June 29: Pietro Angelo Secchi

Father Pietro Angelo Secchi

June 29, 1818 – February 26, 1878

Father Pietro Angelo Secchi SJ was an Italian astronomer. He was Director of the Observatory at the Pontifical Gregorian University (then called the Roman College) for 28 years. He was a pioneer in astronomical spectroscopy, and was one of the first scientists to state authoritatively that the Sun is a star.

He was born in Reggio Emilia, where he studied at the Jesuit gymnasium. At the age of 16, he entered the Jesuit Order in Rome. He continued his studies at the Roman College, and demonstrated great scientific ability. In 1839, he was appointed tutor of mathematics and physics at the College. In 1841, he became Professor of Physics at the Jesuit College in Loreto. In 1844 he began theological studies in Rome, and was ordained a priest on 12 September 1847. In 1848, due to the Roman Revolution, the Jesuits had to leave Rome. Fr. Secchi spent the next two years in Britain and the United States, where he taught for a time at Georgetown University in Washington, DC. He also took his doctoral examination in theology there.

During his stay in America, he met Commander Matthew Fontaine Maury, the first Director of the United States Naval Observatory in Washington. He studied with Maury and corresponded with him for many years.

He returned to Rome in 1850. On the recommendation of his late colleague Francesco de Vico, he became head of the Observatory of the College at age 32. Under his direction, the crumbling Observatory was relocated to a new facility on top of the Church of St. Ignatius (the chapel of the the College). Fr. Secchi served as Director until his death.

His position was challenged after 1870, when the remnant of the Papal States around Rome was taken over by the Kingdom of Italy. In 1873, the College was declared property of the Italian government. When the government moved to take over the Observatory as well, Fr. Secchi protested vigorously, and threatened to leave the Observatory for one of several positions offered to him by foreign observatories. He was offered important scientific positions and political dignities by the government, but refused to pledge allegiance to the Kingdom in place of the Pope. The royal government did not dare to interfere with him, and he continued as Director.

Father Secchi made contributions to many areas of astronomy.

• He revised Struve's catalog of double stars, compiling data for over 10,000 binaries.
• He discovered three comets, including Comet Secchi.
• He produced an exact map of the lunar crater Copernicus.
• He drew a detailed map of Mars.

Fr. Secchi was especially interested in the Sun, which he observed continually throughout his career.

• He observed and made drawings of solar eruptions and sunspots, and compiled records of sunspot activity.
• In 1860 and 1870, he organized expeditions to observe solar eclipses.
• He proved that the solar corona and coronal prominences observed during a solar eclipse were part of the Sun, and not artifacts of the eclipse.
• He discovered solar spicules.

However, his main area of interest was astronomical spectroscopy. He invented the heliospectrograph, star spectrograph, and telespectroscope. He showed that certain absorption lines in the spectrum of the Sun were caused by absorption in the Earth's atmosphere.

Starting in 1863, he began collecting the spectra of stars, accumulating some 4,000 stellar spectrograms. Through analysis of this data, he discovered that the stars come in a limited number of distinct types and subtypes, which could be distinguished by their different spectral patterns. From this concept, he developed the first system of stellar classification: the five Secchi classes. While his system was superseded by the Harvard system, he still stands as discoverer of the principle of stellar classification, which is a fundamental element of astrophysics.

The lunar crater Secchi and the Martian crater Secchi are both named after him. The two STEREO (Solar TErrestrial RElations Observatory) spacecraft each carry an instrument package called SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation).

June 27: Charles Glover Barkla

Charles Glover Barkla

27 June 1877 – 23 October 1944

Charles Barkla was an English physicist.

Barkla was born in Widnes and studied at the Liverpool Institute and Liverpool University. In 1899 he went to Trinity College, Cambridge as an Exhibition Scholar to work in the Cavendish Laboratory under J J Thomson. At the end of eighteen months his love of music led him to migrate to King's College, Cambridge where he joined the chapel choir. He gained a BA in 1903 and a MA in 1907.

