Category: Scientists

John Wheeler

John Wheeler was an eminent American theoretical physicist, perhaps best known for having initially coined the terms “black hole,” “wormhole” and several other colorful phrases. In the 1930s, he developed the important “S-matrix” in particle physics and worked with Niels Bohr to explain nuclear fission in terms of quantum physics. Later, he developed the equation of state for cold, dead stars, helped popularize the study of general relativity in the mainstream of theoretical physics, and to firm up the theory and evidence for black holes. He also collaborated with Albert Einstein in his search for a Grand Unified Theory of physics.

Education and Influences

John Archibald Wheeler was born on 9 July 1911 in Jacksonville, Florida, USA, the oldest child in a family of librarians. The family moved around a lot, and over the years they lived in Florida, California, Ohio, Washington D.C., Maryland and Vermont. He attended the Baltimore City College high school, graduating in 1926, and went on to study physics under the supervision of Karl Herzfeld at Johns Hopkins University. He received his doctorate in 1933, with a dissertation on the theory of the dispersion and absorption of helium. Soon after graduating, he traveled to Copenhagen, where he worked for a time with Niels Bohr, the godfather of the quantum theory revolution. He married Janette Hegner in 1935, and they were to have two daughters (Alison Letitia) and a son (James) and were to stay together for the whole of their long lives.

Contributions and Impact

He became a professor of physics at Princeton University in 1938, where he remained, with an interruption during World War II, for 38 years until 1976. During his very early years at Princeton, he introduced the scattering-matrix (or “S-matrix”), which relates the initial state and the final state for an interaction of particles, and which was to become an indispensable tool in particle physics.

Wheeler knew Einstein well and sometimes used to hold seminars with his students in Einstein’s home. When Bohr visited the United States in 1939, with news of the achievement of nuclear fission in Germany, he and Wheeler collaborated on the development of the influential “liquid drop” model of the atom, first proposed by George Gamow, in an attempt to explain the theoretical basis of nuclear fission.

Together with many other leading physicists, Wheeler interrupted his academic career during World War II to participate in the development of the U.S. atomic bomb as part of the Manhattan Project at the Hanford Site in Washington state. Among other things, he correctly anticipated that the accumulation of “fission product poisons” (particularly an isotope of xenon) would eventually impede the ongoing nuclear chain reaction by absorbing neutrons.

After the war, he returned to Princeton to resume his academic career, and began to teach a course on Einsteinian gravity in the early 1950s, when it was still considered not quite an acceptable field of study, although for many years he resisted the idea that the laws of physics could lead to something as apparently absurd as a singularity. He also continued to do government work, however, and was integrally involved in the development of the American hydrogen bomb in the early 1950s at Los Alamos and at Princeton (where he was responsible for setting up Project Matterhorn). At one point, in 1953, he was he officially reprimanded for apparently losing a classified paper on the hydrogen bomb. His somewhat hawkish views on national defense, the Vietnam War, and missile defense often ran counter to those of his more liberal colleagues.

With his government research finished, Wheeler returned to Princeton, where he collaborated with Albert Einstein in the waning years of his life on a “unified field theory” of the physical forces of nature. In 1956, he helped to determine what types of materials are located inside dead, cold stars with the “Harrison-Wheeler Equation of State for Cold, Dead Matter,” ascertaining that it would be largely iron because the efficient fusion process breaks down when the core reaches that state. In 1957, while working on extensions to general relativity, he introduced the word “wormhole” to describe hypothetical tunnels in space-time.

In the late 1950s, he formulated the theory of geometrodynamics, a program of physical and philosophical reduction of all physical phenomena (including gravitation and electromagnetism) to the geometrical properties of curved space-time. However, he later abandoned this theory in the early 1970s, having failed to explain some important physical phenomena, such as the existence of fermions (electrons, muons, etc.) and gravitational singularities.

He always gave a high priority to teaching and continued to teach freshman and sophomore physics even after he had achieved fame, believing that the young minds were the most important. He was known for his high-energy lectures, writing rapidly on chalkboards with both hands, and twirling to make eye contact with his students. Among his graduate students were some important theoreticians of the later 20th Century, including Richard Feynman, Kip Thorne, and Hugh Everett.

He worked extensively on the theory of gravitational collapse, and he is usually credited with coining the term “black hole” during a 1967 talk at the NASA Goddard Institute of Space Studies (although in fact he was prompted to it by a shout from the audience). Along with Dennis Sciama at Cambridge and Yakov Borisovich Zeldovich in Moscow, Wheeler was integral to the so-called “Golden Age of general relativity” of the 1960s and 1970s, a paradigm shift during which the study of general relativity (which had previously been regarded as something of a curiosity) entered into the mainstream of theoretical physics. Under his leadership, Princeton became the leading American center of research into Einsteinian gravity. The comprehensive general relativity textbook “Gravitation,” which he co-wrote with Charles Misner and Kip Thorne, appeared in 1973, and it became the most influential relativity textbook for a generation.

After Einstein’s death, Wheeler continued his pursuit of the role of gravity in a Grand Unified Theory of physics and became something of a pioneer in the field of quantum gravity. This led to his collaboration with Bryce DeWitt and the development of the Wheeler-DeWitt Equation or, as Wheeler preferred to call it, the “wave function of the universe.” Other products of Wheeler’s colourful way with words include the phrase “black holes have no hair” (to describe how black holes should be a perfect, simply definable shape, and not have any sorts of projections out of them), “mass without mass” (to indicate the need to effectively remove any mention of mass from the basic equations of physics), “it from bit” (to describe how information is fundamental to the physics of the universe, just as it is in computing) and “quantum foam” (to describe a space-time churned into a lather of distorted geometry).

In 1976, faced with mandatory retirement at Princeton, Wheeler moved to the University of Texas at Austin, where he held the position as director of the Center for Theoretical Physics from 1976 until his retirement in 1986. It was during this time (specifically in 1978) that he proposed a variation of Thomas Young’s double-slit experiment (and Richard Feynman’s later refinement), often referred to as the “delayed choice” experiment. He posited that the detection of a photon even AFTER passing through a double slit would be sufficient to change the outcome of the experiment and the behavior of the photon. Therefore, if the experimenters know which slit it goes through, the photon will behave as a particle, rather than as a wave with its associated interference behavior. This somewhat counter-intuitive hypothesis was finally verified in a practical experiment in 2007.

Wheeler returned to Princeton as a professor emeritus in 1986, where he remained for the next twenty years. His so-called “Everything Is Fields” phase (in which he viewed the universe and all the particles which make it up as mere manifestations of electrical, magnetic and gravitational fields and space-time itself) gave way to an “Everything Is Information” phase (when he focused on the idea that logic and information is the bedrock of physical theory). He also began to speculate that the laws of physics may be evolving in a manner analogous to evolution by natural selection in biology, and he coined the term “participatory anthropic principle” to describe his version of the anthropic principle, in which observers (i.e., us) are necessary to bring the universe into being.

