Looking backward, we see a time
when the sun must have been more brilliant than it is now. At that
time it probably shone with the blinding white splendor of such stars
as Sirius, Spica, and Vega; now it resembles the relatively dull
Procyon; in time it will turn ruddy and fall into the closing cycle
represented by Antares. Considering that once it must have been more
radiantly powerful than at present, one is tempted to wonder if that
could have been the time when tropical life flourished within the
earth's polar circles, sustained by a vivific energy in the sun which
it has now lost.
The corona, as we have said, varies with the sun-spot cycle. When the
spots are abundant and active the corona rises strong above the
spotted zones, forming immense beams or streamers, which on one
occasion, at least, had an observed length of ten million miles. At
the time of a spot minimum the corona is less brilliant and has a
different outline. It is then that the curved polar rays are most
conspicuous. Thus the vast banners of the sun, shaken out in the
eclipse, are signals to tell of its varying state, but it will
probably be long before we can read correctly their messages.
The Zodiacal Light Mystery
There is a singular phenomenon in the sky -- one of the most puzzling
of all -- which has long arrested the attention of astronomers,
defying their efforts at explanation, but which probably not one in a
hundred, and possibly not one in a thousand, of the readers of this
book has ever seen.
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