First, despite his great contributions to quantum mechanics, he opposed what it evolved into, objecting that nature “does not play dice”. Second, he attempted to devise a unified field theory by generalizing his geometric theory of gravitation to include electromagnetism. As a result, he became increasingly isolated from the mainstream of modern physics.
In 1933, while Einstein was visiting the United States, Adolf Hitler came to power. Einstein did not return to Germany because he objected to the policies of the newly elected Nazi-led government. He settled in the United States and became an American citizen in 1940.
On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential German nuclear weapons program and recommending that the US begin similar research. Einstein supported the Allies, but he generally denounced the idea of nuclear weapons.
On 17 April 1955, Einstein experienced internal bleeding caused by the rupture of an abdominal aortic aneurysm, which had previously been reinforced surgically by Rudolph Nissen in 1948. He took the draft of a speech he was preparing for a television appearance commemorating the state of Israel’s seventh anniversary with him to the hospital, but he did not live to complete it.
Einstein refused surgery, saying, “I want to go when I want. It is tasteless to prolong life artificially. I have done my share; it is time to go. I will do it elegantly.” He died in Princeton Hospital early the next morning at the age of 76, having continued to work until near the end.
*14 March 1879, Ulm, Kingdom of Württemberg, German Empire.
†18 April 1955, Princeton, New Jersey, U.S.
Albert Einstein was a German-born theoretical physicist, widely acknowledged to be one of the greatest physicists of all time. Einstein is known widely for developing the theory of relativity, but he also made important contributions to the development of the theory of quantum mechanics.
Einstein developed an appreciation for music at an early age. In his late journals he wrote: “If I were not a physicist, I would probably be a musician. I often think in music. I live my daydreams in music. I see my life in terms of music… I get most joy in life out of music.”
His mass–energy equivalence formula E = mc2, which arises from relativity theory, has been dubbed “the world’s most famous equation”. His work is also known for its influence on the philosophy of science.
Einstein was born in the German Empire, but moved to Switzerland in 1895, forsaking his German citizenship the following year. In 1901, he acquired Swiss citizenship, which he kept for the rest of his life.
In 1905 Einstein published four groundbreaking papers. These outlined the theory of the photoelectric effect, explained Brownian motion, introduced special relativity, and demonstrated mass-energy equivalence. Einstein thought that the laws of classical mechanics could no longer be reconciled with those of the electromagnetic field, which led him to develop his special theory of relativity. In this year was Einstein also awarded a PhD by the University of Zurich.
He then extended the theory to gravitational fields; he published a paper on general relativity in 1916, introducing his theory of gravitation. In 1917, he applied the general theory of relativity to model the structure of the universe. He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules.
He also investigated the thermal properties of light and the quantum theory of radiation, which laid the foundation of the photon theory of light. However, for much of the later part of his career, he worked on two ultimately unsuccessful endeavors.
At Google’s Zeitgeist Conference in 2011, Hawking said that “philosophy is dead”. He believed that philosophers “have not kept up with modern developments in science” and that scientists “have become the bearers of the torch of discovery in our quest for knowledge”.
In 2006 Hawking expressed concern that life on Earth is at risk from a sudden nuclear war, a genetically engineered virus, global warming, or other dangers humans have not yet thought of. Hawking viewed spaceflight and the colonisation of space as necessary for the future of humanity.
Hawking achieved commercial success with several works of popular science in which he discussed his theories and cosmology in general. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks.
Hawking was a Fellow of the Royal Society, a lifetime member of the Pontifical Academy of Sciences, and a recipient of the Presidential Medal of Freedom, the highest civilian award in the United States.
He died on 14 March 2018 at the age of 76, after living with motor neurone disease for more than 50 years.
*8 January 1942, Oxford, England.
†14 March 2018, Cambridge, England.
Stephen Hawking was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge at the time of his death. He was the Lucasian Professor of Mathematics at the University of Cambridge between 1979 and 2009.
Hawking was born in Oxford into a family of doctors. Hawking began his university education at University College, Oxford in October 1959 at the age of 17, where he received a first-class BA degree in physics. He began his graduate work at Trinity Hall, Cambridge in October 1962, where he obtained his PhD degree in applied mathematics and theoretical physics, specialising in general relativity and cosmology in March 1966.
During this period in 1963 Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually paralysed him over the decades. After the loss of his speech, he was able to communicate through a speech-generating device—initially through use of a handheld switch, and eventually by using a single cheek muscle.
Hawking’s scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Initially, Hawking radiation was controversial.
Hawking was an atheist and believed that “the universe is governed by the laws of science”. He stated: “There is a fundamental difference between religion, which is based on authority and science, which is based on observation and reason. Science will win because it works.”
After the war, Bohr called for international cooperation on nuclear energy. He was involved with the establishment of CERN and the Research Establishment Risø of the Danish Atomic Energy Commission and became the first chairman of the Nordic Institute for Theoretical Physics in 1957.
Heisenberg said of Bohr that he was “primarily a philosopher, not a physicist”. Bohr read the 19th-century Danish Christian existentialist philosopher, Søren Kierkegaard. Richard Rhodes argued in The Making of the Atomic Bomb that Bohr was influenced by Kierkegaard through Høffding. In 1909, Bohr sent his brother Kierkegaard’s Stages on Life’s Way as a birthday gift.
In the enclosed letter, Bohr wrote, “It is the only thing I have to send home; but I do not believe that it would be very easy to find anything better … I even think it is one of the most delightful things I have ever read.” Bohr enjoyed Kierkegaard’s language and literary style, but mentioned that he had some disagreement with Kierkegaard’s philosophy. Some of Bohr’s biographers suggested that this disagreement stemmed from Kierkegaard’s advocacy of Christianity, while Bohr was an atheist.
*7 October 1885, Copenhagen, Denmark.
†18 November 1962, Copenhagen, Denmark.
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research.
Bohr was educated at Gammelholm Latin School, starting when he was seven. In 1903, Bohr enrolled as an undergraduate at Copenhagen University. His major was physics, which he studied under Professor Christian Christiansen, the university’s only professor of physics at that time. He also studied astronomy and mathematics under Professor Thorvald Thiele, and philosophy under Professor Harald Høffding, a friend of his father.
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid.
He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr’s thinking in both science and philosophy.
Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute, which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers, Oskar Klein, George de Hevesy, and Werner Heisenberg. He predicted the existence of a new zirconium-like element, which was named hafnium, after the Latin name for Copenhagen, where it was discovered. Later, the element bohrium was named after him.
During the 1930s Bohr helped refugees from Nazism. After Denmark was occupied by the Germans, he had a famous meeting with Heisenberg, who had become the head of the German nuclear weapon project. In September 1943 word reached Bohr that he was about to be arrested by the Germans, and he fled to Sweden. From there, he was flown to Britain, where he joined the British Tube Alloys nuclear weapons project, and was part of the British mission to the Manhattan Project.
Richard Phillips Feynman
Along with his work in theoretical physics, Feynman has been credited with pioneering the field of quantum computing and introducing the concept of nanotechnology. He held the Richard C. Tolman professorship in theoretical physics at the California Institute of Technology.
Feynman was a keen popularizer of physics through both books and lectures, including a 1959 talk on top-down nanotechnology called There’s Plenty of Room at the Bottom and the three-volume publication of his undergraduate lectures, The Feynman Lectures on Physics.
Feynman also became known through his semi-autobiographical books Surely You’re Joking, Mr. Feynman! and What Do You Care What Other People Think?, and books written about him such as Tuva or Bust! by Ralph Leighton and the biography Genius: The Life and Science of Richard Feynman by James Gleick.
In 1978, Feynman sought medical treatment for abdominal pains and was diagnosed with liposarcoma, a rare form of cancer. Surgeons removed a tumor the size of a football that had crushed one kidney and his spleen. Further operations were performed in October 1986 and October 1987. He was again hospitalized at the UCLA Medical Center on February 3, 1988. A ruptured duodenal ulcer caused kidney failure, and he declined to undergo the dialysis that might have prolonged his life for a few months. Watched over by his wife Gweneth, sister Joan, and cousin Frances Lewine, he died on February 15, 1988, at age 69.
* 11 May 1918, New York City, U.S.
† 15 February 1988, Los Angeles, California, U.S.
Richard Phillips Feynman was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfluidity of supercooled liquid helium, as well as his work in particle physics for which he proposed the parton model. For contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin’ichirō Tomonaga.
Upon starting high school, Feynman was quickly promoted to a higher math class. An IQ test administered in high school estimated his IQ at 125—high but “merely respectable”, according to biographer James Gleick. Years later he declined to join Mensa International, saying that his IQ was too low.
When Feynman was 15, he taught himself trigonometry, advanced algebra, infinite series, analytic geometry, and both differential and integral calculus. Before entering college, he was experimenting with and deriving mathematical topics such as the half-derivative using his own notation.
