General relativity (Physics)

Interview with Surjeet Rajendran, Associate Professor of Physics at Johns Hopkins University. He provides an overview of his current research activities with David Kaplan in black hole physics, new short distance forces, and modifications of quantum mechanics, and he shares his reaction on the recent g-2 muon anomaly at Fermilab. Rajendran explains why he identifies as a “speculator” in physics, he recounts his childhood in Chennai, India, and he discusses his grandparents’ communist activism, his Jesuit schooling, and how science offered a refuge for rebellion from these influences. He explains his decision to transfer from the Indian Institute of Technology to Caltech as an undergraduate, where he worked with Alan Weinstein on LIGO. Rajendran discusses his graduate research at Stanford, where KIPAC had just started, and where Savas Dimopoulos supervised his work on PPN parameters and solving the seismic noise problem on atom interferometers for LIGO. He describes his postdoctoral work, first at MIT and then at Johns Hopkins, when he began to collaborate with Kaplan on axion detection and the electroweak hierarchy problem. Rajendran explains the rise and fall of the BICEP project, and his Simons Foundation supported work on CASPEr. He discusses his interest in bouncing cosmology and firewalls in general relativity, and he conveys optimism that LIGO will advance our understanding of black hole information. At the end of the interview, Rajendran reviews his current interests in the Mössbauer effect, and explains how nice it was to win the New Horizons in Physics prize, and he prognosticates on how the interplay between observational and theoretical cosmology will continue to evolve and perhaps resolve fundamental and outstanding questions in the field.

n this interview, Stephon Alexander discusses current research into quantum gravity and possible extensions to string theory; work to merge quantum mechanics and general relativity; research into the connection between music and cognitive science; experience as a jazz musician; intersections of philosophy and physics; experience as president of the National Society of Black Physicists (NSBP); challenges and stigmas associated with being a Black academic; growing up in both rural Trinidad and the Bronx; undergraduate experience at Haverford; graduate work at Brown; guidance from Robert Brandenberger into the field of quantum gravity, applying particle physics to astrophysics and cosmology; thesis research on solitons and topological defects and its role in string cosmology and theory; decision to take postdoc at Imperial College London focusing on M-theory and integrating string theory with cosmic inflation; influence of Alan Guth; work on D-brane driven inflation; experience in the underground London music scene; decision to go to SLAC in Stanford and work under Michael Peskin; loop quantum gravity; time as faculty at Penn State; the role and responsibility of the Black academic; recruitment by Brown University; intellectual influence of David Finkelstein; the process of becoming president of NSBP. Toward the end of the interview, Alexander reflects on his books, The Jazz of Physics and Fear of a Black Universe; being an outsider in the field of physics; and revisits his current work on quantum gravity. He emphasizes the importance of in-person collaboration and improvisation. 

Physics Graduate student Eline V. A. van den Heuvel (University of Amsterdam) interviews Professor Emeritus of Physics and Senior Research Scientist at the University of Maryland Charles W. Misner. After obtaining his BA at the University of Notre Dame in 1952, Prof. Misner continued his education at Princeton University, where he completed his PhD in Physics under supervision of Prof. John. A. Wheeler (1911-2008) in 1957. In the spring semester of 1956, Prof. Wheeler fulfilled the Lorentz professorship at Leiden University, the Netherlands, accompanied by his student Misner. Prof. Misner discusses this trip, focusing on his personal experience and his work on the Already Unified Field. He also discusses Wheeler’s relativity work and possible motivations for Wheeler to go to Leiden. The remainder of the interview deals with the many-worlds interpretation of Dr. Hugh Everett, a friend of Misner and former a PhD student of Wheeler, and Misner expresses his disappointment in how the physics community has treated Everett.

