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THE FUTURE OF ASTRONOMY

BY PROFESSOR EDWARD C. PICKERING

Reprinted from the POPULAR SCIENCE MONTHLY, August, 1909.




THE FUTURE OF ASTRONOMY[1]

BY PROFESSOR EDWARD C. PICKERING

HARVARD COLLEGE OBSERVATORY


It is claimed by astronomers that their science is not only the oldest,
but that it is the most highly developed of the sciences. Indeed it
should be so, since no other science has ever received such support from
royalty, from the state and from the private individual. However this
may be, there is no doubt that in recent years astronomers have had
granted to them greater opportunities for carrying on large pieces of
work than have been entrusted to men in any other department of pure
science. One might expect that the practical results of a science like
physics would appeal to the man who has made a vast fortune through some
of its applications. The telephone, the electric transmission of power,
wireless telegraphy and the submarine cable are instances of immense
financial returns derived from the most abstruse principles of physics.
Yet there are scarcely any physical laboratories devoted to research, or
endowed with independent funds for this object, except those supported
by the government. The endowment of astronomical observatories devoted
to research, and not including that given for teaching, is estimated to
amount to half a million dollars annually. Several of the larger
observatories have an annual income of fifty thousand dollars.

[1] Commencement address at Case School of Applied Science, Cleveland,
May 27, 1909.

I once asked the wisest man I know, what was the reason for this
difference. He said that it was probably because astronomy appealed to
the imagination. A practical man, who has spent all his life in his
counting room or mill, is sometimes deeply impressed with the vast
distances and grandeur of the problems of astronomy, and the very
remoteness and difficulty of studying the stars attract him.

My object in calling your attention to this matter is the hope that what
I have to say of the organization of astronomy may prove of use to those
interested in other branches of science, and that it may lead to placing
them on the footing they should hold. My arguments apply with almost
equal force to physics, to chemistry, and in fact to almost every branch
of physical or natural science, in which knowledge may be advanced by
observation or experiment.

The practical value of astronomy in the past is easily established.
Without it, international commerce on a large scale would have been
impossible. Without the aid of astronomy, accurate boundaries of large
tracts of land could not have been defined and standard time would have
been impossible. The work of the early astronomers was eminently
practical, and appealed at once to every one. This work has now been
finished. We can compute the positions of the stars for years, almost
for centuries, with all the accuracy needed for navigation, for
determining time or for approximate boundaries of countries. The
investigations now in progress at the greatest observatories have
little, if any, value in dollars and cents. They appeal, however, to the
far higher sense, the desire of the intellectual human being to
determine the laws of nature, the construction of the material universe,
and the properties of the heavenly bodies of which those known to exist
far outnumber those that can be seen.

Three great advances have been made in astronomy. First, the invention
of the telescope, with which we commonly associate the name of Galileo,
from the wonderful results he obtained with it. At that time there was
practically no science in America, and for more than two centuries we
failed to add materially to this invention. Half a century ago the
genius of the members of one family, Alvan Clark and his two sons,
placed America in the front rank not only in the construction, but in
the possession, of the largest and most perfect telescopes ever made. It
is not easy to secure the world's record in any subject. The Clarks
constructed successively, the 18-inch lens for Chicago, the 26-inch for
Washington, the 30-inch for Pulkowa, the 36-inch for Lick and the
40-inch for Yerkes. Each in turn was the largest yet made, and each time
the Clarks were called upon to surpass the world's record, which they
themselves had already established. Have we at length reached the limit
in size? If we include reflectors, no, since we have mirrors of 60
inches aperture at Mt. Wilson and Cambridge, and a still larger one of
100 inches has been undertaken. It is more than doubtful, however,
whether a further increase in size is a great advantage. Much more
depends on other conditions, especially those of climate, the kind of
work to be done and, more than all, the man behind the gun. The case is
not unlike that of a battleship. Would a ship a thousand feet long
always sink one of five hundred feet? It seems as if we had nearly
reached the limit of size of telescopes, and as if we must hope for the
next improvement in some other direction.