He created special symbols for logarithm, sine, cosine and tangent functions so they did not look like three variables multiplied together, and for the derivative, to remove the temptation of canceling out the s in .
Feynman developed a widely used pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams.
During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World, he was ranked the seventh greatest physicist of all time. He assisted in the development of the atomic bomb during World War II and became known to a wide public in the 1980s as a member of the Rogers Commission, the panel that investigated the Space Shuttle Challenger disaster.
Fermi left Italy in 1938 to escape new Italian racial laws that affected his Jewish wife, Laura Capon. He emigrated to the United States, where he worked on the Manhattan Project during World War II. Fermi led the team that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first human-created, self-sustaining nuclear chain reaction.
He was on hand when the X-10 Graphite Reactor at Oak Ridge, Tennessee, went critical in 1943, and when the B Reactor at the Hanford Site did so the next year. At Los Alamos, he headed F Division, part of which worked on Edward Teller’s thermonuclear “Super” bomb. He was present at the Trinity test on 16 July 1945, where he used his Fermi method to estimate the bomb’s yield.
After the war, Fermi served under J. Robert Oppenheimer on the General Advisory Committee, which advised the Atomic Energy Commission on nuclear matters. After the detonation of the first Soviet fission bomb in August 1949, he strongly opposed the development of a hydrogen bomb on both moral and technical grounds. He was among the scientists who testified on Oppenheimer’s behalf at the 1954 hearing that resulted in the denial of Oppenheimer’s security clearance.
*29 September 1901, Rome, Kingdom of Italy
†28 November 1954, Chicago, Illinois, U.S.
Enrico Fermi was an Italian physicist and the creator of the world’s first nuclear reactor, the Chicago Pile-1. He was one of very few physicists to excel in both theoretical physics and experimental physics. Fermi was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements.
With his colleagues, Fermi filed several patents related to the use of nuclear power, all of which were taken over by the US government. He made significant contributions to the development of statistical mechanics, quantum theory, and nuclear and particle physics.
Fermi’s first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his exclusion principle in 1925, Fermi followed with a paper in which he applied the principle to an ideal gas, employing a statistical formulation now known as Fermi–Dirac statistics. Today, particles that obey the exclusion principle are called “fermions”. Pauli later postulated the existence of an uncharged invisible particle emitted along with an electron during beta decay, to satisfy the law of conservation of energy. Fermi took up this idea, developing a model that incorporated the postulated particle, which he named the “neutrino”.
His theory, later referred to as Fermi’s interaction and now called weak interaction, described one of the four fundamental interactions in nature. Through experiments inducing radioactivity with the recently discovered neutron, Fermi discovered that slow neutrons were more easily captured by atomic nuclei than fast ones, and he developed the Fermi age equation to describe this.
After bombarding thorium and uranium with slow neutrons, he concluded that he had created new elements. Although he was awarded the Nobel Prize for this discovery, the new elements were later revealed to be nuclear fission products.
Dirac was known among his colleagues for his precise and taciturn nature. His colleagues in Cambridge jokingly defined a unit called a “dirac”, which was one word per hour. When Niels Bohr complained that he did not know how to finish a sentence in a scientific article he was writing, Dirac replied, “I was taught at school never to start a sentence without knowing the end of it.”
In 1975, Dirac gave a series of five lectures at the University of New South Wales which were subsequently published as a book, Directions in Physics (1978). He donated the royalties from this book to the university for the establishment of the Dirac Lecture Series. The Silver Dirac Medal for the Advancement of Theoretical Physics is awarded by the University of New South Wales to commemorate the lecture.
In 1984, Dirac died in Tallahassee, Florida.
Immediately after his death, two organizations of professional physicists established annual awards in Dirac’s memory. The Institute of Physics, the United Kingdom’s professional body for physicists, awards the Paul Dirac Medal for “outstanding contributions to theoretical (including mathematical and computational) physics”.
* 8 August 1902 Bristol, England
† 20 October 1984 Tallahassee, Florida, U.S.
Paul Adrien Maurice Dirac was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the University of Cambridge, was a member of the Center for Theoretical Studies, University of Miami, and spent the last decade of his life at Florida State University.
Dirac made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics. Among other discoveries, he formulated the Dirac equation which describes the behaviour of fermions and predicted the existence of antimatter. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger “for the discovery of new productive forms of atomic theory”. He also made significant contributions to the reconciliation of general relativity with quantum mechanics.
Dirac was educated first at Bishop Road Primary School and then at the all-boys Merchant Venturers’ Technical College, where his father was a French teacher. The school was an institution attached to the University of Bristol, which shared grounds and staff. It emphasised technical subjects like bricklaying, shoemaking and metal work, and modern languages. This was unusual at a time when secondary education in Britain was still dedicated largely to the classics, and something for which Dirac would later express his gratitude.
Dirac studied electrical engineering on a City of Bristol University Scholarship at the University of Bristol’s engineering faculty, which was co-located with the Merchant Venturers’ Technical College. Shortly before he completed his degree in 1921, he sat for the entrance examination for St John’s College, Cambridge. He passed and was awarded a £70 scholarship, but this fell short of the amount of money required to live and study at Cambridge.
Despite his having graduated with a first class honours Bachelor of Science degree in engineering, the economic climate of the post-war depression was such that he was unable to find work as an engineer. Instead, he took up an offer to study for a Bachelor of Arts degree in mathematics at the University of Bristol free of charge. He was permitted to skip the first year of the course owing to his engineering degree.
Dirac was regarded by his friends and colleagues as unusual in character. In a 1926 letter to Paul Ehrenfest, Albert Einstein wrote of Dirac, “I have trouble with Dirac. This balancing on the dizzying path between genius and madness is awful.” In another letter he wrote, “I don’t understand Dirac at all (Compton effect).”
Frank Donald Drake
He is one of the pioneers of the modern field of the search for extraterrestrial intelligence with Giuseppe Cocconi, Philip Morrison, Iosif Shklovsky, and Carl Sagan.
Drake co-designed the Pioneer plaque with Carl Sagan in 1972, the first physical message sent into space. The plaque was designed to be understandable by extraterrestrials should they encounter it. He later supervised the creation of the Voyager Golden Record. He was elected to the American Academy of Arts and Sciences in 1974.
Drake is a member of the National Academy of Sciences where he chaired the Board of Physics and Astronomy of the National Research Council (1989–1992). He also served as President of the Astronomical Society of the Pacific. He was a Professor of Astronomy at Cornell University (1964–1984) and served as the Director of the Arecibo Observatory. As of 2010, he was involved in “The Carl Sagan Center for the Study of life in the Universe” at the SETI Institute.
He is Emeritus Professor of Astronomy and Astrophysics at the University of California at Santa Cruz where he also served as Dean of Natural Sciences (1984–1988). He serves on the Board of Trustees of the SETI Institute.
Drake Planetarium at Norwood High School in Norwood, Ohio is named for Drake and linked to NASA.
*18 May 1930, Chicago, Illinois
Frank Donald Drake is an American astronomer and astrophysicist. He is involved in the search for extraterrestrial intelligence, including the founding of SETI, mounting the first observational attempts at detecting extraterrestrial communications in 1960 in Project Ozma, developing the Drake equation, and as the creator of the Arecibo Message, a digital encoding of an astronomical and biological description of the Earth and its lifeforms for transmission into the cosmos.
Born on May 28, 1930, in Chicago, Illinois, as a youth Drake loved electronics and chemistry. He reports that he considered the possibility of life existing on other planets as an eight-year-old, but never discussed the idea with his family or teachers due to the prevalent religious ideology.
He enrolled at Cornell University on a Navy Reserve Officer Training Corps scholarship. Once there he began studying astronomy. His ideas about the possibility of extraterrestrial life were reinforced by a lecture from astrophysicist Otto Struve in 1951. After college, he served briefly as an electronics officer on the heavy cruiser USS Albany. He then went on to graduate school at Harvard to study radio astronomy.
Drake’s hobbies include lapidary and the cultivation of orchids.
Although explicitly linked with modern views on the likelihood and detectability of extraterrestrial civilizations, Drake started his career undertaking radio astronomical research at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, and later the Jet Propulsion Laboratory. He conducted key measurements which revealed the presence of a Jovian ionosphere and magnetosphere.
In the 1960s, Drake spearheaded the conversion of the Arecibo Observatory to a radio astronomical facility, later updated in 1974 and 1996. As a researcher, Drake was involved in the early work on pulsars. In this period, Drake was a professor at Cornell University and Director of the National Astronomy and Ionosphere Center (NAIC) – the formal name for the Arecibo facility. In 1974 he wrote the Arecibo message.
J. Robert Oppenheimer
In his first year, he was admitted to graduate standing in physics on the basis of independent study, which meant he was not required to take the basic classes and could enroll instead in advanced ones. He was attracted to experimental physics by a course on thermodynamics that was taught by Percy Bridgman. He graduated summa cum laude in three years.