In 1913, after having worked at the universities of Cambridge, Liverpool and King's College London he was appointed professor of natural philosophy at the University of Edinburgh, a position he held until his death. He married Mary Esther Cowell in 1907.

He evolved the laws of X-ray scattering and the laws governing the transmission of X-rays through matter and excitation of secondary rays. For his discovery of the characteristic X-rays of elements, he received the 1917 Nobel Prize in Physics. He was awarded the Royal Society's Hughes Medal that same year.

The Lunar crater Barkla is named in his honor and a commemorative plaque is in the vicinity of the Canongate, near the Faculty of Education Buildings, University of Edinburgh.

June 26: Charles Messier

Charles Messier

June 26, 1730 – April 12, 1817

Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 103 "Messier objects". The purpose of the catalogue was to help comet hunters, as he was, and to help other astronomical observers to distinguish between permanent and transient objects in the sky.

Charles' interest in astronomy was stimulated by the appearance of the spectacular, great six-tailed comet in 1744 and by an annular solar eclipse visible from his hometown on July 25, 1748.

In 1751 he entered the employ of Joseph Nicolas Delisle, the astronomer of the French Navy, who instructed him to keep careful records of his observations. Messier's first documented observation was that of the Mercury transit of May 6, 1753.

In 1764, he was made a fellow of the Royal Society, and on June 30, 1770, he was elected to the French Academy of Sciences. Messier discovered thirteen comets

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. The final version of the catalogue was published in 1781, in Connoissance des Temps for 1784. The final list of Messier objects had grown to 103.

On several different occasions between 1921 and 1966, astronomers and historians discovered evidence of another seven deep-sky objects that were observed either by Messier or his friend and assistant, Pierre Mechain, shortly after the final version was published. These seven objects, M104 through M110, are accepted by astronomers as "official" Messier objects.

The objects' Messier designations, from M1 to M110, still are in use by professional and amateur astronomers today.

The catalogue is not organized scientifically by object type or by location, as the later New General Catalogue would be. Nonetheless, the Messier catalogue comprises examples of every known deep sky object, including galaxies, planetary nebulae, open clusters, and globular clusters. Because these objects were accessible to the relatively small-aperture telescope (approximately 102 mm, or four inches) used by Messier to study the sky, they are among the most spectacular deep sky objects available to modern amateur astronomers using much better equipment. Furthermore, almost all of the Messier objects are among the closest to our planet in their respective classes, which makes them heavily studied with professional class instruments that today, can resolve very small and visually spectacular details in them. Professional astronomers still refer to objects by their Messier designation, and in amateur astronomy they are among the most frequently observed deep sky objects.

Many of the objects in the Messier catalogue were discovered by his assistant, Pierre Mechain.

The crater Messier on the Moon and the asteroid 7359 Messier were named in his honor.

June 25: Rupert Wildt

Rupert Wildt

June 25, 1905 – January 9, 1976

Rupert Wildt was a German-American astronomer. In 1927 he was awarded a Ph.D. from the University of Berlin. He joined the University of Göttingen, specializing in the properties of atmospheres.

In 1932 he studied the spectra of Jupiter, and other outer planets, and identified certain absorption bands as belonging to the hydrogen-rich compounds of methane and ammonia. The composition appeared consistent with a composition similar to the sun and other stars.

Assuming that the atmosphere was composed of these gases, during the 1940s and 1950s he constructed a model of the structure of these planets. He believed the core of the planets is solid and composed of a mixture of rock and metal, covered by a thick outer shell of ice, overlaid by a dense atmosphere. His model is still widely accepted.

In 1934 he emigrated to the United States, and became a research assistant at Princeton University from 1937 until 1942. He then became an assistant professor at the University of Virginia until 1947, before joining the faculty of the Yale University.

In 1937 he proposed that the atmosphere of Venus was composed of a mist of formaldehyde. His observations of the atmosphere did not find any water at the time, but later balloon-based measurements did show water in the atmosphere and so his proposal was abandoned. In 1940, however, he also hypothesized that the carbon dioxide in the venusian atmosphere trapped heat, a phenomenon later called the greenhouse effect.