The second great advance in astronomy originated in America, and was in
an entirely different direction, the application of photography to the
study of the stars. The first photographic image of a star was obtained
in 1850, by George P. Bond, with the assistance of Mr. J.A. Whipple, at
the Harvard College Observatory. A daguerreotype plate was placed at the
focus of the 15-inch equatorial, at that time one of the two largest
refracting telescopes in the world. An image of [Greek: alpha] Lyræ was
thus obtained, and for this Mr. Bond received a gold medal at the first
international exhibition, that at the Crystal Palace, in London, in
1851. In 1857, Mr. Bond, then Professor Bond, director of the Harvard
Observatory, again took up the matter with collodion wet plates, and in
three masterly papers showed the advantages of photography in many ways.
The lack of sensitiveness of the wet plate was perhaps the only reason
why its use progressed but slowly. Quarter of a century later, with the
introduction of the dry plate and the gelatine film, a new start was
made. These photographic plates were very sensitive, were easily
handled, and indefinitely long exposures could be made with them. As a
result, photography has superseded visual observations, in many
departments of astronomy, and is now carrying them far beyond the limits
that would have been deemed possible a few years ago.

The third great advance in astronomy is in photographing the spectra of
the stars. The first photograph showing the lines in a stellar spectrum
was obtained by Dr. Henry Draper, of New York, in 1872. Sir William
Huggins in 1863 had obtained an image of the spectrum of Sirius, on a
photographic plate, but no lines were visible in it. In 1876 he again
took up the subject, and, by an early publication, preceded Dr. Draper.
When we consider the attention the photography of stellar spectra is
receiving at the present time, in nearly all the great observatories in
the world, it may well be regarded as the third great advance in
astronomy.

What will be the fourth advance, and how will it be brought about? To
answer this question we must consider the various ways in which
astronomy, and for that matter any other science, may be advanced.

First, by educating astronomers. There are many observatories where
excellent instruction in astronomy is given, either to the general
student or to one who wishes to make it his profession. At almost any
active observatory a student would be received as a volunteer assistant.
Unfortunately, few young men can afford to accept an unpaid position,
and the establishment of a number of fellowships each offering a small
salary sufficient to support the student would enable him to acquire the
necessary knowledge to fill a permanent position. The number of these
scholarships should not be large, lest more students should undertake
the work than would be required to fill the permanent paying positions
in astronomy, as they become vacant.

In Europe, a favorite method of aiding science is to offer a prize for
the best memoir on a specified subject. On theoretical grounds this is
extremely objectionable. Since the papers presented are anonymous and
confidential, no one but the judges know how great is the effort wasted
in duplication. The larger the prize, the greater the injury to science,
since the greater will be the energy diverted from untried fields. It
would be much wiser to invite applications, select the man most likely
to produce a useful memoir, and award the prize to him if he achieved
success.

The award of a medal, if of great intrinsic value, would be an unwise
expenditure. The Victoria Cross is an example of a successful
foundation, highly prized, but of small intrinsic value. If made of
gold, it would carry no greater honor, and would be more liable to be
stolen, melted down or pawned.

Honorary membership in a famous society, or honorary degrees, have great
value if wisely awarded. Both are highly prized, form an excellent
stimulus to continued work, and as they are both priceless, and without
price, they in no way diminish the capacity for work. I recently had
occasion to compare the progress in various sciences of different
countries, and found that the number of persons elected as foreign
associates of the seven great national societies of the world was an
excellent test. Eighty-seven persons were members of two or more of
these societies. Only six are residents of the United States, while an
equal number come from Saxony, which has only a twentieth of the
population. Of the six residents here, only three were born in the
United States. Not a single mathematician, or doctor, from this country
appears on the list. Only in astronomy are we well represented. Out of a
total of ten astronomers, four come from England, and three from the
United States. Comparing the results for the last one hundred and fifty
years, we find an extraordinary growth for the German races, an equally
surprising diminution for the French and other Latin races, while the
proportion of Englishmen has remained unchanged.

A popular method of expending money, both by countries and by
individuals, is in sending expeditions to observe solar eclipses. These
appeal both to donors and recipients. The former believe that they are
making a great contribution to science, while the latter enjoy a long
voyage to a distant country, and in case of clouds they are not expected
to make any scientific return. If the sky is clear at the time of the
eclipse, the newspapers of the next day report that great results have
been secured, and after that nothing further is ever heard. Exceptions
should be made of the English Eclipse Committee and the Lick
Observatory, which, by long continued study and observation, are
gradually solving the difficult problems which can be reached in this
way only.

