Donald Howard Menzel

Donald Howard Menzel (April 11, 1901 – December 14, 1976) was one of the first theoretical astronomers and astrophysicists in the United States. He discovered the physical properties of the solar chromosphere, the chemistry of stars, the atmosphere of Mars, and the nature of gaseous nebulae.[1][2] The minor planet 1967 Menzel was named in his honor,[3] as well as a small lunar crater located in the southeast of Mare Tranquilitatis, the Sea of Tranquility.[4]

Donald Howard Menzel
Donald Howard Menzel Portrait
Donald Howard Menzel by Babette Whipple
BornApril 11, 1901
DiedDecember 14, 1976 (aged 75)
NationalityUnited States
Alma materUniversity of Denver, Princeton
Scientific career
FieldsAstronomy, Astrophysics, Star Formation
InstitutionsLick Observatory, Harvard, Harvard–Smithsonian Center for Astrophysics
Doctoral advisorHenry Norris Russell
Doctoral studentsJesse L. Greenstein


Born in Florence, Colorado in 1901 and raised in Leadville, he learned to read very early, and soon could send and receive messages in Morse code, taught by his father. He loved science and mathematics, collected ore and rock specimens, and as a teenager he built a large chemistry laboratory in the cellar. He made a radio transmitter at a time when kits were rarely available and qualified as a radio ham. He was an Eagle Scout, specializing in cryptanalysis, as well as an outdoorsman, hiking and fly fishing throughout much of his life. He married Florence Elizabeth Kreager on June 17, 1926 and had two daughters (Suzanne Kay and Elizabeth Ina).

At 16, he enrolled in the University of Denver to study chemistry. His interest in astronomy was aroused through a boyhood friend (Edgar Kettering), through observing the solar eclipse of June 8, 1918, and through observing the eruption of Nova Aquilae 1918 (V603 Aquilae). He graduated from the University of Denver in 1920 with a degree in chemistry and a master's degree in chemistry and mathematics in 1921. He also found summer positions in 1922, 1923, and 1924 as research assistant to Harlow Shapley at the Harvard College Observatory. At Princeton University he acquired a second master's degree in astronomy in 1923, and in 1924 a Ph.D. in astrophysics for which his advisor was Henry Norris Russell, who inspired his interest in theoretical astronomy. After teaching two years at the University of Iowa and Ohio State University, in 1926 he was appointed assistant Professor at Lick Observatory in San Jose CA, where he worked for several years. In 1932 he moved to Harvard. During World War II Menzel was asked to join the Navy as Lieutenant commander, to head a division of intelligence, where he used his many-sided talents, including deciphering enemy codes. Even until 1955, he worked with the Navy improving radio-wave propagation by tracking the Sun's emissions and studying the effect of the aurora on radio propagation for the Department of Defense (Menzel & Boyd, p. 60[5]). Returning to Harvard after the war, he was appointed acting director of the Harvard Observatory in 1952, and was the full director from 1954 to 1966. The term "Menzel Gap" was used to refer to the absence of astronomical photographic plates during a brief period in the 1950s when plate-making operations were temporarily halted by Menzel as a cost-cutting measure.[6] He retired from Harvard in 1971. From 1964 to his death, Menzel was a U.S. State Department consultant for Latin American affairs.

He received honorary A.M. and Sc.D. degrees from Harvard University in 1942 and the University of Denver in 1954 respectively. From 1946-1948 he was the Vice President of the American Astronomical Society, becoming their President from 1954-1956. In 1965, Menzel was given the John Evans Award of the University of Denver. In May 2001, Harvard-Smithsonian Center for Astrophysics hosted "Donald H. Menzel: Scientist, Educator, Builder," a symposium in honor of the 100th anniversary of the birth of Donald H. Menzel.

Menzel travelled with several expeditions to view solar eclipses to obtain scientific data. On 19 June 1936, he led the Harvard-MIT expedition to the steppes of Russia (at Ak Bulak in southwestern Siberia) to observe a total eclipse. For the 9 July 1945 eclipse, he directed the Joint U.S.-Canadian expedition to Saskatchewan, although they were clouded out. Menzel observed many total solar eclipses, often leading the expeditions, including Catalina, California (10 September 1923, cloudy), Camptonville, California (28 April 1930), Fryeburg, Maine (31 August 1932), Minneapolis-St. Paul, Minnesota (30 June 1954), the Atlantic coast of Massachusetts (2 October 1959), northern Italy (15 February 1951), Orono, Maine (20 July 1963, cloudy), Athens/Sunion Road, Greece (20 May 1966), Arequipa, Peru (12 November 1966), Miahuatlan, south of Oaxaca, Mexico (7 March 1970), Prince Edward Island Canada (10 July 1972), and western Mauritania (30 June 1973), in addition to the other three mentioned above.[7] He proudly held the informal record for greatest number of observed solar eclipses, a "title" later broken by his student, colleague, and co-author Jay Pasachoff.

