AN INTELLECTUAL BIOGRAPHY OF HEBER DO UST CURTIS: ONE MAN'S QUEST FOR ASTRONOMICAL CERTAINTY by Miriam E. Carolin A thesis submitted to Sonoma State University in partial fulfillment of the requirements for the degree of MASTER OF ARTS

m HISTORY

Ste~h en Watrous

:;,hard H. Karas r"L l/9o Date • II

Copyright 1990 By Miriam E. Carolin .Ill

I do not approve the reproduction of this thesis, either in part or in its entirety. Dated s /, I/.? IV

AN INTELLECTUAL BIOGRAPHY OF HEBER DOUST CURTIS: ONE MAN'S QUEST FOR ASTRONOMICAL CERTAINTY Thesis by

Miriam E. Carolin

ABSTRACT

Purpose of this Study:

From 1917 to 1935, a controversy raged over the identification and location of the spiral nebulae. One faction proposed the spiral nebulae as members of the Milky Way. Their opponents insisted that the nebulae were island universes or galaxies far outside the Milky Way. Heber Curtis, who became known as the leadin~ advocate of the island universe theory, concluded that these nebulae were indeed galaxies, while he was working as an astronomer at Lick Observatory. This paper is an intellectual biography of Curtis and a search for the motivations behind his defense of the island universe theory.

Procedure: This study is based on examination of Curtis' private letters, scientific articles, speeches and radio talks. Most of these speeches and talks were made between 1920 and 1938, after the main period of the controversy, hut they reveal his attitude toward the island universe theory. Secondary materials, such as historical treatments of the controversy, were also used.

Findings:

Heber Curtis steadily advocated the island universe theory of the spiral nebulae regardless of the evidence and worked for its acceptance. He based his conclusions partly on the scientific observations concerning the spectroscopy, space distribution, occulting material, space velocity, novae, rotation and lack of proper motion of the spiral nebulae and analogies between the Milky Way and the spiral nebulae, and in part on his world view, his philosophy of life and on his synthesis of science and religion. v

Conclusions:

Curtis based his unswervin$ advocacy of the island universe theory on his interpretation of the scientific evidence. His belief in the concepts of order and infinity, his awe at the majesty of the universe and his deep religious conviction also were important contributory factors in his decision.

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M.A. Program: History Sonoma State University VI

ACKNOWLEDGEMENTS

I would like to thank, first of all, Edgar Morse, without whose support and encouragement, I would not have been able to undertake this thesis. His continuing belief in the value of my subject gave me enough incentive to continue with this project even when I became discouraged, and his guidance was invaluable in assisting me in finding the direction this thesis should take. I would like to give special thanks to the members of my committee, whose patience and understanding eased my task considerably and whose willingness to read the many revisions of this thesis and comment upon them made the task easier for me. Stephen Watrous, as chairman, did far more than could reasonably be expected in helping me bring this project to completion. Richard Karas made extremely cogent comments, which helped greatly to clarify the scientific aspect. Joseph Tenn, the third member of my committee, provided valuable insight into the period and assisted me in keeping my scientific facts accurate. It was in one of Dr. Tenn's courses that I first learned of the subject matter of my thesis. I also wish to thank J.J. Wilson and Ambrose Nichols for their unfailing encouragement during my graduate course of studies. J.J. also edited the fourth chapter of my thesis into a readable form. The Bentley Historical Library at the University of Michigan provided microfilm of Curtis' correspondence and speeches. These provided essential material for my research. I would also like to acknowledge the assistance of the late Mrs. C.D. Shane, curator of the Lick Observatory Archives, for opening archival material on Heber Curtis for me. Last, but definitely not least, I wish to thank Joan Wilbur, who allowed me to use her computer and helped me learn to operate this device. This assistance made working on my thesis much easier than it would have been if I had continued my usual practice of working with a typewriter. f ~ - HEBER DOUST CURTIS 1

AN INTELLECTUAL BIOGRAPHY OF HEBER DOUST CURTIS: ONE MAN'S QUEST FOR ASTRONOMICAL CERTAINTY

There is a unity and an integral agreement in the features of the island universe theory which appeals very strongly tome. Heber D. Curtis 2

TABLE OF CONTENTS

INTRODUCTION ...... 3 CHAPTER 1: HISTORICAL BACKGROUND ...... 8 CHAPTER2: BIOGRAPHY ...... 16 CHAPTER3: SCIENTIFIC BASIS FOR CURTIS' POSITION ...... 29 CHAPTER4: NON-SCIENTIFIC FACTORS INFLUENCING CURTIS ...... 41 APPENDICES ...... 56 CHRONOLOGICAL DEVELOPMENT OF THE ISLAND UNIVERSE CONTROVERSY IN THE TWENTIETH CENTURY ...... 57 HEBER CURTIS' EDUCATION AND CAREER ...... 60 HEBER CURTIS' ECLIPSE EXPEDITIONS ...... 61 BIBLIOGRAPHY ...... 62 3

INTRODUCTION

Curtis led the way in understanding the spirals. Donald Osterbrock1

Since these two 1917 papers by Curtis both specifically mention the island universe theory, it can be seen that Curtis was responsible for res~rrecting the idea and starting the controversy agam. Richard C Hart2

1Donald E. Osterbrock, John R. Gustafson, and W.J. Shiloh Unruh, Eye on the Sky: Lick Observatory's First Century (Berkeley: University of California Press, 1988), 270.

2Richard C. Hart, "Adriaan van Maanen's Influence on the Island Universe Theory" (Ph.D. diss., Boston University, 1973), 29. 4

During the early part of the twentieth century, a controversy concerning the composition and the placement of the spiral nebulae exercised the minds of the astronomical community. Some astronomers contended that these objects were gaseous in nature, probably the first stages of the evolution of stars or of solar systems situated within the Milky Way. Their opponents argued just as forcefully that they were composed of stars and were located far outside the galaxy, that they were island universes. The controversy began in earnest in 1917, when Heber Curtis published articles on novae in spiral nebulae which mentioned the island universe theory.1 Its climax occurred in 1925, when Edwin Hubble, an astronomer at Mt. Wilson Observatory in southern California, produced evidence that the spiral nebulae were indeed located outside the boundaries of our galaxy. The issue was finally resolved in 1935, when Adriaan van Maanen, also an astronomer at Mt. Wilson Observatory, finally conceded that his measurements of the rotation of several of the spiral nebulae were erroneous. His findings had been the major stumbling block to the general acceptance of the island universe theory of the spiral nebulae. Throughout the controversy, Curtis had remained the leading advocate of the theory.

This controversy has received considerable attention. Treatments ranging from mention in astronomical histories to an entire book devoted to the subject have appeared within the decades since the dispute ended. Most of these works have approached the subject from an historical point of view mentioning participants as they appeared. This method of studying the controversy is a valid approach. However, it leaves out one aspect of the controversy which might shed some light on the personal side of the story: the human aspect. It is human beings who do science, who think about it and who accumulate scientific knowledge. This knowledge is useless without the interpretation of the men who obtain it.

1Hart, 26-29. 5

Therefore, it seems natural, when writing about an event in the history of science, to concentrate on the scientist or scientists who contributed to the significance of that event.

In an attempt to deal with the human aspect of the controversy, this thesis will examine the episode from the point of view of one of the participants, Heber Doust Curtis. He was an astronomer at Lick Observatory when the controversy erupted, and has been credited by at least one historian with bringing about a resurgence of the dispute which resulted in its final resolution.2 Despite that recognition, until recently Curtis has not received much credit for the part he played in the drama. Yet, he saw clearly what the nature and position of the spiral nebulae were, and, in addition, he brought his conclusions to the attention of both the scientific and non-scientific communities as often as he could.

Curtis formed his opinion that the spiral nebulae were island universes about 1914. What is remarkable is that, throughout the lifetime of the controversy, when evidence seemed to contradict his view and other astronomers were swayed by seemingly foolproof arguments, Curtis maintained his position as the leading advocate of the island universe theory.3

The only known time Curtis expressed a doubt was with the following statement made in 1921.

Should the results of the next quarter-century show agreement among observers to the effect that the annual motions of translation or rotation

2Ibid. In their book, Osterbrock, Gustafson and Unruh also pay tribute to Curtis' effect on the reintroduction of the island universe controversy. On page 224, they write, "other astronomers were then beginning to realize through Curtis' observational research that spiral 'nebulae' were in reality extremely distant galaxies." In addition, they comment on page 222 that "Curtis had said and Hubble had proved" that the faint anagalactic nebulae were truly galaxies containing many billions of stars.

3Robert W. Smith, The Expanding Universe: Astronomy's "Great Debate" 1900-1931 (Cambridge: Cambridge University Press, 1982), 28. 6 of the spiral nebulae equal or exceed d'.01 in average value, it would seem that the island universe theory must definitely be abandoned.4

After Edwin Hubble had announced his findings that Cepheid variables found in the spirals M31 and M33 confirmed their distances as too remote for them to be included as members of the Milky Way, Curtis reiterated his long-standing advocacy in a letter to his colleague, R.C. Aitken, "As you know I have always believed that the spirals are island universes, and Hubble's recent results appear to clinch this, though I myself did not need the confirmation."5 In the same letter, Curtis also stated his dismissal of van Maanen's measurements,

I have never been able to accept van Maanen's results, the main and sufficient reason being that the spectographic results of Slipher and Pease show motion in exactly the opposite direction. And I have always been a 'fundamentalist' as far as the spectrograph is concerned.6 Where did that assurance come from? Certainly a good deal of it came from the scientific evidence amassed by Curtis and his colleagues. Much of it, however, came from within Curtis himself, from his personality and character, his ideas, philosophy, beliefs and world view. His religious convictions also entered into his scientific decision about the island universe theory. This thesis will attempt to reconstruct just what factors entered into his decision.

A look at the historical background and the astronomical developments at the time of the beginning of the controversy will be followed by a biographical study of Curtis in an attempt to find the man behind the decision. This will be succeeded by an examination of the empirical evidence which supported the island universe theory. Then, Curtis' non-scientific motivations will be investigated.

4Heber Curtis, "The Scale of the Universe," talk given before the National Academy of Sciences, 26 April, 1920. Bulletin of the National Research Council, vol. 2 (Washington, D.C.: The National Research Council of the National Academy of Sciences, 1931): 214. 5Heber Curtis to Robert G. Aitken, 2 January, 1925, Heber Doust Curtis Collection, Michigan Historical Collections, Bentley Historical Library, University of Michigan, Ann Arbor.