After the war ended, Oppenheimer became chairman of the influential General Advisory Committee of the newly created United States Atomic Energy Commission. He used that position to lobby for international control of nuclear power to avert nuclear proliferation and a nuclear arms race with the Soviet Union. He opposed the development of the hydrogen bomb during a 1949–1950 governmental debate on the question and subsequently took stances on defense-related issues that provoked the ire of some factions in the U.S. government and military.
During the Second Red Scare, those stances, together with past associations Oppenheimer had with people and organizations affiliated with the Communist Party, led to him suffering the revocation of his security clearance in a much-written-about hearing in 1954. Effectively stripped of his direct political influence, he continued to lecture, write and work in physics. Nine years later, President John F. Kennedy awarded him with the Enrico Fermi Award as a gesture of political rehabilitation.
Oppenheimer was a chain smoker who was diagnosed with throat cancer in late 1965. After inconclusive surgery, he underwent unsuccessful radiation treatment and chemotherapy late in 1966. He fell into a coma on February 15, 1967, and died at his home in Princeton, New Jersey, on February 18, aged 62.
Oppenheimer’s achievements in physics included the Born–Oppenheimer approximation for molecular wave functions, work on the theory of electrons and positrons, the Oppenheimer–Phillips process in nuclear fusion, and the first prediction of quantum tunneling. With his students he also made important contributions to the modern theory of neutron stars and black holes, as well as to quantum mechanics, quantum field theory, and the interactions of cosmic rays.
As a teacher and promoter of science, he is remembered as a founding father of the American school of theoretical physics that gained world prominence in the 1930s. After World War II, he became director of the Institute for Advanced Study in Princeton, New Jersey.
* 22.4 1904, New York City, New York, U.S.
† 18.2 1967, Princeton, New Jersey, U.S.
J. Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. Oppenheimer was the wartime head of the Los Alamos Laboratory and is among those who are credited with being the “father of the atomic bomb” for their role in the Manhattan Project, the World War II undertaking that developed the first nuclear weapons. The first atomic bomb was successfully detonated on July 16, 1945, in the Trinity test in New Mexico.
Oppenheimer later remarked that it brought to mind words from the Bhagavad Gita: “Now I am become Death, the destroyer of worlds.” In August 1945, the weapons were used in the atomic bombings of Hiroshima and Nagasaki.
Oppenheimer was initially educated at Alcuin Preparatory School; in 1911, he entered the Ethical Culture Society School. Oppenheimer was a versatile scholar, interested in English and French literature, and particularly in mineralogy. He completed the third and fourth grades in one year and skipped half the eighth grade. During his final year, he became interested in chemistry.
He entered Harvard College one year after graduation, at age 18, because he suffered an attack of colitis while prospecting in Joachimstal during a family summer vacation in Europe. To help him recover from the illness, his father enlisted the help of his English teacher Herbert Smith who took him to New Mexico, where Oppenheimer fell in love with horseback riding and the southwestern United States.
Oppenheimer majored in chemistry, but Harvard required science students to also study history, literature, and philosophy or mathematics. He compensated for his late start by taking six courses each term and was admitted to the undergraduate honor society Phi Beta Kappa.
In 2010, Penrose reported possible evidence, based on concentric circles found in Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background sky, of an earlier universe existing before the Big Bang of our own present universe.
He mentions this evidence in the epilogue of his 2010 book Cycles of Time, a book in which he presents his reasons, to do with Einstein’s field equations, the Weyl curvature C, and the Weyl curvature hypothesis (WCH), that the transition at the Big Bang could have been smooth enough for a previous universe to survive it. He made several conjectures about C and the WCH, some of which were subsequently proved by others, and he also popularized his conformal cyclic cosmology (CCC) theory.
In simple terms, he believes that the singularity in Einstein’s field equation at the Big Bang is only an apparent singularity, similar to the well-known apparent singularity at the event horizon of a black hole. The latter singularity can be removed by a change of coordinate system, and Penrose proposes a different change of coordinate system that will remove the singularity at the big bang. One implication of this is that the major events at the Big Bang can be understood without unifying general relativity and quantum mechanics, and therefore we are not necessarily constrained by the Wheeler–DeWitt equation, which disrupts time. Alternatively, one can use the Einstein–Maxwell–Dirac equations.
* 8 August 1931, Colchester, England, UK
Sir Roger Penrose OM FRS is a British mathematical physicist, mathematician, philosopher of science and Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics at the University of Oxford, an emeritus fellow of Wadham College, Oxford, and an honorary fellow of St John’s College, Cambridge, and University College London.
Penrose has made contributions to the mathematical physics of general relativity and cosmology. He has received several prizes and awards, including the 1988 Wolf Prize in Physics, which he shared with Stephen Hawking for the Penrose–Hawking singularity theorems, and one half of the 2020 Nobel Prize in Physics “for the discovery that black hole formation is a robust prediction of the general theory of relativity”.
Penrose spent World War II as a child in Canada where his father worked in London, Ontario. Penrose attended University College School and University College London, where he graduated with a first class degree in mathematics.
In 1955, whilst still a student, Penrose reintroduced the E. H. Moore generalised matrix inverse, also known as the Moore–Penrose inverse, after it had been reinvented by Arne Bjerhammar in 1951. Having started research under the professor of geometry and astronomy, Sir W. V. D. Hodge, Penrose finished his PhD at St John’s College, Cambridge, in 1958, with a thesis on “tensor methods in algebraic geometry” under algebraist and geometer John A. Todd.
He devised and popularised the Penrose triangle in the 1950s, describing it as “impossibility in its purest form”, and exchanged material with the artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it. Escher’s Waterfall, and Ascending and Descending were in turn inspired by Penrose.
In 2004, Penrose released The Road to Reality: A Complete Guide to the Laws of the Universe, a 1,099-page comprehensive guide to the Laws of Physics that includes an explanation of his own theory. The Penrose Interpretation predicts the relationship between quantum mechanics and general relativity, and proposes that a quantum state remains in superposition until the difference of space-time curvature attains a significant level.
John Archibald Wheeler
He received a National Research Council fellowship, which he used to study under Gregory Breit at New York University in 1933 and 1934, and then in Copenhagen under Niels Bohr in 1934 and 1935. In a 1934 paper, Breit and Wheeler introduced the Breit–Wheeler process, a mechanism by which photons can be potentially transformed into matter in the form of electron-positron pairs.
During 1939 he collaborated with Bohr to write a series of papers using the liquid drop model to explain the mechanism of fission. During World War II, he worked with the Manhattan Project’s Metallurgical Laboratory in Chicago, where he helped design nuclear reactors, and then at the Hanford Site in Richland, Washington, where he helped DuPont build them. He returned to Princeton after the war ended, but returned to government service to help design and build the hydrogen bomb in the early 1950s.
Wheeler speculated that reality is created by observers in the universe. “How does something arise from nothing?”, he asked about the existence of space and time. He also coined the term “Participatory Anthropic Principle” (PAP), a version of a Strong Anthropic Principle.
In 1990, Wheeler suggested that information is fundamental to the physics of the universe. According to this “it from bit” doctrine, all things physical are information-theoretic in origin.
For most of his career, Wheeler was a professor of physics at Princeton University, which he joined in 1938, remaining until his retirement in 1976. At Princeton he supervised 46 PhD students, more than any other professor in the Princeton physics department. Wheeler’s graduate students included Jacob Bekenstein, Hugh Everett, Richard Feynman, David Hill, Bei-Lok Hu, John R. Klauder, Charles Misner, Kip Thorne, William Unruh, Robert M. Wald, Katharine Way, and Arthur Wightman.
On April 13, 2008, Wheeler died of pneumonia at the age of 96 in Hightstown, New Jersey.
* 9 July 1911, Jacksonville, Florida, United States
†13 April, 2008, Hightstown, New Jersey, United States
John Archibald Wheeler (July 9, 1911 – April 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 in explaining the basic principles behind nuclear fission. Together with Gregory Breit, Wheeler developed the concept of the Breit–Wheeler process. He is best known for using the term “black hole” for objects with gravitational collapse already predicted during the early 20th century, for inventing the terms “quantum foam”, “neutron moderator”, “wormhole” and “it from bit”, and for hypothesizing the “one-electron universe”.
Wheeler grew up in Youngstown, Ohio, but spent a year in 1921 to 1922 on a farm in Benson, Vermont, where Wheeler attended a one-room school. After they returned to Youngstown he attended Rayen High School.
After graduating from the Baltimore City College high school in 1926, Wheeler entered Johns Hopkins University with a scholarship from the state of Maryland. He published his first scientific paper in 1930, as part of a summer job at the National Bureau of Standards. He earned his doctorate in 1933. His dissertation research work, carried out under the supervision of Karl Herzfeld, was on the “Theory of the Dispersion and Absorption of Helium”.
