Finding The Radiation from the Big Bang P. J. E. Peebles and R. B. Partridge January 9, 2007 4. Preface 6. Chapter 1. Introduction 13. Chapter 2. A guide to cosmology 14. The expanding universe 19. The thermal cosmic microwave background radiation 21. What is the universe made of? 26. Chapter 3. Origins of the Cosmology of 1960 27. Nucleosynthesis in a hot big bang 32. Nucleosynthesis in alternative cosmologies 36. Thermal radiation from a bouncing universe 37. Detecting the cosmic microwave background radiation 44. Cosmology in 1960 52. Chapter 4. Cosmology in the 1960s 53. David Hogg: Early Low-Noise and Related Studies at Bell Lab- oratories, Holmdel, N.J. 57. Nick Woolf: Conversations with Dicke 59. George Field: Cyanogen and the CMBR 62. Pat Thaddeus 63. Don Osterbrock: The Helium Content of the Universe 70. Igor Novikov: Cosmology in the Soviet Union in the 1960s 78. Andrei Doroshkevich: Cosmology in the Sixties 1 80. Rashid Sunyaev 81. Arno Penzias: Encountering Cosmology 95. Bob Wilson: Two Astronomical Discoveries 114. Bernard F. Burke: Radio astronomy from first contacts to the CMBR 122. Kenneth C. Turner: Spreading the Word — or How the News Went From Princeton to Holmdel 123. Jim Peebles: How I Learned Physical Cosmology 136. David T. Wilkinson: Measuring the Cosmic Microwave Back- ground Radiation 144. Peter Roll: Recollections of the Second Measurement of the CMBR at Princeton University in 1965 153. Bob Wagoner: An Initial Impact of the CMBR on Nucleosyn- thesis in Big and Little Bangs 157. Martin Rees: Advances in Cosmology and Relativistic Astro- physics 163. Geoffrey Burbidge and Jayant Narlikar: Some Comments on the Early History of the CMBR 171. David Layzer: My Reaction to the Discovery of the CMBR 175. Michele Kaufman: Not the Correct Explanation for the CMBR 176. Jasper Wall: The CMBR – How to Observe and Not See 184. John Shakeshaft: Early CMBR Observations at the Mullard Radio Astronomy Observatory 189. William “Jack” Welch: Experiments with the CMBR 192. Paul Boynton 193. Robert A. Stokes: Early Spectral Measurements of the Cosmic Microwave Background Radiation 199. Martin Harwit: An Attempt at Detecting the Cosmic Back- ground Radiation in the Early 1960s 210. Kandiah Shivanandan 211. Rainer Weiss: CMBR Research at MIT Shortly After the Dis- covery — is there a Blackbody Peak? 231. Jer T. Yu: Clusters and Super-clusters of Galaxies 235. Rainer Sachs: The Synergy of Mathematics and Physics 2 240. Art Wolfe: CMBR Reminiscences 243. Joe Silk: A Journey Through Time 252. Bruce Partridge: Early Days of the Primeval Fireball 268. Ron Bracewell and Ned Conklin: Early Cosmic Background Studies at Stanford Radio Astronomy Institute 277. Steve Boughn: The Early Days of the CMBR: An Undergradu- ate’s Perspective 282. Paul Henry: A Graduate Student’s Perspective 288. George F. R. Ellis: The Cosmic Background Radiation and the Initial Singularity 294. Chapter 5. Bond and Page: Cosmology since the 1960s 295. Glossary 322. Bibliography 3 Preface Many contributed to this book. The list begins with colleagues who in informal conversations now only vaguely recalled led us to appreciate the two reasons why we have a story worth telling: this is a substantial advance in science, and it is a close to unique opportunity for a near saturation of recollections of what happened. All the main steps in this advance — the detection and identification of the fossil radiation from the big bang — have been clearly and accurately presented in histories of science. But these histories do not have the space to give an impression what it was like to live through those times. We sense a similar feeling of incompleteness in many histories of science written by physicists as well as by professional historians and sociologists. And there is a well-established remedy: assemble recollections from those who were involved in the work. We have been guided by a shining example in the broader field of cosmology, the collection of interviews in Origins: the Lives and Worlds of Modern Cosmologists (Lightman and Brawer 1990). We are indebted to Michael D. Gordin for instructing us on the existence of similar operations in other fields of science, and on the lessons to be drawn from them. The close to unique feature of the recollections of early research on the big bang fossil radiation is the relatively small number of people involved. It means we could hope for complete coverage of recollections from everyone who was involved in a significant way and is still with us. We did not reach completeness: we suppose it is inevitable that a few colleagues would have well-established reasons for not wanting to take taking part. We are grateful that a substantial majority of everyone who was significantly involved in this slice of research in the 1960s and is still with us