6Ibid. 7

This thesis is not a study of the island universe controversy. It is, rather, a study of one of the participants in that controversy and his reasons for unswervingly supporting the island universe theory. Curtis seldom stood alone in his adherence to the theory, but he was considered to be the leader of those astronomers who believed it. 8

CHAPTER 1: HISTORICAL BACKGROUND

... these conglomerations present a subject for investigation too inviting to be neglected, and too vast to be exhausted. Stephen Alexander7

7Stephen Alexander, quoted in J.D. Fernie, "The Historical Quest for the Nature of the Spiral Nebulae," Publications of the Astronomical Society of the Pacific, 82 (December 1970): 1202. 9

Although the active part of the island universe controversy occurred during the early decades of the twentieth century, its antecedents stretched back to the middle of the eighteenth. The term "island universe" was used by eighteenth century philosophers to signify stellar systems comparable to and removed from the Milky Way. This term continued in use into the twentieth century. In this chapter, a brief history of the events leading up to the island universe controversy in the early part of the twentieth century as well as a background for that controversy and a framework for the remainder of the thesis will be provided. A detailed study of the background of the controversy is not intended. Very little actual observational activity occurred before 1750; the earliest speculations concerning the Milky Way's place in the universe and the composition and location of the spiral nebulae were theoretical. These reflections came primarily from four men in the eighteenth century: Emanuel Swedenborg, a Swedish philosopher and scientist; Thomas Wright, an English instrument maker and mathematician; Immanuel Kant, the German philosopher; and Johann Heinrich Lambert, a tailor's apprentice who later became a researcher in photometry.8 This diversity of background and nationality reveals how widespread was the interest in the structure of the universe in the mid eighteenth century. As interest in the universe as a whole began to quicken, people began to concentrate on its component parts. They began treating the phenomena contained in the universe as objects worthy of study. It was this interest, voiced by these four spokesmen, which eventually led to more specific study of the ambiguous objects, and almost two centuries after the advent of interest led to the solution of the island universe mystery. Perhaps the first mention of the Milky Way as part of a larger system was contained in a book by Emanuel Swedenborg titled Principia Rerum Naturalium:

8Fernie, 1191-1192. 10

Sine Novarum Tentaminum Phenomena Mundi Elementaria Philosophia, published in

1734. Swedenborg argued that the Milky Way was only one of numerous star systems in the universe and the solar system was one of many in the Milky Way.9 The influence of the work was not far reaching as the publication was not well known at the time, but it can be said to be the chronological progenitor of the island universe debate.

A better known work was Thomas Wright's An Original Theory or New

Hypothesis of the Universe, published in 1750. Wright attempted to devise a form for the Milky Way, but it is his statement about the composition of the galaxy which is of interest. "Many cloudy spots just perceivable by us .. .in all likelihood may be external creation, bordering upon the known one, too remote for even our telescopes to reach.1110 This comment is based on observation, but the conclusions are speculative. The important point in both Wright and Swedenborg is that the nebulae are conjectured, probably for the first time, as being distinct from the Milky Way. In fact, some of the phrases of these men came close to words used by Curtis over one hundred and fifty years later. The importance of Wright's book was the influence it had upon Immanuel Kant.11

Kant refined the concept still more. He stated the problem concisely.

It is far more natural and conceivable to regard them [nebulae] as being not such enormous single stars but systems of many stars, whose distance presents them in such a narrow space that the light which is individually imperceptible from each of them reaches us, on account of their immense multitude, in a uniform pale glimmer... all this is in perfect harmony with the view that these elliptical figures are just universes and, so to speak, Milky Ways ... 12

9Ibid., 1191.

10Ibid.

11Hart, 4.

12Ibid., 5. 11

There has been some discussion as to whether Kant coined the term "island universe," but the intent of his idea is clear; the nebulae are unmistakably separate from the Milky Way. The reference to the nebulae as single stars came from the idea then prevalent, and which remained so into the twentieth century, that the spiral nebulae were the first stage in the evolution of stars or planetary systems. In an attempt to find order in the solar system, Pierre-Simon, Marquis de Laplace developed a similar theory in 1796, called the "Nebular Hypothesis", which proposed that the spiral nebulae were the first stage in the formation of planetary systems. His intention was to relate the nebulae to the solar system and thus bring them into the Milky Way.13 But, whatever the genesis of the phrase "island universe," whenever the origins of the theory are pondered, Kant's ideas spring to mind.

An additional voice added itself to the consensus on the belief in the nebulae as external star systems. This belonged to Johann Heinrich Lambert, who discussed the makeup of the Milky Way in his publication, Kosmologische Briefe uber die Einrichtung des Weltbaues (1761). He reasoned that the Milky Way, made up of multitudes of distant stars, was probably one of several similar systems. But the lack of evidence frustrated him. He could not relate the Milky Way to other star systems which he knew must be there.14 The paucity of evidence was corrected in the latter half of the eighteenth century by William Herschel, a German musician who had emigrated to England in 1757. It was there, while he practiced his profession as a musician, that he discovered the joys of astronomy.15 His greatest contribution was the manufacture of ever larger telescopes with better optics and resolving power than any produced

13Ibid., 12-13.

14Fernie, 1192. 15Charles A. Whitney, The Discovery of our Galaxy, (New York: Alfred A. Knopf, 1971), 90-93. 12 before his time. With these telescopes, especially those built after 1780, Herschel studied the heavens every clear night and amassed a catalogue of one thousand seven hundred and seven nebulae.16 Because he could resolve some of the nebulae into stars, he concluded that all nebulae were similarly composed. This led him to the opinion that these nebulae, which were located away from the plane of the Milky Way, were star systems similar to it. 17 Until the last two decades of the eighteenth century, most people interested in the subject concurred that the nebulae visible in the telescopes were true island universes. Herschel agreed with the philosophers on the basis of his data. However, starting in 1790, Herschel found some nebulae, notably the Orion nebula, which he could not resolve into stars. He decided from these examples that all nebulae were gaseous rather than stellar. By the end of his life in 1822, he had lapsed into ambivalence and refused to commit himself to either conclusion.18 His failure to come out strongly in favor of island universes paved the way for the next shift in interpretation, so that, during the early decades of the nineteenth century, the island universe theory fell out of favor. 19

By the middle of the nineteenth century, however, William Parsons, the Earl of Rosse, had built a 72-inch telescope which resolved the nebula in Canes Venatici into stars.20 In addition, this telescope was so powerful it could discern the spiral shape of this nebula, called M51. Not only was the shape of M51 revealed, but observers believed they found a spiral pattern in every observable nebula, even

16Gunther Buttman, The Shadow of the Telescope: A Biography of John Herschel, ed. David S. Evans, trans. B.E.J. Pagel (New York: Charles Scribners Sons, 1970), 92.

17Whitney, 105. 18Fernie, 1195.

19Ibid., 1195-1196. 20Ibid., 1196. 13 where no such shape existed.21 The 72-inch instrument, with its greater resolving power, aided the island universe theory in regaining supremacy. However, this preeminence was shortlived. By the end of the nineteenth century, the island universe theory had again lost credibility. Several occurrences worked to bring about its demise. The development of photography with its retention of images, together with additional observations, disclosed the fact that the resolution of all nebulae into stars had not been warranted.

Further, in 1847 Sir John Herschel, William Herschel's son, published observations taken at the Cape of Good Hope, which showed both stellar and nebulous compositions for several of the nebulae. This revealed that not all nebulae were solely of stellar composition. Herschel's 1864 catalogue of nebulae contained not only the description of the nebulae but their positions on the cosmic sphere. It was discovered that the nebulae occupied a location close to the poles of the celestial sphere away from the plane of the Milky Way.22 Herschel used this distribution to argue that this placement of the nebulae affirmed a connection between them and the Milky Way. This was one of the main arguments which clinched the opposition to the island universe theory.

The above-mentioned arguments were weighty reasons for disbelieving the nebulae to be separate entities. However, there were other reasons, such as

Marquis de Laplace's theory about the origin of planetary systems, which assumed that the initial stages of planetary conglomerates within the Milky Way were spiral nebulae.23 The final argument in favor of the spiral nebulae as gaseous bodies, and thus not island universes, was provided by William Huggins, who was an early

21Fernie, 1196-1198.

221bid., 1198-1199.

23Wbitney, 146. 14 early pioneer in the science of spectroscopy. In 1864, he found that the Orion nebula was composed of gas. This and other early spectroscopic observations so convinced him that the nebulae were gaseous in nature, that when he submitted the Andromeda nebula to spectroscopic analysis, he determined that its continuous spectrum, which is indicative of stellar composition, was "the result of gradual loss of heat or the influence of other forces,"24 rather than the representation of the light emitted by stars. The foregoing arguments served to convince astronomers of the second half of the nineteenth century that the spiral nebulae were members of the Milky Way. Not only were astronomers convinced of this, but this consensus was reflected in astronomical histories of the period. Agnes Clerke, a prolific historian of astronomy, writing in 1885, stated categorically that "There is no maintaining nebulae to be simply remote worlds of stars .. .it becomes impossible to resist the conclusion that both nebular and stellar systems are parts of a single scheme."25 However, the fortunes of the spiral nebulae did not end with this pronouncement. Stephen Alexander, a nineteenth century astronomer, concluded that "these conglomerations present a subject for investigation too inviting to be neglected, and too vast to be exhausted."26 Astronomers of the twentieth century heeded this directive. Starting around 1910, they scrutinized these objects carefully.

One of the astronomers who devoted a great deal of time to this enterprise was Heber Doust Curtis, who started photographing these objects while he worked at Lick Observatory in northern California. As he photographed more and more of the enigmatic objects, he became convinced that they were extragalactic. He was not the only astronomer working on this project. Data were compiled by many

24Fernie, 1200. 25Ibid., 1202. 261bid. 15 others, who also believed these objects to be island universes. Although many scientists agreed with Curtis, no other astronomer devoted the same amount of time or energy to disseminating arguments in favor of the theory. Through his steadfast belief in the island universe theory and his talks and articles, both scientific and nonscientific, Curtis was instrumental in keeping the island universe concept before the community. He had taken a leading role in reintroducing the controversy in 1917;27 he also became vitally involved in finally resolving the issue and in determining the nature and the location of the spiral nebulae.

27Hart, 29. 16

CHAPTER 2: BIOGRAPHY

We must take stock of ourselves and know how far we have gone and know what course we are steering: we must know our course and distance. Heber D. Curtis 17

Heber Doust Curtis did something unusual for his time. He obtained university training in the classics, worked as a classical language teacher, and at the age of twenty-eight entered a Ph.D. program in astronomy, a totally unrelated field, which he completed with distinction. After receiving this advanced degree, he entered his new discipline and made many contributions in his new field. Curtis was clearly an independent thinker in his work career. He was also an independent thinker in his attitude toward the spiral nebulae. Scientific evidence augmented by elements from his background and personality provided the basis for Curtis' conclusions about the spiral nebulae. With that caution in mind, it is worthwhile to examine Curtis' background and his character to see what non-scientific clues reveal about Curtis' mind. It is probably impossible to enumerate the exact reasons which convinced Curtis of the veracity of his opinion, but a historical reconstruction can offer a plausible interpretation of these influences. Curtis was born June 17, 1872, in Muskegon, Michigan. He was the elder of two sons. His father, Blair Curtis, came from a family that had resided in America for ten generations. His mother, Sarah Eliza Doust Curtis, the daughter of a

Methodist minister, had been born in England. The family was presumably faithful in church attendance because dancing, card playing and theater attendance were not approved.28 The influence exercised by this deeply religious home lasted all of Curtis' life. As an adult, he was a member of the Methodist Church and enjoyed attending religious services, especially if the minister was an intellectual, and the church choir was good; Curtis particularly enjoyed good choral music. Religion played an important role in Curtis' intellectual life and in his scientific theories. He found no contradiction between science and religion. H e accepted the idea of a

28Robert G. Aitken, "Biographical Memoir of Heber Doust Curtis 1872-1942," Biographical Memoirs, vol. 22, Thirteenth Memoir (Washington, D.C.: National Academy of Sciences of the United States of America, 1942): 275-276. 18

Supreme Being on scientific grounds and often gave talks on the relation of science to religion. Mrs. Curtis read aloud to her sons during evenings at home.29 This family exposure to the best in literature also had a longstanding effect. Curtis retained a love of great literature for the rest of his life. One of his favorite authors, Rudyard

Kipling, was often quoted in his speeches and was used in bis teaching. A stanza or two of one of Kipling's poems was incorporated at least once into a test question on celestial navigation. Dean B. McLaughlin, one of Curtis' colleagues, wrote of walking into a classroom vacated by Curtis to find a quote from Kipling on the blackboard.30 These verses were quoted and inscribed from memory. Another of his favorite authors was Tennyson. Curtis' love of literature is mentioned here to show him as a scientist who did not confine his interests to bis work.