Menzel 2
Planetary nebula PK 329-02.2 also known as Menzel 2, or Mz 2. It was discovered in 1922.[8]

In the late 1930s he built an observatory for solar research at Climax, CO, using a telescope that mimicked a total eclipse of the sun, allowing him and his colleagues to study the sun's corona and to film the spouting flames, called prominences, emitted by the Sun. Menzel initially performed solar research, but later concentrated on studying gaseous nebulae. His work with Lawrence Aller and James Gilbert Baker defined many of the fundamental principles of the study of planetary nebulae. He wrote the first edition (1964) of A Field Guide to the Stars and Planets, part of the Peterson Field Guides. In one of his last papers,[9] Menzel concluded, based on his analysis of the Schwarzschild equations, that black holes do not exist, and he declared them to be a myth.

Menzel was a science fiction author; his "Fin's Funeral" appeared in Galaxy Science Fiction in 1965.[10] He was also an artist, creating watercolor paintings of alien creatures and scenes which often featured 3-dimensional "holes" though characters, clouds, and alien spaceships.[11][12]

Menzel's Field Guide

Menzel wrote the first edition of A Field Guide to the Stars and Planets, published in 1975 by HarperCollins, which rapidly became a best-seller. Subsequent editions were prepared after Menzel's death by his student Jay Pasachoff; the current version is one of the Peterson Field Guides.

In Chapter IV of the first edition, Menzel apportions all 88 of the modern constellations recognized by the International Astronomical Union into 8 broad families, as a way to help observers remember where the constellations are located.[13]

The families are organized by common location or common theme. The Ursa Major, Perseus, Hercules, and Orion families include mainly constellations in the general vicinity of those four constellations. The Zodiac family includes the traditional 12 Zodiac constellations. The Heavenly Waters family includes mostly constellations generally associated with water. The Bayer family includes southern constellations first introduced by Plancius and subsequently included in Johann Bayer's Uranometria in 1603. The La Caille family includes most of the constellations introduced by Lacaille in 1756 from stars charted during his observations at Cape Town.

Menzel Family Constellations in the family
Ursa Major Boötes, Camelopardalis, Canes Venatici, Coma Berenices, Corona Borealis, Draco, Leo Minor, Lynx, Ursa Major, Ursa Minor
Zodiac Aquarius, Aries, Cancer, Capricornus, Gemini, Leo, Libra, Pisces, Sagittarius, Scorpius, Taurus, Virgo
Perseus Andromeda, Auriga, Cassiopeia, Cepheus, Cetus, Lacerta, Pegasus, Perseus, Triangulum
Hercules Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Hydra, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Serpens, Sextans, Triangulum Australe, Vulpecula
Orion Canis Major, Canis Minor, Lepus, Monoceros, Orion
Heavenly Waters Carina, Columba, Delphinus, Equuleus, Eridanus, Piscis Austrinus, Puppis, Pyxis, Vela
Bayer Apus, Chamaeleon, Dorado, Grus, Hydrus, Indus, Musca, Pavo, Phoenix, Tucana, Volans
La Caille Antlia, Caelum, Circinus, Fornax, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, Telescopium

Menzel and UFOs

Galaxy Science Fiction, September 1969 cover
Menzel's cover art, Galaxy Science Fiction, 10/1969.

In addition to his academic and popular contributions to the field of astronomy, Menzel was a prominent skeptic concerning the reality of UFOs. He authored or co-authored three popular books debunking UFOs: Flying Saucers - Myth - Truth - History (1953),[14] The World of Flying Saucers (1963, co-authored with Lyle G Boyd),[5] and The UFO Enigma (1977, co-authored with Ernest H. Taves).[15] All of Menzel's UFO books argued that UFOs are nothing more than misidentification of prosaic phenomena such as stars, clouds and airplanes; or the result of people seeing unusual atmospheric phenomena they were unfamiliar with. He often suggested that atmospheric hazes or temperature inversions could distort stars or planets, and make them appear to be larger than in reality, unusual in their shape, and in motion. In 1968, Menzel testified before the U.S. House Committee on Science and Astronautics - Symposium on UFOs, stating that he considered all UFO sightings to have natural explanations.