The gift of a large telescope to a university is of very doubtful value,
unless it is accompanied, first, by a sum much greater than its cost,
necessary to keep it employed in useful work, and secondly, to require
that it shall be erected, not on the university grounds, but in some
region, probably mountainous or desert, where results of real value can
be obtained.

Having thus considered, among others, some of the ways in which
astronomy is not likely to be much advanced, we proceed to those which
will secure the greatest scientific return for the outlay. One of the
best of these is to create a fund to be used in advancing research,
subject only to the condition that results of the greatest possible
value to science shall be secured. One advantage of this method is that
excellent results may be obtained at once from a sum, either large or
small. Whatever is at first given may later be increased indefinitely,
if the results justify it. One of the wisest as well as the greatest of
donors has said: "Find the particular man," but unfortunately, this plan
has been actually tried only with some of the smaller funds. Any one who
will read the list of researches aided by the Rumford Fund, the
Elizabeth Thompson Fund or the Bruce Fund of 1890 will see that the
returns are out of all proportion to the money expended. The trustees of
such a fund as is here proposed should not regard themselves as patrons
conferring a favor on those to whom grants are made, but as men seeking
for the means of securing large scientific returns for the money
entrusted to them. An astronomer who would aid them in this work, by
properly expending a grant, would confer rather than receive a favor.
They should search for astronomical bargains, and should try to purchase
results where the money could be expended to the best advantage. They
should make it their business to learn of the work of every astronomer
engaged in original research. A young man who presented a paper of
unusual importance at a scientific meeting, or published it in an
astronomical journal, would receive a letter inviting him to submit
plans to the trustees, if he desired aid in extending his work. In many
cases, it would be found that, after working for years under most
unfavorable conditions, he had developed a method of great value and had
applied it to a few stars, but must now stop for want of means. A small
appropriation would enable him to employ an assistant who, in a short
time, could do equally good work. The application of this method to a
hundred or a thousand stars would then be only a matter of time and
money.

The American Astronomical Society met last August at a summer resort on
Lake Erie. About thirty astronomers read papers, and in a large portion
of the cases the appropriation of a few hundred dollars would have
permitted a great extension in these researches. A sad case is that of a
brilliant student who may graduate at a college, take a doctor's degree
in astronomy, and perhaps pass a year or two in study at a foreign
observatory. He then returns to this country, enthusiastic and full of
ideas, and considers himself fortunate in securing a position as
astronomer in a little country college. He now finds himself overwhelmed
with work as a teacher, without time or appliances for original work.
What is worse, no one sympathizes with him in his aspirations, and after
a few years he abandons hope and settles down to the dull routine of
lectures, recitations and examinations. A little encouragement at the
right time, aid by offering to pay for an assistant, for a suitable
instrument, or for publishing results, and perhaps a word to the
president of his college if the man showed real genius, might make a
great astronomer, instead of a poor teacher. For several years, a small
fund, yielding a few hundred dollars annually, has been disbursed at
Harvard in this way, with very encouraging results.

A second method of aiding astronomy is through the large observatories.
These institutions, if properly managed, have after years of careful
study and trial developed elaborate systems of solving the great
problems of the celestial universe. They are like great factories, which
by taking elaborate precautions to save waste at every point, and by
improving in every detail both processes and products, are at length
obtaining results on a large scale with a perfection and economy far
greater than is possible by individuals, or smaller institutions. The
expenses of such an observatory are very large, and it has no pecuniary
return, since astronomical products are not salable. A great portion of
the original endowment has been spent on the plant, expensive buildings
and instruments. Current expenditures, like library expenses, heating,
lighting, etc., are independent of the output. It is like a man swimming
up stream. He may struggle desperately, and yet make no progress. Any
gain in power effects a real advance. This is the condition of nearly
all the larger observatories. Their income is mainly used for current
expenses, which would be nearly the same whatever their output. A
relatively small increase in income can thus be spent to great
advantage. The principal instruments are rarely used to their full
capacities, and the methods employed could be greatly extended without
any addition to the executive or other similar expenses. A man
superintending the work of several assistants can often have their
number doubled, and his output increased in nearly the same proportion,
with no additional expense except the moderate one of their salaries. A
single observatory could thus easily do double the work that could be
accomplished if its resources were divided between two of half the
size.