At the University of Michigan, Curtis majored in the classics with an emphasis on classical languages: Latin, Greek, Hebrew, Sanskrit and Assyrian.31 The facility he acquired in these languages showed up later in the beauty, delicacy, aptness and precision with which he expressed his ideas.32 During high school days, Curtis displayed facility in mathematics, although he later criticized himself for his lack of skill in computing and was later criticized by William Wallace Campbell, director of Lick Observatory, as weJI.33 When Adriaan van Maanen, an astronomer at Mt. Wilson Observatory in southern

California, wrote to Curtis requesting copies of bis measurements, Curtis refused to

29Ibid.

30Dean B. McLaugh lin, "Heber Doust Curtis 1872-1942," Popular Astronomy, 50 (April 1942): 7. 31Aitken, 276. 32Ibid.

33Heber Curtis to William W. Campbell, 11July,1922, Mary Lea Shane Archives of Lick Observatory, Santa Cruz. 19 send van Maanen his figures. Curtis did not trust the accuracy of bis own computations.34 Despite his ease with mathematics in high school, Curtis took no science classes in either high school or college other than the required ones. People who knew him remarked that he never showed any interest in astronomical subjects during his pre-doctoral education.35 Curtis graduated Phi Beta Kappa from the University of Michigan in 1892 and earned a Master of Arts degree in classics from the same university in 1893.36 He married Mary D. Raper in 1895.37 Curtis taught Latin at the Detroit High School before moving to California, where he taught Latin and Greek at Napa College, north of San Francisco, for three years. When Napa College merged with the College of the Pacific in San Jose,

Curtis transferred there. At the beginning of his second year at San Jose, he began teaching mathematics and astronomy. Both at Napa College and at the College of the Pacific, Curtis found small refracting telescopes with which he began to observe the heavens.38 McLaughlin claimed that Curtis' interest in astronomy developed when he had to "teach mathematics 'one jump ahead of bis classes."'39 Others, notably Robert G. Aitken, a colleague at Lick Observatory, have attributed Curtis' initiation into astronomy to the time when he found the telescope at Napa College and started using it.40 There is probably a germ of truth in each

34Ibid. 35 Aitken, 276. 36Jbid. 37Ibid., 278.

38McLaughlin, 2.

39Ibid. 40Aitken, 277. 20 assertion, but the fact remains that Curtis began his lifelong enchantment with astronomy during his tenure as a teacher of classical languages. During the summer of 1898, Curtis volunteered as a worker at Lick Observatory, where he received encouragement from Edward S. Holden, the director. McLaughlin states that Curtis decided to make astronomy his career after receiving Holden's support.41

In 1900, Curtis accepted a Vanderbilt Fellowship offered by the University of Virginia. He studied under Ormond Stone and especially enjoyed his courses in spectroscopy.42 This interest stayed with him all his life. He always relied upon the results of spectroscopic analysis and accepted these findings in preference to other types of measurements.

One of Curtis' main enthusiasms was his participation in eleven eclipse expeditions. Though not all of these were successful, he enjoyed these excursions where he was able to observe the sun and use his skill in working with instruments. Throughout his life, Curtis spent time and energy in improving the performance of the equipment with which he worked. Curtis' mechanical ability did not translate itself into a belief in a mechanistic philosophy of the origin of the universe. Rather,

Curtis held to a view that the best and most scientific explanation for the creation and stewardship of the universe lay in a Supreme Being, a sentient spirit. He believed the concept of a Supreme Being was a "rather scientific attempt to explain the existence of infinite data."43

Upon completion of his Ph.D. work at Virginia in 1902, he joined the Lick Observatory staff on Mt. Hamilton in California. During an eclipse expedition to

41 McLaughlin, 2.

42Aitken, 278.

43Joel Stebbins, "Heber Curtis and the Michigan Telescope," reprinted from The Structure of the Galaxy, Publications of the University of Michigan, 10 (1951): 5. 21

Thomaston, Georgia, in 1900, Curtis had impressed W.W. Campbell, leader of the expedition and director of Lick Observatory, with his capability and resourcefulness in assisting with setting up, testing and using the eclipse instruments. Campbell invited Curtis on this basis to join the Lick Observatory staff when he was ready.44 In 1904, he was promoted to Assistant Astronomer.45 Curtis' first major assignment at Lick Observatory was to work on a radial velocity program begun by Campbell to determine the velocity of the brighter stars. In 1906, he headed the radial velocity program in Santiago, Chile.

After his return from South America in 1910, Curtis assumed direction of the program begun by James Keeler of photographing the spiral nebulae.46 It was this assignment which piqued his interest in the spiral nebulae. He improved the quality of the reflecting telescope donated by the English amateur astronomer, Edward Crossley, to Lick Observatory. With this newly restored intrument, he took photographs of the spiral nebulae that had great clarity. These, together with other scientific data, convinced him that the spiral nebulae were indeed island universes. Curtis' photographs together with descriptions of the spiral nebulae were published

in Volume 13 of the Lick Obse1Vatory Publications in 1918. 47

In 1920, Curtis and Harlow Shapley spoke before the National Academy of

Sciences on "The Scale of the Universe." Curtis concentrated on the spiral nebulae,

and Shapley discussed primarily the size of the Milky Way. Curtis was invited to

defend the island universe theory after George E. Hale had seen his articles on the

44Aitken, 278.

45Robert R. McMath, "Heber Doust Curtis 1872-1942," Publications of the Astronomical Society of the Pacific, hereinafter cited as PASP, 54 (April 1942): 70.

46Ibid. 47McLaughlin, 4. 22 spiral nebulae in the Publications of the Lick Obse1Vatory. Curtis was known as the spokesman on the topic for Lick Observatory,48 and he was also acknowledged to be the leader of the faction which espoused the theory. This confrontation, which years later became known as The Great Debate, did not answer any questions about the spiral nebulae but provided a national scientific forum for the arguments. Curtis upheld his conclusions that the spiral nebulae were island universes, and Shapley maintained that they were part of the Milky Way because our galaxy was so large in diameter (300,000 light years) that the spiral nebulae could not be of comparable size nor could they be located so far away as to be outside. And, of course, no proof of either view was forthcoming. Though neither gentleman conclusively answered the other's criticisms, this "debate" can be considered the high point of the controversy; it was one occasion when the arguments for both sides were brought before the scientific community.

Curtis remained at Lick Observatory for eighteen years, from 1902 until 1920.49 Before he left, Curtis took a leave of absence to serve his country as a civilian during the first World War. He organized and conducted a navigation school in San Diego, California. Following that, he taught navigation at the Naval

Officers School in Berkeley, California.50 His last assignment was to the Bureau of

Standards in Washington, D.C., where he designed instruments for the study of optics.51 In 1920, Curtis accepted the directorship of the Allegheny Observatory in

Pittsburgh, Pennsylvania, because he "couldn't wait much longer if he were going to

48Smith, 79. 49McMath, 70.

50Ibid.

51Keivin Burns, "Are Astronomers Folks?," The Sky, 5 (July 1941): 4. 23

try his hand as director."52 When Campbell became president of the University of California, Berkeley in 1923, and Robert G. Aitken became the associate director of Lick Observatory, Curtis may have regretted this decision, when he was informed by Campbell that the position would go to a current member of the Lick Observatory staff.

Curtis had at first intended to continue with his photographic program which had been so successful at Lick Observatory, but he soon had to abandon this. I have naturally had in the back of my mind various plans for changing the character of the work here but am gradually coming around to the conviction that what we are doing is not only the thing we can do best, but also the field most needed today.53 Therefore, he decided to continue the program already in progress at the Allegheny Observatory of studying the parallaxes of stars. Parallax is the apparent displacement of a nearby star against the background of distant stars as seen from opposite ends of the earth's orbit around the sun.54 Distances to stars can be calculated by using these stellar parallaxes. Upon accepting the directorship, he had been unaware that his greatest enemy to such an undertaking would be the

bright sky illumination from the lights of a large and far-flung city: .. .it was evident that I could not expose with the reflector for more than half an hour without getting a plate so black as to be useless.55

Faced with the necessity of relinquishing his photographic activity and the research

that went along with it, Curtis did regret leaving Mt. Hamilton. In letters to Campbell, he lamented that the "California combination of instruments plus climate

52Heber Curtis to family, Heber Doust Curtis Collection, University of Michigan, Ann Arbor, n.d. 53Heber Curtis to W.W. Campbell, 26 July, 1921, Mary Lea Shane Archives of Lick. Obs., Santa Cruz.

54George 0. Abell, Exploration of the Universe, 3d. ed. (New York: Rinehart and Winston, 1974 ), 386, 688.

55Heber Curtis, "Reminiscences of a Pittsburgh Astronomer in the 20's," Heber Doust Curtis Collection, University of Michigan, Ann Arbor, n.d. 24 is a hard one to beat," and "there is no place like the hill (Mt. Hamilton) for astronomical work and that any man who leaves these opportunities is bound to be sorry for it."56

After ten years in Pittsburgh, Curtis received an invitation to head the Observatory at the University of Michigan with the promise that funds would be available to build a large reflecting telescope for the institution. Although Curtis spent many hours designing the telescope he hoped to build, he was disappointed. The Depression dried up the intended funds, and Curtis' plans remained on the shelves, to be taken down from time to time and updated or revised. 57 The telescope was not built until after Curtis' death, when it was dedicated to him. Curtis did, however, increase the diversity of the observatory in another way.

When he arrived in Ann Arbor in 1930, amateur astronomers at the McMath­ Hulbert Observatory, a private installation at Lake Angelus, were engaged in the pioneer work of taking moving pictures of the sun and planets. Some of the observatory's most spectacular achievements consisted of obtaining movies of solar prominences. The observatory grew into an important solar research institution. Thanks to Curtis' encouragement, backing and activity on behalf of the McMath­

Hulbert Observatory, it became the fourth member of the Observatories of the

University of Michigan.58 Five months before he was scheduled to retire' Curtis died at the age of 69 on January 9, 1942.59 At the time of his death, Curtis was the Director Emeritus of the Observatories of the University of Michigan.

560sterbrock, Gustafson, and Unruh, 146. 57Heber Curtis to family, Heber Doust Curtis Collection, University of Michigan, Ann Arbor, n.d.

