November 20: Edwin Powell Hubble

Edwin Powell Hubble

November 20, 1889 – September 28, 1953

Edwin Hubble was an American astronomer. He profoundly changed our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. He also discovered that the degree of redshift observed in light coming from a galaxy increased in proportion to the distance of that galaxy from the Milky Way. This became known as Hubble's law, and would help establish that the known universe is expanding.

In 1919, Hubble was offered a staff position in California by George Ellery Hale, the founder and director of the Carnegie Institution's Mount Wilson Observatory, near Pasadena, California, where he remained on the staff until his death. Shortly before his death, Mount Palomar's giant 200-inch (5.1 m) reflector Hale Telescope was completed, and Hubble was the first astronomer to use it. Hubble continued his research at the Mount Wilson and Mount Palomar Observatories, where he remained active until his death.

Edwin Hubble's arrival at Mount Wilson, California, in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope, then the world's largest telescope. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star; see also standard candle) in several spiral nebulae, including the Andromeda Nebula. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own. This idea had been opposed by many in the astronomy establishment of the time, in particular by the Harvard University-based Harlow Shapley. Hubble's discovery, announced on January 1, 1925, fundamentally changed the view of the universe.

Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence.

Hubble was awarder the Bruce Medal (1938) and the Gold Medal of the Royal Astronomical Society (1940).

The Lunar crater Hubble, asteroid 2069 Hubble and the orbiting Hubble Space Telescope are named in his honor.

August 26: Johann Lambert

Johann Heinrich Lambert

August 26, 1728 – September 25, 1777

Johann Heinrich Lambert was a Swiss mathematician, physicist and astronomer.

He was born in Mülhausen (now Mulhouse, Alsace, France; then an exclave of Switzerland). His father was a poor tailor, so Johann had to struggle to gain an education. He first worked as a clerk in an ironworks, then gained a position in a newspaper office. The editor recommended him as a private tutor to a family, which gave him access to a good library and provided enough leisure time in which to explore it. In 1759 he moved to Augsburg, then in 1763 he dwelt in Berlin. In the final decade of his life he gained the sponsorship of Frederick II of Prussia, and passed the rest of his life in reasonable comfort. He died in Berlin, Prussia (today Germany).

Lambert studied light intensity and was the first to introduce hyperbolic functions into trigonometry. Also, he made conjectures regarding non-Euclidean space. Lambert is credited with the first proof that π is irrational in 1768 and of several map projections in 1772, such as the Lambert cylindrical equal-area projection. Lambert also devised theorems regarding conic sections that made the calculation of the orbits of comets simpler. The first practical hygrometer and photometer were invented by Lambert.

Lambert devised a formula for the relationship between the angles and the area of hyperbolic triangles. These are triangles drawn on a concave surface, as on a saddle, instead of the usual flat Euclidean surface. Instead of expressing the area of the triangle in terms of the lengths of its sides, as in Euclid's geometry, the area of Lambert's hyperbolic triangle can be expressed in terms of its angles.

In his main philosophical work, "New Organon" (1764), Lambert studied the rules for distinguishing subjective from objective appearances. This connects with his work in the science of optics. In 1760, he published a book on light reflection in Latin, the Photometria, in which the word albedo was introduced and the Lambert-Beer law was formulated that describes the way in which light is absorbed. Lambert also wrote a classic work on perspective and also contributed to geometrical optics.

Lambert also developed a theory of the generation of the universe that was similar to the nebular hypothesis that Thomas Wright and Immanuel Kant had (independently) developed. Wright published his account in "An Original Theory or New Hypothesis of the Universe" (1750), Kant in "Allgemeine Naturgeschichte und Theorie des Himmels", published anonymously in 1755. Shortly afterward, Lambert published his own version of the nebular hypothesis of the origin of the solar system in "Cosmologische Briefe über die Einrichtung des Weltbaues" (1761). Lambert hypothesized that the stars near the sun were part of a group which travelled together through the Milky Way, and that there were many such groupings (star systems) throughout the galaxy. The former was later confirmed by Sir William Herschel.