Wheeler received numerous honors over the years, including the National Medal of Science, the Albert Einstein Prize, the Enrico Fermi Award, the Franklin Medal, the Niels Bohr International Gold Medal and the Wolf Foundation Prize. He was a past president of the American Physical Society, and a member of the American Philosophical Society, the Royal Academy, the Accademia Nazionale dei Lincei, the Royal Academy of Science and the Century Association. He was awarded honorary degrees from 18 institutions.

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Scientists

Karl Schwarzschild

Karl Schwarzschild was a German physicist, best known for providing the first exact solution to Einstein’s field equations of general relativity in 1915 (the very same year that Einstein first introduced the concept of general relativity). His work generated many original concepts which now bear his name, such as Schwarzschild coordinates, the Schwarzschild metric, the Schwarzschild radius, Schwarzschild black holes and Schwarzschild wormholes.

Education and Influences

Karl Schwarzschild was born on 9 October 1873 in Frankfurt am Main, Germany, the oldest of six children. The family was Jewish and quite well-off, his father being a respected member of the business community in Frankfurt. Schwarzschild attended a Jewish primary school in Frankfurt up to the age of eleven, before entering the Gymnasium there. He was something of a child prodigy, constructing his own telescope and publishing a paper on celestial mechanics (specifically, on the theory of orbits of double stars) when he was only sixteen. He studied at the University of Strasbourg from 1891 to 1893, where he learned a great deal of practical astronomy, and then at the University of Munich where he obtained his doctorate in 1896 with a work on Henri Poincaré’s theories.

Contributions and Impact

From 1896 to 1899, he worked as an assistant at the Kuffner Observatory in Vienna, Austria, and then spent two years lecturing at the University of Munich. From 1901 until 1909, he was a professor at the prestigious University of Göttingen, where he had the opportunity to work with some significant figures, including the mathematicians David Hilbert and Hermann Minkowski, and where he also became director of the Göttingen observatory. In 1909, he married Else Posenbach, and they had three children, Agathe, Martin, and Alfred. His son, Martin, born in 1912, would also become an eminent physicist whose work led to greater understanding in the fields of stellar structure and stellar evolution.

In 1909, Schwarzschild moved to a post as director of the Astrophysical Observatory in Potsdam, the most prestigious post available for an astronomer in Germany at that time, and in 1913 he was elected a member of the Berlin Academy of Science. In 1914, at the outbreak of World War I, he joined the German army, despite being over 40 years old, serving on both the western and eastern fronts, and rising to the rank of lieutenant in the artillery. While serving on the front in Russia in 1915, he began to suffer from a rare and painful skin disease called pemphigus.

Despite serving in the war and suffering this painful debility, Schwarzschild nevertheless managed to write three outstanding papers during in 1915, two on relativity theory and one on quantum theory. His papers on general relativity produced the first exact solutions to Albert Einstein’s field equations, and a minor modification of these results gives the well-known solution that now bears his name, the Schwarzschild metric. Einstein himself was pleasantly surprised to learn that the field equations admitted exact solutions, partly because of their prima facie complexity, but partly because at that time he had only produced an approximate solution. Schwarzschild’s more elegant “polar-like” coordinate system (which has since become known as Schwarzschild coordinates), based on a spherically symmetric space-time, was able to produce an exact solution.

Schwarzschild’s solution identified a radius for any given mass, known as the Schwarzschild radius, where, if that mass could be compressed to fit within that radius, no known force or degeneracy pressure could stop it from continuing to collapse into a gravitational singularity or black hole. Thus, where the radius of the body is less than its Schwarzschild radius, everything, even photons of light, must inevitably fall into the central body. As a corollary, when the mass density of this central body exceeds a particular limit, it triggers a gravitational collapse to what is known as a Schwarzschild black hole, a non-charged, non-rotating black hole. A general acceptance of the possibility of a black hole did not occur until the second half of the 20th Century, and Schwarzschild himself did not believe in the physical reality of black holes, believing his theoretical solution to be physically meaningless.

Although Schwarzschild’s best-known work lies in the area of general relativity, his research interests were broad, including work in celestial mechanics, observational stellar photometry, quantum mechanics, instrumental astronomy, stellar structure, stellar statistics, Halley’s comet and spectroscopy. In particular, earlier in his career, he pioneered the measurement of variable stars using photography and worked on the improvement of optical systems.

Scientists

Erwin Schrödinger

Erwin Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics. The philosophical issues raised by his 1935 “Schrödinger’s cat” thought experiment perhaps remains his best-known legacy, but the Schrödinger equation, which he formulated in 1926 to describe the quantum state of a system, is his most enduring achievement at a more technical level. It is celebrated as one of the most significant achievements in 20th Century physics, and it revolutionized quantum mechanics and earned Schrödinger a share in the 1933 Nobel Prize in Physics.

Education and Influences

Erwin Rudolf Josef Alexander Schrödinger was born on 12 August 1887 in Vienna, Austria (Austria-Hungary at that time). His father was an Austrian Catholic, and his mother was an Austrian-English Lutheran, and Schrödinger grew up speaking German and English. He attended the Akademisches Gymnasium high school in Vienna from 1898 to 1905, and then studied at the University of Vienna between 1906 and 1910 under Franz Serafin Exner and Friedrich Hasenöhrl, as well as conducting experimental work with K.W.F. Kohlrausch. From an early age, Schrödinger was strongly influenced by the philosophy and Eastern religion of the Austrian philosopher Arthur Schopenhauer.

In 1911, Schrödinger became an assistant to Exner at the University of Vienna, earning his habilitation in 1914. During World War I, between 1914 and 1918, he participated in war work as a commissioned officer in the Austrian fortress artillery, and after the War, in 1920, he married Annemarie Bertel. The same year, he became the assistant to Max Wien at the University of Jena, and then quickly obtained a series of promotions, working in the universities of Stuttgart, Breslau and finally Zürich in 1921.

Contributions and Impact

In 1926, Schrödinger published a remarkable series of four papers in the prestigious “Annalen der Physik” journal, which marked the central achievement of his career, and which were at once recognized as having great significance by the international physics community:

A paper on wave mechanics, in which he derived what is now known as the Schrödinger equation, an equation that describes how the quantum state of a physical system changes over time, and giving the correct energy eigenvalues for a hydrogen-like atom with one electron. This paper has been universally celebrated as one of the most important achievements of the 20th Century and created a revolution in quantum mechanics.
A paper solving the quantum harmonic oscillator, the rigid rotor, and the diatomic molecule, and giving a new derivation of the Schrödinger equation.
A paper showing the equivalence of his approach to that of Heisenberg, and giving the treatment of the Stark effect (the shifting and splitting of spectral lines of atoms and molecules due to the presence of an external static electric field).
A paper showing how to treat problems in which the system changes with time, as in scattering problems.