Interview with Rainer Weiss, professor emeritus of physics at MIT. Weiss recounts his family history in pre-war Europe and the circumstances of his parents' marriage. He describes his childhood in New York City, and he explains his interests in experimenting and tinkering from an early age. Weiss explains the circumstances leading to his undergraduate study at MIT and his original plan to study electrical engineering before focusing on physics. He recounts his long and deep relationship with Jerrold Zacharias, who singularly championed Weiss's interests over the years. He discusses his graduate work on the hyperfine structure of hydrogen fluoride. Weiss describes his formative work with Bob Dicke at Princeton, and he explains how technological advances was beginning to offer new advances in general relativity. He explains how Dicke's influence served as an intellectual underpinning for the creation and success of LIGO. Weiss emphasizes the importance of Richard Isaacson as one of the founding heroes of LIGO, and he describes the fundamental importance of joining his research institutionally with Caltech. He describes his early research with John Mather, and the numerous administrative challenges in working with the NSF throughout the LIGO endeavor. Weiss describes the geographical decisions that went into building LIGO, the various episodes when LIGO's ongoing viability was in doubt, and how both Barry Barish and Kip Thorne contributed to ensuring its success. At the end of the interview, Weiss describes some of the sensitivities regarding who has been recognized in LIGO and who has not, in light of all the attention conferred by the Nobel prize, and he reflects on how LIGO will continue to push discoveries forward on the nature and origins of the universe.

Interview with William H. Press, Leslie Suringer Professor in Computer Science and Integrative Biology at the University of Texas at Austin. Press recounts his childhood in Pasadena and the influence of his father Frank Press, who was a prominent geophysicist, Caltech professor, and who would become science advisor to President Jimmy Carter. He describes the impact of Sputnik on his budding interests in science, and he discusses his undergraduate experience at Harvard, where Dan Kleppner, Norman Ramsey, Ed Purcell and Dick McCray were influential in his development, and where he realized he had an aptitude for applying abstract equations to understanding physical reality. Press describes trying his hand with experimentation in Gerald Holton’s high-pressure physics lab, he recounts his involvement in student activism in the late 1960s, and he discusses his involvement in computer hacking in its earliest form. He explains his decision to attend Caltech for graduate school and his interest in studying with Dick Feynman and Kip Thorne. Press describes the opportunity leading to his work at Lawrence Livermore, how he got involved with Thorne’s group of mathematical general relativists, the origins of Thorne’s work on gravitational waves, and his collaborations with Saul Teukolsky and Paul Schechter. He describes the formative influence of Chandrasekhar. Press discusses his first faculty position at Princeton where he joined John Wheeler’s relativity group, and he describes his research interests flowing more toward astrophysics. He explains the opportunities leading to his tenure at Harvard, where he was given separate appointments in physics and astronomy and where he founded theoretical astrophysics within the Center for Astrophysics. Press describes his entrée into science policy work in Washington with the NSF Physics Advisory Committee and then later on the National Academy of Science and the National Research Council, and he explains the origins of his long-term association with the JASON Study Group. He describes his interest in gravitational collapse, Ia supernovae and galaxy formation, and why the study of black holes reinvigorated the field of general relativity. Press describes the singular genius of Freeman Dyson, and he recounts his contributions to nuclear risk reduction in science policy and his service with the Defense Science Board and the Institute for Defense Analyses. He discusses his tenure as chair in Harvard’s Department of Astronomy, his experience with the Numerical Recipes books, and his collaboration with Adam Riess and Robert Kirshner. Press recounts his decision take a position at Los Alamos as Deputy Director to John Browne, he describes his education there in the concept of leadership which he never received in his academic career, and he provides his perspective on the Wen Ho Lee spy case and the existential crisis this caused at the Lab. He describes the Lab’s role in the early days of computational biology and how this field sparked his interest. Press contextualizes this interest within his conscious decision not to stay connected to astrophysics during his time at Los Alamos, and he explains the opportunity leading to him joining UT-Austin where he remains invested in computational biology. He describes his work for the President’s Council of Advisors in Science and Technology during the Obama administration, he describes Obama’s unique interest in science and science policy, and he narrates the difficulties in the transition to the Trump administration. Press reflects on what it means to be a member of the rarified group of scientists who did not win a Nobel Prize but who were advised by and taught scientists who did. At the end of the interview, Press explains that he has always been a dilettante, which has and will continue to inform how he devotes his time to science, service, and policy matter, and he advises young scientists to aspire to mastery in a specific discipline early in their career before branching out to new pursuits.