58Burns, 5. 59 Aitken, 288. 25

Among his colleagues Curtis was remembered as a teacher who was skillfully able to bring an understanding of science to everyone.60 In addition to his stints at teaching high school students, college students and naval personnel, Curtis taught classes at Allegheny and regularly gave lectures while serving as director of the Observatories of the University of Michigan.61 His influence as a teacher is attested to by the founding of the Morrison Planetarium in Golden Gate Park in San Francisco. While a student at the San Jose campus of the College of the Pacific, Mary L. Glide was so impressed by the "intellectual and moral stimulus of a professor of mathematical astronomy" that she visualized building a "popular institution of astronomy for the commonwealth." Fifty years later her vision became reality when the Morrison Planetarium was built.62 Curtis was a member of the Astronomical Society of the Pacific and served as its president in 1912. As a member of the publication committee, he put his dicta of good writing to use. These directives would also serve writers today. They were to be as brief as possible, even telegraphically so; never to make a thing complicated if it could be made simple. He felt words should convey ideas, not obscure them.63 He was also a member of the American Astronomical Society and the American Association for the Advancement of Science, of which he was at times an officer. He was a foreign associate of the Royal Astronomical Society of London and a member of the National Academy of Science. Two other organizations he joined were the Astronomische Gesellschaft and the International Astronomical

Union, Commission 13 of solar eclipses.64

60Burns, 6. 61Aitken, 281. 62Kathryn C. Kemp, (Curator of the Pacific Center for Western Historical Studies, University of the Pacific, Stockton, CA), private correspondence, 29 March, 1977.

63McLaughlin, 6. 64Aitken, 283. 26

Along with his scientific memberships, Curtis was always interested in intellectual activity. In Pittsburgh, as later in Ann Arbor, Curtis joined many clubs devoted to the promulgation of ideas. Other members of these organizations were ministers of various religious denominations, business leaders and educators. Curtis enjoyed these meetings and often spoke on his favorite topic, astronomy. One group he particularly enjoyed met at members' houses for dinner followed by a lecture delivered by the host. Keivin Bums, an astronomer and colleague, describes one such experience.

In public speaking one address stands out from all others. It was a talk on astronomy before the Hungry Club of Pittsburgh in the early '20's. Here Curtis brought astronomy to these listeners in such a manner that the facts were grasped, and the spirit of the science stirred a depth g! feeling akin to that experienced m the appreciation of noble music. Perhaps one incident in Curtis' life will illustrate his standing in the community. On July 19, 1925, he received a telegram from Clarence Darrow, asking him to testify in the anti-evolution trial in Dayton, Tennessee, as an astronomer. He declined Darrow's invitation because be "could not afford to train with that crowd of self- advertisers and notoriety seekers, and I see anyway that they have since barred out scientific witnesses."66 Curtis wired Darrow his regrets, reaffirming bis belief in his own personal religious view, "many, perhaps most of us, are compelled by reason rather than by faith to postulate a Divine Being behind it all."67

Curtis firmly believed in the course of evolution, as evinced by the following statement.

As far as evolution is concerned, it is today accepted by every scientist in the world, and by probably the great majority of thinking

65Burns, 6. 66Heber Curtis to family, 19 July, 1925, Heber Doust Curtis Collection, University of Michigan, Ann Arbor. 67Heber Curtis to Clarence Darrow, telegram, 19 July, 1925, Heber Doust Curtis Collection, University of Michigan, Ann Arbor. 27 churchmen ... Evolution, plus God gives us a more wonderful God, a more wonderful Bible, and a more wonderful future than that of those who hold to a flat earth and helpmeets who were originally ribs.68 One factor that helped convince Curtis of the truth of evolution was the evolution of stars. Astronomers studying the stars found several different types of stars showing varying temperatures and luminosities. These, plotted on graphs, revealed all classes of stars from young, cool infrared bodies of gas through stars of various colors to aging red giants and supergiants. Scientists interpreted these graphs to mean that stars evolved from cool, non-glowing prototypes into light emitting objects. These stars ended their existences as novae, supernovae or black dwarfs. Curtis believed that a concept demonstrated by astronomical research helped him to accept the same idea in another aspect of his life. Curtis' belief in evolution notwithstanding, he was a conservative as far as most scientific matters were concerned. He believed people were intrinsically conservative and accepted new things slowly. In keeping with this belief, he opted for the traditional approach, as shown by his unsuccessful plea in 1928 for the continued use of the term "light year" in scientific discussions after the designation "parsec" had been adopted as the astronomical distance unit six years earlier. 69 Curtis had other traits which steered him toward the conclusions he derived about the island universe theory. He was tenacious; this was revealed in his continuing support for the theory even when alternative evidence seemed to contradict it. He had difficulty in making up his mind,70 but "once he reached a conclusion, he held to his views tenaciously and was always ready to defend them."71

68Heber Curtis to Clarence Darrow, 19 July, 1925, Heber Doust Curtis Collection, University of Michigan, Ann Arbor.

69Heber Curtis, "Light Year versus Parsec," Nature, 12 (May 18, 1928): 789. 70Heber Curtis to family, 1 February, 1920, Heber Doust Curtis Collection, University of Michigan, Ann Arbor.

71 Aitken, 271. 28

After his death, his wife wrote of him, "Those of you who know Heber know that he was a very determined man who wasn't easily persuaded to do something he was averse to doing."72 Curtis himself summed up this characteristic by saying, "but it goes against the grain to drop anything I have started."73 Above all Curtis was a scientist. His right to that identification was proved by his position, by certain work he had done and by his membership in "some very exclusive scientific societies."74 Curtis prided himself upon being a scientist. This

work gave him enormous satisfaction. It enabled him to appreciate the majesty of the universe in which he lived; it helped him to appreciate his religion; it aided him in adopting a world view which brought together his religious and his scientific proclivities.

72Mary D. Curtis, Letter, 10 January, 1942, Heber Doust Collection, University of Michigan, Ann Arbor. 73Heber Curtis to family, 8 April, 1920, Heber Doust Curtis Collection, University of Michigan, Ann Arbor.

74Heber Curtis, "Religion from the Standpoint of Science," in Religion and the Modern Mind, ed. Charles C. Cooper (New York: Harper and Brothers Publishers, 1929), 61-62. HEBER DOUST CURTIS AND THE CROSSLEY REFLECTOR 29

CHAPTER 3: SCIENTIFIC BASIS FOR CURTIS' POSITION

While there are thus some conflicting points in the evidence, the writer feels that there are fewer contradictions and difficulties in the island universe theory of the spirals than in any alternative theory, and for that reason prefers to hold to the island universe theory until much additional evidence shall be secured against it. Heber D. Curtis 30

The island universe controversy concerned those unidentified fuzzy objects seen so plentifully at the poles of the Milky Way. It centered around the identity of those objects and their place in the universe. It was Curtis' contention that these enigmas were situated far outside our galaxy and were themselves galaxies.75 But he faced stiff opposition. Using the same evidence, astronomers argued that the nebulae were members of the Milky Way. The first obstacle was Adriaan van Maanen's measurements of the rotation of the nebulae published in articles in 1921, 1922 and 1923, which reported angular speeds so great that, if the nebulae were at the distances calculated by Curtis, their velocities would have torn them apart.

A second salient obstacle was Harlow Shapley's estimation around 1919 that the Milky Way was three hundred thousand light years in diameter. If the Milky Way was as large as Shapley estimated, and if the spiral nebulae were of the same size, astronomers thought they would disintegrate with any appreciable rotational motion. In addition, they would have to be at enormous distances. This then was the situation during the early years of the twentieth century. A mystery of the universe had astronomers lined up on both sides in an attempt to hammer out a solution that would convince a solid majority of them. Many astronomers realigned themselves as each new piece of evidence, such as the discovery of novae in spirals in 1917, was unearthed, but not Curtis; he remained fixed in his position. In fact, in the ensuing struggle, he played a major role. Many

75The term "galaxy" is used here to distinguish stellar systems from gaseous or dust nebulae. Stellar systems had been identified as external galaxies as early as 1838, and this designation was used now and then throughout the nineteenth and early twentieth centuries. During the 1930's, the term "galaxy" began to replace t]Je word "nebula" as a permanent appellation in referring to stellar conglomerates. However, the transition was not completed until after 1936. Edwin Hubble, The Realm of the Nebulae (New Haven, CT: Yale University Press, 1936; New York: Dover Pufilications, Inc., 1958), 16-18. 31 of his fellow astronomers turned to him when they had a question about the conflict.76

Although Curtis often lamented the scantiness of the data which supported the island universe theory, he found enough to substantiate his arguments.77 It has long been the custom of astronomers to support their results with few data points, and Curtis was no exception. The spiral nebulae controversy occurred as the specialty of astrophysics was becoming refined as a valuable tool in astronomical research. The science of spectroscopy enabled astronomers for the first time to ascertain the composition of objects under study. Astronomy had advanced from a field where its practitioners thought solely of the positions of objects to a discipline where their compositions could be known. A second addition to the astronomical arsenal which advanced the acquisition of knowledge and aided in the resolution of the island universe controversy was the manufacture of large telescopes.78 While at Lick Observatory, Curtis obtained clear, beautiful pictures of the spiral nebulae with the 36-inch Crossley reflector, one of the largest telescopes of the time. One method which meant a good deal to Curtis was spectroscopy. This revealed that the spectra of the spirals were different from those of other nebulae. In addition, their space distribution was different, and their radial velocities were higher than those of other objects. Those who placed the spiral nebulae inside the

Milky Way attempted to prove that the spirals, which resembled other nebulae in appearance, were integral members of the Milky Way. However, Curtis realized that the measurements for each of the above-mentioned features were contradictory

76Hart, 105. 77Heber Curtis, "Island Universes," speech, 1920, 8.

78Fernie, 1202. 32 as far as the spirals were concerned. Furthermore, the spirals were located in the wrong section of the galaxy to be contained within its borders. Astronomical spectroscopy consists of analyzing the light from objects in space. Such information as temperature, composition, direction and speed of travel along the line of sight can be obtained. The spiral nebulae lay too distant to be resolved into individual stars, even though analysis of their light showed them to consist of great clouds of stars.79 , The great majority of objects in the spiral class revealed a continuous spectrum crossed by the dark lines of elements characteristic of stellar spectra. These spectra were duplicates of the integrated spectrum of the Milky Way,80 which appeared as a cloud of stars similar to the spirals that were resolvable only through large telescopes.81 In this similarity, Curtis found confirmation that the spiral nebulae were galaxies comparable to our own. Another anomalous feature was the distribution of the spiral nebulae in space. On a galactic map, the spiral nebulae were found only at the poles.82 With the exception of a single spiral found by Curtis in 1918 just two degrees from the galactic plane, no other spirals were found in the plane of our galaxy.83 One of the favorite interpretations of the nature of the spirals was that they were the initial stages of solar systems. The Chamberlin-Moulton theory of 1905 for example,

"examined the trajectories assumed by the tidal material pulled from the sun by a passing star" and concluded it would form "a double-branched logarithmic spiral."84

79Heber Curtis, ''The Nebulae," The Adolfo Stahl Lectures in Astronomy, hereinafter known as A.S. Lee., (San Francisco: Stanford University Press, 1919), 105.

80tteber Curtis, The Nebulae, Handbuch der Astrophysik, Band V /2 (Berlin: Verlag von Julius Springer, 1933), 853.

81Curtis, ''The Nebulae," A.S.Lec., 105.

82Ibid., 106. 83Heber Curtis, "A Spiral Nebula in the Milky Way," PASP, 30 (1918): 161.

