so long a period as fifty thousand years, produce a great change in
the perspective of the heavens as seen from the earth, by carrying us
nearly nineteen trillion miles from our present place, why, it may be
asked, seek to represent future appearances of the constellations
which we could not hope to see, even if we could survive so long? The
answer is: Because these things aid the mind to form a picture of the
effects of the mobility of the starry universe. Only by showing the
changes from some definite point of view can we arrive at a due
comprehension of them. The constellations are more or less familiar to
everybody, so that impending changes of their forms must at once
strike the eye and the imagination, and make clearer the significance
of the movements of the stars. If the future history of mankind is to
resemble its past and if our race is destined to survive yet a million
years, then our remote descendents will see a ``new heavens'' if not a
``new earth,'' and will have to invent novel constellations to
perpetuate their legends and mythologies.

If our knowledge of the relative distances of the stars were more
complete, it would be an interesting exercise in celestial geometry to
project the constellations probably visible to the inhabitants of
worlds revolving around some of the other suns of space. Our sun is
too insignificant for us to think that he can make a conspicuous
appearance among them, except, perhaps, in a few cases. As seen, for
instance, from the nearest known star, Alpha Centauri, the sun would
appear of the average first magnitude, and consequently from that
standpoint he might be the gem of some little constellation which had
no Sirius, or Arcturus, or Vega to eclipse him with its superior
splendor. But from the distance of the vast majority of the stars the
sun would probably be invisible to the naked eye, and as seen from
nearer systems could only rank as a fifth or sixth magnitude star,