In 1927, Schrödinger succeeded Max Planck at the Friedrich Wilhelm University in Berlin, and his career seemed to be flourishing. However, when Adolf Hitler seized power in 1933, Schrödinger decided to leave Germany as a protest against the anti-Semitism of the Nazi regime, and he settled in Oxford, England, becoming a Fellow of Magdalen College at the University of Oxford. Soon after, he received the 1933 Nobel Prize in Physics, shared with Paul Dirac, “for the discovery of new productive forms of atomic theory.”

His position at Oxford, though, did not work out (it is likely that his unconventional personal life – he lived with two women, his wife, Annemarie Bertel, and his pregnant mistress, Hilde March – did not meet with acceptance in the proper Oxford of the 1930s). He was offered a permanent position at Princeton University in the United States in 1934, but he did not accept it, and again his lifestyle may have posed a problem. In the end, he took up a position at the University of Graz in Austria in 1936.

Somewhere in the midst of all these tenure issues, he found time for an extensive correspondence with his personal friend Albert Einstein and, as a result, he proposed in 1935 what has become known as the “Schrödinger’s cat” thought experiment or paradox in order to illustrate the problem of the so-called “Copenhagen interpretation” of quantum mechanics (as propounded by Niels Bohr and Werner Heisenberg). The thought experiment proposed a scenario in which a cat was hidden in a sealed box, where the cat’s life or death was dependent on the state of a particular sub-atomic particle. According to the Copenhagen interpretation, the cat remains both alive and dead until the box is opened, and it is the act of measurement that causes the calculated set of probabilities in the wave function to “collapse” to the value defined by the measurement.

In 1939, after the unification of Austria into Greater Germany, Schrödinger’s known opposition to Nazism and his earlier flight from Germany led to threats and eventually to dismissal from his job at the University of Graz (despite his public recantation, which he later much regretted). He was under orders not to leave the country, but he and his wife managed to escape to Italy, and from there to visiting positions in Oxford University and Ghent University.

In 1940, he accepted an invitation to help establish an Institute for Advanced Studies in Dublin, Ireland, and he became the Director of the School for Theoretical Physics there. He remained in Dublin until his retirement in 1955, during which time he became a naturalized Irish citizen. He continued his scandalous involvements with students, however, fathering at least two children by two different Irish women.

During his time in Dublin, he wrote about 50 further publications on various topics, including his explorations of unified field theory. His influential 1944 book “What is Life?” discussed the idea that life feeds on negative entropy, and introduced the concept of a complex molecule containing the genetic code for living organisms. Schrödinger’s speculations about how genetic information might be stored in molecules gave James Watson and Francis Crick the inspiration to research the gene that led to the discovery of the DNA double-helix structure.

In 1956, Schrödinger returned to Vienna. He continued to court controversy, including his refusal to speak on nuclear energy at a major energy conference due to his skepticism about it (he gave a lecture on philosophy instead), and his turn, late in life, away from the wave-particle duality espoused by mainstream quantum mechanics in favor of the wave idea alone.

Scientists

Andrei Sakharov

Andrei Sakharov was an eminent Soviet Russian nuclear physicist, although he is perhaps better known as a dissident, human rights activist, advocate of civil liberties and reforms in the Soviet Union and Nobel Peace Prize winner. Although much of his early career was spent contributing to the military might of the Soviet Union through the development of the atomic bomb and the hydrogen bomb, he later became one of the program’s fiercest critics. In later life, he devoted his prodigious intellect to fundamental theoretical physics, particle physics and cosmology, contributing essential insights on the matter-antimatter imbalance in the universe, and hypothesizing about singularities linking parallel universes.

Education and Influences

Andrei Dmitrievich Sakharov was born in Moscow, Russia (then the USSR) on 21 May 1921. His father was a physics teacher, an amateur pianist, and a vehement atheist, and, despite his pious mother’s insistence on baptizing him, religion did not play an important role in Sakharov’s life. He entered Moscow State University in 1938, although he was evacuated in 1941 during the Great Patriotic War to Ashgabat (in today’s Turkmenistan), where he completed his studies and graduated.

After graduating, he was assigned laboratory work in Ulyanovsk, during which period he met and married Klavdia Alekseyevna Vikhireva. They married in 1943 and raised together two daughters and a son. He returned to Moscow in 1945 to study at the Theoretical Department of FIAN (the Physical Institute of the Soviet Academy of Sciences), receiving his Ph.D. in 1947.

Contributions and Impact

After the war, Sakharov spent some time researching cosmic rays but gradually became involved in weapons research. In 1948, he participated in the Soviet atomic bomb project under Igor Kurchatov and was present at the testing of the first Soviet nuclear device in 1949. After moving to the “closed” (or restricted) town of Sarov in 1950, Sakharov played a key role in the next stage, the development of the thermonuclear hydrogen bomb, which was first tested in 1953, followed by the first megaton-range Soviet hydrogen bomb, which was tested in 1955.

In 1950, in association with Igor Tamm, he also proposed an idea for a controlled nuclear fusion reactor, the tokamak, which is still the basis for the majority of work in the area, based on the premise of confining extremely hot ionized plasma by torus-shaped magnetic fields in order to control the thermonuclear fusion process. He also worked on generating extremely high-power electromagnetic pulses by compressing magnetic flux using high explosive.

In 1953, Sakharov received his DSc degree, was elected a full member of the Soviet Academy of Sciences and was awarded the first of his three Hero of Socialist Labour titles. By the late 1950s, however, Sakharov had become concerned about the moral and political implications of his nuclear weapons work. He became politically active during the 1960s, warning against nuclear proliferation and pushing for an end to atmospheric tests. He played a prominent role in the Partial Test Ban Treaty, signed in Moscow in 1963. In 1967, when anti-ballistic missile defense became a core issue in US-Soviet relations, he argued for a bilateral rejection of such weapons on the grounds that an arms race in this new technology would only increase the likelihood of nuclear war.

