came to the conclusion that the spirals
must be millions of fight-years away.
This conclusion, which was confirmed
by Hubble from observations of the
variable stars in the spirals, afforded a
much more decisive means of estimat-
ing the distance. It is now univer-
388
NATURAL HISTORY
sally accepted that the spiral nebula
are millions of light-years distant. The
angular size under which the}^ appear
to us then indicates that they must be
tens of thousands of Hght-years in size,
large enough to merit the name "island
universes." The latest edition of the
social register of the Cosmos includes,
therefore, all these spirals as full-fledged
universes entitled to all rights and
privileges of a universe.
As for the rotation of spiral nebulae,
the great distances recently derived
have made rapid rotation impossible,
and the quick internal motion meas-
ured some years ago is now univers-
ally regarded as an optical illusion.
Although it is obvious from a mere
inspection of the structure of spirals
that they must be rotating, it is in-
conceivable that they should revolve
so rapidly as to make one complete
turn in eighty-thousand years. The
large hnear dimensions indicated by the
present-day distances of milUons of
hght-years would result, for the out-
lying portions of the spirals, in a speed
greater than that of Hght. Such a
thing was immediately condemned as
unconstitutional; the modern constitu-
tion of the cosmos, the doctrine of rela-
tivity, does not permit any material
object to move faster than hght. Con-
sequently the speed of rotation of
spiral nebulae has been assigned an
upper limit ; one revolution in a milhon
years or more is all that is allowed
them.
The best known of all island universes
is undoubtedly the Andromeda nebula,
a great spiral, just one miUion hght-
years away, and about fifty thousand
hght-years in diameter. It contains
milhons and possibly bilhons of stars,
the vast majority being too faint to be
seen individuaUy. The only stars we
can see are thousands of times brighter
than the sun, indeed, the sun could not
possibly be seen or photographed at a
distance of a million light-years.
During the time that the Andromeda
nebula has been under observation, a
great number of new stars have been
seen to appear in it. The first one to be
observed burst out in 1885; it reached
the seventh magnitude, which means
that, in reahty, it was one hundred
milhon times brighter than the sun, one
tenth as bright as the whole Andromeda
universe! During the few days of its
maximum splendor it reigned supreme
in the cosmos, it was the brightest star
we have ever observed. It was also the
most wasteful, for at that time it was
radiating so much light and energy into
space that, according to the theory of
relativity, it was losing more than two
hundred trillion tons of matter every
second. Yet it could have gone on at
this rate for over a year without losing
as much as our earth weighs. In addi-
tion to this phenomenally bright nova,
almost j&fty other new stars have been
discovered in the nebula, most of them
being of the fifteenth or sixteenth
magnitude. On the average, the Andro-
meda nebula seems to produce more
than two novae a year, a little more than
our Milky Way system seems capable
of. So frequent are these outbursts of
novae that they make us worry what
their cause is. It does not seem reason-
able to suppose that the past fifty
years have been any different in the
Andromeda nebula and in the Galaxy
from the past fifty billion years, and
we have every right to suppose that in
that tune at least fifty billion new stars
have appeared on the scene. To this
we must add that fifty bilhon years is
but a short interval in the life of the
average star and certainly small com-
pared with the life of a universe. Our
Milky Way system contains about fifty
SPIRAL NEBULA MESSIER 33 IX TRIAXGULITM. EXPOSURE EICxHT HOURS, THIRTY
MIXUTES, AUGUST 5, 6, 7, 1910. SIXTY-IXCH REFLECTOR
Photograph by Mount Wilson Observatory
CENTRAL PORTION OF THE GREAT NEBULA IN ANDROMEDA, MESSIER 31. EXPOSURE
TWO HOURS, OCTOBER 13, 1909. SIXTY-INCH REFLECTOR
Photograph by Mount Wilson Observatory
SPIRAL NEBULA MESSIER 101 IN URSxA MAJOR. EXPOSURE FOUR HOURS,
MINUTES, FEBRUARY 5, 1910. SIXTY-INCH REFLECTOR
Photograph by Mount Wilson Observatory
FIFTEEN
A UNIVERSE SEEN ON EDGE. SPIRAL NEBULA H.V. 24 IN COMA BERENICES EXPOSURE
FIVE HOURS, MARCH 6 AND 7, 1910, SIXTY-INCH REFLECTOR.