84Femie, 1205. 33

Curtis' reply to that idea was to ask why the spirals, if they, indeed, represented the first stage in the evolution of solar systems, were located so far from most of the other stars in the galaxy.85 The very fact that the spirals seemed to avoid the most highly concentrated areas of stars pointed to the likelihood that these objects were unrelated to the Milky Way. Curtis found another point of similarity when he compared the occulting matter found in the spiral nebulae with that in the Milky Way. He speculated that this absorbing material helped to prove that the spiral nebulae were similar entities. This theory was unsupported by direct evidence,86 because at that time, in the early 1920's, it was impossible to determine what kind of material it was, as studies of the dark matter were just beginning to be made. Outside our galaxy, nearly in its plane, Curtis assumed the existence of a ring of absorbing matter. This ring cut off our view of other universes that might lie beyond87 and might explain the peculiar grouping of the spiral nebulae, which seemed to gather only around the poles.88 Curtis found evidence of absorbing matter inside the Milky Way. It appeared around diffuse nebulosities, in denser portions of the Milky Way and in what seemed to be dark nebulae.89 Rifts in the Milley Way itself, as seen from Earth, were attributed to occulting matter.90 By 1918, Curtis was able to show that the

85Heber Curtis, "Modern Theories of the Spiral Nebulae," abstract in Washington Academy of Sciences (March 1919): 127. 86Heber Curtis, "Occulting Matter in the Spiral Nebulae," Publications of the Lick Observatory, 13 (March 1918): 51. 87Ibid. 88Curtis, "The Nebulae," A.S. Lee., 106.

89Curtis, "Modern Theories," 131.

90Ibid., 130. 34 dark lanes of occulting material were common in spiral nebulae.91 These dark lanes were most easily observed when the spiral was seen edge on. Space velocity refers to the velocity of stars or other celestial objects with respect to the sun.92 It is the radial component of the space velocity that can be measured. The difference between the space velocities of the spirals and those of stars was an additional factor separating these enigmas from the objects within the Milky Way. The average space velocity of the spirals was thirty times greater than the velocity of stars,93 showing that the spiral nebulae were a class apart,94 and Curtis made this fact a telling argument in the defense of the island universe theory. Curtis correctly construed the high velocities of the Magellanic Clouds to be evidence that they were irregular spiral nebulae located relatively close to our galaxy.95

In 1917, both George W. Ritchey and Curtis discovered novae or new stars in the spiral nebulae.96 A nova or new star is an explosive event. It is now known to be a white dwarf, which is always one of a close pair. The dwarf star flares up when material drawn from the larger companion onto it disturbs the equilibrium of the smaller star. The nova will brighten several magnitudes, non-periodically, many times.97

91Fernie, 1205.

92Jay M. Pasachoff, Contemporary Astronomy, 2d. ed., (Philadelphia: Saunders College Publishing, 1981), A4 l. 93Curtis, "Modern Theories," 127.

94Ibid., 126.

95Ibid., 131. 96Fernie, 1216.

97Robert Jastrow and Malcolm H. Thomson, Astronomy: Foundations and Frontiers, 2d. ed. (New York: John Wiley and Sons, Inc., 1974), 137-138. 35

When these novae were found to occur in a few spiral nebulae, it was conjectured that they were similar in nature to novae in the Milky Way and thus might be used as distance indicators to prove that the spiral nebulae were outside our galaxy.98 Curtis commented, after finding evidence of several events, that one nova could be the manifestation of an object in our line of sight, (that is, it could be in our galaxy but appear to be in a spiral nebula), but the chance of six such occurrences stretched "the bounds of probability." Curtis had no doubt that the novae were actually in the spiral nebulae.99 Curtis calculated that the novae in the spiral nebulae would have been at least of thirtieth magnitude before they flared. It is now known that these were supernovae and were, therefore, much brighter than ordinary novae. Curtis believed that novae in the Milky Way brightened from an average of fifteenth magnitude to fifth magnitude.100 Comparison of the average magnitude of novae in spiral nebulae and of the novae in the Milky Way indicated distances to the spirals of at least ten million light years.101 Since Curtis believed the Milky Way to be thirty thousand light years in diameter, spiral nebulae, which could be placed ten million light years away, had to be situated far outside our galaxy. 102

In order to understand the significance of the presence or lack of rotation of the spiral nebulae, it is necessary to review the work of Adriaan van Maanen, an astronomer who went to Mt. Wilson Observatory in 1912. Since the form of the

98Curtis, "The Nebulae," A.S. Lee., 107.

99Heber Curtis, "New Stars in Spiral Nebulae," PASP 29 (July 1917): 181-182.

100Heber Curtis, "Three Novae in Spiral Nebulae," Lick ObsetVatory Bulletin, 13 (Berkeley: University of California Publications, 1917): 109.

101Curtis, "The Nebulae," A.S. Lee., 107. 102Curtis, "Scale of the Universe," 110. 36 spirals suggested that they should be rotating, Ritchey, a fellow astronomer at Mt. Wilson, asked van Maanen to attempt to discover if proper motion could be detected in the spiral nebulae, specifically in MlOl. Van Maanen used a machine called a stereocomparator. This device compared points on photographic plates taken years apart to find out if the points had moved over the period of time between the taking of the first and the last plates. If such a displacement had occurred, the distance moved could be measured with a micrometer screw. Van Maanen found large displacements for the points he studied. His findings indicated not only that the spiral nebulae were rotating, but that their spiral arms were unwinding.103 In 1921, when van Maanen first published bis results, he did not believe in the island universe theory.104 While working at Lick Observatory, Curtis had attempted to measure the rate of rotation of some of the spiral nebulae over a thirteen year period and had found no appreciable movement. This lack of evidence of rotation indicated that the spiral nebulae were remote.105 Because of his own measurements and because of the spectroscopic work of V.M. Slipher, which showed the arms of the spirals to be traveling in a direction opposite to that proposed by van Maanen, Curtis remained firm in his opposition to the latter's measurements.106 The spectrum of a celestial object shows dark lines of the elements contained in the object at the wavelength characteristic of the radiation put out by the element. These lines are compared to a laboratory spectrum which contains the wavelengths of certain elements such as iron. If the object is moving away from the

103Hart, 53-55. 104Ibid., 95. lOSeurtis, "Modern Theories," 131. l06Heber Curtis to Robert G. Aitken, 2 January, 1925, Mary Lea Shane Archives, Santa Cruz. 37 observer, the wavelength line will be shifted toward the long or red end of the spectrum, and if the object is moving toward the observer, the wavelength will be shifted toward the short or blue end of the spectrum. This is known as the Doppler shift. Spectrograms of all but a few of the spiral nebulae revealed shifts toward the red end of the spectrum. Similarly, spectra of the spirals revealed that the arms of the spirals were winding up. Van Maanen's measurements showed the arms to be unwinding. These two methods resulted in contradictory findings. As has been mentioned earlier, Curtis believed that the spectroscopic technique gave more accurate results.

Proper motion is the rate at which a celestial object changes its position in the sky; it is measured in arc seconds per year.107 Study of the proper motion of the nebulae aided in the investigation of their size and distance, which helped to ascertain their place in the structure of the universe.108 In a paper of 1915, Curtis wrote that the proper motions of the spirals plus their radial velocities could be used to determine distances to the spiral nebulae.109 As of that date, very few radial velocities of spiral nebulae had been measured. V.M. Slipher had calculated a mean of four hundred kilometers per second, an extremely large value, when compared to the velocities of stars.110

Proper motion, however, was another matter. As early as 1919, Curtis concluded that failure to detect proper motion indicated that the spiral nebulae must be extremely remote.111 As late as 1933, Curtis stated that no proper motion

107Dixon, 216. l08Heber Curtis, "Proper Motions of the Nebulae," PASP, 27 (1915): 214. 109Curtis believed that measuring photographic plates ensured the only trustworthy means for determining nebular proper mot10n. [Ibid.)

11°Fernie, 1212. 111Curtis, "Modern Theories," 127. 38 had been detected for any of the spirals. And by 1935, he argued that detection of the proper motion of the spirals was beyond the capability of the equipment and methods available; there was no certain knowledge of the proper motion of any spiral.112

Distances to the spiral nebulae could be obtained in several ways. One method was the use of Cepheid variable stars as distance indicators. Cepheid variables are stars which vary periodically in brightness. The brighter the star, the longer the period; this relationship had been discovered by Henrietta Leavitt in 1908. Beginning in 1912, Harlow Shapley calibrated the relation between the period and the luminosity of the Cepbeids and, with the aid of this technique, determined the distances to Cepheids in our galaxy. By this method it became possible to measure the distances to the spiral nebulae as soon as advances in telescopes and photographic emulsions allowed the detection of Cepheids in them.113 This was first achieved in 1924 by Edwin Hubble, who found distances of eight hundred thousand and nine hundred thousand light years for two of the spirals.114 These measurements put the spiral nebulae well outside the galaxy. Additional theoretical arguments which buttressed Curtis' belief that the spiral nebulae were island universes were analogies between them and the Milky Way. At the time of the controversy, these comparisons were purely speculative because the shape and size of the Milky Way and the content of the spiral nebulae were unknown, although there was some evidence for a spiral structure for our galaxy, as there was some evidence of the contents of the spiral nebulae. The evidence for the Milky Way consisted of the occulting matter found in the galaxy.115

112Curtis, The Nebulae, Handbuch, 850. 113Abell, 409. 114Curtis, The Nebulae, Handbuch, 861. 115Curtis, "Modern Theories," 132. 39

Although a few astronomers assumed a great deal in postulating an identical essence for the obscuring material in the diffuse nebulae and the dark bands in the spiral nebulae, which were so different in space distribution, spectra and space velocity, they believed that this matter caused analogous effects in both our galaxy and in the spirals.116 Curtis thought the lack of spiral nebulae in the plane of our galaxy was caused by a band of absorbing matter around the periphery of the Milky Way.117 Professor Easton of Amsterdam had first proposed a spiral form for the Milky Way in 1900. By 1913, after close study of the configurations and star densities in it, 118 he developed this model further, and by 1919 other astronomers agreed with him. Curtis speculated that the Milky Way, relocated to a distance of ten million light years, would be ten minutes of arc in diameter or the size of the larger spirals. The proportions of our galaxy accorded with the degree of flattening observed in the majority of the spirals.119 The island universe .theory-did not have clear sailing through the first four decades of the twentieth century. Adriaan van Maanen found evidence of such large rotations in some of the spiral nebulae that these objects would have to be located within the Milky Way or be torn apart. Harlow Shapley proposed a size so large for the Milky Way that it seemed impossible for the spiral nebulae to be distant enough to be located outside it. However, such factors as spectroscopy, space distribution, occulting material, space velocity, novae in spirals, lack of rotation, lack of proper motion and analogies between the Milky Way and the spiral nebulae supported Curtis' claim that the spiral nebulae were island universes. Properties such as space distribution and space velocity highlighted the special

116Curtis, ''The Nebulae," A.S Lee., 2-3. 117Curtis, "Modern Theories," 132.

118Ibid., 129.

119Ibid. 40 nature of the spiral nebulae. Distance calculations, lack of rotation and the absence of proper motion placed the spiral nebulae far outside our galaxy. Curtis, along with his colleagues, had collected evidence which had assisted them in ascertaining the nature and identity of the spiral nebulae. 41

CHAPTER 4: NON-SCIENTIFIC FACTORS INFLUENCING CURTIS

Entirely aside from the fact that the island universe theory combines into an orderly whole so many of the characteristics of the spirals, otherwise inexplicable, there is a grandeur and majesty in the concept and an agreement with the general cosmical continuity expected on philosophical grounds, which is both inspiring and alluring. Few greater concepts have ever been formed in the mind of thinking men than this one, namely,--that we, the microbic inhabitants of a minor satellite of one of the millions of suns which form our galaxy, may look out beyond its confines and behold other similar galaxies, tens of thousands of light-years in diameter, each composed, like ours, of a thousand million or more suns, and that, in so doing, we are penetrating the greater cosmos to distances of from half a million to a hundred million light-years. Heber D. Curtis 42

Heber Curtis advocated the island universe theory of the spiral nebulae for well-founded scientific reasons, which have been detailed in the previous chapter. Although the scientific data provided adequate evidence for acceptance of the theory, there were other factors in Curtis' personality and way of thinking which influenced his devotion to this theory. Those factors included his deep religious conviction, his awe at the majesty of the universe and of its creator, his dependence upon his ability to reason and his belief in the concepts of order and infinity.

