Expanding universe

In this interview, Saul Perlmutter, Professor of Physics at UC Berkeley and Staff Scientist and senior faculty member at Lawrence Berkeley National Laboratory, discusses his life and career. Perlmutter shares that his research has not been slowed down by the pandemic by happy coincidence that he is currently focused on remote data analysis, and he recounts his childhood in Philadelphia where he was educated in Quaker schools. He discusses his early fascination with quantum mechanics and his decision to go to Harvard for his undergraduate education, where he cemented his interests in experimental physics. Perlmutter explains his decision to go to Berkeley for graduate school, where he worked in Buford Price’s group before Richard Muller became his graduate advisor. He discusses his early awareness of the cosmic microwave background and how he became involved with robotic searches for supernovae. Perlmutter describes the importance of NASA’s BITNET program as a way to connect observatory data worldwide to the computer systems at Berkeley, and he explains the intellectual and observational connections between the inflation, expansion, and acceleration of the universe. He discusses his postdoctoral research at Berkeley, and the circumstances leading to him becoming leader of the supernova group and how the DOE became more involved in astrophysics funding. Perlmutter explains the group’s focus on deceleration and he conveys the difficulties in scheduling telescope time to demonstrate spectroscopy proof of type Ia supernovae. He describes the origins of the SNAP satellite project, some of the early theoretical discussions on the nature of dark energy, and when, finally, his group secured long-term support from the Lab. Perlmutter narrates his first interactions with Brian Schmidt and Adam Riess and he describes the batch technique that could predict the discovery of supernovae, which vastly improved the efficiency of scheduling time on large telescopes. He explains the role of dark matter in speeding up the universe’s expansion, and he narrates the celebration with his team when he won the Nobel Prize and how he has chosen the use the political platform that comes with this recognition. Perlmutter discusses his interest in studying climate change, and at the end of the interview, he conveys his excitement about future observational discovery in astrophysics and cosmology.

Interview with Andrei Linde, Harald Trap Friis Professor of Physics at Stanford. This discussion continues from the interview with Linde conducted by Alan Lightman in October 1987. He provides a detailed history on his improvement of Alan Guth’s work on inflation, which Linde dubbed “new inflation” and subsequently “chaotic inflation.” Linde describes the impact of Perestroika on Soviet scientists, and the pressures he felt in preparing for a series of talks in Italy, which contributed to his development of “eternal inflation.” He discusses his formative early communication with American physicists including Lenny Susskind and Norman Coleman, he describes his two-year visit at CERN as the Cold War was winding down, and he explains his decision to accept a faculty appointment at Stanford. Linde describes the alternating feelings of hope and despair in the 1980s regarding the possibility that inflation could be observationally verified. He explains the intellectual origins of self-generating fractals that sprout other inflationary universes and the value of compactification theory, and he explains the cultural relevance of his Russian heritage which compels him to value theoretical notions and not treat them in a throwaway manner that capitalism can encourage. Linde explains how and why multiverses can be testable and he reflects on the obvious philosophical or even spiritual implications of this proposition. He discusses the impact of the discovery of the accelerating universe and dark energy and how WMAP strained the theoretical viability of inflation. Linde explains why many string theorists have moved into investigating theories of quantum information, and at the end of the interview, he reflects on the value of competing theories to inflation and why, ultimately, he wants to see a major convergence of theories so that the origins of the universe are well understood. 

Interview with Marcelle Soares-Santos, assistant professor of physics at the University of Michigan. Soares-Santos recounts her childhood in Brazil, her early interests in science, and her graduate work in physics at the University of São Paulo. She describes her graduate visit to Fermilab to study galaxy clusters as a way to map the history of the expanding universe, which formed the basis of her thesis research. Soares-Santos discusses her return to Fermilab as a postdoctoral researcher, where she joined the Dark Energy Survey, and she explains how DES is getting us closer to understanding what dark energy is. She describes Fermilab’s broad-scale transition into astrophysics, and she explains the opportunities that led to her faculty appointment first at Brandeis before moving to Michigan. Soares-Santos discusses her current work in gravitational waves, and she prognosticates on what the discovery of dark energy (or energies) will look like. She shares her perspective on recent efforts to improve diversity and inclusivity in STEM. At the end of the interview, Soares-Santos explains why observation is leading theory in the current work of astrophysics and cosmology and why she is optimistic for fundamental advances in the field.