From 1965 until 1968 he was president of the Association of Universities for Research in Astronomy. In the period 1966-1968 he also held the post of the chairman of the department of astronomy at Yale, and from 1973 until his death he was professor emeritus.

Asteroid 1953 Rupertwildt and the Lunar crater Wildt are named in his honor.

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 23: Alan Turing

Alan Mathison Turing

June 23, 1912 – June 7, 1954

Alan Turing, OBE, FRS was a British mathematician, logician, cryptanalyst and computer scientist.

Turing is often considered to be the father of modern computer science. He provided an influential formalisation of the concept of the algorithm and computation with the Turing machine. Of his role in the modern computer, Time Magazine in naming Turing one of the 100 most influential people of the 20th century, states:

"The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine."

With the Turing test, meanwhile, he made a significant and characteristically provocative contribution to the debate regarding artificial intelligence: whether it will ever be possible to say that a machine is conscious and can think. He later worked at the National Physical Laboratory, creating one of the first designs for a stored-program computer, the ACE, although it was never actually built in its full form. In 1948, he moved to the University of Manchester to work on the Manchester Mark 1, then emerging as one of the world's earliest true computers.

During the Second World War, Turing worked at Bletchley Park, Britain's codebreaking centre, and was for a time head of Hut 8, the section responsible for German naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including the method of the bombe, an electromechanical machine that could find settings for the Enigma machine.

Near the end of his life Turing became interested in chemistry. He wrote a paper on the chemical basis of morphogenesis and he predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, which were first observed in the 1960s.

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 21: Maximilian Wolf

Maximilian Wolf

June 21, 1863 – October 3, 1932

Maximilian Franz Joseph Cornelius Wolf was a German astronomer, a pioneer of astrophotography.

He was born in Heidelberg, Germany. In 1888 he was awarded a Ph.D. by the University of Heidelberg, and joined the staff of that institution in 1890.

Working at Landessternwarte Heidelberg-Königstuhl, he discovered more than 200 asteroids with the Bruce double-astrograph since 1891. The first one, 323 Brucia, was named after Catherine Wolfe Bruce, who had donated $10,000 for the construction of the telescope. He pioneered the use of astrophotographic techniques to automate the discovery of asteroids, as opposed to older visual methods, as a result of which asteroid discovery rates sharply increased. In time-exposure photographs, asteroids appear as short streaks due to their planetary motion with respect to fixed stars.

Among his many discoveries was 588 Achilles (the first Trojan asteroid) in 1906, as well as two other Trojans: 659 Nestor and 884 Priamus. He also discovered 887 Alinda in 1918, which is now recognized as an Earth-crossing Amor asteroid (or sometimes classified as the namesake of its own Alinda family). Shortly after his last discovery (on February 6, 1932), his record 248 discoveries were beaten by his pupil Karl Wilhelm Reinmuth, on July 24, 1933.

He also discovered or co-discovered some comets, including 14P/Wolf and 43P/Wolf-Harrington, and four supernovae: SN 1895A (a.k.a. VW Vir), 1909A (a.k.a. SS UMa), 1920A, and 1926A (the latter co-discovered by Reinmuth).

He also discovered Wolf 359, a red dwarf that is one of the nearest stars to our solar system. Note that Wolf-Rayet stars were co-discovered by French astronomer Charles Wolf and not by him.

In 1910 Wolf proposed to the Carl Zeiss optics firm the creation of a new instrument, now known as the planetarium. World War I intervened before this could be developed, but the Zeiss company returned to this after peace was restored, and the first successful planetarium was completed in 1923.

June 20: John S. Paraskevopoulos

The Lunar crater Paraskevopoulos

John S Paraskevopoulos

June 20, 1889 – March 15, 1951

John Stefanos Paraskevopoulos was a Greek/South African astronomer. He was known as Dr Paras to the astronomical community. He was born in Piraeus, Greece and graduated from the University of Athens.

He served in the Greek army during the Balkan Wars and World War I. In 1919, he went to America for two years, spending part of that time working at Yerkes Observatory where he met and married Dorothy W. Block. In 1921, he returned to Athens where he became head of the Athens Observatory.

