I
RECENT ADVANCES IN
STELLAR ASTRONOMY1
THE LIGHT OF THE STARS
THE study of the stars is the oldest of the sciences:
yet it rests on the slenderest physical basis. Were
our atmosphere always cloudy—instead of about half the
time—human affairs, and most of human science, would
go on very much the same. We could see nothing of the
great universe beyond the clouds; yet the light of the Sun
and Moon would penetrate them, and their attraction
would still set the tides in motion, and reasoning from
these data, we might deduce a good deal about the Sun
and Moon. But the very existence of the stars would be
unsuspected, for it is only by their light that we know them,
and this light is far too feeble to pierce the clouds.
How feeble, indeed, it is, is one of the things which
most of us fail to realize. The light even of Sirius—the
brightest of the stars—is equal to that of a 25-candle lamp
a mile away. Ordinary artificial light, such as is commonly
used to read by, is a million times brighter, and full sun-
light is ten thousand times stronger still. It is only because
of the amazing range of adaptation of the human eye—
which incomparably surpasses that of any instrument which
has ever been constructed—that we can see the stars at
1A eourɪe of three lectures delivered by Professor Henry Norris Russell,
Ph.D., of Princeton University, in the Physics Amphitheatre of the Rice
Institute, January 26, 27, and 28, 1922.
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