Interview with Robert M. Wald, Charles H. Swift Distinguished Service Professor of Physics at the University of Chicago, where he also has appointments with the Kadanoff Center and the Kavli Institute for Cosmological Physics. Wald recounts his childhood in New York, he describes the tragedy of losing his parents in an airplane crash when he very young, and he explains the ongoing legacy of his father Abraham Wald who was a prominent professor of statistics at Columbia. He describes his high school education at Stuyvesant and his decision to pursue a physics degree at Columbia, where he became close with Alan Sachs, who supervised him at Nevis Laboratory. Wald explains his decision to focus on general relativity for graduate school and his interest in working with John Wheeler at Princeton. He describes the excitement surrounding recent advances in approaching astrophysics through relativity, the significance of the discovery of pulsars and the field of black hole uniqueness, and he discusses his postdoctoral research with Charles Misner at the University of Maryland. Wald describes the impact of Saul Teukolsky’s discovery of a variable Weyl tensor component that satisfied a decoupled equation, and he explains the circumstances leading to his faculty position at Chicago, where he was motivated to work with Bob Geroch. He reflects on the experience writing Space, Time, and Gravity, the advances in black hole collapse research, and he explains why he felt the field needed another textbook which motivated him to write General Relativity. Wald discusses his work on the Hawking Effect and his long-term interest in quantum field theory, and he explains the influence of Chandrasekhar on his research. He describes his contributions to the LIGO collaboration, and he explains what is significant about the Event Horizon Telescope’s ability to capture an image of a black hole. Wald explains the state of gravitational radiation research and the accelerating universe, he prognosticates on what advances might allow for a unification of gravity and the Standard Model, and he explains why dark energy is apparently a cosmological constant. At the end of the interview, Wald discusses his recent work on the gravitational memory effect and, looking to the future, he explains his interest to continue working to understand the S-matrix in quantum electrodynamics.

Interview with Mark Trodden, Fay R. and Eugene L. Langberg Professor of Physics, and Co-Director of the Center for Particle Cosmology at the University of Pennsylvania. Trodden describes the overlap between astronomy, astrophysics, and cosmology, and he recounts his working-class upbringing in England. He discusses his undergraduate education at Cambridge, where he focused on mathematics, and he explains his decision to switch to physics for graduate school at Brown, where he worked under the direction of Robert Brandenberger. Trodden describes the impact of the COBE program during this time, and he discusses his work on the microphysics of cosmic strings and topological defects and their effect on baryon asymmetry. He explains his decision to return to Cambridge for his postdoctoral research with Anne Davis and his subsequent postdoctoral appointment at MIT to work with Alan Guth. Trodden discusses his next postdoctoral position at Case Western, which he describes as a tremendously productive period, and he discusses the opportunities that led to his first faculty position at Syracuse. He notes the excellent graduate students he worked with at Syracuse, and he explains what is known and not known with regard to the discovery of the accelerating universe. Trodden describes why the theory of cosmic inflation remains outside the bounds of experimental verification, and he explains the decisions that led to his decision to join the faculty at Penn and his subsequent appointment as chair of the department. He discusses the work that Penn Physics, and STEM in general, needs to do to make diversity and inclusivity more of a top-line agenda, and he describes much of the exciting work his current and former graduate students are involved in. At the end of the interview, Trodden looks to the future and offers ideas on how physicists may ultimately come to understand dark energy and dark matter.