He left this post due to a lack of funding and went to Arequipa, Peru to work at Boyden Station, a branch of Harvard Observatory, with a view to finding a more suitable location for it. The decision was made to move Boyden Station to South Africa due to better weather conditions, and Paraskevopoulos served there as director of Boyden Observatory in South Africa from 1927 to 1951.

He co-discovered a couple of comets. The crater Paraskevopoulos on the Moon is named in his honor.

June 19: Wallace John Eckert

Wallace John Eckert

June 19, 1902 – August 24, 1971

Wallace John Eckert was an astronomer, and Director of the Thomas J. Watson Astronomical Computing Bureau at Columbia University. In January 1940, Eckert published Punched Card Methods in Scientific Computation, which solved the problem of predicting the orbits of the planets, using the IBM electric tabulating machines, based on the punched card. This slim book is only 136 pages, including the index.

Born in Pittsburgh, Pennsylvania, he earned his PhD from Yale in 1931 in astronomy.

The Astronomical Computing Bureau was supported by Dr. Thomas J. Watson, President of IBM, including customer service and hardware circuit modifications needed to tabulate numbers, create mathematical tables, add, subtract, multiply, reproduce, verify, crossfoot, create tables of differences, create tables of logarithms and perform Lagrangian interpolation, all to solve differential equations for astronomical applications.

When Dana Mitchell saw these operations in action, and later served in the Manhattan Project (the wartime project to develop the first nuclear weapons), he mentioned this technique to the T-6 section of the Theoretical Division of the Los Alamos National Laboratory in the Manhattan Project; they were using the electromechanical calculators of that time to perform the mathematical computations for mathematical expressions by hand, using human computers, one person to perform the cube, one to add a number, etc. Nicholas Metropolis and Richard Feynman immediately set about organizing a punched card solution for a crucial mathematical expression, utilizing the techniques pioneered by Eckert and his IBM methods, such as the use of colored punched cards to signal the end of a series of cards, etc.

Eckert understood the significance of his laboratory, keenly aware of the advantage of scientific calculations performed without human interventions for long stretches of computation.

He won the James Craig Watson Medal in 1966. The Lunar crater Eckert is named in his honor.

June 18: William Lassell

William Lassell

June 18, 1799 – October 5, 1880

William Lassell was an English astronomer who discovered moons of Neptune, Saturn and Uranus.

Born in Bolton, he made his fortune as a beer brewer, which enabled him to indulge his interest in astronomy. He built an observatory near Liverpool with a 24-inch (610 mm) reflector telescope, for which he pioneered the use of an equatorial mount for easy tracking of objects as the earth rotates. He ground and polished the mirror himself, using equipment he constructed.

In 1846 Lassell discovered Triton, the largest moon of Neptune, just 17 days after the discovery of Neptune itself by German astronomer Johann Gottfried Galle. In 1848 he independently co-discovered Hyperion, a moon of Saturn. In 1851 he discovered Ariel and Umbriel, two new moons of Uranus.

When Queen Victoria visited Liverpool in 1851, Lassell was the only local she specifically requested to meet.

In 1855, he built a 48-inch (1,200 mm) telescope, which he installed in Malta because of the better observing conditions compared to England.

He won the Gold Medal of the Royal Astronomical Society in 1849, and served as its president for two years starting in 1870. Lassell died in Maidenhead in 1880. Upon his death, he left a fortune of £80,000 (equivalent to millions of American dollars by today's standards).

The crater Lassell on the Moon, a crater on Mars and a ring of Neptune are named in his honour.

June 17: William Parsons, 3rd Earl of Rosse

William Parsons, 3rd Earl of Rosse

June 17, 1800 – October 31, 1867

William Parsons, 3rd Earl of Rosse, built several telescopes including the world's largest telescope in 1845 and it remained the world's largest for the rest of the century. Using this telescope he saw and cataloged a large number of galaxies. His 72-inch (6 feet/1.8 m) Leviathan was the first to see the spiral structure of what was later known as the Whirlpool Galaxy, then called M51.