A third, and perhaps the best, method of making a real advance in
astronomy is by securing the united work of the leading astronomers of
the world. The best example of this is the work undertaken in 1870 by
the Astronomische Gesellschaft, the great astronomical society of the
world. The sky was divided into zones, and astronomers were invited to
measure the positions of all the stars in these zones. The observation
of two of the northern and two of the southern zones were undertaken by
American observatories. The zone from +1° to +5° was undertaken by the
Chicago Observatory, but was abandoned owing to the great fire of 1871,
and the work was assumed and carried to completion by the Dudley
Observatory at Albany. The zone from +50° to +55° was undertaken by
Harvard. An observer and corps of assistants worked on this problem for
a quarter of a century. The completed results now fill seven quarto
volumes of our annals. Of the southern zones, that from -14° to -18° was
undertaken by the Naval Observatory at Washington, and is now finished.
The zone from -10° to -14° was undertaken at Harvard, and a second
observer and corps of assistants have been working on it for twenty
years. It is now nearly completed, and we hope to begin its publication
this year. The other zones were taken by European astronomers. As a
result of the whole, we have the precise positions of nearly a hundred
and fifty thousand stars, which serve as a basis for the places of all
the objects in the sky.

Another example of cooperative work is a plan proposed by the writer in
1906, at the celebration of the two-hundredth anniversary of the birth
of Franklin. It was proposed, first to find the best place in the world
for an astronomical observatory, which would probably be in South
Africa, to erect there a telescope of the largest size, a reflector of
seven feet aperture. This instrument should be kept at work throughout
every clear night, taking photographs according to a plan recommended by
an international committee of astronomers. The resulting plates should
not be regarded as belonging to a single institution, but should be at
the service of whoever could make the best use of them. Copies of any,
or all, would be furnished at cost to any one who wished for them. As an
example of their use, suppose that an astronomer at a little German
University should discover a law regulating the stars in clusters.
Perhaps he has only a small telescope, near the smoke and haze of a
large city, and has no means of securing the photographs he needs. He
would apply to the committee, and they would vote that ten photographs
of twenty clusters, each with an exposure of an hour, should be taken
with the large telescope. This would occupy about a tenth part of the
time of the telescope for a year. After making copies, the photographs
would be sent to the astronomer who would perhaps spend ten years in
studying and measuring them. The committee would have funds at their
disposal to furnish him, if necessary, with suitable measuring
instruments, assistants for reducing the results, and means for
publication. They would thus obtain the services of the most skilful
living astronomers, each in his own special line of work, and the latter
would obtain in their own homes material for study, the best that the
world could supply. Undoubtedly, by such a combination if properly
organized, results could be obtained far better than is now possible by
the best individual work, and at a relatively small expense. Many years
of preparation will evidently be needed to carry out such a plan, and to
save time we have taken the first step and have sent a skilful and
experienced observer to South Africa to study its climate and compare it
with the experience he has gained during the last twenty years from a
similar study of the climate of South America and the western portion of
the United States.

The next question to be considered is in what direction we may expect
the greatest advance in astronomy will be made. Fortunate indeed would
be the astronomer who could answer this question correctly. When Ptolemy
made the first catalogue of the stars, he little expected that his
observations would have any value nearly two thousand years later. The
alchemists had no reason to doubt that their results were as important
as those of the chemists. The astrologers were respected as much as the
astronomers. Although there is a certain amount of fashion in astronomy,
yet perhaps the best test is the judgment of those who have devoted
their lives to that science. Thirty years ago the field was narrow. It
was the era of big telescopes. Every astronomer wanted a larger
telescope than his neighbors, with which to measure double stars. If he
could not get such an instrument, he measured the positions of the stars
with a transit circle. Then came astrophysics, including photography,
spectroscopy and photometry. The study of the motion of the stars along
the line of sight, by means of photographs of their spectra, is now the
favorite investigation at nearly all the great observatories of the
world. The study of the surfaces of the planets, while the favorite
subject with the public, next to the destruction of the earth by a
comet, does not seem to appeal to astronomers. Undoubtedly, the only way
to advance our knowledge in this direction is by the most powerful
instruments, mounted in the best possible locations. Great astronomers
are very conservative, and any sensational story in the newspapers is
likely to have but little support from them. Instead of aiding, it
greatly injures real progress in science.