June 24: Fred Hoyle

Fred Hoyle

June 24, 1915 – August 20, 2001

Sir Fred Hoyle FRS was an English astronomer primarily remembered today for his contribution to the theory of stellar nucleosynthesis and his often controversial stance on other cosmological and scientific matters, in particular his rejection of the Big Bang theory. In addition to his work as an astronomer, Hoyle was a writer of science fiction, including a number of books co-authored with his son Geoffrey Hoyle. Hoyle spent most of his working life at the Institute of Astronomy at Cambridge and served as its director for a number of years.

An early paper of Hoyle's made an interesting use of the anthropic principle. In trying to work out the routes of stellar nucleosynthesis, he observed that one particular nuclear reaction, the triple-alpha process, which generated carbon, would require the carbon nucleus to have a very specific energy for it to work. The large amount of carbon in the universe, which makes it possible for carbon-based life-forms (e.g. humans) to exist, demonstrated that this nuclear reaction must work. Based on this notion, he made a prediction of the energy levels in the carbon nucleus that was later borne out by experiment.

While having no argument with the Lemaître theory, (later confirmed by Edwin Hubble's observations) that the universe was expanding, Hoyle disagreed on its interpretation. He found the idea that the universe had a beginning to be philosophically troubling, as many argued that a beginning implies a cause, and thus a creator. Instead, Hoyle, along with Thomas Gold and Hermann Bondi, argued for the universe as being in a "steady state". The theory tried to explain how the universe could be eternal and essentially unchanging while still having the galaxies we observe moving away from each other. The theory hinged on the creation of matter between galaxies over time, so that even though galaxies get further apart, new ones that develop between them fill the space they leave. The resulting universe is in a "steady state" in the same manner that a flowing river is - the individual water molecules are moving away but the overall river remains the same.

The theory was the only serious alternative to the Big Bang which agreed with key observations of the day, namely Hubble's red shift observations, and Hoyle was a strong critic of the Big Bang. Ironically, he is responsible for coining the term "Big Bang" on BBC radio's Third Programme broadcast at 1830 GMT on 28 March 1949. It is popularly reported that Hoyle intended this to be pejorative, but the script from which he read aloud clearly shows that he intended the expression to help his listeners. In addition, Hoyle explicitly denied that he was being insulting and said it was just a striking image meant to emphasize the difference between the two theories for radio listeners.

The evidence that resulted in the Big Bang's victory over the steady state model, at least in the minds of most cosmologists, included the discovery of the cosmic microwave background radiation in the 1960s, the distribution of "young galaxies" and quasars throughout the Universe in the 1980s, a more consistent age estimate of the universe and most recently the observations of the COBE satellite in the 1990s and the Wilkinson Microwave Anisotropy Probe launched in 2001, which showed unevenness in the microwave background in the early universe, which corresponds to currently observed distributions of galaxies.

Hoyle appeared in a series of radio talks on astronomy for the BBC in the 1950s; these were collected in the book The Nature of the Universe, and he went on to write a number of other popular science books. In 1957 he was elected a Fellow of the Royal Society, and he was knighted in 1972. He was jointly awarded the Crafoord Prize by the Royal Swedish Academy of Sciences.

June 22: Hermann Minkowski

Hermann Minkowski

June 22, 1864 – January 12, 1909

Hermann Minkowski was a German mathematician of Jewish and Polish descent, who created and developed the geometry of numbers and who used geometrical methods to solve difficult problems in number theory, mathematical physics, and the theory of relativity.

Minkowski taught at the universities of Bonn, Göttingen, Königsberg and Zürich. At the Eidgenössische Polytechnikum, today the ETH Zurich, he was one of Einstein's teachers.

Minkowski explored the arithmetic of quadratic forms, especially concerning n variables, and his research into that topic led him to consider certain geometric properties in a space of n dimensions. In 1896, he presented his geometry of numbers, a geometrical method that solved problems in number theory.