Photograph by Mount Wilson Observatory
ISLAND UNIVERSES
389
billion stars; we conclude therefore
that during the past fifty billion years
there have appeared as many novse as
our Galaxj' contains ordinary stars.
We are faced with the alternative,
either that all stars have once been
novse or will become so in time, or, that
"once a nova always a nova." Either
the nova stage is one of the follies in the
life of every ordinary star, or it is a
disease, a habit, w^hich, once contracted,
recurs again and again.
The Andromeda nebula is not the
only spiral that has new stars to its
credit. These outbursts have been ob-
served in about other eight spirals. Only
ver}' recently, in May, 1926, a new star
of the fourteenth magnitude was dis-
covered in the small spiral nebula
Messier 61, in the constellation Virgo,
— a fourteenth magnitude star, — in ap-
pearance an insignificant event, yet it
was the echo of a powerful explosion
which happened ten million years ago,
transforming a perfectly normal-look-
ing star into a veritable blast furnace,
ten million times brighter than the sun.
Though the nearest of all spirals, the
Andromeda nebula is not the nearest
universe. Three others are known to
be nearer, viz., the tw^o Magellanic
Clouds, situated at a distance of about
100,000 light-years, and a small star-
cloud, (technical^ known as N. G. C.
6822) 700,000 light-years distant.
These three are universes in vest-pocket
edition, the size of the largest being
no more than fourteen thousand light-
years and that of the smallest only four
thousand light-years.
It was from the Magellanic Clouds
that the first clue to the distances of
island universes came, for it was here
that Miss Leavitt at Harvard first dis-
covered that a relation exists between
the apparent brightness of variable
stars and the time it takes them to com-
plete one cycle of their variation.
Hertzsprung was the first to realize the
extreme importance of this relation and
to use it for determining distances in
the cosmos. Later on, much use was
made of it, in a modified form, by
Shapley in his extension of the limits of
the Galaxy from twenty thousand
light-years to two hundred thousand.
Now it has provided the basis for fixing
the distance of the spiral nebulae,
extending our knowledge of space to
tens and hundreds of millions of light-
years.
In practically all respects the Magel-
lanic Clouds are similar to our Galaxy;
they contain star-clusters, nebulae,
variable stars of different types, blue
stars, red stars, in short all the essential
features of a universe. They are
singularly lacking in one character-
istic, however; thej^ have never shown
any new stars. Our Galaxy, the Andro-
meda nebula, and probably all spirals
abound in them, but in spite of the
close scrutiny with which the Magel-
lanic Clouds have been watched, no new
star has ever been observed in them.
The same holds for N. G. C. 6822.
Why this is so we do not know but, at
any rate, this deficiency is not con-
sidered sufficient cause to cross the
names of these three universes off our
books, or even to put them on probation.
We do not know much about the
constitution of these far-distant uni-
verses (outside the few mentioned
specifically) but there is one thing
which we know accurately about many
of them, their speed in the line of sight.
Observations with the spectroscope
made principally at the Lowell and the
]Mt. Wilson observatories have shown
us that the Andromeda nebula is
approaching us with a speed of 200
miles a second, the Magellanic Clouds
are receding from us at the rate of 170
390
NATURAL HISTORY
miles a second. Most of the other
spirals seem to be running away from
us, all have great velocities, hundreds
of miles per second. One spiral is
even known to hurry away from us at
the speed of 1 100 miles a second . With
reference to the whole system of spiral
nebulae, our Galaxy, and the sun with
it, seems to be moving toward the
constellation Cassiopeia, with a speed
of 250 miles a second.
In addition to the spirals, we know
thousands of small, amorphous-looking
nebulae, nebulae which might be spirals
so far distant that the most powerful
telescope cannot reveal their structure.
Yet it seems that these nebulae, al-
though obviously related to the family
of spirals, are not identical with them ;
they are, perhaps, embryonic uni-
verses. The fact that so many of these
amorphous nebulae seem to crowd
together in the sky, has given rise to
speculations concerning possible colli-
sions. Now collisions are things the
astronomer does not worry about very
often. In our Milky Way system a
collision between two stars would not
happen more than once in a triUion
years on the average. But among these
nebula the case is different. Charlier
has calculated that nebulae may collide
once in a thousand years. And what is
a thousand years in the life of a uni-
verse? When two such amorphous
nebulae meet or come very near each
other, it is quite possible that a spiral
nebula will result. At present we
possess photographs of many cases
where, in a few million years a spiral
nebula may be generated. We have
never witnessed the birth of a universe,
nor are we likely to. The process in-
volved is too slow and does not at all
compare as a spectacle with that of
the birth of a new star. All that
happens is that two swarms of stars
meet, and gravitate around their
common center of gravity. Indeed,
there are indications that the Galactic
system is at this moment in "collision "
with another universe, manifesting it-
self as a swarm of stars penetrating the
Milky Way at high speed.