He was born in York in Yorkshire, England. He was educated at Trinity College, Dublin, and Magdalen College, Oxford, graduating with first-class honors in mathematics in 1822. He inherited an earldom and a large estate in King's County (now County Offaly) in Ireland when his father died in 1841.

In addition to his astronomical pursuits, Rosse served as an Member of Parliament (MP) for King's County from 1821 to 1834, an Irish representative peer after 1845, president of the Royal Society (1848–1854), and chancellor of Trinity College, Dublin (1862–1867).

In the 1840s, he built the Leviathan of Parsonstown, a 72-inch (183-cm) telescope at Birr Castle, Parsonstown, County Offaly. He had to invent many of the techniques he used in constructing this telescope, both because its size was without precedent and because earlier telescope builders had guarded their secrets or had simply failed to publish their methods. Rosse's telescope was considered a marvelous technical and architectural achievement, and images of it were circulated widely within the British commonwealth. Building of the telescope began in 1845 and in 1847 it was put into service. The 72-inch (1.8 m) telescope replaced a 36-inch (910 mm) one that he had built previously.

Lord Rosse carried out pioneering astronomical studies and discovered the spiral nature of some nebulas, today known to be spiral galaxies. The first spiral galaxy he detected was M51, and his drawings of it closely resemble modern photographs (today it is known as the Whirlpool Galaxy).

Rosse named the Crab Nebula, based on an earlier drawing made with his older 36-inch (91cm) telescope in which it resembled a crab. A few years later, when the 72-inch (183cm) telescope was in service, he produced an improved drawing of considerably different appearance, but the original name stuck.

A main component of Rosse's nebular research was attempting to resolve the nebular hypothesis, which posited that planets and stars were formed by gravity acting on gaseous nebulae. Rosse himself did not believe that nebulas were truly gaseous, but rather that they were made of such an amount of fine stars that most telescopes could not resolve them individually (that is, he considered nebulas to be stellar in nature). Rosse and his technicians claimed to resolve the Orion nebula into its individual stars, which would have both political and cosmological implications, as at the time there was considerable debate over whether or not the universe was "evolved" (in a pre-Darwinian sense), a concept Rosse disagreed with strongly. Rosse's primary opponent in this was John Herschel, who used his own instruments to claim that the Orion nebula was a "true" nebula, and discounted Rosse's instruments as flawed (an insult Rosse returned about Herschel's own). In the end, neither man (nor telescope) could establish sufficient scientific authority in its results to solve the question by themselves (the convincing evidence for the gaseous nature of the nebula would come later from spectroscopic evidence, though it would not resolve the philosophical issues).

One of Rosse's telescope admirers was Thomas Langlois Lefroy, a fellow Irish MP, who said, "The planet Jupiter, which through an ordinary glass is no larger than a good star, is seen twice as large as the moon appears to the naked eye/.../But the genius displayed in all the contrivances for wielding this mighty monster even surpasses the design and execution of it. The telescope weighs sixteen tons, and yet Lord Rosse raised it single-handed off its resting place, and two men with ease raised it to any height."

Lord Rosse's son published his father's findings, including the discovery of 226 NGC objects in Observations of Nebulae and Clusters of Stars Made With the Six-foot and Three-foot Reflectors at Birr Castle From the Year 1848 up to the Year 1878, Scientific Transactions of the Royal Dublin Society Vol. II, 1878.

Lord Rosse built a variety of optical reflecting telescopes. His telescopes used cast speculum metal parabolicly grounded and polished.

The Lunar crater Rosse is 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.

June 15: Johann Gottlob Frederick von Bohnenberger

Johann Gottlob Frederick von Bohnenberger
June 15, 1765 - April 19, 1831

Johann Gottlob Frederick von Bohnenberger was an astronomer and mathematician. He contributed to the development of early electrical devices and instruments. The best known is the Bohnenberger electroscope.

Johann Gottlob Frederick von Bohnenberger was born on June 15, 1765, in Simmezheim, Germany. His father, Gottlieb Christoph Bohnenberger, was a minister and he made some study in electricity.