Curtis was a man of many interests and diverse ideas. As has been shown in the biographical chapter, he was first of all a scientist, committed to all the ideals and procedures employed by the scientific community. He was also deeply religious, a conviction that not only deepened with every year, but was based on reason. When he was fifty-one years of age he wrote:

I feel certain that I have a deeper and more sincere religious feeling and belief than I did at twenty or thirty. If age has ripened anything in me, it has been the conviction that there is a God behind it all. It isn't a question of "faith," but my reason forces my brain to that conclusion.120 Curtis' basic view of the world envisioned a rather passive role for men. They were spectators at a remarkable show, possibly the only one they could attend, where they remained for approximately three score and ten years--almost exactly the length of Curtis' life. Reality, perhaps the only absolute reality, consisted in men thinking about the show. The audience did not know what went on behind the backdrop, who produced the show or why. But science attempted to discover the laws behind the show. The spectators did not even know they were in an audience.121

120Heber Curtis to family, 21 January, 1923, Heber Doust Curtis Collection, University of Michigan, Ann Arbor.

121Heber Curtis, "Religion from the Standpoint of Science," address before the Hungry Club of Pittsburgh, 19 November, 1928, 30-31. 43

Within that world view, Curtis saw the scientific and the religious as two sides of the same coin. In order to understand and appreciate him, it is essential to be very clear about this. "I think the realization of the immensity of things, the study of the heavens, or for that matter any form of scientific knowledge, has a marked moral and ethical, even a religious effect."122 Perhaps this synthesis is stated most clearly in the following quotation.

When one assumes a God and a universe created by Him, it has always seemed to me the height of absurdity to imagine that there could be any contradiction, that is, - any so-called conflict between religion and science in their absolute and ideal senses. It is more than an absurdity, it is an impossibility.123

Although Curtis wrote scientific speeches, papers and articles, and he wrote articles, papers and speeches that were predominantly religious in tone, the two subjects were inextricably intertwined. Thus his scientific speeches might contain references to the spiritual quality of life, and a talk on religion might combine that topic with some aspect of the scientist's relation to it. Knowledge of other universes is valuable for its own sake. We are made bigger and better of soul by knowing how vast and wonderful is the universe compared with which our sun and all his planets is smaller than a mote in the sunshine."124 One of Curtis' favorite sayings was, "an undevout astronomer is mad."125 Even though he made a disclaimer admitting that not all astronomers were religious,

Curtis firmly believed that religion and science enhanced each other to the extent that either field would be less than it could be without the other.126

122Curtis, "Island," 15. 123Curtis, "Standpoint of Science," 64.

124Curtis, "Island," 11. 125Ibid., 17. 126Curtis, "Standpoint of Science," 90. 44

Astronomy was the science which Curtis believed first posed such unanswerable queries as: What is man's place in the universe? Why is man here?

What does man amount to in the great scheme of things?127 Astronomy also provided man with the "best conception of his place in the universe."128 If man's place was subordinate in this universe, it did not matter; the wonder and exaltation provided by the marvels of the cosmos more than compensated for his universal unimportance.129

This cosmos, this universe, which ennobled Curtis and his fellow men, "had divinity in it and over it." This concept was the cornerstone of Curtis' thinking. His scientifically-oriented mind led him to the conclusion that a Supreme Being created and guided the universe. He firmly believed in the "assumption of a God and a universe created by Him."130

Although Curtis believed in religion and connected that with science in his mind, his belief in religion and his career in science were both based on reason.

Faith was not involved. His religion and his reason were connected in yet another way; they had to encompass intelligence. He believed that "ignorance is spiritual death."131 Reason provided an additional ingredient of change. Theories could be changed, beliefs could be changed, but all change had to conform to reason.

Curtis believed astronomy was of the greatest value to religion in offering support for a belief in a God or a Higher Power. The concept of a Supreme Being

127Heber Curtis, "The Influence of Astronomy upon Modern Thought," radio talk, University of Michigan Broadcasting Station, December 5, 1933, 2.

128Ibid., 9.

129Heber Curtis, "Astronomy and Modern Thought," address at Wittenberg College, Springfield, Ohio, June 3, 1931, 12.

130Curtis, "Standpoint of Science," 54.

131Curtis, "Island," 17. 45 was a "rather scientific attempt to explain the existence of infinite data."132 He believed that the finite mind of man would never truly grasp the infinite. However, astronomy offered a concept of the infinite, and this concept of infinity provided by science made it easier for people's minds to accept the infinite nature of God. "Give my mind some fact which science admits as possibly infinite, then any other infinite fact becomes easier to adopt." 133

Curtis had no problem in assuming an Infinity to control an infinity.

As we come to a greater understanding of the laws, the majesty of the universe, whether it is the wonderful outer universe or the equally wonderful smaller universe in and all about us, our minds partake of these infinite truths, our mental horizons are broadened, our souls become nobler and better.134 Curtis' reliance upon reason, supported by his work in astronomy, led him to a belief in a religion headed by a God. To Curtis, the "increased knowledge of the physical universe given by modern science must be regarded as the main inspiration and support of a sane and reasoned religious belief."135 Thus Curtis, the advocate of a religion based on reason as well as a religion and science combined into one harmonious whole, put his belief into words.

In addition to Curtis' need for reason, two concepts, order and infinity, stand out as he expounded upon the island universe theory. The concept of order was of prime importance to Curtis, the scientist. His presentations were orderly and logical, and his reasoning also reveals an orderly mind. Beyond this generalization, Curtis was concerned with the order of things in nature. He concluded his article in Scientia with a statement that the island universe theory unites otherwise inexplicable qualities of the spiral nebulae into an "orderly

132Stebbins, 5. 133Curtis, "Standpoint of Science," 44.

134Curtis, "Island," 16. 135Curtis, "Modern Science," 74. 46 whole."136 Similarly, one of Curtis' characterizations of science defined it as the

"body of things known with the attempt to arrange all things in an orderly fashion."137

There are two ways to determine order. One is the attempt to impose order upon nature. The second method is the attempt to discover the order already prevailing in nature. Curtis operated in both arenas. He felt it was necessary to have "connections uniting the totality of data in an orderly fashion." He also believed that the spectators of the universal show speculated about the origin and the purpose of the spectacle.138 But he did not define order as he had defined science. Instead, he averred,

My entire cosmos must be orderly. I care little how we define 'order'; whether we call it cause and effect, sequential harmony or the concept of purpose or end. Neither do I worry lest this order I am postulating for the universe is simply a projecting outward into the universe of my own laws of thought, and this a conceivably fallacious analogy with entirely unallied developmental gamuts. I have no other process and this must serve.139

In his attempts to impose an astronomical order upon the universe, Curtis, as a scientist, first of all demanded a theory for every phenomenon. Curtis' concept of a theory agreed with the Greek definition, "it saves the phenomena."140 He quoted

Poincare: "A theory rationalizes the greatest number of facts." 141

Analogy or probability provided the basis for theories. It was Harold

Jeffries, an English mathematician and scientist, who pointed out mathematically

136Heber Curtis, "The Spiral Nebulae and the Constitution of the Universe," Scientia, 35 (1923): 8.

137Curtis, "Modern Science," 57. 138Heber Curtis, "A Scientist Looks at Religion," radio talk, n.d., 1.

139Heber Curtis, "A Scientist's Right to Religious Speculation," radio talk, n.d., 7.

140Stebbins, 5. 141Curtis, "Standpoint of Science," 74. 47 that the simplest theory to explain a fact would nearly always have the greatest a priori probability.142 Therefore it was the function of a scientist to adopt the simplest and best explanation. Theories possessed another quality. They were temporary explanations at best; they included the possibility of replacement at any time. Curtis said, "Theories can be changed overnight by new experimental data or by mathematical analysis."143

Finally, Curtis believed that theories engendered more problems than they solved. He believed this applied to the island universe theory. As he said, "it is impossible to do more than to mention a few of these problems, with an attempt to divine those which may ultimately be presented to us." In his treatment of the island universe theory, Curtis certainly utilized that approach; he attempted, with a high

degree of success, to divine the problems connected to its acceptance.144 In order to understand the universe, a theory was essential. Finding a theory

to explain the workings of nature is the initial step in the scientist's imposition of

order on the phenomena be is studying. Curtis adopted one theory about the spiral nebulae as galaxies and one

theory abo'ut the origin and the running of the universe. Then he welded these two

theories into a cohesive whole by concluding that the best scientific theory included

a sentient Supreme Being overseeing an infinite universe whose building blocks were galaxies located at varying intervals throughout that infinity. Curtis attempted to seek the order of the universe with the aid of the

scientific tools at his command. "That science, as a whole, gives us a revelation of

the established order of the universe, no scientist will deny, but let us not be too

142Curtis, "Speculation,' 5.

143Curtis, "Modern Science," 61.

144Curtis, "Modern Theories," 227. 48 cock-sure that the present picture is final."145 Despite his insistence upon the concept of order, he acknowledged the transitory nature of the explanations of science. Paradoxically, his theory of the spiral nebulae held fast. The spiral nebulae turned out to be galaxies, and the island universe theory seems to be correct and final.

Curtis was concerned with the unanswerable questions, a facet of his attempt to find order in the universe. Were man just an accident, Curtis' sense of order would have been violated. With his deep sense of the purpose held by the intelligence behind the universe, unknown as this purpose was, man had to have a place in the universe. In one of his talks, Curtis told a fable about visitors from outer space missing the earth in their swing through our section of the galaxy. But, he stressed, when they missed the earth, these visitors would have passed by the most significant component of our galaxy: thinking beings who were capable of plotting the orbit of the visitors.146 Curtis believed that man's mind was the most important thing in the universe, even though men seemed to occupy such a small place in it. Astronomy had also turned man away from his traditional geocentric view of the universe toward bis proper role in it. Fitting man into the order of the universe was one of Curtis' objectives. He demanded the same order for the universe as for his mind or for his work. Just as reason was a way of life for Curtis, so was order imperative to his existence. Curtis' reliance upon order was expressed in other ways than those discussed above. He gave examples of orderly arrangements in astronomy. The spectroscopic order of the stars showed relatively few classes.147 Studies of the distribution of

145Curtis, "Intolerance in Science," radio talk, n.d., 2. 146Curtis, "Modern Thought," 13.

