Black holes (Astronomy)

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 Feryal Ozel, professor of astronomy and physics at the University of Arizona. Ozel recounts her childhood and family background in Istanbul and how her interest in science was fostered both at home and at the all-girls international school she attended through 12th grade. She describes the opportunities that led to her enrollment at Columbia University for her undergraduate education, where she majored in physics and applied math and where Jacob Shaham influenced her interest in neutron stars. She describes a formative summer internship at CERN where she worked on supersymmetric decays of the Higgs boson, and a postgraduate year at the Niels Bohr Institute, before she began her graduate work at Harvard. Ozel discusses her thesis research on magnetars under the direction of Ramesh Narayan and she describes her postdoctoral position at the Institute for Advanced Study as a Hubble fellow. She describes the academic and family considerations that made Arizona an attractive option and she explains the mechanics behind funding from NASA and the NSF. Ozel describes her favorite physics classes to teach, how she sees her role as a mentor to women students and students of under-represented groups, and she surveys recent developments in neutron star astrophysics and the interaction of gas and black holes. She discusses her contributions to the Event Horizon collaboration, and she relates her ideas on the significance of seeing a photograph of a black hole without needing observational evidence to know that black holes exist. Ozel describes her motivations in serving in scientific advisory roles and the importance of science communication and how advances in computational power have revolutionized astrophysics. At the end of the interview, Ozel discusses the outstanding question mark about making gravity compatible with how we understand the subatomic world and how this serves as a starting point for future research oriented toward fundamental discovery, and why she is particularly interested in continuing to work on black hole imaging.

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 Scott Tremaine, emeritus professor at the Institute for Advanced Study in Princeton. Tremaine discusses his current affiliation with the University of Toronto, and he provides a historical overview of the boundaries between astronomy and astrophysics. He recounts his childhood in a town north of Toronto, and he explains his early interests in science. Tremaine describes his undergraduate experience at McMaster, the opportunities that led to his graduate admission to Princeton, and the exciting developments that compelled him to focus his thesis research on astrophysics. He describes his dissertation on the dynamics of galaxies done under the direction of Jerry Ostriker, who at the time was focused on the earliest research on dark matter. Tremaine discusses his postdoctoral term at Caltech where he worked with Jim Gunn and Peter Goldreich, and he explains his decision to take a second postdoctoral position at the Institute of Astronomy at Cambridge. He describes his appointment at the Institute for Advanced Study, his decision to join the faculty at MIT, and he explains his ongoing research collaboration with Goldreich on studying Saturn's rings. Tremaine describes the intellectual origins of his book, co-authored with James Binney, Galactic Dynamics, and he explains his decision to join the University of Toronto to become the director of CITA. He describes his interests in the origins of comets, his contributions to black hole research, and his appointment at the Institute for Advanced Study. Tremaine discusses his work on exoplanets, and at the end of the interview, he surveys the importance of increasing computational power over the course of his career, the exciting advances that have been made in understanding galaxy development, and why the "three-legged" stool upon which cosmology rests - namely, on inflation, dark matter, and dark energy, is problematic.

Interview with Juan Maldacena, Carl P. Feinberg Professor at the Institute for Advanced Study. Maldacena recounts his childhood in Buenos Aires, he discusses his undergraduate education at the University of Buenos Aires and his advanced work in physics at Instituto Balseiro where he had his initial exposure to string theory. He explains his decision to pursue a graduate degree at Princeton where he worked with Curt Callan and where he benefited from Ed Witten’s lectures on dualities in quantum field theory and in string theory. Maldacena describes his thesis research on conformal field theories with boundaries and the significance of Joe Polchinski’s discovery of D-branes, and he conveys the importance of his collaboration with Andy Strominger as a postdoctoral researcher at Rutgers. He describes his paper on AdS/CFT while at Harvard and he explains his work on non-gaussianities and his realization that string theory would be useful for cosmology. Maldacena explains his decision to leave the faculty at Harvard to join the Institute, and he describes his subsequent research on space-time and entanglement, the chaos of black holes and the likelihood that they are rapidly thermalizing systems. He explains the contributions of string theory research as offering physics a model for quantum gravity and for the quantum mechanics of spacetime itself, and he shares his perspective on broader debates about how many researchers should or should not be involved in string theory work. At the end of the interview, Maldacena describes his hope in the future to better understand the interiors of black holes.