In April 1885, the University of Kiel appointed Planck as associate professor of theoretical physics. Further work on entropy and its treatment, especially as applied in physical chemistry, followed. He published his Treatise on Thermodynamics in 1897. He proposed a thermodynamic basis for Svante Arrhenius’s theory of electrolytic dissociation.
In 1905, the three epochal papers by Albert Einstein were published in the journal Annalen der Physik. Planck was among the few who immediately recognized the significance of the special theory of relativity. Thanks to his influence, this theory was soon widely accepted in Germany. Planck also contributed considerably to extend the special theory of relativity. For example, he recast the theory in terms of classical action.
Planck’s son Erwin was arrested by the Gestapo following the attempted assassination of Hitler in the 20 July plot. Erwin was hanged at Berlin’s Plötzensee Prison in January 1945. The death of his son destroyed much of Planck’s will to live. After the end of the war Planck, his second wife, and his son by her were brought to a relative in Göttingen, where Planck died on 4 October 1947. His grave is situated in the old Stadtfriedhof in Göttingen.
In 1948, the German scientific institution Kaiser Wilhelm Society (of which Planck was twice president) was renamed Max Planck Society (MPS). The MPS now includes 83 institutions representing a wide range of scientific directions.
*23 April 1858, Kiel, Duchy of Holstein
†4 October 1947, Göttingen, Lower Saxony, Allied-occupied Germany
Max Karl Ernst Ludwig Planck, ForMemRS was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of quantum theory, which revolutionized human understanding of atomic and subatomic processes.
War was common during Planck’s early years and among his earliest memories was the marching of Prussian and Austrian troops into Kiel during the Second Schleswig War in 1864. In 1867 the family moved to Munich, and Planck enrolled in the Maximilians gymnasium school, where he came under the tutelage of Hermann Müller, a mathematician who took an interest in the youth, and taught him astronomy and mechanics as well as mathematics. It was from Müller that Planck first learned the principle of conservation of energy. Planck graduated early, at age 17. This is how Planck first came in contact with the field of physics.
Planck was gifted when it came to music. He took singing lessons and played piano, organ and cello, and composed songs and operas. However, instead of music he chose to study physics.
The Munich physics professor Philipp von Jolly advised Planck against going into physics, saying, “In this field, almost everything is already discovered, and all that remains is to fill a few holes.” Planck replied that he did not wish to discover new things, but only to understand the known fundamentals of the field, and so began his studies in 1874 at the University of Munich.
In 1877, he went to the Friedrich Wilhelms University in Berlin for a year of study with physicists Hermann von Helmholtz and Gustav Kirchhoff and mathematician Karl Weierstrass. He wrote that Helmholtz was never quite prepared, spoke slowly, miscalculated endlessly, and bored his listeners, while Kirchhoff spoke in carefully prepared lectures which were dry and monotonous.
James Clerk Maxwell
*13 June 1831, Edinburgh, Scotland, United Kingdom
†5 November 1879, Cambridge, England, United Kingdom
James Clerk Maxwell FRSE FRS was a Scottish scientist in the field of mathematical physics. His most notable achievement was to formulate the classical theory of electromagnetic radiation, bringing together for the first time electricity, magnetism, and light as different manifestations of the same phenomenon. Maxwell’s equations for electromagnetism have been called the “second great unification in physics” where the first one had been realised by Isaac Newton.
Maxwell was fascinated by geometry at an early age, rediscovering the regular polyhedra before he received any formal instruction. Despite his winning the school’s scripture biography prize in his second year, his academic work remained unnoticed until, at the age of 13, he won the school’s mathematical medal and first prize for both English and poetry.
Maxwell’s interests ranged far beyond the school syllabus and he did not pay particular attention to examination performance. He wrote his first scientific paper at the age of 14. In it he described a mechanical means of drawing mathematical curves with a piece of twine, and the properties of ellipses, Cartesian ovals, and related curves with more than two foci.
He helped develop the Maxwell–Boltzmann distribution, a statistical means of describing aspects of the kinetic theory of gases. He is also known for presenting the first durable colour photograph in 1861 and for his foundational work on analysing the rigidity of rod-and-joint frameworks (trusses) like those in many bridges.
Maxwell died in Cambridge of abdominal cancer on 5 November 1879 at the age of 48. His mother had died at the same age of the same type of cancer.
His discoveries helped usher in the era of modern physics, laying the foundation for such fields as special relativity and quantum mechanics. Many physicists regard Maxwell as the 19th-century scientist having the greatest influence on 20th-century physics.
His contributions to the science are considered by many to be of the same magnitude as those of Isaac Newton and Albert Einstein. On the centenary of Maxwell’s birthday, Einstein described Maxwell’s work as the “most profound and the most fruitful that physics has experienced since the time of Newton”.
Einstein, when he visited the University of Cambridge in 1922, was told by his host that he had done great things because he stood on Newton’s shoulders; Einstein replied: “No I don’t. I stand on the shoulders of Maxwell.”
Maxwell left the Academy in 1847 at age 16 and began attending classes at the University of Edinburgh. He had the opportunity to attend the University of Cambridge, but decided, after his first term, to complete the full course of his undergraduate studies at Edinburgh.
In October 1850, already an accomplished mathematician, Maxwell left Scotland for the University of Cambridge. He initially attended Peterhouse, however before the end of his first term transferred to Trinity, where he believed it would be easier to obtain a fellowship.
In 1854, Maxwell graduated from Trinity with a degree in mathematics. He scored second highest in the final examination, coming behind Edward Routh and earning himself the title of Second Wrangler. He was later declared equal with Routh in the more exacting ordeal of the Smith’s Prize examination.
With the publication of “A Dynamical Theory of the Electromagnetic Field” in 1865, Maxwell demonstrated that electric and magnetic fields travel through space as waves moving at the speed of light.He proposed that light is an undulation in the same medium that is the cause of electric and magnetic phenomena. The unification of light and electrical phenomena led his prediction of the existence of radio waves. Maxwell is also regarded as a founder of the modern field of electrical engineering.
Susskind was an assistant professor of physics, then an associate professor at Yeshiva University, after which he went for a year to the Tel Aviv University, returning to Yeshiva to become a professor of physics. Since 1979 he has been professor of physics at Stanford University, and since 2000 has held the Felix Bloch professorship of physics.
Susskind was one of at least three physicists, alongside Yoichiro Nambu and Holger Bech Nielsen, who independently discovered during or around 1970 that the Veneziano dual resonance model of strong interactions could be described by a quantum mechanical model of oscillating strings, and was the first to propose the idea of the string theory landscape.
Susskind was awarded the 1998 J. J. Sakurai Prize for his “pioneering contributions to hadronic string models, lattice gauge theories, quantum chromodynamics, and dynamical symmetry breaking.” Susskind’s hallmark, according to colleagues, has been the application of “brilliant imagination and originality to the theoretical study of the nature of the elementary particles and forces that make up the physical world.” Also Susskind was awarded the the 2018 Oskar Klein Medal.
In 2007, Susskind joined the faculty of Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, as an associate member. He has been elected to the National Academy of Sciences and the American Academy of Arts and Sciences.
He is a member of the US National Academy of Sciences, and the American Academy of Arts and Sciences, an associate member of the faculty of Canada’s Perimeter Institute for Theoretical Physics, and a distinguished professor of the Korea Institute for Advanced Study.
Susskind is the author of several popular science books like The Cosmic Landscape, The Black Hole War and The Theoretical Minimum book series.
*20 May 1940, New York City, New York, US
Leonard Susskind is an American physicist, who is a professor of theoretical physics at Stanford University, and founding director of the Stanford Institute for Theoretical Physics. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology.
Susskind is widely regarded as one of the fathers of string theory. He was the first to give a precise string-theoretic interpretation of the holographic principle in 1995 and the first to introduce the idea of the string theory landscape in 2003.
Leonard Susskind was born in the South Bronx in New York City. He began working as a plumber at the age of 16, taking over from his father who had become ill. Later, he enrolled in the City College of New York as an engineering student, graduating with a B.S. in physics in 1962.
In an interview in the Los Angeles Times, Susskind recalls a discussion with his father that changed his career path: “When I told my father I wanted to be a physicist, he said, ‘Hell no, you ain’t going to work in a drug store.’ I said, ‘No, not a pharmacist.’ I said, ‘Like Einstein.’ He poked me in the chest with a piece of plumbing pipe. ‘You ain’t going to be no engineer,’ he said. ‘You’re going to be Einstein.'” Susskind then studied at Cornell University under Peter A. Carruthers, where he earned his Ph.D. in 1965.
*12 August 1887, Vienna, Austria-Hungary
†4 January 1961, Vienna, Austria
Erwin Rudolf Josef Alexander Schrödinger was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in quantum theory. For example in January 1926 he developed the Schrödinger equation provides a way to calculate the wave function of a system and how it changes dynamically in time.
