The New Heavens | Page 3

of the earliest astronomers. The conceptions of the stellar
universe, except those that ignored the solid ground of observation,
were limited by the small aperture of the human eye. But the dawn of
another age was at hand.
[Illustration: Fig. 2. The Great Nebula in Orion (Pease).
Photographed with the 100-inch telescope. This short-exposure
photograph shows only the bright central part of the nebula. A longer

exposure reveals a vast outlying region.]
The dominance of the sun as the central body of the solar system,
recognized by Aristarchus of Samos nearly three centuries before the
Christian era, but subsequently denied under the authority of Ptolemy
and the teachings of the Church, was reaffirmed by the Polish monk
Copernicus in 1543. Kepler's laws of the motions of the planets,
showing them to revolve in ellipses instead of circles, removed the last
defect of the Copernican system, and left no room for its rejection. But
both the world and the Church clung to tradition, and some visible
demonstration was urgently needed. This was supplied by Galileo
through his invention of the telescope.
[Illustration: Fig. 3. Model by Ellerman of summit of Mount Wilson,
showing the observatory buildings among the trees and bushes.
The 60-foot tower on the extreme left, which is at the edge of a
precipitous cañon 1,500 feet deep, is the vertical telescope of the
Smithsonian Astrophysical Observatory. Above it are the "Monastery"
and other buildings used as quarters by the astronomers of the Mount
Wilson Observatory while at work on the mountain. (The offices,
computing-rooms, laboratories, and shops are in Pasadena.) Following
the ridge, we come successively to the dome of the 10-inch
photographic telescope, the power-house, laboratory, Snow horizontal
telescope, 60-foot-tower telescope, and 150-foot-tower telescope, these
last three used for the study of the sun. The dome of the 60-inch
reflecting telescope is just below the 150-foot tower, while that of the
100-inch telescope is farther to the right. The altitude of Mount Wilson
is about 5,900 feet.]
The crystalline lens of the human eye, limited by the iris to a maximum
opening about one-quarter of an inch in diameter, was the only
collector of starlight available to the Greek and Arabian astronomers.
Galileo's telescope, which in 1610 suddenly pushed out the boundaries
of the known stellar universe and brought many thousands of stars into
range, had a lens about 2-1/4 inches in diameter. The area of this lens,
proportional to the square of its diameter, was about eighty-one times
that of the pupil of the eye. This great increase in the amount of light

collected should bring to view stars down to magnitude 10.5, of which
nearly half a million are known to exist.
It is not too much to say that Galileo's telescope revolutionized human
thought. Turned to the moon, it revealed mountains, plains, and valleys,
while the sun, previously supposed immaculate in its perfection, was
seen to be blemished with dark spots changing from day to day. Jupiter,
shown to be accompanied by four encircling satellites, afforded a
picture in miniature of the solar system, and strongly supported the
Copernican view of its organization, which was conclusively
demonstrated by Galileo's discovery of the changing phases of Venus
and the variation of its apparent diameter during its revolution about
the sun. Galileo's proof of the Copernican theory marked the downfall
of mediævalism and established astronomy on a firm foundation. But
while his telescope multiplied a hundredfold the number of visible stars,
more than a century elapsed before the true possibilities of sidereal
astronomy were perceived.
[Illustration: Fig. 4. The 100-inch Hooker telescope.]
STRUCTURE OF THE UNIVERSE
Sir William Herschel was the first astronomer to make a serious attack
upon the problem of the structure of the stellar universe. In his first
memoir on the "Construction of the Heavens," read before the Royal
Society in 1784, he wrote as follows:
"Hitherto the sidereal heavens have, not inadequately for the purpose
designed, been represented by the concave surface of a sphere in the
centre of which the eye of an observer might be supposed to be
placed.... In future we shall look upon those regions into which we may
now penetrate by means of such large telescopes, as a naturalist regards
a rich extent of ground or chain of mountains containing strata
variously inclined and directed as well as consisting of very different
materials."
On turning his 18-inch reflecting telescope to a part of the Milky Way
in Orion, he found its whitish appearance to be completely resolved

into small stars, not separately seen with his former telescopes. "The
glorious multitude of stars of all possible sizes that presented
themselves here to my view are truly astonishing; but as the dazzling
brightness of glittering stars may easily mislead us so far as to estimate
their number greater than it really is,