Interview with John Preskill, Richard P. Feynman Professor of Theoretical Physics at Caltech, and Director of the Institute for Quantum Information and Matter at Caltech. Preskill describes the origins of IQIM as a research pivot from the initial excitement in the 1970s to move beyond Standard Model physics and to understand the origin of electroweak symmetry breaking. He emphasizes the importance of Shor’s algorithm and the significance of bringing Alexei Kitaev into the project. Preskill discusses the support he secured from the NSF and DARPA, and he recounts his childhood in Chicago and his captivation with the Space Race. He describes his undergraduate experience at Princeton and his relationship with Arthur Wightman and John Wheeler. Preskill explains his decision to pursue his thesis research at Harvard with the intention of working with Sidney Coleman, and he explains the circumstances that led to Steve Weinberg becoming his advisor. He discusses the earliest days of particle theorists applying their research to cosmological inquiry, his collaboration with Michael Peskin, and his interest in the connection of topology with particle physics. Preskill describes his research on magnetic monopoles, and the relevance of condensed matter theory for his interests. He explains the opportunities that led to his appointment to the Harvard Society of Fellows and his eventual faculty appointment at Harvard, his thesis work on technicolor, and the excitement surrounding inflation in the early 1980s. Preskill discusses the opportunities that led to his tenure at Caltech and why he started to think seriously about quantum information and questions relating to thermodynamic costs to computing. He explains the meaning of black hole information, the ideas at the foundation of Quantum Supremacy, and he narrates the famous story of the Thorne, Hawking, and Preskill bets. Preskill describes the advances in quantum research which compelled him to add “matter” to the original IQI project which was originally a purely theoretical endeavor. He discusses the fact that end uses for true quantum computing remain open questions, and he surveys IQIM’s developments over the past decade and the strategic partnerships he has pursued across academia, industry, and at the National Labs. Preskill surveys the potential value of quantum computing to help solve major cosmological mysteries, and why his recent students are captivated by machine learning. At the end of the interview, Preskill reflects on his intersecting interests and conveys optimism for future progress in understanding quantum gravity from laboratory experiments using quantum simulators and quantum gravity.

In this interview, David Zierler, Oral Historian for AIP, interviews Cumrun Vafa, Hollis Professor of Mathematicks and Natural Philosophy in the Department of Physics at Harvard. Vafa surveys the current state of the field in string theory, and he recounts his upbringing in Iran and his family’s goal for him to pursue education in the United States. He explains the opportunities that led to his acceptance to MIT, and his intellectual journey from being practical-minded in his study of economics and engineering, to his blossoming love for mathematics and physics. Vafa describes his early difficulties reconciling the formalism of math with the intuition he sensed pervaded concepts in physics, and he explains how this changed as a student of Ed Witten’s at Princeton. He describes his entrée into string theory at the time that Witten had committed himself to learning string theory, and he describes the evolution of the field from the first to the second “revolutions” from 1984 to 1994. Vafa describes his time as a junior fellow at Harvard and some of the tensions that existed in the physics department between senior faculty who were not interested in string theory, and the junior faculty who were. He explains the circumstances that led to his rapid tenure at Harvard and he describes the ideas that became his “Swampland” concept. Vafa discusses his collaborations with Andy Strominger on black holes and with Robert Brandenberger on string gas cosmology and his solo research on F-theory. He talks about the long-term prospects for a truer understanding of quantum gravity, and at the end of the interview, Vafa engages with critics and string theory, and delineates between those who are not interests themselves (which he understands and respects) and those who wish to make it more difficult for others to study string theory (which he finds problematic). Vafa acknowledges the current gap between string theory and experimental verification but asserts that this gap is a function of current technological limitations in observation, and not a shortcoming of string theory itself.

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. 

Interview with Gerard 't Hooft, University Professor of Physics (Emeritus) at Utrecht University in the Netherlands. 't Hooft considers the possibility that the g-2 muon anomaly experiment at Fermilab is suggestive of new physics, and he reflects broadly on the current shortcomings in our understanding of quantum mechanics and general relativity. 't Hooft recounts his childhood in postwar Holland and the influence of his great uncle, the Nobel Prize winner Frits Zernike and his uncle, the theoretical physicist Nico van Kampen. He describes his undergraduate education at Utrecht University where he got to know Martinus Veltman, with whom he would pursue a graduate degree and ultimately share the Nobel Prize. 't Hooft explains the origins of what would become the Standard Model and the significance of Yang-Mills fields and Ken Wilson’s theory of renormalization. He describes Veltman’s pioneering use of computers to calculate algebraic manipulations and why questions of scaling were able to be raised for the first time. 't Hooft discusses his postdoctoral appointment at CERN, his ideas about grouping Feynman diagrams together, and how he became involved in quantum gravity research and Bose condensation. He explains the value in studying instantons for broader questions in QCD, the significance of Hawking’s work on the black hole information paradox, the holographic principle, and why he has diverged with string theorists. 't Hooft describes being present at the start of supersymmetry, and the growing “buzz” that culminated in winning the Nobel Prize. He describes his overall interest in the past twenty years in thinking more deeply about quantum mechanics and he places the foundational disagreement between Einstein and Bohr in historical context. At the end of the interview, 't Hooft surveys the limitations that prevent us from understanding how to merge quantum mechanics and general relativity and why this will require an understanding of how to relate the set of all integer numbers to phenomena of the universe.