After 1965, Sakharov returned to fundamental science and began working on particle physics and cosmology, particularly the search for an explanation for the “baryon asymmetry” of the universe (the huge preponderance of matter, as opposed to antimatter, in the known universe). He was the first scientist to introduce the concept of two universes called “sheets,” which may have been linked at the time of the Big Bang. The “other” universe would exhibit complete “CPT symmetry” (the inversion of charge, parity and time), having an opposite arrow of time and being mainly populated by antimatter. Sakharov called the singularities, where these two sheets could theoretically interact without being separated by space-time, a “collapse” and an “anticollapse,” similar to the black hole and white hole of wormhole theory. He also proposed the idea of induced gravity (or emergent gravity) as an alternative theory of quantum gravity.

After his continued agitation against the deployment of nuclear weapons, he was banned from all military-related research in 1968 and returned to FIAN in Moscow. In 1970 he founded the Moscow Human Rights Committee, together with Valery Chalidze and Andrei Tverdokhlebov, and came under increasing pressure from the regime. He married a fellow human rights activist, Yelena Bonner, in 1972. He was awarded the Prix Mondial Cino Del Duca in 1974 and the Nobel Peace Prize in 1975, although he was not allowed to leave the Soviet Union to collect it (his wife read his speech at the ceremony in Oslo).

Sakharov was arrested in early 1980 after his public protests against the 1979 Soviet invasion of Afghanistan and was sent to internal exile in the city of Gorky (now Nizhny Novgorod), a closed city inaccessible to foreign observers. He remained under tight Soviet police surveillance, subject to repeated searches and heists, until 1986, when he was allowed to return to Moscow under the perestroika and glasnost policies of Mikhail Gorbachev. There, he helped to initiate the first independent legal political organizations and became prominent in the Soviet Union’s growing political opposition. He was elected to the new parliament in 1989, and briefly co-led the democratic opposition.

Scientists

Ernest Rutherford

Ernest Rutherford, 1st Baron Rutherford of Nelson was a New Zealand chemist who has become known as the “father of nuclear physics.” In 1911, he was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model (or planetary model) of the atom. He is also credited with the discovery of the proton in 1919 and hypothesized the existence of the neutron. He was awarded the Nobel Prize in Chemistry in 1908 “for his investigations into the disintegration of the elements, and the chemistry of radioactive substances.”

Education and Influences

Ernest Rutherford was born on 30 August 1871 in Spring Grove (now called Brightwater) near Nelson, New Zealand, the fourth of twelve children of a Scottish farmer and an English schoolteacher. He was educated at Havelock School and then, at age 16, Nelson Collegiate School, before winning a scholarship to study at Canterbury College at the University of New Zealand in Wellington in 1889. He graduated with an MA in 1893, with a double first in Mathematics and Physical Science.

He continued with research work at Canterbury College for a short time, receiving a BSc degree in 1894, before traveling to England in 1895 for postgraduate study at the Cavendish Laboratory at the University of Cambridge, where he studied under J. J. Thompson (soon to become the discoverer of the electron). During Rutherford’s investigation of radioactivity at Cambridge, he invented an ingenious detector for electromagnetic waves and coined the terms “alpha” and “beta” to describe the two distinct types of radiation emitted by thorium and uranium. In 1897, he was awarded a BA Research Degree and the Coutts-Trotter Studentship of Trinity College, Cambridge.

Contributions and Impact

In 1898, Rutherford was appointed to the vacant chair of physics at McGill University in Montreal, Canada. In 1900, he married Mary Georgina Newton, and they had a daughter, Eileen Mary, the next year.

During his nine years in Montreal, Rutherford collaborated with the young Frederick Soddy (winner of the Nobel Prize in Chemistry in 1921) on ground-breaking research into the transmutation of elements. His “disintegration theory” of radioactivity identified radioactive phenomena as atomic, not molecular, processes, due to the spontaneous disintegration of atoms. He also noticed that a sample of radioactive material invariably took the same amount of time for half the sample to decay (known as its “half-life”) and suggested a practical application using this constant rate of radioactive decay as a clock, which could then be used to help determine the age of the Earth (which turned out to be much older than most of the scientists at the time believed). It was for this work that he was the Nobel Prize in Chemistry in 1908. Otto Hahn (who later discovered nuclear fission) worked under Rutherford at the Montreal Laboratory in 1905 – 1906.

In 1907, Rutherford was appointed a professor of physics at the University of Manchester, England. He directed Hans Geiger and Ernest Marsden in the famous Geiger-Marsden experiment (or “gold-foil experiment”) in 1909, which demonstrated the nuclear nature of atoms. It was his interpretation of these experiments in 1911 that led him to the Rutherford model of the atom, involving a tiny positively-charged nucleus orbited by even tinier negatively-charged electrons, a great advance on J. J. Thomson’s so-called “plum pudding” model.

In 1912, Niels Bohr joined him at Manchester, and Bohr adapted Rutherford’s nuclear structure to Max Planck’s quantum theory, and so obtained a theory of atomic structure which essentially remains valid to this day. In 1913, together with H. G. Moseley, Rutherford used cathode rays to bombard atoms of various elements and showed that the inner structures correspond with a group of lines which characterize the elements. Each element could then be assigned an atomic number which would define its specific properties.

In 1919, Rutherford returned to Cambridge when he was offered the Directorship of the Cavendish Laboratory in Cambridge, a position he retained for many years, effectively until the end of his life. He was considered an inspiring leader of the Cavendish Laboratory, and steered numerous future Nobel Prize winners towards their great achievements (including James Chadwick, Patrick Blackett, John Cockcroft and Ernest Walton) as well as working with many others for shorter or more extended periods (including George Thomson, Edward Appleton, Cecil Powell and Francis Aston).

In 1919, he became the first person to transmute one element into another when he converted nitrogen into oxygen through a nuclear reaction involving the shooting of alpha particles into nitrogen gas. He is also credited with the discovery of the proton when he noticed the signatures of hydrogen nuclei being emitted during this process. While working with Niels Bohr in 1921, he theorized about the existence of neutrons, which could somehow compensate for the repelling effect of the positive charge of protons by causing an attractive nuclear force and thus keeping the nuclei from breaking apart. Rutherford’s theory of neutrons was eventually proved in 1932 by his associate James Chadwick.

Rutherford had been knighted in 1914 and was subsequently awarded the Order of Merit in 1925. In 1931, he was created the 1st Baron Rutherford of Nelson and Cambridge. In addition to directing the Cavendish Laboratory, he also went on to take up several additional positions including Chairman of the Advisory Council of the Department of Scientific and Industrial Research, Professor of Natural Philosophy at the Royal Institution in London and Director of the Royal Society Mond Laboratory in Cambridge. He had been elected a Fellow of the Royal Society back in 1903, and he acted as its President from 1925 to 1930. He was awarded many prizes and honors, including the Rumford Medal, the Copley Medal, the Bressa Prize, the Albert Medal and the Faraday Medal, as well as countless honorary degrees and doctorates.