Frederick studied theology in Tubingen, and in 1789 he became a priest. However, he went to study mathematics and astronomy first to Zach and then to Gottingen. Since 1796 he was an assistant at the Tubingen observatory and from 1803 professor of mathematics and astronomy there. In 1811 Frederick von Bohnenberger published a book, the “Astronomy”, which made him well known. From 1818 up to his death he was a chief inspector of munitions in Wuttenberg.

Frederick von Bohnenberger made important contributions to the study of electricity. He made electrostatic machines and Bohnenberger electroscope that was an important electrometric instrument.

This curious machine is a primitive influence (electrostatic) machine, proposed by Bohnenberger in 1798, as a rotating implementation of Bennet’s doubler (1787, used as an electromer). About 1814 J.F.G. von Bohnenberger suggested a form of electroscope in which the single leaf was attracted to one of two conductors placed symmetrically on either side of it. The conductors were, in turn, connected to the two poles of a dry pile, thus allowing the sign of the charge applied to the leaf to be determined.

The Bohnenberger electroscope comprises two batteries connected by a common base producing a constant potential difference of the order of 1000 volts. The free terminals have two small brass spheres. The unit is mounted in such a way that these two spheres have symmetrical electric charges. A piece of gold leaf suspended on the stem of the electroscope is attracted by the sphere of one of the batteries when an electrically charged body is brought close to the electroscope. It is thus possible, with this electroscope, to determine the nature of the charge of an electrically charged body. To do so, the charges on the spheres should first be known; this can be ascertained by observing the behaviour of the gold leaf when the electroscope is influenced by a body whose electrical charge is known.

However, Bohnenberger’s main interests were in the fields of geodesy and geophysics. Bohnenberger and Soldner were the pioneers of the German geodesy. Bohnenberger has constructed a gyroscope. The gyroscope in the form we know it today was invented in 1852 by Leon Foucault. However, it had an ancestor in the device developed by Johann von Bohnenberger in 1817. Napoleon I was so much impressed by this device that he recommended to introduce it in French schools.

The construction and operation of the Bohnenberger’s gyroscope are discussed in the 1856 first volume of Benjamin Pike, Jr.’s Illustrated Descriptive Catalogue of Optical, Mathematical and Philosophical Instruments: “Bohnenberger’s Machine. This apparatus consists of three movable rings, ..., mounted on a stout base. The two inner rings are mounted on pivots; those on the smallest ring at right angles to the middle one; in the smallest ring is supported a metal ball, having a roller on one of its pivots; around the roller a string may be wound, and when pulled off a rapid rotary motion may be given to the ball. This motion may be given with the axis in any position required, and when communicated, the ring supporting the ball will resist considerable effort to alter its position, and whatever way the instrument may be turned, its axis will continue to maintain the position it had when set in motion, illustrating the inertia, or that property of matter which resists any change of state, whether of rest or motion.”

The Lunar crater Bohnenberger is named in his honor.

June 14: Knut Lundmark

Knut Emil Lundmark
June 14, 1889 – April 23, 1958

Knut Lundmark was a Swedish astronomer, professor of astronomy and head of the observatory at Lund University 1929-1955.

Lundmark received his astronomical education at the observatory of Uppsala University. His dissertation (1920) was titled: The relations of the globular clusters and spiral nebulae to the stellar system. In the 1920s he worked at several observatories in the US, mainly Lick Observatory and Mount Wilson Observatory.

Knut Lundmark was one of the pioneers in the modern study of the galaxies and their distances. He was one of the first to suspect that the galaxies are remote stellar systems at vast distances and not nearby objects belonging to our own galaxy, the Milky Way. In 1919 he measured the distance to M31 - the Andromeda Galaxy, to 650 000 light years (about a fourth of the present day value) using magnitudes of novae found in M31 and comparing them to nearby ones with known distances. Lundmark's work contributed to the later famous Great Debate.

Lundmark also studied the light distribution in the galaxies, and discovered that the distribution could only properly be explained if the galaxies contained vast amounts of light-blocking dark clouds.