147Curtis, "Influence," 7. 49 stars over the entire sky and counts of the numbers of stars of different brightnesses gave an idea of the size of the universe of stars.148 Studies of the stars also revealed the shape of the Milky Way. It was flat and round like a thin pocket-watch in shape.149 In another example, Curtis stated that atoms broadcast on the same wavelength no matter where they are.150

Still another facet of the order evident in the universe was the consensus that external galaxies were "fairly uniformly distributed in exterior space."151 Curtis noted that remarkable uniformity in distribution as well as in form and density of the galaxies. He assumed that space continued indefinitely with the same distribution.152 Before astronomical instruments became sophisticated enough to detect unusual galaxies, they all appeared alike to Curtis' reflector. He remarked that no "new, strange or aberrant forms of Milky Ways" were in evidence; continuity of structural form and an essential simplicity of the external universe impressed him.153 The universe everywhere was constructed of the same elements; the universe exhibited a oneness throughout its extent. Curtis could rejoice, order triumphed. Though order was of paramount importance to Curtis, he did step outside its boundaries once, in what was to him a very important endeavor. This was his right to speculate, which he defended passionately. According to Curtis, philosophers alone traditionally retained the right to speculate on metaphysical and religious

14scurtis, "Island," 746.

149Curtis, "Influence," 7.

150Heber Curtis, "The Unity of the Universe," Journal of the Royal Astronomical Society of Canada, 22 (December 1928): 406. l51Heber Curtis, "Receding Horizons," Scientific Monthly, 47 (1938): 245.

152Ibid., 245.

153Ibid. 50 matters,154 but he claimed that right for himself and other scientists as well. It can be said of Curtis that he demanded order in his thinking and in his universe, but he also knew when to break out of that order by utilizing the technique of speculation, a use he felt was not quite legitimate. Curtis summed up the connection between order and speculation very nicely in the following statement.

My cosmos must be orderly, and to make it orderly I may use, with entire freedom the same license which science is today employing in classes of inference which differ but slightly from pure speculation.155 Do not be deceived. Curtis here is exercising his prerogative to project his laws of thought outward upon nature. He believed an orderly universe was a component in the great scheme of things, and that science would uncover the established order of the universe.156

The concept of infinity was equally important to Curtis. Infinity stood with order and reason as the tripod upon which his work was balanced. Reason was second nature to Curtis. Order was essential to his work as a scientist. Infinity brought his world view of science and religion into an harmonious whole. Astronomy could neither prove nor disprove the existence of infinity, but for the "first time in the history of human thought astronomy had adduced certain lines of observational evidence that made some postulation of a spatial infinity at least more probable to the physical scientist."157 Curtis continued to bolster his conviction that "observational evidence shows nothing against the assumption of an

154Ibid. l55curtis, "Standpoint of Science," 4. l56curtis, "Intolerance," 2. 157Ibid. 51 infinite universe and a certain amount of indirect evidence in favor of it.11158 However, he did not specify what this evidence was.

It is possible that the evidence consisted of his photographs of the spiral nebulae. These nebulae were found to be located at great distances from each other in space, and to contain billions of stars. The importance of this arrangement of stars and other matter in the universe was contained in a paper published in 1921 by C.V.L. Charlier entitled, "How an Infinite World can be Built Up." The argument in this paper used the "three dimensions of experience and Newtonian physics."159 This was exceedingly germane to Curtis' way of thinking because he advocated Newtonian physics and repudiated Einstein's theory of relativity, because he felt that men could not even begin to visualize four-dimensional space with their three-dimensional minds.16° Charlier proved the mathematical possibility of an infinite universe. This would occur if the stars were arranged in great groups which obeyed a certain mathematical relation governing their distances apart and the number of stars contained in each group. The repetition of this relation in larger and larger systems assured the existence of an infinite universe. Curtis found to his satisfaction that his data produced evidence that the stars were distributed in just such groupings as Charlier postulated.161

Other factors led Curtis to his defense of the island universe theory.

According to him, these factors were at least five thousand years old; they stemmed from beliefs praising the "majesty and wonder of the universe. "162 One of the basic

158Curtis, "Horizons," 244.

159Ibid., 246. jp2 160Curtis, "Speculation," 9. 161Ibid.

162Ibid., 12-13. 52 underlying, possibly unconscious, influences which led Curtis to defend the island universe theory so vigorously was his reverence for the universe and its creator, and this probably is one of the reasons Curtis entered the field of astronomy. Familiarity with these mighty concepts most certainly does not breed contempt, does not dull our awe at the mightiness of the universe in which we play so small a part. It is very doubtful if any of those who are seriously studying the heavens ever lose their feeling of reverence for this supremely wonderful universe and for Whoever or Whatever must be behind it all.163

The arguments from astronomy together with the more modern knowledge that men are members of a structure infinitely greater and more wonderful than "the little cosmos of five hundred years earlier," gave Curtis an "exaltation of soul."164 One of Curtis' characteristics, which contributed to his espousal of the island universe theory, was his consistency of thought, as shown by his reluctance to change his mind once he had made a decision. This quality was revealed in two articles written fifteen years apart.165 The arguments in the second paper, written long after the majority of astronomers had accepted the island universe theory, mirrored those

arguments contained in the first paper. In 1933, Curtis wrote, Some doubts have been expressed as to the provenance of the countless very small round or elliptical objects and their right to be classed with the ~enus of spirals. The writer in 1918 made the following generalization.1

It is my belief that all the many thousands of nebulae not definitely to be classed as diffuse or planetary are true spirals, and that the very minute spirals appear as textureless disks or ovals solely because of their small size. There is an unbroken progression from such minute objects up to the Great Nebula in Andromeda itself; I see no reason to believe

163Curtis, "Scientist Looks," 6.

164Curtis, "The Nebulae," A.S. Lee., 109. 165Heber Curtis, "Descriptions of 762 Nebulae and Clusters Photographed with the Crossley Reflector," Publications of the Lick Observatory, 13 (Berkeley: University of California Publications, 1918): 12.

166Curtis, The Nebulae, Handbuch, 843. 53 that very small nebulae are of a different type from their larger neighbors.167 He concluded,

Though this conclusion has been objected to as a "daring extrapolation," the writer feels that all the evidence as to distribution, character, radial velocity, etc., which has been obtained since 1918, serves only to strengthen this opinion, and were he re-writing it today, his only modifications would be minor changes in the phrasing so as to avoid the word "nebula" as far as possible.168 This single-minded consistency, which kept Curtis from wavering on the island universe theory with each new development, allowed him to concentrate on honing his arguments to make them more precise and more conclusive. One last suggestion for explaining Curtis' stance, though impossible to prove, is the intangible quality of intuition, which may form an integral and inherent part of the scientific process. In one of his articles, Curtis wrote of William Herschel, The history of scientific discovery affords many instances where men with some strange gift of intuition have looked ahead from meager data, and have glimpsed truths which have been fully verified only after decades or centuries.169 If one chooses the word decades, this is exactly what happened to Curtis in the case of the spiral nebulae. The intention here is not to imply that Curtis was the only scientist who advocated the island universe theory; the idea of this thesis is that Curtis was one of a few astronomers who did not waver in their advocacy of the theory throughout the period of the controversy. Intuition is hard to pin down; there is no test nor scientific proof for it. Often, however, a scientist's certainty that he is on the right track in his research comes not only from the evidence at hand but from deep inside his mind where, perhaps unknown to him, the data have been compiled into the solution of his problem by that mysterious quality known only by the appellation of intuition.

167 Curtis, "Descriptions," 12. l68Curtis, The Nebulae, Handbuch, 843-844. l69curtis, "Modern Theories," 217. 54

During the years of the spiral nebulae controversy, Curtis maintained bis position that the nebulae were island universes or galaxies. This was demonstrated by Curtis' letter to Robert Aitken in 1925 and by his continued mention of bis position in his many articles and talks. Curtis' view was supported by the scientific data and was also supported and nourished by his views on religion, reason, order and infinity as well as his awe and reverence for the universe and its creator. Reason supports scientific endeavor, and Curtis employed this ability to the best possible purpose. His approach to religion also had lasting influence on his support for the island universe theory. His belief in an infinite God, supported by his belief in astronomical infinity, bound his world view into a united and orderly body of thought which extended the spiral nebulae into infinity to populate the cosmos. Curtis never doubted that a meaning or purpose existed in the universe. One of the ideas that came to Curtis' mind when he mentioned purpose was the end for which galaxies were destined, possibly as the home for men like himself. Order and infinity were combined in bis philosophy. Galaxies extending throughout infinity were arranged in an order created only by the divine intelligence, but knowable to man. Curtis' insistence on order and infinity provided a beautiful and majestic cosmos. This blending of science and religion satisfied Curtis' need for unity in his life and in his work. Heber Curtis played an important and leading role in one of the most serious astronomical controversies of the early twentieth century. Moreover, many astronomers identified Curtis more than anyone else as the leading advocate of the island universe theory. Not only did he consistently agree with the theory that would eventually prevail, but he brought this theory repeatedly to the attention of the public, both scientific and non-scientific. His persistence and clarity of thought and 55 attention to observational detail paid off for him by setting his thoughts on the finally accepted track. Curtis had persevered, and he had won. 56

APPENDICES 57 CHRONOLOGICAL DEVELOPMENT OF THE ISLAND UNIVERSE CONTROVERSY IN THE TWENTIETH CENTURY

1895 Edward Crossley, an English amateur astronomer, donated his 36-inch reflector to Lick Observatory. This reflector was the instrument with which Curtis took his photographs of the spiral nebulae. · 1899 H.C. Wilson took a twelve hour exposure of the Andromeda nebula, which revealed structure in the outer parts of the nebula. He made two contradictory conclusions. First, he believed this confirmed the nebular hypothesis, and, second, he thought the Milky Way would look like this from the inside; therefore, it was similar to the Milky Way. 1899 J. Scheiner took a seven and one-half hour exposure which produced a useful spectrogram of M31. This was similar to the solar spectrum. He suggested comparing M31 to the Milky Way. 1905 Moulton discovered that trajectories of material pulled tidally from a spiral nebula would form a double-branched logarithmic spiral. He interpreted this to mean that the spirals were the first manifestations of planetary systems. 1907 Karl Bohlin, Stockholm, measured the trigonometric parallax of the Andromeda nebula and found it to be 0.171. He interpreted this to mean that M31 was a member of our sidereal system. 1909, 1911, E.A. Fath took spectra which confirmed 1913 Scheiner's work. 1910 T.J.J. See wrote a paper explaining why the spirals were removed from the plane of the galaxy. He believed that the spirals were formed of dust and had been expelled from the central star during its formation. As the Milky Way nebula formed into stars surrounded by planets, the spirals were probably drawn back into the starry layer of the Milky Way by the attraction of the stars. 1911 F.W. Very compared the nova, S. Andromedae, of 1885 with Nova Persei of 1901 and found an absolute magnitude for the former. He calculated the distance to Andromeda as sixteen hundred light years. He estimated the distances to the smaller spirals to be as large as one million light years. 1912 M. Wolf compared dark holes in the Milky Way and in M31 and found the distance to the latter to be thirty thousand light years. 1912 No consensus existed as to the nature of the spiral nebulae. J.H. Reynolds believed the spirals were stars with dust arms. 58 Also, at this time no consensus existed about the Milky Way. K. Bohlin believed the Milky Way to be the equatorial belt of a planetary nebula, not a disk of stars. There was strong support for B.G. Harrison's belief that the thinning out of stars toward the poles and their crowded appearance in the galaxy was an optical illusion.

1909-1913 Astronomers studied interstellar absorption. 1909, 1913 C. Easton proposed a spiral structure for the Milky Way.