Scientists

Max Planck

Max Planck was a German theoretical physicist, considered to be the initial founder of quantum theory and one of the most important physicists of the 20th Century. Around the turn of the century, he realized that light and other electromagnetic waves were emitted in discrete packets of energy that he called “quanta” – “quantum” in the singular – which could only take on certain discrete values (multiples of a certain constant, which now bears the name the “Planck constant”). This is generally regarded as the first essential stepping stone in the development of quantum theory, which has revolutionized the way we see and understand the sub-atomic world.

Education and Influences

Karl Ernst Ludwig Marx Planck, better known as Max, was born in Kiel in Holstein, northern Germany on 23 April 1858. His family was traditional and intellectual (his father was a law professor, and his grandfather and great-grandfather had been theology professors). In 1867, the family moved to Munich, where Planck attended the Ludwig Maximilians gymnasium school. There, he came under the tutelage of Hermann Müller, who taught him astronomy and mechanics as well as math , and awoke Planck’s early interest in physics.

Although a talented musician (he sang, played the piano, organ and cello, and composed songs and even operas), he chose to study physics at the University of Munich in 1874, soon transferring to theoretical physics, before going on to Berlin for a year of further study in 1877. Having completed his habilitation thesis on heat theory in 1880, Planck became an unpaid private lecturer in Munich, waiting until he was offered an academic position. In April 1885, the University of Kiel appointed him as an associate professor of theoretical physics, and he continued to pursue work on heat theory and on Rudolph Clausius’ ideas about entropy and its application in physical chemistry.

Contributions and Impact

In 1889, Planck moved to the University of Berlin, becoming a full professor in 1892. He had married Marie Merck in 1887, and they went on to have four children, Karl (1888), the twins Emma and Grete (1889) and Erwin (1893), of whom only Erwin was to survive past the First World War. The Planck home in Berlin became a social and cultural center for academics, and many well-known scientists, including Albert Einstein, Otto Hahn, and Lise Meitner, were frequent visitors.

In 1894, Planck turned his attention to the problem of blackbody radiation, the observation that the greatest amount of energy being radiated from a “black body” (or any perfect absorber) falls near the middle of the electromagnetic spectrum, rather than in the ultraviolet region as classical theory would suggest. In particular, he investigated how the intensity of the electromagnetic radiation emitted by a black body depends on the frequency of the radiation (e.g., the color of the light) and the temperature of the body. After some initial frustrations, he derived the first version of his black body radiation law in 1900. However, although it described the experimentally observed blackbody spectrum well, he realized that it was not perfect.

The previous year, though, in 1899, he had noted that the energy of photons could only take on certain discrete values which were always a full integer multiple of a specific constant, which is now known as the “Planck constant.” Thus, light and other waves were emitted in discrete packets of energy that he called “quanta.” Defining the Planck constant enabled him to go on to establish a new universal set of physical units or Planck units (such as the Planck length, the Planck time, the Planck temperature, etc), all based on five fundamental physical constants: the speed of light in a vacuum, the gravitational constant, the Coulomb force constant, the Boltzmann constant and his own Planck constant.

Later in 1900, then, he revised his black body theory to incorporate the supposition that electromagnetic energy could be emitted only in “quantized” form, so that the energy could only be a multiple of an elementary unit E = hv (where h is the Planck constant, previously introduced by him in 1899, and v is the frequency of the radiation). Although quantization was a purely formal assumption in Planck’s work at this time and he never fully understood its radical implications (which had to await Albert Einstein’s interpretations in 1905), its discovery has come to be regarded as effectively the birth of quantum physics, and the most significant intellectual accomplishment of Planck’s career. It was in recognition of this accomplishment that he was awarded the Nobel Prize in Physics in 1918.

Planck was among the few who immediately recognized the significance of Einstein’s 1905 Special Theory of Relativity, and he used his influence in the world of theoretical physics (he was president of the newly formed German Physical Society from 1905 to 1909) to ensure that the theory was soon widely accepted in Germany, as well as making his own contributions to extending the theory. After Planck had been appointed the dean of Berlin University, it became possible for him to call Einstein to Berlin and to establish a new professorship specifically for him in 1914, and the two scientists soon became close friends and frequently met to play music together.

Planck’s wife Marie died in 1909, possibly from tuberculosis, and, in 1911, he married his second wife, Marga von Hoesslin, who bore him a third son, Hermann, the same year. By the time of the German annexation and the First World War in 1914 (which Planck initially welcomed, but later argued against), he was effectively the highest authority of German physics, as one of the four permanent presidents of the Prussian Academy of Sciences, and a leader in the influential umbrella body, the Kaiser Wilhelm Society. By the end of the 1920s, Niels Bohr, Werner Heisenberg, and Wolfgang Pauli had worked out the so-called “Copenhagen interpretation” of quantum mechanics, and the quantum theory which Planck’s work had triggered became ever more established, even if Planck himself (like Einstein) was never entirely comfortable with some of its philosophical implications.

When the Nazis seized power in 1933, Planck was an old man of 74, and he generally avoided open conflict with the Nazi regime, although he did organize a somewhat provocative official commemorative meeting after the death in exile of fellow physicist Fritz Haber. He also succeeded in secretly enabling a number of Jewish scientists to continue working in institutes of the Kaiser Wilhelm Society for several years.

The “Deutsche Physik” movement attacked Planck, Arnold Sommerfeld, and Werner Heisenberg among others for continuing to teach the theories of Einstein, calling them “white Jews.” When his term as president of the Kaiser Wilhelm Society ended in 1936, the Nazi government pressured him to refrain from seeking another term. At the end of 1938, the Prussian Academy of Sciences lost its remaining independence and was taken over by Nazis, and Planck protested by resigning his presidency. He steadfastly refused to join the Nazi party, despite being under significant political pressure to do so.

Allied bombing campaigns against Berlin during the Second World War forced Planck and his wife to leave the city temporarily to live in the countryside, and his house in Berlin was completely destroyed by an air raid in 1944. He continued to travel frequently, giving numerous public lectures, including talks on Religion and Science (he was a devoted and persistent adherent of Christianity all his life), and at the advanced age of 85, he was still sufficiently fit to climb 3,000-metre peaks in the Alps.

At the end of the Second World War (during which his youngest son Erwin was implicated in the attempt on Hitler’s life in 1944 and hanged), Planck, his second wife, and his remaining son moved to Göttingen. He died there on 4 October 1947, aged 89, from the consequences of a fall and several strokes.

Scientists

Wolfgang Pauli

Wolfgang Pauli was an Austrian theoretical physicist noted for his work on spin theory and quantum theory, and for the remarkable discovery of the Pauli exclusion principle, which underpins the structure of matter and the whole of chemistry.