Interview with Saul Teukolsky, Hans A. Bethe Professor of Physics and Astrophysics at Cornell and Robinson Professor of Theoretical Astrophysics at Caltech. Teukolsky recounts his childhood born in a Jewish family in South Africa, and he explains the tensions between his parents’ politics, who were accepting of apartheid, and his own views which rejected this as a national injustice. He describes his undergraduate education at the University of Witwatersrand and the impact of the Feynman Lectures on his intellectual development. Teukolsky explains his interest in pursuing general relativity for graduate school, and he discusses the circumstances leading to his enrollment at Caltech, where he studied Newman-Penrose equations and perturbations of the Kerr metric under the direction of Kip Thorne. He discusses his year-long postdoctoral research position at Caltech and his subsequent decision to join the faculty at Cornell, where he developed the gravitational theory program. Teukolsky explains the significance of the Hulse-Taylor discovery at Arecibo on general relativity, and he describes the early impact of computers on advancing GR research and specifically on numerical relativity which he worked on with Bill Press. He discusses the rise of computational astrophysics, and he surveys his interests in pedagogical issues in physics and his early involvement in LIGO and the LISA collaboration. At the end of the interview, Teukolsky explains how he has tried to communicate astrophysical concepts to broad audiences, and he expresses optimism that massive advances in computational abilities will continue to drive forward fundamental advances in the field.

Interview with William "Bill" Unruh, Professor of Physics and Astronomy at the University of British Columbia, and Hagler Fellow at the Institute for Quantum Science and Engineering at Texas A&M. He credits his mentor John Wheeler for the steady progress of interest and work in general relativity over the decades, and he reflects broadly on the original debates among the relativists and the founders of quantum mechanics. Unruh explains the inability to merge these foundations of physics as the source of his attempts to understand the black hole evaporation as found by Hawking. He recounts his upbringing in Manitoba as part of a Mennonite community and his early interests in Euclidean geometry, and he describes his undergraduate education at the University of Manitoba. Unruh explains his decision to pursue a PhD with Wheeler at Princeton on topology and general relativity, and scattering cross sections of black holes to scalar fields. He describes his postgraduate appointment at Birkbeck College where he worked with Roger Penrose and he narrates the origins of his collaboration with Stephen Fulling and Paul Davies. Unruh discusses his time at Berkeley and then at McMaster and he historicizes the point at which observations made black holes more "real," and he explains his first involvement with decoherence. He explains his involvement with LIGO from its origins and its quantum mechanical nature, and he narrates his reaction of amazement when gravitational waves were detected. Unruh describes the impact of his work in quantum mechanics on computation, and he explains some of the advances that have made observation more relevant to his recent research. At the end of the interview, Unruh describes his efforts to launch a Gravity Archive at UBC, he expresses his frustration with people who insist we do not know quantum mechanics, and he quotes Wheeler, quoting his favorite Grook to convey that he is having fun and wants to learn as much as he can, while he can.

Interview with Gabriela Gonzalez, Louisiana State University Boyd Professor in the Department of Physics and Astronomy. Gonzalez explains how the pandemic has slowed down data analysis for LIGO, and she recounts her childhood in Cordoba, Argentina. She describes her early interests in science and her physics education as an undergraduate in Cordoba. Gonzalez explains the circumstances that led to her graduate studies at Syracuse University where she studied relativity under the direction of Peter Saulson, and where she first became involved with LIGO. She discusses her postdoctoral appointment at MIT to work in Rai Weiss’s group, and she explains LIGO’s dual goals of detecting gravitational waves and building precision instruments toward that end. Gonzalez explains her decision to join the faculty at Penn State and she describes the site selection that led to the detection facility in Livingston, Louisiana. She describes the necessary redundancy of the LIGO detectors at Livingston and Hanford, Washington, and the importance of “locking” the mirrors on the detectors. Gonzalez describes the overall scene at LIGO in the months up to the detection and the theoretical guidance that improved the likelihood of success. She describes the intensive communication and data analysis to confirm the detection prior to the announcement, and she explains how she felt honored as part of the overall Nobel Prize award and subsequent celebration. Gonzalez describes LIGO’s work in the current post-detection period, and her own focus on diagnostics of the data, and she explains why this work, and the constant concern in missing something important, can be stressful. At the end of the interview, Gonzalez surveys what mysteries LIGO can, and cannot, solve, and she conveys optimism for LIGO’s long-term prospects to continue to push fundamental discovery.