In addition, he was the author of many works on various aspects of physics: statistical mechanics and thermodynamics, physics of dielectrics, colour theory, electrodynamics, general relativity, and cosmology, and he made several attempts to construct a unified field theory. In his book What Is Life? Schrödinger addressed the problems of genetics, looking at the phenomenon of life from the point of view of physics.
In 1911, Schrödinger became an assistant to Exner. At an early age, Schrödinger was strongly influenced by Arthur Schopenhauer. As a result of his extensive reading of Schopenhauer’s works, he became deeply interested throughout his life in colour theory and philosophy. In his lecture “Mind and Matter”, he said that “The world extended in space and time is but our representation.”
In the first years of his career Schrödinger became acquainted with the ideas of quantum theory, developed in the works of Max Planck, Albert Einstein, Niels Bohr, Arnold Sommerfeld, and others. This knowledge helped him work on some problems in theoretical physics, but the Austrian scientist at the time was not yet ready to part with the traditional methods of classical physics.
In 1920 he became the assistant to Max Wien, in Jena, and in September 1920 he attained the position of ao. Prof. (associate professor) in Stuttgart. In 1921, he became o. Prof. (full professor), in Wrocław. In 1921, he moved to the University of Zürich.
In 1927, he succeeded Max Planck at the Friedrich Wilhelm University in Berlin. In 1933, Schrödinger decided to leave Germany because he disliked the Nazis’ antisemitism. He became a Fellow of Magdalen College at the University of Oxford. Soon after he arrived, he received the Nobel Prize together with Paul Dirac.
His position at Oxford did not work out well; his unconventional domestic arrangements, sharing living quarters with two women, were not met with acceptance. In the midst of these tenure issues in 1935, after extensive correspondence with Albert Einstein, he proposed what is now called the Schrödinger’s cat thought experiment.
On 4 January 1961, Schrödinger died of tuberculosis, aged 73, in Vienna.
He paid great attention to the philosophical aspects of science, ancient and oriental philosophical concepts, ethics, and religion. He also wrote on philosophy and theoretical biology. He is also known for his “Schrödinger’s cat” thought experiment.
Between 1906 and 1910 Schrödinger studied at the University of Vienna under the physicists Franz S. Exner and Friedrich Hasenöhrl. He received his doctorate at Vienna under Hasenöhrl. He also conducted experimental work with Karl Wilhelm Friedrich “Fritz” Kohlrausch.
Early in his life, Schrödinger experimented in the fields of electrical engineering, atmospheric electricity, and atmospheric radioactivity, but he usually worked with his former teacher Franz Exner. He also studied vibrational theory, the theory of Brownian movement, and mathematical statistics.
He also formulated an empirical law of cooling, made the first theoretical calculation of the speed of sound, and introduced the notion of a Newtonian fluid. In addition to his work on calculus, as a mathematician Newton contributed to the study of power series, generalised the binomial theorem to non-integer exponents, developed a method for approximating the roots of a function, and classified most of the cubic plane curves.
Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge. He was a devout but unorthodox Christian who privately rejected the doctrine of the Trinity.
Unusually for a member of the Cambridge faculty of the day, he refused to take holy orders in the Church of England. Beyond his work on the mathematical sciences, Newton dedicated much of his time to the study of alchemy and biblical chronology, but most of his work in those areas remained unpublished until long after his death.
Politically and personally tied to the Whig party, Newton served two brief terms as Member of Parliament for the University of Cambridge, in 1689–1690 and 1701–1702.
He was knighted by Queen Anne in 1705 and spent the last three decades of his life in London, serving as Warden (1696–1699) and Master (1699–1727) of the Royal Mint, as well as president of the Royal Society (1703–1727).
Newton died in his sleep in London on 20 March 1727.
*25 December 1642, Woolsthorpe-by-Colsterworth, Lincolnshire, England
†31 March 1727, Kensington, Middlesex, Great Britain
Sir Isaac Newton PRS was an English mathematician, physicist, astronomer, theologian, and author (described in his time as a “natural philosopher”) who is widely recognised as one of the greatest mathematicians and most influential scientists of all time and as a key figure in the scientific revolution.
His book Philosophiæ Naturalis Principia Mathematica, first published in 1687, established classical mechanics. Newton also made seminal contributions to optics, and shares credit with German mathematician Gottfried Wilhelm Leibniz for developing the infinitesimal calculus.
In Principia, Newton formulated the laws of motion and universal gravitation that formed the dominant scientific viewpoint until it was superseded by the theory of relativity. Newton used his mathematical description of gravity to derive Kepler’s laws of planetary motion, account for tides, the trajectories of comets, the precession of the equinoxes and other phenomena, eradicating doubt about the Solar System’s heliocentricity.
He demonstrated that the motion of objects on Earth and celestial bodies could be accounted for by the same principles. Newton’s inference that the Earth is an oblate spheroid was later confirmed by the geodetic measurements of Maupertuis, La Condamine, and others, convincing most European scientists of the superiority of Newtonian mechanics over earlier systems.
Newton built the first practical reflecting telescope and developed a sophisticated theory of colour based on the observation that a prism separates white light into the colours of the visible spectrum. His work on light was collected in his highly influential book Opticks, published in 1704.
He received his doctorate in 1923 at Munich under Sommerfeld. At Göttingen, under Born, he completed his habilitation in 1924 with a Habilitationsschrift (habilitation thesis) on the anomalous Zeeman effect.
From 1924 to 1927, Heisenberg was a Privatdozent at Göttingen, meaning he was qualified to teach and examine independently, without having a chair. From 17 September 1924 to 1 May 1925, under an International Education Board Rockefeller Foundation fellowship, Heisenberg went to do research with Niels Bohr, director of the Institute of Theoretical Physics at the University of Copenhagen.
In 1928, the British mathematical physicist Paul Dirac had derived his relativistic wave equation of quantum mechanics, which implied the existence of positive electrons, later to be named positrons. In 1932, from a cloud chamber photograph of cosmic rays, the American physicist Carl David Anderson identified a track as having been made by a positron. In mid-1933, Heisenberg presented his theory of the positron.
Following World War II, he was appointed director of the Kaiser Wilhelm Institute for Physics, which soon thereafter was renamed the Max Planck Institute for Physics. He was director of the institute until it was moved to Munich in 1958. He then became director of the Max Planck Institute for Physics and Astrophysics from 1960 to 1970.
Heisenberg was also president of the German Research Council, chairman of the Commission for Atomic Physics, chairman of the Nuclear Physics Working Group, and president of the Alexander von Humboldt Foundation.
Heisenberg died of kidney cancer at his home, on 1 February 1976. The next evening, his colleagues and friends walked in remembrance from the Institute of Physics to his home, lit a candle and placed it in front of his door.
* 5 December 1901, Würzburg, Bavaria, German Empire
†1 February 1976, Munich, Bavaria, West Germany
Werner Karl Heisenberg was a German theoretical physicist and one of the key pioneers of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, this matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. Heisenberg was awarded the 1932 Nobel Prize in Physics “for the creation of quantum mechanics”.
Heisenberg also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles. He was a principal scientist in the German nuclear weapons program during World War II. He was also instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957.
His autobiography starts with the young Heisenberg in his late teenage years, reading Plato’s Timaeus while hiking in the Bavarian Alps.Heisenberg recounted the philosophical conversations with his fellow students and teachers on understanding the atom while receiving his scientific training in Munich, Göttingen and Copenhagen.
Heisenberg would later state that “My mind was formed by studying philosophy, Plato and that sort of thing”. and that “Modern physics has definitely decided in favor of Plato. In fact the smallest units of matter are not physical objects in the ordinary sense; they are forms, ideas which can be expressed unambiguously only in mathematical language”
Heisenberg arrived at Munich in 1919 as a member of the Freikorps to fight the Bavarian Soviet Republic established a year earlier. Five decades later he recalled those days as youthful fun, like “playing cops and robbers and so on; it was nothing serious at all.”
He studied physics and mathematics from 1920 to 1923 at the Ludwig Maximilian University of Munich and the Georg-August University of Göttingen. At Munich, he studied under Arnold Sommerfeld and Wilhelm Wien. At Göttingen, he studied physics with Max Born and James Franck and mathematics with David Hilbert.
The German annexation of Austria in 1938 made Pauli a German citizen, which became a problem for him in 1939 after World War II broke out. In 1940, he tried in vain to obtain Swiss citizenship, which would have allowed him to remain at the ETH.
In 1940, Pauli moved to the United States, where he was employed as a professor of theoretical physics at the Institute for Advanced Study. In 1946, after the war, he became a naturalized U.S. citizen and returned to Zurich, where he mostly remained for the rest of his life. In 1949, he was granted Swiss citizenship.