Education and Influences

Wolfgang Ernst Pauli was born on 25 April 1900 in Vienna, Austria (then Austria-Hungary). He was raised as a Roman Catholic, although both his parents came from prominent Jewish families, and his godfather was the noted Austrian physicist and philosopher Ernst Mach. He was something of a youth prodigy, graduating with distinction from the Döblinger-Gymnasium in Vienna in 1918, despite paying scant attention to his classes and publishing his first paper (on Albert Einstein’s General Theory of Relativity) just two months after graduation. He attended the Ludwig Maximilian University in Munich, working under Arnold Sommerfeld, and he received his Ph.D. there in 1921 for his thesis on the quantum theory of ionized molecular hydrogen. His 1921 monograph on the Theory of Relativity remains a standard reference on the subject to this day.

Pauli spent 1922 at the University of Göttingen as the assistant to Max Born, and 1923 at Niels Bohr’s Institute for Theoretical Physics in Copenhagen. From 1923 to 1928, he lectured at the University of Hamburg, during which time he was instrumental in the development of the modern theory of quantum mechanics, particularly his formulation of the exclusion principle and the theory of non-relativistic spin.

Contributions and Impact

In 1924, he had proposed a quantum number for the “spin” of electrons, with two possible values, “up” and “down.” He then extended this to formulate the Pauli exclusion principle in 1925, perhaps his best known and most important work, which states that no two electrons (or, technically, fermions) can exist in the same quantum state (i.e., no two electrons in an atom can have the same four quantum numbers).

By the end of 1925, he had used Heisenberg’s newly developed matrix theory of quantum mechanics (which Pauli saw as the only way forward for quantum physics) to derive the observed spectrum of the hydrogen atom, which was an essential step in securing credibility for Heisenberg’s theory. He went on to use a 2 × 2 matrix as a basis of spin operators, thus solving the non-relativistic theory of spin.

Pauli seldom published papers, preferring lengthy correspondences with colleagues such as Niels Bohr and Werner Heisenberg, with whom he had close friendships. Many of his ideas and results were therefore never actually published and appeared only in his letters, which were often copied and circulated by their recipients, with Pauli apparently unconcerned that much of his work thus went uncredited. He earned a reputation as a perfectionist, both concerning his own work and that of others, but he could also appear arrogant and was particularly scathing about theories which were untestable or unevaluatable, famously dismissing one such idea with: “Not only is it not right, it’s not even wrong.”

In 1928, Pauli was appointed Professor of Theoretical Physics at the Swiss Federal Institute of Technology in Zürich, where Einstein had earlier studied and taught. In 1929, (two years after his mother, to whom he had been very close, committed suicide), he officially left the Roman Catholic Church, and later that year, he married Käthe Margarethe Deppner. The marriage was an unhappy one, however, ending in divorce after less than a year.

In 1930, while considering the problem of beta decay, he proposed the existence of a hitherto unobserved neutral particle with a small mass (less than 1% the mass of a proton), which he initially proposed to call the “neutron”, but which became better known under the name given to it later by Enrico Fermi, the “neutrino”. Neutrinos were finally confirmed experimentally in 1956 (the neutron which makes up part of the nucleus of an atom had been discovered in the meantime by James Chadwick in 1932).

Pauli was awarded the Lorentz Medal for outstanding contributions to theoretical physics in 1931, but his failed marriage and the strain of his work resulted in a nervous breakdown around this time. He began drinking heavily and had consultations with the psychologist Carl Jung, who also lived near Zürich. He re-married in 1934 to Franciska Bertram, and this marriage was much more successful. Franciska proved a great support to him over the years, although they were to have no children.

In addition to his post at the Swiss Federal Institute of Technology, Pauli also held visiting professorships in the United States, at the University of Michigan in 1931, and at the Institute for Advanced Study at Princeton, New Jersey in 1935. The German annexation of Austria in 1938 made him a de facto German national, which became a difficulty with the outbreak of World War II in 1939, and made the decision to move to the United States in 1940.

From 1940, he held the position of Professor of Theoretical Physics at Princeton (during which time he showed that particles with half-integer spin are fermions, while particles with integer spin are bosons). This was followed by more visiting professorships at the University of Michigan in 1941 and at Purdue University in 1942. In 1945, he received the Nobel Prize in Physics (nominated by Albert Einstein) for his “decisive contribution through his discovery in 1925 of a new law of Nature, the Exclusion Principle or Pauli Principle”.

After the end of the War, in 1946, he became a naturalized citizen of the United States, but then returned to Zürich, where he mostly remained for the rest of his life. During the last ten to fifteen years of his life, Pauli spent much time studying the history and philosophy of science. He was elected a Fellow of the Royal Society of London in 1953, and he was also elected a member of the Swiss Physical Society, the American Physical Society and the American Association for the Advancement of Science.

In 1958, Pauli was awarded the Max Planck Medal for extraordinary achievements in theoretical physics.

Scientists

Alexander Oparin

Alexander Oparin was a Russian biochemist, notable for his contributions to the theory of the origin of life on Earth, and particularly for the “primordial soup” theory of the evolution of life from carbon-based molecules. Oparin also devoted considerable effort to enzymology and helped to develop the foundations of industrial biochemistry in the USSR. He received numerous decorations and awards for his work, and has been called “the Darwin of the 20th Century”.

Education and Influences

Alexander (or Aleksandr) Ivanovich Oparin was born in 1894 in Uglich, Russia. When he was nine years old, his family moved to Moscow because there was no secondary school in their village. He attended Moscow State University, majoring in plant physiology, where he was influenced by K. A. Timiryazev, a Russian plant physiologist who had known the English naturalist Charles Darwin, and Darwin’s work was to greatly influence Oparin’s later ideas. He graduated from the Moscow State University in 1917 and became a professor of biochemistry there in 1927.

Contributions and Impact

In 1924, Oparin officially put forward his influential theory that life on Earth developed through a gradual chemical evolution of carbon-based molecules in a “primordial soup,” at just about the same time as the British biologist J. B. S. Haldane was independently proposing a similar theory. As early as 1922, at a meeting of the Russian Botanical Society, he had first introduced his concept of a primordial organism arising in a brew of already-formed organic compounds. He asserted the following tenets:

There is no fundamental difference between a living organism and lifeless matter, and the complex combination of manifestations and properties so characteristic of life must have arisen in the process of the evolution of matter.
The infant Earth had possessed a strongly reducing atmosphere, containing methane, ammonia, hydrogen and water vapor, which were the raw materials for the evolution of life.
As the molecules grew and increased in complexity, new properties came into being, and a new colloidal-chemical order was imposed on the simpler organic chemical relations, determined by the spatial arrangement and mutual relationship of the molecules.
Even in this early process, competition, the speed of growth, struggle for existence and natural selection determined the form of material organization that has become characteristic of living things.
Living organisms are open systems, and so must receive energy and materials from outside themselves, and are not therefore limited by the Second Law of Thermodynamics (which is applicable only to closed systems in which energy is not replenished).