He was the leading writer of popular astronomy among the professional astronomers in Sweden from the 1930s and onwards. He also often appeared in the Swedish national radio with programs on popular astronomy and the history of science. He made generations of Swedes fascinated and interested in astronomy.

The crater Lundmark on the Moon was named after him. The Wolf-Lundmark-Melotte Galaxy is named after Lundmark, Max Wolf and Philibert Jacques Melotte.

June 13: Giovanni Antonio Magini

Giovanni Antonio Magini
June 13, 1555 – February 11, 1617

Giovanni Antonio Magini (in Latin, Maginus) was an Italian astronomer, astrologer, cartographer, and mathematician. He was born in Padua, and completed studies in philosophy in Bologna in 1579. Dedicating himself to astronomy, in 1582 he wrote Ephemerides coelestium motuum, translated into Italian the following year.

In 1588 he was chosen over Galileo to occupy the chair of mathematics at the University of Bologna after the death of Egnatio Danti. Magini supported a geocentric system of the world, in preference to Copernicus’ heliocentric system. Magini devised his own planetary theory, in preference to other existing ones. The Maginian System consisted of eleven rotating spheres, which he described in his Novæ cœlestium orbium theoricæ congruentes cum observationibus N. Copernici (Venice, 1589).

In his De Planis Triangulis (1592), he described the use of quadrants in surveying and astronomy. In 1592 Magini published Tabula tetragonica, and in 1606 devised extremely accurate trigonometric tables. He also worked on the geometry of the sphere and applications of trigonometry, for which he invented calculating devices. He also worked on the problem of mirrors and published on the theory of concave spherical mirrors.

He also published a commentary on Ptolemy’s Geographia (Cologne, 1596).

As a cartographer, his life's work was the preparation of Italia or the Atlante geografico d'Italia (Geographic Atlas of Italy), printed posthumously by Magini's son in 1620. This was intended to include maps of every Italian region with exact nomenclature and historical notes. A major project, its production (begun in 1594) proved expensive and Magini assumed various additional posts in order to fund it, including becoming tutor in mathematics to the sons of Vincenzo I of Gonzaga, Duke of Mantua, a major patron of the arts and sciences. He also served as court astrologer. The Duke of Mantua, to whom the atlas is dedicated, assisted him with this project and allowed for maps of the various states of Italy to be brought to Magini. The governments of Messina and Genoa also assisted Magini financially in this project. Magini did not do any of the mapping himself.

He was also interested in pursuits which today would be considered pseudoscientific. A strong supporter of astrology, he defended its use in medicine in his De astrologica ratione (Venice, 1607). He was also interested in metoposcopy.

He corresponded with Tycho Brahe, Clavius, Abraham Ortelius, and Johann Kepler. His correspondence was edited in 1886 by Antonio Favaro.

The lunar crater Maginus is named in his honor.

June 9: Johann Gottfried Galle

Johann Gottfried Galle

June 9, 1812 – July 10, 1910

Johann Gottfried Galle was a German astronomer at the Berlin Observatory who, with the assistance of student Heinrich Louis d'Arrest, was the first person to view the planet Neptune, and know what he was looking at (September 23, 1846). He used the calculations of Urbain Le Verrier to know where to look.

Born in Radis, Galle studied at the University of Berlin from 1830-33. He had started to work as an assistant to Johann Franz Encke in 1835 immediately following the completion of the Berlin observatory. In 1851 he moved to Breslau (Wrocław) to become professor of astronomy and the director of the local observatory.

Throughout his career he studied comets, and in 1894 (with the help of his son Andreas Galle) he published a list with 414 comets. He himself had previously discovered three comets in the short span from December 2, 1839 to March 6, 1840.

Galle's Ph.D. thesis, finished in the year of 1845, was a reduction and critical discussion of Ole Rømer's observation of meridian transits of stars and planets on the days from October 20 to October 23, 1706. Around 1845 he sent a copy of his thesis to Urbain Le Verrier, but only received an answer a year later on September 18, 1846. It reached Galle on September 23 and in it Le Verrier asked him to look at a certain region of sky to find a predicted new planet, which would explain the perturbations of the planet Uranus. The same night, after Encke gave him the permission against his own judgment, an object fitting the description was found, and it was confirmed as being a planet over the next two evenings.