In 1958, Pauli was awarded the Max Planck medal. The same year, he fell ill with pancreatic cancer. When his last assistant, Charles Enz, visited him at the Rotkreuz hospital in Zurich, Pauli asked him, “Did you see the room number?” It was 137. Throughout his life, Pauli had been preoccupied with
the question of why the fine-structure constant, a dimensionless fundamental constant, has a value nearly equal to 1/137. Pauli died in that room on 15 December 1958.
*25 April 1900, Vienna, Austria-Hungary
†15 December 1958, Zurich, Switzerland
Wolfgang Ernst Pauli was an Austrian theoretical physicist and one of the pioneers of quantum physics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics for his “decisive contribution through his discovery of a new law of Nature, the exclusion principle or Pauli principle”. The discovery involved spin theory, which is the basis of a theory of the structure of matter.
Pauli attended the Döblinger-Gymnasium in Vienna, graduating with distinction in 1918. Two months later, he published his first paper, on Albert Einstein’s theory of general relativity. He attended the Ludwig-Maximilians University in Munich, working under Arnold Sommerfeld, where he received his PhD in July 1921 for his thesis on the quantum theory of ionized diatomic hydrogen (H2+)
Sommerfeld asked Pauli to review the theory of relativity for the Encyklopädie der mathematischen Wissenschaften (Encyclopedia of Mathematical Sciences). Two months after receiving his doctorate, Pauli completed the article, which came to 237 pages. Einstein praised it; published as a monograph, it remains a standard reference on the subject.
Pauli spent a year at the University of Göttingen as the assistant to Max Born, and the next year at the Institute for Theoretical Physics in Copenhagen (later the Niels Bohr Institute). From 1923 to 1928, he was a professor at the University of Hamburg. During this period, Pauli was instrumental in the development of the modern theory of quantum mechanics. In particular, he formulated the exclusion principle and the theory of nonrelativistic spin. He also wrote a paper on colloid chemistry and medicine in 1924.
In 1928, Pauli was appointed Professor of Theoretical Physics at ETH Zurich in Switzerland. He was awarded the Lorentz Medal in 1930. He held visiting professorships at the University of Michigan in 1931 and the Institute for Advanced Study in Princeton in 1935.
At the end of 1930, shortly after his postulation of the neutrino and immediately after his divorce and his mother’s suicide, Pauli experienced a personal crisis. In January 1932 he consulted psychiatrist and psychotherapist Carl Jung, who also lived near Zurich. Jung immediately began interpreting Pauli’s deeply archetypal dreams based on the I Ching, and Pauli became one of Jung’s best students.
He developed a new statistical method based on the apparent drift of two background stars, winning him the Smith’s Prize in 1907. In 1914 Eddington was named the director of the entire Cambridge Observatory.
Eddington also investigated the interior of stars through theory, and developed the first true understanding of stellar processes. He began this in 1916 with investigations of possible physical explanations for Cepheid variable stars. He began by extending Karl Schwarzschild’s earlier work on radiation pressure in Emden polytropic models.
Around 1920, he foreshadowed the discovery and mechanism of nuclear fusion processes in stars, in his paper “The Internal Constitution of the Stars”. At that time, the source of stellar energy was a complete mystery; Eddington was the first to correctly speculate that the source was fusion of hydrogen into helium.
Eddington wrote a number of articles that announced and explained Einstein’s theory of general relativity to the English-speaking world. World War I had severed many lines of scientific communication, and new developments in German science were not well known in England.
He also conducted an expedition to observe the solar eclipse of 29 May 1919 that provided one of the earliest confirmations of general relativity, and he became known for his popular expositions and interpretations of the theory.
Eddington died of cancer in the Evelyn Nursing Home, Cambridge, on 22 November 1944.
* 28 December 1882, Kendal, Westmorland, England, United Kingdom
†22 November 1944, Cambridge, Cambridgeshire, England, United Kingdom
Sir Arthur Stanley Eddington OM FRS was an English astronomer, physicist, and mathematician. He was also a philosopher of science and a populariser of science. The Eddington limit, the natural limit to the luminosity of stars, or the radiation generated by accretion onto a compact object, is named in his honour.
In 1893 Eddington entered Brynmelyn School. He proved to be a most capable scholar, particularly in mathematics and English literature. His performance earned him a scholarship to Owens College, Manchester (University of Manchester) in 1898, which he was able to attend, having turned 16 that year.
He spent the first year in a general course, but turned to physics for the next three years. Eddington was greatly influenced by his physics and mathematics teachers, Arthur Schuster and Horace Lamb. At Manchester, Eddington lived at Dalton Hall, where he came under the lasting influence of the Quaker mathematician J. W. Graham. His progress was rapid, winning him several scholarships and he graduated with a BSc in physics with First Class Honours in 1902.
Based on his performance at Owens College, he was awarded a scholarship to Trinity College, Cambridge, in 1902. His tutor at Cambridge was Robert Alfred Herman and in 1904 Eddington became the first ever second-year student to be placed as Senior Wrangler.
After receiving his M.A. in 1905, he began research on thermionic emission in the Cavendish Laboratory. This did not go well, and meanwhile he spent time teaching mathematics to first year engineering students. This hiatus was brief. Through a recommendation by E. T.
Whittaker, his senior colleague at Trinity College, he secured a position at the Royal Observatory in Greenwich where he was to embark on his career in astronomy, a career whose seeds had been sown even as a young child when he would often “try to count the stars”.
In January 1933, the Nazi Party came to power in Germany, and Born, who was Jewish, was suspended from his professorship at the University of Göttingen. He emigrated to the United Kingdom, where he took a job at St John’s College, Cambridge, and wrote a popular science book, The Restless Universe, as well as Atomic Physics, which soon became a standard textbook.
In October 1936, he became the Tait Professor of Natural Philosophy at the University of Edinburgh, where, working with German-born assistants E. Walter Kellermann and Klaus Fuchs, he continued his research into physics. Born became a naturalised British subject on 31 August 1939, one day before World War II broke out in Europe. He remained in Edinburgh until 1952.
He died at age 87 in hospital in Göttingen on 5 January 1970, and is buried in the Stadtfriedhof there, in the same cemetery as Walther Nernst, Wilhelm Weber, Max von Laue, Otto Hahn, Max Planck, and David Hilbert.
*11 December 1882, Breslau, German Empire, (now Wrocław, Poland)
†5 January 1970, Göttingen, West Germany
Max Born was a German physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 1930s. Born won the 1954 Nobel Prize in Physics for his “fundamental research in quantum mechanics, especially in the statistical interpretation of the wave function”.
Born entered the University of Göttingen in 1904, where he met the three renowned mathematicians Felix Klein, David Hilbert, and Hermann Minkowski. He wrote his Ph.D. thesis on the subject of “Stability of Elastica in a Plane and Space”, winning the University’s Philosophy Faculty Prize.
In 1905, he began researching special relativity with Minkowski, and subsequently wrote his habilitation thesis on the Thomson model of the atom. A chance meeting with Fritz Haber in Berlin in 1918 led to discussion of how an ionic compound is formed when a metal reacts with a halogen, which is today known as the Born–Haber cycle.
In World War I, after originally being placed as a radio operator, he was moved to research duties regarding sound ranging due to his specialist knowledge. In 1921, Born returned to Göttingen, arranging another chair for his long-time friend and colleague James Franck. Under Born, Göttingen became one of the world’s foremost centres for physics.
In 1925, Born and Werner Heisenberg formulated the matrix mechanics representation of quantum mechanics. The following year, he formulated the now-standard interpretation of the probability density function for ψ*ψ in the Schrödinger equation, for which he was awarded the Nobel Prize in 1954.
His influence extended far beyond his own research. Max Delbrück, Siegfried Flügge, Friedrich Hund, Pascual Jordan, Maria Goeppert-Mayer, Lothar Wolfgang Nordheim, Robert Oppenheimer, and Victor Weisskopf all received their Ph.D. degrees under Born at Göttingen, and his assistants included Enrico Fermi, Werner Heisenberg, Gerhard Herzberg, Friedrich Hund, Pascual Jordan, Wolfgang Pauli, Léon Rosenfeld, Edward Teller, and Eugene Wigner.
In June 1832, the University of Oxford granted Faraday an honorary Doctor of Civil Law degree. During his lifetime, he was offered a knighthood in recognition for his services to science, which he turned down on religious grounds, believing that it was against the word of the Bible to accumulate riches and pursue worldly reward, and stating that he preferred to remain “plain Mr Faraday to the end”.
Elected a member of the Royal Society in 1824, he twice refused to become President. He became the first Fullerian Professor of Chemistry at the Royal Institution in 1833.
In 1832, Faraday was elected a Foreign Honorary Member of the American Academy of Arts and Sciences. He was elected a foreign member of the Royal Swedish Academy of Sciences in 1838. In 1840, he was elected to the American Philosophical Society. He was one of eight foreign members elected to the French Academy of Sciences in 1844.
