a variable star. Of course its variations are slight, else they would have a disastrous effect upon the ■earth. The regularity with which sun-spots gradually increase and then decrease in number and size is, however, a sufficient indication that tj-s viewed from a great distance in apace and with sufficiently delicate means of observation, the sun would run through a cycle of variations in brightness once in every eleven years. It might well be supposed that if such changes took place they would be more easily perceived from the earth than from a greater distance. As a matter of fact, however, there are practical! difficulties that render it almost impossible to get an accurate measure of the variation frum year to year in the amount of the sun's radiation that falls upon the earth. It has even been undecided whether the sun is hotter or colder when it is most-spotted. Some observations have indicated that the I sun is hotter when the disturbances | that create sun-spots are most active I while other observations have, at the same time, tended to show that less heat is then received, on the face of the earth than is received when there are practically 110 sun-spots. The reports of French scientists ;in recent years strongly go to show that not only is the sun hotter when it is most spotted, but that it is precisely at such times that the surface of the earth feels the greatest intensity <o£ | solar radiation. .But the question is far from settled.