Interview with Adam Riess, Bloomberg Distinguished Professor at Johns Hopkins, and Distinguished Astronomer at the Space Telescope Science Institute. Riess explains the value of his dual affiliation and his focus on calibrating the Hubble Telescope for cosmological experiments. He recounts his childhood in New Jersey and the “boot camp” style of physics education he received at MIT. Riess explains his decision to go to Harvard for his graduate work, where Bob Kirshner advised his thesis research on supernovae, while he worked closely with Bill Press on data analysis. He describes his field work at Mount Hopkins in Arizona and his use of the early internet to collect and share data, and he explains what we did not previously understand about supernovae and how that prevented an earlier understanding that the universe’s expansion is accelerating. Riess describes working closely with Brian Schmidt and Nick Suntzeff and how the High-Z team came together, and he explains the decision to use the term “accelerating” to describe the findings from the research. He describes being unprepared for the enormous reaction the High-Z team received after it published its findings, and he explains the opportunities that led to his staff appointment at Space Telescope. Riess narrates his sense of when the “buzz” for the Nobel Prize started and he related the sense of bedlam when the announcement was made and his immediate plan to make this a recognition for the entire High-Z team. He explains how the world of dark energy research has opened up since the discovery and he surveys advances in instrumentation that have propelled the field forward in the last twenty years. At the end of the interview, Riess discusses his current focus on the Hubble tension, he conveys his excitement for the launch of the James Webb Telescope, and he shares that he can’t wait to meet students that he has never seen in person after a year of pandemic-mandated virtual interactions.

More discussion of the reasons why particle physicists began working on cosmology in the 1970s; importance of theoretical work by Kirzhnitz and Linde in 1972 on broken symmetries and phase transitions; current unreality of work on the very early universe; attitude toward the inflationary universe model; successes of the inflationary universe model; aesthetic attraction of a flat universe; acceptability of postulating that we live in a flat universe; introduction to and attitude toward the horizon problem; attitude toward the inflationary universe model; incidences of being worried about scientific problems that no one else is worried about; the anthropic principle and Dirac's large number hypothesis; reaction to de Lapparent, Geller, and Huchra's work on large-scale inhomogeneities; Weinberg worried that perhaps we have misinterpreted the cosmic background radiation; Weinberg's philosophy about strategy in science; the role of consensus in science and the importance of "standard" models; outstanding problems in cosmology: distance scale of the universe, value of the deceleration parameter, origin of structure; failure of theory to explain the observed large-scale structure; possible importance of WIMPs; prematurity of work on the early universe; ideal design of the universe; preference for universes in which initial conditions do not have to be specified; Weinberg's statement in The First Three Minutes about the lack of point to the universe.

Awareness in high school of the Sandage Program to observe the rate of expansion of the universe and awareness of the impending operation of the Mt. Palomar telescope; early reading in cosmology; prejudice toward the steady state model in graduate school because of its definite predictions; the reality of cosmology as a legitimate science; Weinberg's early interest in cosmology: influence of Herman Bondi's book; concern in the early 1960s over limited contact between theory and observations; early work in the 1960s on the neutrino version of Olber's Paradox and the possibility of a degenerate sea of neutrinos; preference for an oscillating universe as the next best thing after a steady state universe because you don't have to specify initial conditions; design of an experiment to search for degenerate neutrinos; Weinberg didn't take seriously his own work in cosmology in the 1960s; the importance of the discovery of the cosmic background radiation for making cosmology a legitimate science; the origin of Weinberg's book Gravitation and Cosmology; Weinberg's regret that he spent 1969-1971 working on a textbook when he should have been working on gauge theories in particle physics; history of the application of particle physics to cosmology.

Brian Schmidt studied as an undergraduate at the University of Arizona, where he worked on discovering supernovae with the CCD Transit Instrument under John McGraw. He continued his graduate studies in Astronomy at Harvard University, with Robert Kirshner as his thesis advisor, from 1989-1993. He stayed on at Harvard as a postdoctoral fellow before moving to The Australian National University in 1995. When he attended a summer school in Les Houches, France, in 1990, on Supernova, he met many of the supernova greats and marks this as his induction into supernova astronomy. Schmidt started the High-z Supernova Search Team in 1994 at the age of 27. He wrote the supernova search software, much of the simulation software, as well as one of several cosmological fitting software used by the team and led them to their 1998 discovery of the accelerating universe. In this series of interviews, Schmidt discusses the spaces of scientific work, supernovae as scientific objects, and scientific visualization. Schmidt’s outstanding good humor is infectious, and he is an astronomer and an observer highly respected within the profession.

Brian Schmidt studied as an undergraduate at the University of Arizona, where he worked on discovering supernovae with the CCD Transit Instrument under John McGraw. He continued his graduate studies in Astronomy at Harvard University, with Robert Kirshner as his thesis advisor, from 1989-1993. He stayed on at Harvard as a postdoctoral fellow before moving to The Australian National University in 1995. When he attended a summer school in Les Houches, France, in 1990, on Supernova, he met many of the supernova greats and marks this as his induction into supernova astronomy. Schmidt started the High-z Supernova Search Team in 1994 at the age of 27. He wrote the supernova search software, much of the simulation software, as well as one of several cosmological fitting software used by the team and led them to their 1998 discovery of the accelerating universe. In this series of interviews, Schmidt discusses the spaces of scientific work, supernovae as scientific objects, and scientific visualization. Schmidt’s outstanding good humor is infectious, and he is an astronomer and an observer highly respected within the profession.