Two craters, one on the Moon and the "happy face" one on Mars, the asteroid 2097 Galle, and a ring of Neptune, have been named in his honor.

June 8: Giovanni Domenico Cassini

Giovanni Domenico Cassini

June 8, 1625 – September 14, 1712

Giovanni Domenico Cassini was an Italian/French mathematician, astronomer, engineer, and astrologer.

Cassini was an astronomer at the Panzano Observatory from 1648 to 1669. He was a professor of astronomy at the University of Bologna and in 1671 became director of the Paris Observatory. He thoroughly adopted his new country, to the extent that he became interchangeably known as Jean-Dominique Cassini —although that is also the name of his great-grandson.

Along with Robert Hooke, Cassini is given credit for the discovery of the Great Red Spot on Jupiter (ca. 1665). Cassini was the first to observe four of Saturn's moons, which he called Sidera Lodoicea; he also discovered the Cassini Division (1675). Around 1690, Cassini was the first to observe differential rotation within Jupiter's atmosphere.

In 1672 he sent his colleague Jean Richer to Cayenne, French Guiana, while he himself stayed in Paris. The two made simultaneous observations of Mars and thus found its parallax to determine its distance, thus measuring for the first time the true dimensions of the solar system.

Cassini was the first to make successful measurements of longitude by the method suggested by Galileo, using eclipses of the satellites of Jupiter as a clock.

The Lunar crater Cassini is named in his honor.

June 6: Regiomontanus

Johannes Müller von Königsberg
June 6, 1436 – July 6, 1476

Johannes Müller von Königsberg, known by his Latin pseudonym Regiomontanus, was an important German mathematician, astronomer and astrologer.

At eleven years of age, he became a student at the university in Leipzig, Saxony. Three years later he continued his studies at Alma Mater Rudolfina, the university in Vienna, Austria. There he became a pupil and friend of Georg von Peurbach. In 1457 he graduated with a degree of "magister artium" (Master of Arts) and held lectures in optics and ancient literature. He built astrolabes for Matthias Corvinus of Hungary and Cardinal Bessarion, and in 1465 a portable sundial for Pope Paul II. His work with Peurbach brought him to the writings of Nicholas of Cusa (Cusanus), who held a heliocentric view. Regiomontanus, however, remained a geocentrist after Ptolemy. Following Peurbach's death, he continued the translation of Ptolemy's Almagest which Peurbach had begun at the initiative of Basilios Bessarion. From 1461 to 1465 Regiomontanus lived and worked at Cardinal Bessarion's house in Rome. He wrote De Triangulis omnimodus (1464) and Epytoma in almagesti Ptolemei. De Triangulis (On Triangles) was one of the first textbooks presenting the current state of trigonometry and included lists of questions for review of individual chapters. In it he wrote:

"You who wish to study great and wonderful things, who wonder about the movement of the stars, must read these theorems about triangles. Knowing these ideas will open the door to all of astronomy and to certain geometric problems."

In the Epytoma he critiqued the translation, pointing out inaccuracies. Later Nicolaus Copernicus would refer to this book as an influence on his own work. In 1467 Regiomontanus left Rome to work at the court of Matthias Corvinus of Hungary. There he calculated extensive astronomical tables and built astronomical instruments.

In 1471 he moved to the Free City of Nuremberg, in Franconia, then one of the Empire's important seats of learning, publication, commerce and art. He associated with the humanist and merchant Bernhard Walther who sponsored the observatory and the printing press. Regiomontanus remains famous for having built at Nuremberg the first astronomical observatory in Germany. In 1472 he published the first printed astronomical textbook, the "Theoricae novae Planetarum" of his teacher Georg von Peurbach.

A prolific author, Regiomontanus was internationally famous in his lifetime. Despite having completed only a quarter of what he had intended to write, he left a substantial body of work. Nicolaus Copernicus' teacher, Domenico Maria Novara da Ferrara, referred to Regiomontanus as having been his own teacher.

The Lunar crater Regiomontanus is named in his honor.