Man's Place in the Universe: A Study of the Results of Scientific Research in Relation to the Unity or Plurality of Worlds, 3rd EditionWallace, Alfred Russel
Science
Man's Place in the Universe: A Study of the Results of Scientific Research in Relation to the Unity or Plurality of Worlds, 3rd Edition
Wallace, Alfred Russel
Life; Plurality of worlds; Stars
the whole heavens would be filled with a blaze of light as bright as the
sun.'
But the whole light given us by the stars is variously estimated at from
one-fortieth to one-twentieth or, as an extreme limit, to one-tenth of
moonlight, while the sun gives as much light as 300,000 full moons, so
that starlight is only equivalent at a fair estimate to the six-millionth
part of sunlight. Keeping this in mind, the possible causes of the
extinction of almost the whole of the light of the stars (if they are
infinite in number and distributed, on the average, as thickly beyond the
Milky Way as they are up to its outer boundary) are absurdly inadequate.
These causes are (1) the loss of light in passing through the ether, and
(2) the stoppage of light by dark stars or diffused meteoritic dust. As to
the first, it is generally admitted that there is not a particle of
evidence of its existence. There is, however, some distinct evidence that,
if it exists, it is so very small in amount that it would not produce a
perceptible effect for any distances less remote than hundreds or perhaps
thousands of times as far as the farthest limits of the Milky Way are from
us. This is indicated by the fact that the brightest stars are _not_
always, or even generally, the nearest to us, as is shown both by their
small proper motions and the absence of measurable parallax. Mr. Gore
states that out of twenty-five stars, with proper motions of more than two
seconds annually, only two are above the third magnitude. Many first
magnitude stars, including Canopus, the second brightest star in the
heavens, are so remote that no parallax can be found, notwithstanding
repeated efforts. They must therefore be much farther off than many small
and telescopic stars, and perhaps as far as the Milky Way, in which so many
brilliant stars are found; whereas if any considerable amount of light were
lost in passing that distance we should find but few stars of the first
two or three magnitudes that were very remote from us. Of the twenty-three
stars of the first magnitude, only ten have been found to have parallaxes
of more than one-twentieth of a second, while five range from that small
amount down to one or two hundredths of a second, and there are two with no
ascertainable parallax. Again, there are 309 stars brighter than magnitude
3.5, yet only thirty-one of these have proper motions of more than 100" a
century, and of these only eighteen have parallaxes of more than
one-twentieth of a second. These figures are from tables given in Professor
Newcomb's book, and they have very great significance, since they indicate
that the brightest stars are _not_ the nearest to us. More than this, they
show that out of the seventy-two stars whose distance has been measured
with some approach to certainty, only twenty-three (having a parallax of
more than one-fiftieth of a second) are of greater magnitudes than 3.5,
while no less than forty-nine are smaller stars down to the eighth or ninth
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