Sidelights on Astronomy and Kindred Fields of Popular Science | Page 4

THE UNSOLVED PROBLEMS OF ASTRONOMY II. THE NEW
PROBLEMS OF THE UNIVERSE III. THE STRUCTURE OF THE
UNIVERSE IV. THE EXTENT OF THE UNIVERSE V. MAKING
AND USING A TELESCOPE VI. WHAT THE ASTRONOMERS
ARE DOING VII. LIFE IN THE UNIVERSE VIII. HOW THE
PLANETS ARE WEIGHED IX. THE MARINER'S COMPASS X.
THE FAIRYLAND OF GEOMETRY XI. THE ORGANIZATION OF
SCIENTIFIC RESEARCH XII. CAN WE MAKE IT RAIN? XIII.

THE ASTRONOMICAL EPHEMERIS AND NAUTICAL
ALMANAC XIV. THE WORLD'S DEBT TO ASTRONOMY XV.
AN ASTRONOMICAL FRIENDSHIP XVI. THE EVOLUTION OF
THE SCIENTIFIC INVESTIGATOR XVII. THE EVOLUTION OF
ASTRONOMICAL KNOWLEDGE XVIII. ASPECTS OF
AMERICAN ASTRONOMY XIX. THE UNIVERSE AS AN
ORGANISM XX. THE RELATION OF SCIENTIFIC METHOD TO
SOCIAL PROGRESS XXI. THE OUTLOOK FOR THE
FLYING-MACHINE

ILLUSTRATIONS
SIMON NEWCOMB
PHOTOGRAPH OP THE CORONA OP THE SUN, TAKEN IN
TRIPOLI DURING TOTAL ECLIPSE OF AUGUST 30, 1905.
A TYPICAL STAR CLUSTER-CENTAURI
THE GLASS DISK
THE OPTICIAN'S TOOL
THE OPTICIAN'S TOOL
GRINDING A LARGE LENS
IMAGE OF CANDLE-FLAME IN OBJECT-GLASS
TESTING ADJUSTMENT OF OBJECT-GLASS
A VERY PRIMITIVE MOUNTING FOR A TELESCOPE
THE HUYGHENIAN EYE-PIECE
SECTION OF THE PRIMITIVE MOUNTING
SPECTRAL IMAGES OF STARS, THE UPPER LINE SHOWING

HOW THEY APPEAR WITH THE EYE-PIECE PUSHED IN, THE
LOWER WITH THE EYE-PIECE DRAWN OUT
THE GREAT REFRACTOR OF THE NATIONAL OBSERVATORY
AT WASHINGTON
THE "BROKEN-BACKED COMET-SEEKER"
NEBULA IN ORION
DIP OF THE MAGNETIC NEEDLE IN VARIOUS LATITUDES
STAR SPECTRA
PROFESSOR LANGLEY'S AIR-SHIP

PREFACE
In preparing and issuing this collection of essays and addresses, the
author has yielded to what he could not but regard as the too flattering
judgment of the publishers. Having done this, it became incumbent to
do what he could to justify their good opinion by revising the material
and bringing it up to date. Interest rather than unity of thought has
determined the selection.
A prominent theme in the collection is that of the structure, extent, and
duration of the universe. Here some repetition of ideas was found
unavoidable, in a case where what is substantially a single theme has
been treated in the various forms which it assumed in the light of
constantly growing knowledge. If the critical reader finds this a defect,
the author can plead in extenuation only the difficulty of avoiding it
under the circumstances. Although mainly astronomical, a number of
discussions relating to general scientific subjects have been included.
Acknowledgment is due to the proprietors of the various periodicals
from the pages of which most of the essays have been taken. Besides
Harper's Magazine and the North American Review, these include

McClure's Magazine, from which were taken the articles "The
Unsolved Problems of Astronomy" and "How the Planets are
Weighed." "The Structure of the Universe" appeared in the
International Monthly, now the International Quarterly; "The Outlook
for the Flying-Machine" is mainly from The New York Independent,
but in part from McClure's Magazine; "The World's Debt to
Astronomy" is from The Chautauquan; and "An Astronomical
Friendship" from the Atlantic Monthly.
SIMON NEWCOMB. WASHINGTON, JUNE, 1906.

I
THE UNSOLVED PROBLEMS OF ASTRONOMY
The reader already knows what the solar system is: an immense central
body, the sun, with a number of planets revolving round it at various
distances. On one of these planets we dwell. Vast, indeed, are the
distances of the planets when measured by our terrestrial standards. A
cannon-ball fired from the earth to celebrate the signing of the
Declaration of Independence, and continuing its course ever since with
a velocity of eighteen hundred feet per second, would not yet be
half-way to the orbit of Neptune, the outer planet. And yet the
thousands of stars which stud the heavens are at distances so much
greater than that of Neptune that our solar system is like a little colony,
separated from the rest of the universe by an ocean of void space
almost immeasurable in extent. The orbit of the earth round the sun is
of such size that a railway train running sixty miles an hour, with never
a stop, would take about three hundred and fifty years to cross it.
Represent this orbit by a lady's finger-ring. Then the nearest fixed star
will be about a mile and a half away; the next more than two miles; a
few more from three to twenty miles; the great body at scores or
hundreds of miles. Imagine the stars thus scattered from the Atlantic to
the Mississippi, and keep this little finger-ring in mind as the orbit of
the earth, and one may have some idea of the extent of the universe.

One of the most beautiful stars in the heavens, and one that can be seen
most of the year, is a Lyrae, or Alpha of the Lyre, known also as Vega.
In a spring evening it may be seen in the northeast, in the later summer