What, then, is the present-day pic-
ture of the cosmos? To begin with what,
is a star? A sphere of glowing gas,
varying in size from a globe not much
larger than the earth, to one a thousand
times larger than the sun in diameter,
large enough to take in the entire orbit
of Jupiter. In density it may vary from
a thousand times rarer than our at-
mosphere, to fifty thousand times
denser than water. Next comes, what is
a universe? One answer would be: a
vacuum. Take our Milky Way system,
e. g., although it contains more than 50
billion stars, the space over which these
are scattered is so enormous that we
may compare the whole Galaxy to a
cubic foot of normal air, spread out over
ten cubic miles !
In size, the lens-shaped core of the
Milky Way system is about fifty
thousand light-years in diameter and
no more than ten thousand light-years
thick. Outside this nucleus there lie
the globular clusters, at distances up to
200,000 light-years, and perhaps some
of the more distant Milky Way star-
clouds. The first strangers we meet be-
yond are small islands, tlie Magellanic
Clouds, and N. G. C. 6822, then, at one
million light-years, the spirals in Andro-
meda and Triangulum, not more than
fifty thousand light-years in size. So far
we have struck only real "Island" uni-
verses ; a continent as large as our own
we have yet to find. But who knows
what Space beyond contains? Universe
upon universe, some small, some large,
and undoubtedly some very large.
Following the tendency of all science
ISLAND UNIVERSES
391
toward "unity ami siiupliciiy," asti-o-
nomical opinion has repeatedly con-
sidered everything as part of "our"
universe. Equally frequently, how-
ever, the dual tendency toward "diver-
sity and complexity" has led us to
views like those held now, supposing the
existence of numberless universes. Per-
haps the future will see us again re-
turning to the Single Universe. Again,
everything material will be contained
in one system, of much increased dimen-
sions, of course, billions of light-years
in size perhaps.
I >ul IK) mat lci- how far we nui^'^go, we
shall nev(M- i-each the end, neither in
space nor in time. No matter how far
we proceed in space oi- in time we never
advance against infinity and eternity.
The ubiquitous myriads of scintillat-
ing flashes confront us everywhere, they
stagger the mind and overwhelm the
intellect — an infmitas in aeternitate.
And yet, as Pascal, we may feel satisfied
with our acconi])lishments:
We are little, almost the least and weakest
of things; but we know that we are little
and therein we are great.
NIKOLAUS COPERNICUS
From the original in the Royal Observatory at Berlin.
After Weltall und Menschheit
L,. 5^.
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General Building Plan of the Ameeican Museum of Natural History
An Ideal Astronomic Hall
By HOWARD RUSSELL BUTLER
THE proposal of tlu' Aineiican
iMiiseum of Natural History to
construct a hall to be devoted
to astronomical and Idndred subjects
has been conceived at the right time,
for it can now be made far more
serviceable than would have been
possible had it been erected a few
years ago. Advance in the line of
astronomical exhibits has been rapid
lately. Take for instance the Zeiss
Planetarium. This marvelous instru-
ment projects on the inner surface of a
dome about 4,500 fixed stars, and even
the Milky Way is shown as a starry
mist. It reproduces the diurnal and
annual motions at any desired speed.
It also pictures the sun, the moon,
and planets, giving their motions
within an error, it is claimed, of less
than one per cent. It can show the
precession of the equinoxes, not in
26,000 years, but in twenty-six minutes.
The enormous educational value of this
instrument, which solves the problem
by optical means rather than by
mechanical, and which has awakened
such phenomenal interest in Germany,
makes it an absolutely necessary
adjunct to an astronomic hall — if not
its chief attraction. Had the Museum
built its hall ten 3^ears ago, provision
for this unique device would not have
been made, and instead, cumbrous
mechanical contrivances for showing
the movements of a few of the heavenly
bodies would have been attempted,
necessarily on a limited scale. So I
congratulate the Museum on not hav-
ing been too hasty.
