106 The Sky 
strength, moving back and forth like great celestial search- 
lights. Photographs of such sights are always welcomed by 
the scientists who study them. From photographs taken si- 
multaneously in several different places several miles apart, 
it is possible to estimate the height of the displays. They 
have been placed at heights from 50 to 500 miles. Their 
nature is not completely understood, but it is supposed that 
they are caused by the impact upon the upper air of charged 
electric particles shot out by sunspots on the sun. That they 
are electric disturbances originating in the sun cannot be 
doubted because they follow the sunspot cycles of the sun 
very closely, and are in general accompanied by disturbances 
in the earth’s magnetic field and heavy earth currents. Radio 
and cable communication are severely disturbed during the 
more brilliant auroras. ” 
There is always a faint aurora in the sky, but it is not neces- 
sarily visible to our eyes. The spectroscope is able to discern 
its presence however. Only when it becomes sufficiently 
strong does it appear to us as the most magnificent of the 
manifestations of the upper air—an auroral display. 
SHOOTING STARS 
“When beggars die there are no comets seen, 
The heavens themselves blaze forth the death of princes.” 
The ignorant have always attached a supernatural mean- | 
ing to the appearance of meteors. A particularly brilliant 
shooting star was supposed to foreshadow certain war or 
pestilence. As late as 1833, during a spectacular meteor 
shower, there were reports of people retiring in terror to 
their cellars, or if caught upon the road climbing under their 
: 
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