1914, 1915 V. Slipher determined radial velocities for some of the spirals and found a value of -300 km/sec for M31. Fifteen nebulae were studied. Some had radial velocities as high as 1100 km/sec. 1914, 1916 V. Slipher discovered the rotational velocities of some spirals. F.G. Pease discovered that the rotation increased linearly with distance from the center. The projected velocity of rotation two degrees from the nucleus of NGC 4594 was 330 km/sec. 1914, 1915 C.O. Lampland and Curtis determined proper motions for a number of nebulae. Lampland found a proper motion for the spiral M51 to be in excess of 0.1. Curtis found an average proper motion of 0.033 fo r 66 large spirals. 1916, 1917 Adriaan van Maanen found large rotational values for the spirals, which seemed to indicate that they were inside the Milky Way. 1918, 1919 Harlow Shapley estimated the size of our galaxy at three hundred thousand light years.

1914, 1917 W.S. Adams, J.C. Kapteyn, J.H. Moore, H. Spencer Jones and J. Halm accumulated evidence that indicated that the absence of spirals in the plane of the Milky Way was due to an obscuring band of material.

1917 G.W. Ritchey and Curtis found novae in the spirals.

1917, 1919 James Jeans argued that the spirals were planetary systems in the making caused by the tidal interaction of two passing bodies.

1921, 1923 Van Maanen used his measurements of the 1923 rotations of the spiral nebulae as arguments against the island universe theory.

1920 F.H. Seares measured the surface brightnesses of the spiral nebulae and found that they exceeded the surface brightness of the Milky Way. He argued that if the spirals were galaxies, their surface brightnesses would have been the same as the surface brightness of the Milky Way. 59 1920 The Great Debate took place. This did not resolve the mystery of the spiral nebulae. 1925 Edwin Hubble announced his discovery of Cepheids in M31 and in M33. His calculations of their distance based on the distance luminosity calibration of Cepheids worked out by Shapley placed them far outside the Milky Way. 1935 Hubble measured the plates used by van Maanen but failed to find the large displacements found by van Maanen, who measured them again. When he failed to find his earlier large measurements, he capitulated and conceded that the spiral nebulae were galaxies.170

170pe rnie, 1202-1226, passim. 60

HEBER CURTIS' EDUCATION AND CAREER

1892 University of Michigan B.A. 1893 University of Michigan M.A. 1902 University of Virginia Ph.D. 1893-1894 Detroit High School, Teacher 1894-1896 Napa College, CA, Professor of Greek and Latin 1896-1900 College of the Pacific, Professor of Mathematics and Astronomy 1900-1902 University of Virginia, Vanderbilt Fellowship in Astronomy 1902-1905 Lick Observatory, Assistant and Associate Astronomer 1906-1910 D.O. Mills Expedition to Southern Hemisphere, Santiago, Chile, Acting Astronomer in charge 1911-1920 Lick Observatory, Astronomer

1920-1930 Allegheny Observatory, Pittsburgh, PA, Director

1930-1942 University of Michigan, Director of the Observatories and Astronomer

1942 University of Michigan, Director Emeritus171

171 Aitken, 284. 61

HEBER CURTIS' ECLIPSE EXPEDITIONS

YEAR DESTINATION SPONSOR 1900 Thomaston, GA Lick Observatory 1901 Sumatra U.S. Naval Obs. 1905 Labrador Lick Observatory 1914 Russia Lick Observatory 1918 Goldendale, WA Lick Observatory 1923 Mexico Sproul Observatory, Swarthmore, PA

1925 New Haven, CT Sproul Observatory, Swarthmore, PA

1926 Sumatra Sproul Observatory, Swarthmore, PA

1929 Sumatra Sproul Observatory 1930 Nevada Curtis 1932 Fryeburg, ME University of Michigan172

172McLaughlin, 2,3. 62 BIBLIOGRAPHY

Abell, George 0. Exploration of the Universe. 3d ed. New York: Holt, Rinehard and Winston, 1974.

Aitken, Robert, G. "Biographical Memoir of Heber Doust Curtis 1872-1942." Biographical Memoir 22, Thuteenth Memoir. Washington, D.C.: National Academy of Sciences of the United States of America, 1942. 275-294.

Burns, Keivin. "Are Astronomers Folks?" The Sky 5 (July 1941). 3-6.

Buttman, Gunther. The Shadow ofthe Telescope. ed. David C. Evans. trans. B.E.J. Page 1. New York: Charles Scribners Sons, 1970. Curtis, Heber. "Astronomy and Modern Thought." address at Wittenberg College, Springfield, Ohio. 3 June, 1931. 1-14 .

. "Descriptions of 762 Nebulae and Clusters Photographed with the ..,...C..... ro_s_s.,..le-y Reflector." Publications of the Lick Observatory 13, Part 1. Berkeley: University of California Publications, 1918. 11-42 .

. "The Influence of Astronomy UJ?On Modern Thought." radio talk . ...-O.-ru~v-e-r~s 1ty of Michigan Broadcasting Station. 3 December, 1933. 4-11.

. "Intolerance in Science." speech. Heber Doust Curtis Collection. -M-1 c~h...-1g-an Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. n.d. 1-7.

. "Island Universes." address before the Hungry Club of Pittsburg. Heber -n-ou_s_t -Curtis Collection, Michigan Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. 1920. 1-17.

. Letter to Family. 8 April, 1908. Heber Doust Curtis Collection. -M-1 c~h...-1g-an Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor .

. Letter to Family. 2 January, 1920. Heber Doust Curtis Collection. -M-1c~h...-1g-an Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. . Letter to Family. 15 March, 1920. Heber Doust Curtis Collection. -M-1c~h...-1g-an Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. . Letter to William W. Campbell. 26 July, 1921. Mary Lea Shane Archives. -L~1c~k-O...-bservatory , Santa Cruz.

. Letter to W.W. Campbell. 1January,1922. Mary Lea Shane Archives. -L1~ck...... O...-b servatory, Santa Cruz.

. Letter to Family. 21 January, 1923. Heber Doust Curtis Collection...... M..... 1c ...... h...-1 g-an Historical Collection. Bentley Historical Library. University of Michigan, Ann Arbor. 63 ...--.-....,-.,~· Letter to Robert G. Aitken. 1January,1925. Mary Lea Shane Archives. Lick Observatory, Santa Cruz.

...... ,...... -· ~tter .to Family. 19 July, 1925. Heber Doust Curtis Collection. M~ch~gan H1stoncal Collections. Bentley Historical Library. University of M1ch1gan, Ann Arbor.

~-~· Letter to Family. 3 April, 1932. Heber Doust Curtis Collection. M~ch~gan Historical Collections. Bentley Historical Library. University of M1ch1gan, Ann Arbor.

___. "Light-Year versus Parsec." Nature 121(May,1928). 789.

~--· "Modern Physical Science: Its Relation to Religion." in Has Science DLScovered God: A Symposium of Modem Scientific Of!inion. ed. Edward H. Cotton. Freeport, N.Y.: Books for Libraries Press, 1931. repnnt 1968. 53-74 .

. "Modern Theories of the Spiral Nebulae." abstract in Proceedings of the ,..,.W...-as_,h...... in-gton Academy of Science 9 (1919). 217-227 .

. 'The Nebulae." The Adolfo Stahl Lectures in Astronomy. San Francisco: .,...S,...... ta-n.... fo-r""""d University Press, 1919. 95-109 .

. The Nebulae. Handbuch der Astrophysik. Band V /2 Berlin: Verlag von .....Ju-.l ~m-s.....,S~pringer , 1933 .

. "New Stars in Spiral Nebulae." Publications of the Astronomical Society of t-.-h-e~P,.-ac-.-ifi· c 29 (July 1917). 180-182 .

. "Occulting Matter in the Spiral Nebulae." Publications of the Lick "?"OC"T"b-se_rv_a-tory 13 Berkeley: University of California Publications (March 1918). 51-54.

. "Proper Motions of the Nebulae." Publications of the Astronomical Society o-1..-th..-e__,P,....acific 17 (1915). 214-218 .

---. "Receding Horizons." Scientific Monthly 47 (1938). 242-251. . "Religion from the Standpoint of Science". in Religion and the Modem M'T'""...... in-d r-. -ed. Charles C. Cooper. New York: Harper & Brothers Publishers, 1929. 55- 92.

. "Reminiscences of a Pittsburgh Astronomer in the 20's." speech. Heber ....D...... o_u_s_t C.,..:Urtis Collection. Michigan Historical Collections. Bentley Historical Library. University of Michigan, Arm Arbor. n.d. 1-7. . 'The Scale of the Universe." talk given before the National Academy of -s~c1~e-n-ce-s, 26 April, 1920. Bulletin of the National Research Council. vol. 2. Washington, D.C. The National Research Council of the National Academy of Sciences, 1931. 171-217.

---. "A Scientist Looks at Religion." speech. n.d. 1-7. . "The Scientist's Right to Religious Speculation." speech. Heber Doust 7"C.-u-rt...,..is_C.,..ollection. Michigan Historical Collections. Bentley Historical Library. University of Michigan, Arm Arbor. n.d. 1-16. 64 ___. "A Spiral Nebula in the Milky Way:' PASP, 30 (1918): 161.

. ''The Spiral Nebulae and the Constitution of the Universe." Scientia 35 .,,..,..(1...... 92...... 3)-. 1-9 .

...... -~· Telegram to Clarence Darrow. 19 July, 1925. Heber Doust Curtis Collection. Michigan Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. ____. "Three Novae in Spiral Nebulae." Lick Observatory Bulletin 13, num. 300. Berkeley: University of california Publications, 1917. 108-110.

...... ~-· "The Unity of the Universe." speech. Heber Doust Curtis Collection. Michigan Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. 1928. 399-415.

Curtis, Mary D. Letter. 10 January, 1942. Heber Doust Curtis Collection. Michigan Historical Collections. Bentley Historical Library. University of Michigan, Ann Arbor. Dixon, Robert T. Dynamic Astronomy. Englewood Cliffs, N.J.: Prentice-Hall, Inc., 1971. Fernie, J.D. ''The Historical Quest for the Nature of the Spiral Nebulae." Publications of the Astronomical Society ofthe Pacific. 82 (December 1970). 1189-1230. Hart, Richard C. "Adriaan van Maanen's Influence on the Island Universe Theory." Ph.D. diss. Boston University, 1973. Hubble, Edwin. The Realm of the Nebulae. New Haven, CT: Yale University Press, 1936; New York: Dover Publications, Inc., 1958.

Jastrow, Robert and Thomson, Malcolm H. Astronomy: Fundamentals and Frontiers. 2d. ed. New York: John Wiley and Sons, Inc., 1974.

McLaughlin, Dean B. "Heber Doust Curtis 1872-1942." Popular Astronomy 50 (April 1942). 1-7. · McMath, Robert R. "Heber Doust Curtis 1872-1942." Publications ofthe Astronomical Society of the Pacific 54 (April 1942). 69-71.

Osterbrock, Donald E., Gustafson, John R., and Unruh, W.J. Shiloh. Eye on the Sky: Lick Observatory's First Century. Berkeley: University of California Press, 1988.

Pasachoff, Jay M. Contemporary Astronomy. 2d. ed. Philadelphia: Saunders College Publishing, 1981. Smith, Robert W. The Expanding Universe: Astronomy's "Great Debate" 1900-1931. Cambridge: Cambridge University Press, 1982. 65 Stebbins, Joel. "Heber Curtis and the Michigan Telescope." reprint from The Structure of the Galaxy. Publications of the University ofMi chigan. vol. 10, 1951.

Whitney, Charles A. The Discovery of our Galaxy. New York: Alfred A. Knopf, 1971.