Oparin showed how organic chemicals in solution may spontaneously form droplets and layers, and outlined a way in which basic organic chemicals might form into localized microscopic systems (possible precursors of cells) from which primitive living things could develop. He suggested that different types of coacervates might have formed in the Earth’s primordial ocean and, subsequently, been subject to a selection process, eventually leading to life.

He effectively extended Charles Darwin’s theory of evolution backward in time to explain how simple organic and inorganic materials might have combined into more complex organic compounds, which could then have formed primordial organisms. His proposal that life developed effectively by chance, through a progression from simple to complex self-duplicating organic compounds, initially met with strong opposition, but has since received experimental support (such as the famous 1953 experiments of Stanley Miller and Harold Urey at the University of Chicago), and has been accepted as a legitimate hypothesis by the scientific community.

In 1935, Oparin helped found the A. N. Bakh Institute of Biochemistry (part of the USSR Academy of Sciences). His definitive work, “The Origin of Life,” was first published in 1936. He became a corresponding member of the USSR Academy of Sciences in 1939 and a full member in 1946, and he served as director of the Institute of Biochemistry from 1946 until his death. In the 1940s and 1950s, he supported the pseudo-scientific theories of Trofim Lysenko and Olga Lepeshinskaya, seen by some as a cynical effort to “take the party line” and thereby to advance his own career.

Oparin organized the first international meeting on the origin of life in Moscow in 1957, which was to be followed by other meetings in 1963 and in 1970. He was nominated as a Hero of Socialist Labour in 1969 and, the next year was elected President of the International Society for the Study of the Origins of Life. He received the Lenin Prize in 1974 and the Lomonosov Gold Medal in 1979 “for outstanding achievements in biochemistry.” He was also awarded five Orders of Lenin, the highest decoration bestowed by the Soviet Union.

Scientists

Georges Lemaître

Monsignor Georges Lemaître was a Belgian Roman Catholic priest, physicist, and astronomer. He is usually credited with the first definitive formulation of the idea of an expanding universe and what was to become known as the Big Bang theory of the origin of the universe, which Lemaître himself called his “hypothesis of the primeval atom” or the “Cosmic Egg.”

Education and Influences

Georges Henri Joseph Édouard Lemaître was born on 17 July 1894 at Charleroi, Belgium. After a classical education at a Jesuit secondary school, the Collège du Sacré-Coeur in Charleroi, he began studying civil engineering at the Catholic University of Leuven (Louvain) at the age of 17. In 1914, he interrupted his studies to serve as an artillery officer in the Belgian army for the duration of World War I, at the end of which he received the Military Cross with palms.

After the war, Lemaître studied physics and math and simultaneously began to prepare for the priesthood. He obtained his doctorate in 1920 and was ordained a priest in 1923. That same year, he became a graduate student in astronomy at the University of Cambridge in England, working with Arthur Eddington, who initiated him into modern cosmology, stellar astronomy, and numerical analysis. He spent 1924 at Harvard College Observatory in Massachusetts, U.S.A., and at the Massachusetts Institute of Technology. In 1925, he returned to Belgium and became a part-time lecturer (and later a full-time professor) at the Catholic University of Leuven, where he remained for the rest of his career.

Contributions and Impact

In 1927, he discovered a family of solutions to Einstein’s field equations of relativity that described not a static universe, but an expanding universe (as, independently, had the Russian Alexander Friedmann in 1922). The report which would eventually bring him international fame, entitled “A homogeneous universe of constant mass and growing radius accounting for the radial velocity of extragalactic nebulae” in translation, was published later in 1927 in the little-known journal “Annales de la Société Scientifique de Bruxelles.” In this report, he presented his new idea of an expanding universe, and also derived the first statement of what would later become known as Hubble’s Law (that the outward speed of distant objects in the universe is proportional to their distance from us), and provided the first observational estimation of the Hubble constant.

In 1929, after nearly a decade of observations, Edwin Hubble published his definitive report that the redshift in light coming from distant galaxies is proportional to their distance, effectively confirming Lemaître’s prediction of an expanding universe. However, Lemaître’s model of the universe received little notice until it was publicized by the prominent English astronomer Arthur Eddington, who described it as a “brilliant solution” to the outstanding problems of cosmology, and arranged for Lemaître’s theory to be translated and reprinted in the “Monthly Notices of the Royal Astronomical Society” in 1931.

Later in 1931, at a meeting of the British Association in London to discuss the relationship between the physical universe and spirituality, Lemaître first voiced his proposal that the universe had expanded from an initial point, which he called the “primeval atom” or “the Cosmic Egg, exploding at the moment of the creation”, a theme he developed further in a report published in the journal “Nature” later that year.

Lemaître argued that, if matter is everywhere receding, it would seem natural to suppose that in the distant past it was closer together, and that, if we go far enough back, we reach a time at which the entire universe was in an extremely compact and compressed state. He spoke, somewhat vaguely, of some instability being produced by radioactive decay of the primal atom that was sufficient to cause an immense explosion that initiated the expansion of the universe. The theory later became much better known as the “Big Bang” theory after a sarcastic remark of the English astronomer Fred Hoyle in 1949, and its importance today is arguably due more to the revival and revision it received at the hands of George Gamow in 1946.

Lemaître’s proposal initially met with skepticism from his fellow scientists at the time, and even the supportive Eddington found Lemaître’s notion “repugnant.” Einstein was initially unwilling to accept Lemaître’s idea of an expanding universe, although he did appreciate Lemaître’s argument that the static-Einsteinian model of the universe could not be sustained indefinitely into the past, commenting “Your math is correct, but your physics is abominable.”

However, by 1933, the theory had become more widely accepted, and newspapers around the world began calling him a famous Belgian scientist and describing him as the leader of the new cosmological physics. Some claim that Einstein’s 1933 comment that “this is the most beautiful and satisfactory explanation of creation to which I have ever listened” was in direct reference to Lemaître’s theory, although others dispute this.

Lemaître received the highest Belgian scientific distinction, the Francqui Prize, in 1934 (proposed by Albert Einstein, among others). He was elected a member of the Pontifical Academy of Sciences in 1936, and remained an active member until his death, accepting the position of president in 1960. In 1941, he was elected member of the Royal Academy of Sciences and Arts of Belgium, and he received the very first Eddington Medal awarded by the Royal Astronomical Society in 1953.