In 1849 he was elected as associated member to the Royal Institute of the Netherlands, which two years later became the Royal Netherlands Academy of Arts and Sciences and he was subsequently made foreign member.
Faraday died at his house at Hampton Court on 25 August 1867, aged 75. He had some years before turned down an offer of burial in Westminster Abbey upon his death, but he has a memorial plaque there, near Isaac Newton’s tomb.
*22 September 1791, Newington Butts, England
†25 August 1867, Hampton Court, Middlesex, England
Michael Faraday FRS was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic induction, diamagnetism and electrolysis.
Although Faraday received little formal education, he was one of the most influential scientists in history. It was by his research on the magnetic field around a conductor carrying a direct current that Faraday established the basis for the concept of the electromagnetic field in physics. Faraday also established that magnetism could affect rays of light and that there was an underlying relationship between the two phenomena.
He similarly discovered the principles of electromagnetic induction and diamagnetism, and the laws of electrolysis. His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, and it was largely due to his efforts that electricity became practical for use in technology.
As a chemist, Faraday discovered benzene, investigated the clathrate hydrate of chlorine, invented an early form of the Bunsen burner and the system of oxidation numbers, and popularised terminology such as “anode”, “cathode”, “electrode” and “ion”. Faraday ultimately became the first and foremost Fullerian Professor of Chemistry at the Royal Institution, a lifetime position.
Faraday was an excellent experimentalist who conveyed his ideas in clear and simple language; his mathematical abilities, however, did not extend as far as trigonometry and were limited to the simplest algebra. James Clerk Maxwell took the work of Faraday and others and summarized it in a set of equations which is accepted as the basis of all modern theories of electromagnetic phenomena.
On Faraday’s uses of lines of force, Maxwell wrote that they show Faraday “to have been in reality a mathematician of a very high order – one from whom the mathematicians of the future may derive valuable and fertile methods.” The SI unit of capacitance is named in his honour: the farad.
Albert Einstein kept a picture of Faraday on his study wall, alongside pictures of Arthur Schopenhauer and James Clerk Maxwell. Physicist Ernest Rutherford stated, “When we consider the magnitude and extent of his discoveries and their influence on the progress of science and of industry, there is no honour too great to pay to the memory of Faraday, one of the greatest scientific discoverers of all time.”
With James Hartle, Thorne derived from general relativity the laws of motion and precession of black holes and other relativistic bodies, including the influence of the coupling of their multipole moments to the spacetime curvature of nearby objects, as well as writing down the Hartle-Thorne metric, an approximate solution which describes the exterior of a slowly and rigidly rotating, stationary and axially symmetric body.
Thorne’s work has dealt with the prediction of gravitational wave strengths and their temporal signatures as observed on Earth. These “signatures” are of great relevance to LIGO (Laser Interferometer Gravitational Wave Observatory), a multi-institution gravitational wave experiment for which Thorne has been a leading proponent – in 1984, he cofounded the LIGO Project to discern and measure any fluctuations between two or more ‘static’ points; such fluctuations would be evidence of gravitational waves, as calculations describe. A significant aspect of his research is developing the mathematics necessary to analyze these objects.
On February 11, 2016, a team of four physicists representing the LIGO Scientific Collaboration, announced that in September 2015, LIGO recorded the signature of two black holes colliding 1.3 billion light-years away.
In June 2009, he resigned his Feynman Professorship (he is now the Feynman Professor of Theoretical Physics, Emeritus) to pursue a career of writing and movie making.
He continues to do scientific research and scientific consulting, most notably for the Christopher Nolan film Interstellar. Thorne was awarded the 2017 Nobel Prize in Physics along with Rainer Weiss and Barry C. Barish “for decisive contributions to the LIGO detector and the observation of gravitational waves”.
*1 June 1940, Logan, Utah, U.S.
Kip Stephen Thorne is an American theoretical physicist known for his contributions in gravitational physics and astrophysics. A longtime friend and colleague of Stephen Hawking and Carl Sagan, he was the Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology (Caltech) until 2009 and is one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity.
Thorne’s research has principally focused on relativistic astrophysics and gravitation physics, with emphasis on relativistic stars, black holes and especially gravitational waves. He is perhaps best known to the public for his controversial theory that wormholes can conceivably be used for time travel. However, Thorne’s scientific contributions, which center on the general nature of space, time, and gravity, span the full range of topics in general relativity.
Thorne rapidly excelled at academics early in life, winning recognition in the Westinghouse Science Talent Search as a senior at Logan High School. He received his B.S. degree from the California Institute of Technology (Caltech) in 1962, and his Ph.D. from Princeton University in 1965 under the supervision of John Archibald Wheeler.
While he was studying for his Ph.D. in Princeton University, his mentor John Wheeler gave him an assignment problem for him to think over: find out whether or not a cylindrical bundle of repulsive magnetic field lines will implode under its own attractive gravitational force. After several months wrestling with the problem, he proved that it was impossible for cylindrical magnetic field lines to implode.
Why is it that a cylindrical bundle of magnetic field lines will not implode, while spherical stars will implode under their own gravitational force? Thorne tried to explore the theoretical ridge between the two phenomena. He found out eventually that the gravitational force can overcome all interior pressure only when an object has been compressed in all directions.
Thorne returned to Caltech as an associate professor in 1967 and became a professor of theoretical physics in 1970, becoming one of the youngest full professors in the history of Caltech at age 30. He became the William R. Kenan, Jr. Professor in 1981, and the Feynman Professor of Theoretical Physics in 1991. He was an adjunct professor at the University of Utah from 1971 to 1998 and Andrew D. White Professor at Large at Cornell University from 1986 to 1992.
With Anna Żytkow, Thorne predicted the existence of red supergiant stars with neutron-star cores (Thorne–Żytkow objects). He laid the foundations for the theory of pulsations of relativistic stars and the gravitational radiation they emit.
His solution to this complex dynamical problem involved a set of twenty partial differential equations, describing a new quantity he termed “dynamical friction”, which has the dual effects of decelerating the star and helping to stabilize clusters of stars. Chandrasekhar extended this analysis to the interstellar medium, showing that clouds of galactic gas and dust are distributed very unevenly.
A long-time professor at the University of Chicago, he did some of his studies at the Yerkes Observatory, and served as editor of The Astrophysical Journal from 1952 to 1971. He was on the faculty at Chicago from 1937 until his death in 1995 at the age of 84, and was the Morton D. Hull Distinguished Service Professor of Theoretical Astrophysics.
Chandrasekhar died of a sudden heart attack at the University of Chicago Hospital in 1995, having survived a prior heart attack in 1975.
*19 October 1910, Lahore, Punjab, British India (present-day Punjab, Pakistan)
†21 August 1995, Chicago, Illinois, U.S.
Subrahmanyan Chandrasekhar was an Indian-American astrophysicist who spent his professional life in the United States. He was awarded the 1983 Nobel Prize for Physics with William A. Fowler for “…theoretical studies of the physical processes of importance to the structure and evolution of the stars”.
His mathematical treatment of stellar evolution yielded many of the current theoretical models of the later evolutionary stages of massive stars and black holes.
Chandrasekhar was tutored at home until the age of 12. In middle school his father taught him Mathematics and Physics and his mother taught him Tamil. He later attended the Hindu High School, Triplicane, Madras during the years 1922–25. Chandrasekhar studied at Presidency College, Madras (now Chennai) and the University of Cambridge.
Chandrasekhar worked on a wide variety of problems in physics during his lifetime, contributing to the contemporary understanding of stellar structure, white dwarfs, stellar dynamics, stochastic process, radiative transfer, the quantum theory of the hydrogen anion, hydrodynamic and hydromagnetic stability, turbulence, equilibrium and the stability of ellipsoidal figures of equilibrium, general relativity, mathematical theory of black holes and theory of colliding gravitational waves.
At the University of Cambridge, he developed a theoretical model explaining the structure of white dwarf stars that took into account the relativistic variation of mass with the velocities of electrons that comprise their degenerate matter. He showed that the mass of a white dwarf could not exceed 1.44 times that of the Sun – the Chandrasekhar limit.
Chandrasekhar revised the models of stellar dynamics first outlined by Jan Oort and others by considering the effects of fluctuating gravitational fields within the Milky Way on stars rotating about the galactic centre.
Louis de Broglie
In his 1924 PhD thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as the de Broglie hypothesis, an example of wave–particle duality, and forms a central part of the theory of quantum mechanics.
De Broglie won the Nobel Prize for Physics in 1929, after the wave-like behaviour of matter was first experimentally demonstrated in 1927.
The 1925 pilot-wave model, and the wave-like behaviour of particles discovered by de Broglie was used by Erwin Schrödinger in his formulation of wave mechanics. The pilot-wave model and interpretation was then abandoned, in favor of the quantum formalism, until 1952 when it was rediscovered and enhanced by David Bohm.
Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the French Academy of Sciences. De Broglie became the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN).
He died on 19 March 1987 in Louveciennes, France.
*15 August 1892, Dieppe, France
†19 March 1987, Louveciennes, France
Louis Victor Pierre Raymond, 7th Duc de Broglie was a French physicist and aristocrat who made groundbreaking contributions to quantum theory.
De Broglie had intended a career in humanities, and received his first degree in history. Afterwards he turned his attention toward mathematics and physics and received a degree in physics. With the outbreak of the First World War in 1914, he offered his services to the army in the development of radio communications.
After graduation, Louis de Broglie as a simple sapper joined the engineering forces to undergo compulsory service. It began at Fort Mont Valérien, but soon, on the initiative of his brother, he was seconded to the Wireless Communications Service and worked on the Eiffel Tower, where the radio transmitter was located.
Prince Louis was demobilized in August 1919 with the rank of adjudant. Later, the scientist regretted that he had to spend about six years away from the fundamental problems of science that interested him.
The first works of Louis de Broglie (early 1920s) were performed in the laboratory of his older brother Maurice and dealt with the features of the photoelectric effect and the properties of x-rays.
These publications examined the absorption of X-rays and described this phenomenon using the Bohr theory, applied quantum principles to the interpretation of photoelectron spectra, and gave a systematic classification of X-ray spectra.
Chandrasekhara Venkata Raman
He joined the Indian Finance Service in Calcutta as Assistant Accountant General at age 19. There he became acquainted with the Indian Association for the Cultivation of Science (IACS), the first research institute in India, which allowed him to do independent research and where he made his major contributions in acoustics and optics.
In 1917, he was appointed as the first Palit Professor of Physics by Ashutosh Mukherjee at the Rajabazar Science College under the University of Calcutta.
On his first trip to Europe, seeing the Mediterranean Sea motivated him to identify the prevailing explanation for the blue colour of the sea at the time, namely the reflected Rayleigh-scattered light from the sky, as being incorrect. He founded the Indian Journal of Physics in 1926.
He moved to Bangalore in 1933 to become the first Indian director of the Indian Institute of Science. He founded the Indian Academy of Sciences the same year.
He established the Raman Research Institute in 1948 where he worked to his last days.
His last interests in the 1960s were on biological properties such as the colours of flowers and the physiology of human vision.
*7 November 1888, Tiruchirapalli, Madras Presidency, British India
†21 November 1970, Bangalore, Mysore State, India
Sir Chandrasekhara Venkata Raman was an Indian physicist known for his work in the field of light scattering.
Using a spectrograph that he developed, he and his student K. S. Krishnan discovered that when light traverses a transparent material, the deflected light changes its wavelength and frequency. This phenomenon, a hitherto unknown type of scattering of light, which they called “modified scattering” was subsequently termed the Raman effect or Raman scattering.
Raman received the 1930 Nobel Prize in Physics for the discovery and was the first Asian to receive a Nobel Prize in any branch of science.
Born to Tamil Brahmin parents, Raman was a precocious child, completing his secondary and higher secondary education from St Aloysius’ Anglo-Indian High School at the ages of 11 and 13, respectively.
He topped the bachelor’s degree examination of the University of Madras with honours in physics from Presidency College at age 16.
His first research paper, on diffraction of light, was published in 1906 while he was still a graduate student. The next year he obtained a master’s degree.
He worked at White Sands Missile Range in the early 1950s, and taught astronomy at New Mexico State University from 1955 until his retirement in 1973.
The asteroid 1604 Tombaugh, discovered in 1931, is named after him. He discovered hundreds of asteroids, beginning with 2839 Annette in 1929, mostly as a by-product of his search for Pluto and his searches for other celestial objects. Tombaugh named some of them after his wife, children and grandchildren.
Direct visual observation became rare in astronomy. By 1965 Robert S. Richardson called Tombaugh one of two great living experienced visual observers as talented as Percival Lowell or Giovanni Schiaparelli.
In 1980, Tombaugh and Patrick Moore wrote a book Out of the Darkness: The Planet Pluto.
In August 1992, JPL scientist Robert Staehle called Tombaugh, requesting permission to visit his planet. “I told him he was welcome to it,” Tombaugh later remembered, “though he’s got to go one long, cold trip.” The call eventually led to the launch of the New Horizons space probe to Pluto in 2006.
Following the passage of Pluto by New Horizons on July 14, 2015, the “Heart of Pluto” was named Tombaugh Regio.
*4 February 1906 Streator, Illinois, U.S.
†17 January 1997 Las Cruces, New Mexico, U.S.
Clyde William Tombaugh was an American astronomer. He discovered Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper belt. At the time of discovery, Pluto was considered a planet, but was reclassified as a dwarf planet in 2006. Tombaugh also discovered many asteroids, and called for the serious scientific research of unidentified flying objects.
Starting in 1926, he built several telescopes with lenses and mirrors by himself. To better test his telescope mirrors, Tombaugh, with just a pick and shovel, dug a pit 24 feet long, 8 feet deep, and 7 feet wide. This provided a constant air temperature, free of air currents, and was also used by the family as a root cellar and emergency shelter.
He sent drawings of Jupiter and Mars to the Lowell Observatory, at Flagstaff, Arizona, which offered him a job. Tombaugh worked there from 1929 to 1945.
It was at Lowell in 1930 that Tombaugh discovered Pluto. Following his discovery, Tombaugh earned bachelor’s and master’s degrees in astronomy from the University of Kansas in 1936 and 1938.
Tombaugh continued searching for over a decade after the discovery of Pluto, and the lack of further discoveries left him satisfied that no other object of a comparable apparent magnitude existed near the ecliptic. No more trans-Neptunian objects were discovered until 15760 Albion, in 1992.
However, more recently the relatively bright object Makemake has been discovered. It has a relatively high orbital inclination, but at the time of Tombaugh’s discovery of Pluto, Makemake was only a few degrees from the ecliptic, near the border of Taurus and Auriga, at an apparent magnitude of 16.
In 2009, Broderick and Loeb predicted the shadow of the black hole in the giant elliptical galaxy Messier 87, which was imaged in 2019 by the Event Horizon Telescope. In 2013, a report was published on the discovery of the “Einstein Planet” Kepler-76b, the first Jupiter size exoplanet identified through the detection of relativistic beaming of its parent star, based on a technique proposed by Loeb and Gaudi in 2003.
In addition, a pulsar was discovered around the supermassive black hole, Sagittarius A*, following a prediction by Pfahl and Loeb in 2004. Also, a hypervelocity star candidate from the Andromeda galaxy was discovered, as predicted by Sherwin, Loeb, and O’Leary in 2008.
Together with his postdoc, James Guillochon, Loeb predicted the existence of a new population of stars moving near the speed of light throughout the universe. Together with his postdoc John Forbes and Howard Chen of Northwestern University, Loeb made another prediction that sub-Neptune sized exoplanets have been transformed into rocky super-Earths by the activity of Milky Way’s central supermassive black hole Sagittarius A*.
In 2018, he attracted media attention for suggesting that alien space craft may be in our solar system, using the anomalous behavior of ʻOumuamua as an example.
In 2019, and together with his Harvard undergraduate student, Amir Siraj, Loeb reported discovering a meteor that potentially originated outside the Solar System.
*26 February 1962, Beit Hanan, Israel
Abraham “Avi” Loeb is an Israeli-American theoretical physicist who works on astrophysics and cosmology. Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University. He had been the longest serving chair of Harvard’s Department of Astronomy (2011–2020), founding director of Harvard’s Black Hole Initiative (since 2016) and director of the Institute for Theory and Computation (since 2007) within the Harvard-Smithsonian Center for Astrophysics.
Loeb has written eight books and authored or co-authored about 800 papers on a broad range of research areas in astrophysics and cosmology, including the first stars, the epoch of reionization, the formation and evolution of massive black holes, the search for extraterrestrial life, gravitational lensing by planets, gamma-ray bursts at high redshifts, 21-cm cosmology, the use of the Lyman-alpha forest to measure the acceleration/deceleration of the universe in real time, the future collision between the Milky Way and Andromeda galaxies, the future state of extragalactic astronomy, astrophysical implications of black hole recoil in galaxy mergers, tidal disruption of stars, and imaging black hole silhouettes.
In 1992, Loeb suggested, with Andy Gould, that exoplanets could be detected through gravitational microlensing. In 1993, he proposed the use of the C+ fine-structure line to discover galaxies at high redshifts.
In 2005, he predicted, in a series of papers with his postdoc at the time, Avery Broderick, how a hot spot in orbit around a black hole would appear; their predictions were confirmed in 2018 by the GRAVITY instrument on the Very Large Telescope which observed a circular motion of the centroid of light of the black hole at the center of the Milky Way, Sagittarius A*.