The music of the spheres : $b A nature lover's astronomyGrondal, Florence Armstrong
Science
The music of the spheres : $b A nature lover's astronomy
Grondal, Florence Armstrong
Astronomy
"in a scene of fertility and beauty such as will scarcely be found in
another country at any season of the year. The vivid green of the
springing corn, the groves of pomegranate trees ablaze with the rich
scarlet of their blossoms, the fresh breeze laden with the perfumes of
gardens of roses and orange thickets, every tree and every shrub covered
with sweet-scented flowers."
No wonder that the appearance of Sirius was hailed with reverence when
its rising just before the sun meant also the rise of the life-giving
river and the prosperity of the inhabitants of Egypt! However, as
mentioned before, with the precession of the equinoxes, the heliacal
rising of Sirius has changed and its brilliant light no longer announces
the rising of the Nile.
Sirius is one of our nearest stars for its light requires only 8½ years
to reach the earth. Yet its nearness does not account altogether for its
quite exceptional brightness, for our sun at the same distance would
appear as a star of the 6th magnitude and be invisible to the unaided
eye. Only two stars, as far as has yet been discovered, lie closer to
the earth than Sirius. The second brightest star in the sky is Canopus,
visible from the southern hemisphere, but so far away that its distance
can scarcely be estimated.
Halley, a celebrated English astronomer born 1656, made the first
discovery of the relative motion of the stars when he noted that Sirius
had moved from the position assigned to it on Ptolemy's map of 150 A. D.
We have now reliable data for discussing the proper motion of about
10,000 stars. The proper motion of stars consists of a displacement in
various directions of the individual stars. Thus the configuration of a
constellation may slowly change, and, although many groups of stars all
travel in the same direction, there are also conspicuous instances where
they move in different directions. The Big Dipper and the Southern Cross
are two star groups whose stars are traveling along different courses
and after a period of time extending over thousands of years, the
'dipper' and the 'cross' effect of these two constellations will have
altogether disappeared.
Public-domain text, read in full here on John Shaqi.
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