Robert M. Wald (; born June 29, 1947 in

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

) is an American

theoretical A theory is a systematic and rational form of abstract thinking about a phenomenon, or the conclusions derived from such thinking. It involves contemplative and logical reasoning, often supported by processes such as observation, experimentation, ...

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

and professor at the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...

. He studies general relativity, black holes, and quantum gravity and has written textbooks on these subjects.

Life and education

He is the son of the mathematician and statistician

Abraham Wald Abraham Wald (; ; , ; – ) was a Hungarian and American mathematician and statistician who contributed to decision theory, geometry and econometrics, and founded the field of sequential analysis. One of his well-known statistical works was ...

and great-grandson of the chief rabbi

Moshe Shmuel Glasner Rabbi Moshe Shmuel Glasner (1856–1924), a Hungarian Talmudic scholar and communal leader, served as chief rabbi of Klausenburg (Kolozsvár in Hungarian, Cluj in Romanian) from 1877 to 1923. In 1923 he left Klausenburg for Jerusalem where he ...

. Wald's parents died in a plane crash when he was three years old. He earned his Bachelor's degree from Columbia University in 1968 and his PhD in physics from Princeton University in 1972, under the supervision of

John Archibald Wheeler John Archibald Wheeler (July 9, 1911April 13, 2008) was an American theoretical physicist. He was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr to e ...

. His doctoral dissertation was titled ''Nonspherical Gravitational Collapse and Black Hole Uniqueness''.

Career and contributions

Between 1972 and 1974, Robert Wald worked as a research associate in physics at the

University of Maryland The University of Maryland, College Park (University of Maryland, UMD, or simply Maryland) is a public land-grant research university in College Park, Maryland, United States. Founded in 1856, UMD is the flagship institution of the Univ ...

. He then moved to the University of Chicago, spending two years as a postdoctoral fellow before joining the faculty in 1976. He wanted to move to Chicago in order to work with

Robert Geroch Robert Geroch (born 1 June 1942 in Akron, Ohio) is an American theoretical physicist and professor at the University of Chicago. He has worked prominently on general relativity and mathematical physics and has promoted the use of category theory ...

and other specialists in gravitation. In 1977, Wald published a popular-science book titled ''Space, Time, and Gravity: The Theory of the Big Bang and Black Holes'' explaining Albert Einstein's general theory of relativity, and its implications in cosmology and astrophysics. The book also gives a survey of what was then ongoing research on

gravitational collapse Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity. Gravitational collapse is a fundamental mechanism for structure formati ...

and

black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...

s. This book grew out of a series of lectures Wald gave as part of the Compton Lectures at the University of Chicago in the spring of 1976. The Compton Lectures, given every Spring and Fall quarter, are intended to explain notable advances in the physical sciences to members of the general public. He published the textbook ''

General Relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...

'' in 1984. Aimed at beginning graduate students, it covers

spinor In geometry and physics, spinors (pronounced "spinner" IPA ) are elements of a complex numbers, complex vector space that can be associated with Euclidean space. A spinor transforms linearly when the Euclidean space is subjected to a slight (infi ...

s, the

variational principle A variational principle is a mathematical procedure that renders a physical problem solvable by the calculus of variations, which concerns finding functions that optimize the values of quantities that depend on those functions. For example, the pr ...

s, the initial-value formulation, (exact) gravitational waves, singularities,

Penrose diagram In theoretical physics, a Penrose diagram (named after mathematical physicist Roger Penrose) is a two-dimensional diagram capturing the causal relations between different points in spacetime through a conformal treatment of infinity. It is an e ...

Hawking radiation Hawking radiation is black-body radiation released outside a black hole's event horizon due to quantum effects according to a model developed by Stephen Hawking in 1974. The radiation was not predicted by previous models which assumed that onc ...

, and black-hole thermodynamics. Wald has taught first-year graduate courses covering a broad range of topics, including classical mechanics, quantum mechanics, statistical mechanics, and electromagnetism. He has also taught courses on

general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...

, his specialty, at both introductory and advanced levels. A particularly effective teacher, he received the Graduate Teaching Award from the University of Chicago in 1997. Wald investigates black holes and their thermodynamics, and gravitational radiation-reaction (or self-force). Due to quantum-mechanical processes, black holes emit particles and therefore have a definite temperature and entropy. Wald has published over 100 research papers on general relativity and

quantum field theory in curved spacetime In theoretical physics, quantum field theory in curved spacetime (QFTCS) is an extension of quantum field theory from Minkowski spacetime to a general curved spacetime. This theory uses a semi-classical approach; it treats spacetime as a fixed ...

, many of which have been cited by hundreds of subsequent papers. In 1993, he described the Wald entropy of a

, which is dependent simply on the area of the event horizon of the black hole. He organized The Symposium on Black Holes and Relativistic Stars in 1996, in honor of the late Nobel Prize-winning theoretical astrophysicist

Subrahmanyan Chandrasekhar Subrahmanyan Chandrasekhar (; 19 October 1910 – 21 August 1995) was an Indian Americans, Indian-American theoretical physicist who made significant contributions to the scientific knowledge about the structure of stars, stellar evolution and ...

. Distinguished speakers of this event included

Stephen Hawking Stephen William Hawking (8January 194214March 2018) was an English theoretical physics, theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between ...

Roger Penrose Sir Roger Penrose (born 8 August 1931) is an English mathematician, mathematical physicist, Philosophy of science, philosopher of science and Nobel Prize in Physics, Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics i ...

and

Martin Rees Martin John Rees, Baron Rees of Ludlow,