Again I would congratulate the
Museum on the wise decision to locate
the Astronomic Hall in the exact
center of its great .sy.stem of exiiiljition
buiklings. It is indeed appropriate
that this should be the central unit, —
the celestial hub, so to speak, — from
which all the halls containing terrestrial
exhibits will I'adiate. Natural history
must begin with astronomy, the earth
being but one of the heavenly bodies,
and a somewhat insignificant one at
that.
The plans, as recently completed,
show a building octagonall}' shaped,
with a diameter of 126 feet and a height
of five stories, surmounted by a dome.
The ground dimensions having been
fixed, the Trustees and their archi-
tects, Messrs. Trowbridge and Li\ing-
ston, evolved a general plan along
broad and practical fines. Interior
divisions were not finally deternuned,
as these would be dependent upon the
uses to which the building would be put.
At this stage, I was invited to the
position of adviser to the architects.
Before the plan could be perfected
in detail, it was necessary to catalogue
so far as possible the long fist of exhibits
to be housed in the bmlding, and my
first effort was to canvass the field. A
complete fist is of course impossible,
and the future will also bring many
UTiportant additions for which space
must now be allowed. A wise principle
adopted by the Museum is to adnfit no
exhibits except those approved for
accurac}^ by experts. Sensational
effects and shallow exaggerations, not
based on facts, would do more harm
than good. Nature, unassisted, affords
enough thriUs.
In making the fist, the ad^'iser had
the assistance of the late Dr. John
Tatlock, president of the New York
393
394
NATURAL HISTORY
Academy of Sciences; Dr. Henry
Norris Russell, who made many valu-
able suggestions; Professor William
F. Magie, in regard to the Foucault
Pendulum; Dr. Clyde Fisher, of the
Museum; and Messrs. Bennett &
Bauer, of the Zeiss Company, on the
subject of the. planetarium.
The next problem was that of classifi-
cation, and after that came the problem
of adaptation of the spaces in the
building to such classification. This
was really the determining factor in
the final plans for construction. The
arrangement of floor spaces, (rotundas,
alcoves, camera booths, and ambula-
tories) as well as the size of the dome,
have been made to suit the classified
exhibits.
â– The final plan calls for a dome 75
feet -in diameter, supported at its
circumference by a series of steel
columns penetrating the building from
the ground to the base of the dome.
These leave a space for circumferential
ambulatories about 20 feet wide, one
on every floor between the columns
and the outside walls. Another and
inner series of columns strengthens the
whole structure, leaving spaces for
central rotundas on the first, second,
and fourth floors, — all 62 feet in
diameter.
The exhibits natvu'ally fall into two
classes: those which have to be shown
in dark rooms by special illumination,
like lantern projections, transparencies,
underlit pictures, etc.; and those
requiring ordinary diffused hght (day-:
light or full electric light) such as
globes, photographs on paper, charts,
instruments, etc.
A building of this shape and in this
position, surrounded by others, is
necessarily cut off to a great degree
from daylight. Little daylight can
reach the central rotunda, and the
same is true of much of the ambulatory
space. It is therefore fortunate that
its mission is one which calls especially
for artificial light.
DARK SECTION
SIDEREAL HALL
An early decision was reached in
conference to keep the fourth floor
(with its dome, rotunda, and ambula-
tory) dark, and to have diffused light
(windows supplemented by electric
light) on all the lower floors.
Beginning at the top, as visitors
should, and working down, the exhibits
of the dark section fall into four
classes.
I. Siderial projections on the inner
surface of the dome. For these the
Zeiss planetarium will be used, a tower
being provided to bring it to the proper
altitude. The inner surface of the
dome is white and the effect of stars is
obtained by means of a powerful lantern
which throws slides made from draw-
ings based on photographs of the heav-
ens. There are thirty-one of these dia-
positives, which fitting together, give
the complete heavens. Special pro-
jections are used for the Milky Way
and others for the sun, moon, and
visible planets. A gallery on the level
of the fifth floor, bringing the eye of
the observer to the horizon, encircles
the room considerably above the main
floor of the rotunda, which is the
fourth story of the building. This
separates those interested particularly
in the projections on the dome from
the visitors on the main floor of the
rotunda. An alternative to this plan
would be to make the fourth floor
rotunda only one story high, to abolish
the tower and place the lantern of the
planetarium in the center of the floor
of the fifth story.