There is no doubt that, during the next half century, much time and
energy will be devoted to the study of the fixed stars. The study of
their motions as indicated by their change in position was pursued with
great care by the older astronomers. The apparent motions were so small
that a long series of years was required and, in general, for want of
early observations of the precise positions of the faint stars, this
work was confined mainly to the bright stars. Photography is yearly
adding a vast amount of material available for this study, but the
minuteness of the quantities to be measured renders an accurate
determination of their laws very difficult. Moreover, we can thus only
determine the motions at right angles to the line of sight, the motion
towards us or from us being entirely insensible in this way. Then came
the discovery of the change in the spectrum when a body was in motion,
but still this change was so small that visual observations of it proved
of but little value. Attaching a carefully constructed spectroscope to
one of the great telescopes of the world, photographing the spectrum of
a star, and measuring it with the greatest care, provided a tool of
wonderful efficiency. The motion, which sometimes amounts to several
hundreds of miles a second could thus be measured to within a fraction
of a mile. The discovery that the motion was variable, owing to the
star's revolving around a great dark planet sometimes larger than the
star, added greatly not only to the interest of these researches, but
also to the labor involved. Instead of a single measure for each star,
in the case of the so-called spectroscopic binaries, we must make enough
measures to determine the dimensions of the orbit, its form and the
period of revolution.

What has been said of the motions of the stars applies also, in general,
to the determination of their distances. A vast amount of labor has been
expended on this problem. When at length the distance of a single star
was finally determined, the quantity to be measured was so small as to
be nearly concealed by the unavoidable errors of measurement. The
parallax, or one half of the change in the apparent position of the
stars as the earth moves around the sun, has its largest value for the
nearest stars. No case has yet been found in which this quantity is as
large as a foot rule seen at a distance of fifty miles, and for
comparatively few stars is it certainly appreciable. An extraordinary
degree of precision has been attained in recent measures of this
quantity, but for a really satisfactory solution of this problem, we
must probably devise some new method, like the use of the spectroscope
for determining motions. Two or three illustrations of the kind of
methods which might be used to solve this problem may be of interest.
There are certain indications of the presence of a selective absorbing
medium in space. That is, a medium like red glass, for instance, which
would cut off the blue light more than the red light. Such a medium
would render the blue end of the spectrum of a distant star much
fainter, as compared with the red end, than in the case of a near star.
A measure of the relative intensity of the two rays would servo to
measure the distance, or thickness of the absorbing medium. The effect
would be the same for all stars of the same class of spectrum. It could
be tested by the stars forming a cluster, like the Pleiades, which are
doubtless all at nearly the same distance from us. The spectra of stars
of the tenth magnitude, or fainter, can be photographed well enough to
be measured in this way, so that the relative distances of nearly a
million stars could be thus determined.

Another method which would have a more limited application, would depend
on the velocity of light. It has been maintained that the velocity of
light in space is not the same for different colors. Certain stars,
called Algol stars, vary in light at regular intervals when partially
eclipsed by the interposition of a large dark satellite. Recent
observations of these eclipses, through glass of different colors, show
variations in the time of obscuration. Apparently, some of the rays
reach the earth sooner than others, although all leave the star at the
same time. As the entire time may amount to several centuries, an
excessively small difference in velocity would be recognizable. A more
delicate test would be to measure the intensity of different portions of
the spectrum at a time when the light is changing most rapidly. The
effect should be opposite according as the light is increasing or
diminishing. It should also show itself in the measures of all
spectroscopic binaries.