During the 1950s, he gradually gave up part of his teaching workload at Leuven, and he retired altogether in 1964, devoting his time to numerical calculation, as well as keeping up his keen interest in the development of computers and in the problems of language and programming.

He died on 20 June 1966, shortly after having learned of the discovery of cosmic microwave background radiation, which provided further evidence for his own intuitions about the birth of the universe.

Scientists

Edwin Hubble

Edwin Hubble was an American astronomer who, in 1925, was the first to demonstrate the existence of other galaxies besides the Milky Way, profoundly changing the way we look at the universe. Later, in 1929, he also definitively demonstrated that the universe was expanding (considered by many as one of the most important cosmological discoveries ever made) and formulated what is now known as Hubble’s Law to show that the other galaxies are moving away from the Milky Way at a speed directly proportionate to their distance from it. He has been called one of the most influential astronomers since the times of Galileo, Kepler, and Newton.

Education and Influences

Edwin Powell Hubble was born on 20 November 1889 in Marshfield, Missouri, U.S.A., although the family moved to Wheaton, Illinois, soon after his birth. At school, he earned good grades in most subjects, although he was more noted for his athletic prowess than his intellectual abilities (in 1906, he won seven first places and a third place in a single high school track meet and set a state record for high jump). He was also a keen fisherman, basketball player, and amateur boxer.

From 1907 to 1910, he studied math, astronomy, and philosophy at the University of Chicago, leading to a BSc degree in 1910. He spent the next three years as one of the first Rhodes Scholars at Oxford University, where he studied jurisprudence before switching his major to Spanish and receiving an MA degree. On returning to the United States in 1913, he taught Spanish, physics, and math (and coached the basketball team) at a high school in New Albany, Indiana, and also practiced law half-heartedly for a year in Louisville, Kentucky.

Hubble returned to the University of Chicago to study astronomy at the Yerkes Observatory in 1914, earning his Ph.D. in 1917, and was then offered a staff position by George Ellery Hale, the founder and director of Carnegie Institution’s Mount Wilson Observatory, near Pasadena, California. However, World War I intervened, and Hubble enlisted in the infantry, quickly advancing to the rank of major. On his return to the United States in the summer of l9l9, he went immediately to take up his position at Mount Wilson, where he was to remain until his death, and which was to be the scene of all his major discoveries.

Contributions and Impact

Hubble’s arrival at Mount Wilson in 1919 coincided roughly with the completion of the 100-inch Hooker Telescope, then the world’s largest telescope, which allowed him to observe hitherto unheard-of distances into the universe. During the period from 1922 to 1923, he was able to identify Cepheid variables (a class of variable stars notable for a tight correlation between their period of variability and their absolute luminosity, which makes them useful as a “standard candle” to determine distances) in several spiral nebulae, including the Andromeda Nebula.

His meticulously documented observations announced at the beginning of 1925 proved conclusively that these nebulae were nearly a million light-years away, much too distant to be part of the Milky Way, and were, in fact, entire galaxies outside our own. At that time, this was a revolutionary idea, the prevailing view being that the universe consisted entirely of the Milky Way, and it was opposed vehemently by many in the astronomy establishment, particularly by Harvard-based Harlow Shapley, who had made his reputation by measuring the size of the Milky Way.

Hubble went on to devise the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images, in what became known as the Hubble sequence. But an even more dramatic and important discovery was still to come.

Using the recently discovered concept of the redshift of galaxies (a measure of recession speed, based on the idea that visible light emitted or reflected by an object is shifted towards the less energetic red end of the electromagnetic spectrum as it moves away from the observer), and combining his own measurements with those of Vesto Slipher, Hubble and his assistant, Milton Humason, discovered a rough proportionality of the objects’ distances with their redshifts. This led to the statement in 1929 of the “redshift-distance law of galaxies,” now better known as Hubble’s Law, which states that the greater the distance between any two galaxies, the greater their relative speed of separation.

Hubble’s initial estimate of the rate of expansion (the constant term in his equation linking the recession velocity of galaxies and their distance, known as Hubble’s constant) was perhaps ten times too great due to measurement errors, and its exact value still remains a contentious subject. However, the general concept of an expanding universe was consistent with the solutions to Einstein’s equations of general relativity for a homogeneous, isotropic expanding space. Thus, it provided the first observational support for the expanding universe theory, which had been proposed in theory by Alexander Friedmann in 1922 and Georges Lemaître in 1927, and for the Big Bang explanation of the birth of the universe.

Albert Einstein, whose general relativity equations had seemed to indicate that the universe must be either expanding or contracting, had introduced a compensatory “cosmological constant” into his equations back in 1917 because he could not believe that the universe was anything but static and infinite. When he heard of Hubble’s discovery, however, he said that changing his equations was “the biggest blunder” of his life, and he was grateful to Hubble for negating the need for such a fudge factor in his equations. Einstein traveled to Mount Wilson to see the telescope and to thank Hubble personally for delivering him from folly.

Hubble had married Grace Burke in Pasadena in 1924, and for a time, during the 1930s and 1940s, the Hubbles basked in the celebrity of these important astronomical discoveries. Hubble had affected British mannerisms and clothing since his time as a young man in Cambridge and had a tendency towards vanity, pretentiousness, and racism, but he was handsome, fit, and an imposing presence at well over six feet tall, as well as an engaging conversationalist. He became a personal friend to the likes of Charlie Chaplin, Harpo Marx, Helen Hayes, Lillian Gish, and William Randolph Hearst, and also a great confidant of Aldous Huxley and his wife.

During World War II, from 1942 to 1946, he served in the U.S. Army as head of ballistics at the Aberdeen Proving Ground, for which he received the Legion of Merit decoration. He remained active in astronomy research until his death, both at Mount Wilson Observatory and also at Palomar Observatory, where he had a central role in the design and construction of the 200-inch Hale Telescope. When the Hale Telescope was completed in 1948, Hubble was the first to use it.

However, soon after that, he suffered a major heart attack, and he never fully regained the stamina needed to spend all night in a freezing-cold observatory. Hubble died of cerebral thrombosis on 28 September 1953 in San Marino, California. No funeral was held, and his wife, Grace, never revealed what happened to his body.

Although he had been awarded the Bruce Medal in 1938, the Gold Medal of the Royal Astronomical Society in 1940, and the Medal of Merit for outstanding contribution to ballistics research in 1946, Hubble, as an astronomer, was ineligible for the Nobel Prize in Physics (a rule which always irked him, although it was changed just after his death). He was, however, honored posthumously in other ways, including the naming of an asteroid and a crater on the Moon and, most famously, the orbiting Hubble Space Telescope, which was launched in 1990 and which continues to provide us with astounding pictures of deep space.