were willing to contribute their recollections. The contributors are well along in life now, but they have not slowed down: all had to break away from other commitments to complete their assignments. We are deeply indebted to these people for taking the time and trouble to make this collection possible, and for their patience in enduring the chaos of assembly of the book. We are indebted to participants also for their help in weeding out flaws in the introductory chapters, the ensemble of essays, and the glossary and bibliography that are meant to guide the reader through the essays. John Shakeshaft must be specially mentioned for his substantial reduction of the error rate, though he certainly does not share the blame for the remaining flaws in commission and omission. 4 Some steps toward the organization of this project ought to be recorded. Bernie Burke, Lyman Page, Jim Peebles, Tony Tyson, Dave Wilkinson and Bob Wilson met in Princeton on 9 February 2001, for an informal discussion over dinner of the story of the detection and identification of the fossil radia- tion. Wilson’s written notes agree with Peebles’ undocumented recollection of the general agreement that the story is complicated, and worth telling for that reason. But that enthusiastic agreement led nowhere; we all returned to other interests. In a second attempt to get the project started, George Field, Jim Peebles, Pat Thaddeus and Bob Wilson met at Harvard on 8 August 2003. That led to a proposal that was circulated to some 12 proposed con- tributors. (The number is uncertain because we have failed record keeping.) It yielded three essays — they are in this collection — but attention again drifted back to other things. The third attempt commenced with a chance encounter between Bruce Partridge and Jim Peebles in September 2005 at the Princeton Institute for Advanced Study. Our discussion led us to a blunt actuarial assessment: if the story were to be told in a close to complete way it would have to be done before too many more years had passed. That generated the momentum that led to completion of this project. We sent a proposed outline of the book with an invitation to contribute to 28 people on 7 December 2005. The project continued to mature. As one might expect, the outline changed as we better understood what we were attempting to do. More unnerving is that, although we had given the list of contributors careful thought, we have continued to identify people who ought to contribute: we have some half dozen additions to the December 2005 list. A simple extrapolation suggests we have forgotten still others: we likely have not been as complete as we ought to have been. We hope those we inadvertently did not include will accept our regrets for our inefficiency. We hope all who did contribute to this book, in many ways, are aware of our gratitude. 5 Chapter 1. Introduction This is the story of the discovery of thermal radiation that smoothly fills space. The radiation is a fossil, a remnant from a time when our universe was radically different from now, denser and hotter. Its discovery is memorable because, like other fossils, measurements of its properties tell us a good deal about the past. The story of how this fossil radiation was discovered is memorable too for the complex set of considerations, in some cases overlooked for quite a while, in the many lines of research that led to the realization that this fossil exists, may be measured, and may inform us about the large-scale nature of the physical universe. The complexity of this discovery story is well known. We suspect that is largely because the result was a big enough advance in a small enough subject then that people were led to look with particular care at how it happened. Look into the details of any other significant advance in science and you are likely to find a complicated story. That is, we believe our particular story offers some general lessons on how science actually is done. The essays in this volume tell what happened when the fossil radiation was recognized and first studied in the 1960s in the most complete way we can manage, by collecting remembrances of what they were thinking and doing from most of the scientists who were involved in this slice of research. The stories of search and discovery in science that we tell each other usually are much too schematic to show what research is really like: they ignore all the wrong paths taken and the painstaking learning curves that experimentalists, observers and theorists follow in sometimes finding better paths. Scientists as well as historians and sociologists complain about the distortions, but our “tidied up” stories do serve a useful purpose in helping us keep track of the central ideas as well as in reminding us that our subject does have a history.