A third method of great promise depends on a remarkable investigation
carried on in the physical laboratory of the Case School of Applied
Science. According to the undulatory theory of light, all space is
filled with a medium called ether, like air, but as much more tenuous
than air as air is more tenuous than the densest metals. As the earth is
moving through space at the rate of several miles a second, we should
expect to feel a breeze as we rush through the ether, like that of the
air when in an automobile we are moving with but one thousandth part of
this velocity. The problem is one of the greatest delicacy, but a former
officer of the Case School, one of the most eminent of living
physicists, devised a method of solving it. The extraordinary result was
reached that no breeze was perceptible. This result appeared to be so
improbable that it has been tested again and again, but every time, the
more delicate the instrument employed, the more certainly is the law
established. If we could determine our motion with reference to the
ether, we should have a fixed line of reference to which all other
motions could be referred. This would give us a line of ever-increasing
length from which to measure stellar distances.

Still another method depends on the motion of the sun in space. There is
some evidence that this motion is not straight, but along a curved line.
We see the stars, not as they are now, but as they were when the light
left them. In the case of the distant stars this may have occurred
centuries ago. Accordingly, if we measure the motion of the sun from
them, and from near stars, a comparison with its actual motion will
give us a clue to their distances. Unfortunately, all the stars appear
to have large motions whose law we do not know, and therefore we have no
definite starting point unless we can refer all to the ether which may
be assumed to be at rest.

If the views expressed to you this morning are correct, we may expect
that the future of astronomy will take the following form: There will be
at least one very large observatory employing one or two hundred
assistants, and maintaining three stations. Two of these will be
observing stations, one in the western part of the United States, not
far from latitude +30°, the other similarly situated in the southern
hemisphere, probably in South Africa, in latitude -30°. The locations
will be selected wholly from their climatic conditions. They will be
moderately high, from five to ten thousand feet, and in desert regions.
The altitude will prevent extreme heat, and clouds or rain will be rare.
The range of temperature and unsteadiness of the air will be diminished
by placing them on hills a few hundred feet above the surrounding
country. The equipment and work of the two stations will be
substantially the same. Each will have telescopes and other instruments
of the largest size, which will be kept at work throughout the whole of
every clear night. The observers will do but little work in the daytime,
except perhaps on the sun, and will not undertake much of the
computation or reductions. This last work will be carried on at a third
station, which will be near a large city where the cost of living and of
intellectual labor is low. The photographs will be measured and stored
at this station, and all the results will be prepared for publication,
and printed there. The work of all three stations will be carefully
organized so as to obtain the greatest result for a given expenditure.
Every inducement will be offered to visiting astronomers who wish to do
serious work at either of the stations and also to students who intend
to make astronomy their profession. In the case of photographic
investigations it will be best to send the photographs so that
astronomers desiring them can work at home. The work of the young
astronomers throughout the world will be watched carefully and large
appropriations made to them if it appears that they can spend them to
advantage. Similar aid will be rendered to astronomers engaged in
teaching, and to any one, professional or amateur, capable of doing work
of the highest grade. As a fundamental condition for success, no
restrictions will be made that will interfere with the greatest
scientific efficiency, and no personal or local prejudices that will
restrict the work.

These plans may seem to you visionary, and too Utopian for the twentieth
century. But they may be nearer fulfilment than we anticipate. The true
astronomer of to-day is eminently a practical man. He does not accept
plans of a sensational character. The same qualities are needed in
directing a great observatory successfully, as in managing a railroad,
or factory. Any one can propose a gigantic expenditure, but to prove to
a shrewd man of affairs that it is feasible and advisable is a very
different matter. It is much more difficult to give away money wisely
than to earn it. Many men have made great fortunes, but few have learned
how to expend money wisely in advancing science, or to give it away
judiciously. Many persons have given large sums to astronomy, and some
day we shall find the man with broad views who will decide to have the
advice and aid of the astronomers of the world, in his plans for
promoting science, and who will thus expend his money, as he made it,
taking the greatest care that not one dollar is wasted. Again, let us
consider the next great advance, which perhaps will be a method of
determining the distances of the stars. Many of us are working on this
problem, the solution of which may come to some one any day. The present
field is a wide one, the prospects are now very bright, and we may look
forward to as great an advance in the twentieth century, as in the
nineteenth. May a portion of this come to the Case School and, with your
support, may its enviable record, in the past, be surpassed by its
future achievements.





End of Project Gutenberg's The Future of Astronomy, by Edward C. Pickering