II. Twelve panels, carrying trans-
I
PROPOSED ASTRONOMICAL HALL
AMERICAN MUSEUM OF NATURAL HISTORY
I
I
.4.V IDEAL ASTRONOMIC HALL
395
View in proposed Astronomic Hall showing dome of projection planetarium
lucent screens are arranged around
the rotunda. Lanterns, placed behind
these screens, in the spaces between
the two series of columns, throw pro-
jections on the screens of astronomic
sHdes of great variety. These can be
shown automatically and rotatively.
It was a matter of nice calculation to
determine the size of these pictures
and the spaces required for the lanterns
between the series of columns. An
experimental camera booth was erected,
and demonstrations made by represen-
tatives of the firm of Bausch & Lomb.
A wide-angle projector was determined
upon and the deUmitations of con-
Til ^
>
AN IDEAL ASTRONOMIC HALL
397
struction were thus accurately fixed.
III. The inuer face of the am-
bulatory, which surrounds the loliuida
and is approached lliroujili foui- open-
ings, is devoted entirely to t i'ansi)aren-
cies, which fall into foui- divisions,
as follows :
(a) Solar eclipses, arranged chrono-
logically.
(b) Solar and lunar eclipse phenom-
ena.
(c) Meteoric division.
(d) Geologic division.
IV. The outer face of the fourth
floor ambulatory is devoted to underHt
pictures, such as the triptych of
eclipses (1918, 1923, 1925) recently
placed on view in the temporary
astronomic hall of the Museum of
Natural History; lunar landscapes;
eclipse photographs; a frieze of hydro-
gen prominences; and such geologic
pictures as have astronomic bearing.
A wing on one of the faces of the
building provides a space availed of
on this floor as a "Lunar Hall,"
accommodating a lunar globe, ten feet
in diameter, with a system of Hghting
to show phases.
LIGHT SECTION
HALL OF THE UNIVERSE
Second or Main Floor
Everything below the fourth floor is
shown by diffused Light. A rotunda,
two stories high, occupies the space
between the second and the fourth
floor. Here in the center will be a
miniature universe — a number of fixed
stars being selected, represented by
electric lamps, showing relative
distances apart and color, but without
any attempt to show relative dimen-
sions. The position of our sun in this
group will be a point of great interest.
Above this, about fifteen feet above the
floor, is a miniature solar system sus-
pended in mid air, somewliat similar
lo that in the Munich Museum. The
illuminated globe in the center repre-
sents the sun. The six planets nearest
the sun, with satelhtes, (the planets
and satellites all revolving at their
pi-oper relative speeds), are shown.
The orbits of Uranus and Neptune
are left out in order not to diminish
the scale too much. The diameter
given to the orbit of Saturn would be
about 60 feet.
Surrounding the rotunda are four
alcoves divided by columns, making
three openings in each. In the central
openings are large globes;
(1) Sidereal globe.
(2) Solar globe.
(3) Terrestrial globe.
(4) Lunar globe.
Smaller planetary globes are placed
in the other openings, and the interior
walls of the alcoves are hung with
pictures appropriate to the globes.
The inner face of the ambulatory is
also divided into four corresponding
sections.
(1) Navigation (sidereal globe sec-
tion) .
(2) Cosmogony (solar globe section).
(3) Time and calendars (terrestrial
globe section).
(4) Lunar, tides, etc. (lunar globe
section).
Around the outer walls of the second
floor ambulatory are cases of instru-
ments, above which are hung photo-
graphs of astronomical subjects, por-
traits of astronomers, etc.
Thus the student of navigation will
find everj-thing pertaining to that
subject in one di\dsion — maps, charts,
and log tables on the wall and in
near by cases, sextants, chronometers,
nautical almanacs, etc. The student of
cosmogon^^ finds a section giving him
398
NATURAL HISTORY
information about the Ptolemaic and
Copernican theories, the nebular hypo-
thesis, the planetesimal theory and the
"island universes." In the "Time
Section" the investigator learns about
the various calendars, the differences
between sidereal, mean solar and
standard times, the principles of the
sun-dial with examples of the various
types near at hand. An investigator of
power sources could find out all about
tides in the "Lunar Section." The
educational value of these sections
cannot be overestimated.
A Memorial Hall is provided on this
floor designed to commemorate the
donor or donors of Astronomic Hall.
It would open from the ambulatory of
the main floor, while, if the funds
should be given by a single individual,
a statue of the donor could be placed
at the main entrance to the hall as
shown in the plans, — this in line with
the central entrance to the Museum
on Eighth Avenue.
The third story consists of an am-