In 1902, he joined the Mathematics Department of Göttingen and became one of the close colleagues of David Hilbert, whom he first met in Königsberg. Constantin Carathéodory was one of his students there.

By 1907 Minkowski realized that the special theory of relativity, introduced by Einstein in 1905 and based on previous work of Lorentz and Poincaré, could be best understood in a four dimensional space, since known as "Minkowski spacetime", in which the time and space are not separated entities but intermingled in a four dimensional space-time, and in which the Lorentz geometry of special relativity can be nicely represented. The beginning part of his address delivered at the 80th Assembly of German Natural Scientists and Physicians (September 21, 1908) is now famous:

The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.

The asteroid 12493 Minkowski, M-matrices and the Lunar crater Minkowski are named in his honor.

June 16: Alexander Friedman

Alexander Alexandrovich Friedman
June 16, 1888 – September 16, 1925

Alexander Alexandrovich Friedman or Friedmann was a Russian and Soviet cosmologist and mathematician.

Alexander Friedman lived much of his life in Leningrad. He fought in World War I (on behalf of Imperial Russia) as a bomber and later lived through the Russian Revolution of 1917.

Friedman obtained his degree in St. Petersburg State University (1910), became a lecturer in St.-Petersburg State College of Mines, and a professor in Perm State University in 1918.

He discovered the expanding-universe solution to the general relativity field equations in 1922, which was corroborated by Edwin Hubble's observations in 1929 (Ferguson, 1991: 67). Friedman's 1924 papers, including "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" (On the possibility of a world with constant negative curvature of space) published by the German physics journal Zeitschrift für Physik (Vol. 21, pp. 326-332), demonstrated that he had command of all three Friedman models describing positive, zero and negative curvature respectively, a decade before Robertson and Walker published their analysis.

This dynamic cosmological model of general relativity would come to form the standard for the Big Bang and steady state theories. Friedman's work supports both theories equally, so it was not until the detection of the cosmic microwave background radiation that the steady state theory was abandoned in favor of the current favorite Big Bang paradigm.

The classic solution of the Einstein field equations that describes a homogeneous and isotropic universe is called the "Friedmann-Lemaître-Robertson-Walker metric", or "FLRW", after Friedman, and Robertson, Walker and Georges Lemaître who worked on the problem in 1920's and 30's independently of Friedman.

In addition to general relativity, Friedman's interests included hydrodynamics and meteorology. In June 1925 he was given the job of the director of Main Geophysical Observatory in Leningrad. In July 1925 he participated in a record-setting balloon flight, reaching the elevation of 7,400 m (24,000 ft).

Friedman died on September 16, 1925, at the age of 37, from typhoid fever that he contracted during a vacation in Crimea.

Another famous physicist, George Gamow, was a student of Friedman.

April 1: Carl Charlier

Carl Vilhelm Ludwig Charlier

April 1, 1862 – November 5, 1934

Carl Charlier was a Swedish astronomer. He received his Ph.D. from Uppsala University in 1887, later worked there and at the Stockholm Observatory and was Professor of Astronomy and Director of the Observatory at Lund University from 1897.

After working in celestial mechanics, the calibration of photographic photometry, and the theory of lenses, he turned to statistics. He made contributions to pure statistics, especially the theory of errors, and made extensive statistical studies of the distribution and motions of stars in the solar neighborhood. 

Related to his work on galactic structure, he also developed a cosmological theory based on the work of Johann Heinrich Lambert. In the resulting Lambert-Charlier Hierarchical Cosmology, increasingly large areas of space contain decreasing densities of matter, the principle being introduced to avoid the observational inconsistency that would otherwise emerge from Olbers Paradox.

In his later years he became interested in the history of astronomy and translated Newton’s Principia into Swedish.

He received the James Craig Watson Medal in 1924 and the Bruce Medal in 1933. The Lunar crater Charlier, asteroid 8677 Charlier and a crater on Mars are named in his honor.