He was among the first prominent scientists to offer an opinion on the matter. One of Menzel's earliest public involvements in UFO matters was his appearance on a radio documentary directed and narrated by Edward R. Murrow in mid-1950. (Swords, 98)

Menzel had his own UFO experience when he observed a 'flying saucer' while returning on 3 March 1955 from the North Pole on the daily Air Force Weather "Ptarmigan" flight. His account is in both Menzel & Boyd[5] and Menzel & Taves.[15] He later identified it as a mirage of Sirius, but Steuart Campbell claims that it was a mirage of Saturn.[16]


  1. ^ Goldberg, L.; Aller, L. H. (1991). Donald Howard Menzel (PDF). National Academy of Sciences.
  2. ^ Gingerich, Owen (May 1977). "Donald H. Menzel". Physics Today. 30 (5): 67–69. Bibcode:1977PhT....30e..96G. doi:10.1063/1.3037558. Archived from the original on 2013-09-28.
  3. ^ Schmadel, Lutz D. (2003). "(1967) Menzel". Dictionary of Minor Planet Names – (1967) Menzel. Springer Berlin Heidelberg. p. 158. doi:10.1007/978-3-540-29925-7_1968. ISBN 978-3-540-29925-7.
  4. ^ "Menzel". Gazetteer of Planetary Nomenclature. International Astronomical Union. Retrieved November 9, 2017.
  5. ^ a b c Menzel, D. H.; Boyd, L. G. (1963). The World Of Flying Saucers: A Scientific Examination of a Major Myth of the Space Age. Doubleday. LCCN 63012989.
  6. ^ Johnson, G. (July 10, 2007). "A Trip Back in Time and Space". The New York Times. Retrieved 2012-04-21.
  7. ^ Pasachoff, J. M. (2002). "Menzel and Eclipses". Journal for the History of Astronomy. 33 (111): 139–156. Bibcode:2002JHA....33..139P. doi:10.1177/002182860203300205.
  8. ^ "Waving goodbye". Retrieved 7 October 2015.
  9. ^ Menzel, D. H. (1976). "Superstars and the black hole myth". Mémoires de la Société Royale des Sciences de Liège. 9: 343–353. Bibcode:1976MSRSL...9..343M.
  10. ^ Galaxy v23n03 (1965 02).
  11. ^ Menzel, Donald (1969). "cover art". Galaxy Science Fiction. image provided by
  12. ^ Epps, Garrett (1970). "Menzel's Martians Frolic". The Harvard Crimson.
  13. ^ Donald H. Menzel (1975). A Field Guide to the Stars and Planets. HarperCollins. Retrieved 27 June 2017. The text of Chapter IV is available in a PDF file.
  14. ^ Menzel, D. H. (1953). Flying Saucers. Harvard University Press. LCCN 52012419.
  15. ^ a b Menzel, D. H.; Taves, E. H. (1977). The UFO Enigma: The Definitive Explanation of the UFO Phenomenon. Doubleday. ISBN 978-0-385-03596-5. LCCN 76016255.
  16. ^ Campbell, S. (1994). The UFO Mystery Solved. Explicit Books. pp. 61–64. ISBN 978-0-9521512-0-3.



Menzel published over 270 scientific and other papers.

He also wrote a popular account of astronomy: A Field Guide to the Stars and Planets Including the Moon, Satellites, Comets and Other Features of the Universe (1975); 2nd edition (1984) by Menzel and Pasachoff, 3rd edition (1992) by Pasachoff and Menzel, 4th edition (2000) by Pasachoff.

External links

  1. ^ Budrys, Algis; Pohl, Frederik (April 1965). "Galaxy Bookshelf". Galaxy Science Fiction. pp. 137–145.
1967 Menzel

1967 Menzel, provisional designation A905 VC, is a stony asteroid from the inner regions of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 1 November 1905, by German astronomer Max Wolf at Heidelberg Observatory in southern Germany, and later named after American astrophysicist Donald Howard Menzel.

American Astronomical Society

The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the advancement of astronomy and closely related branches of science, while the secondary purpose includes enhancing astronomy education and providing a political voice for its members through lobbying and grassroots activities. Its current mission is to enhance and share humanity's scientific understanding of the universe.

Andrew M. Gleason

Andrew Mattei Gleason (1921–2008) was an American mathematician who as a young World War II naval officer broke German and Japanese military codes, then over the succeeding sixty years made fundamental contributions to widely varied areas of mathematics, including the solution of Hilbert's fifth problem, and was a leader in reform and innovation in math­e­mat­ics teaching at all levels. Gleason's theorem in quantum logic and the Greenwood–Gleason graph, an important example in Ramsey theory, are named for him.

Gleason's entire academic career was at Harvard University, from which he retired in 1992. His numerous academic and scholarly leadership posts included chairmanship of the Harvard Mathematics Department and Harvard Society of Fellows, and presidency of the American Mathematical Society. He continued to advise the United States government on cryptographic security, and the Commonwealth of Massachusetts on math­e­mat­ics education for children, almost until the end of his life.

Gleason won the Newcomb Cleveland Prize in 1952 and the Gung–Hu Distinguished Service Award of the American Mathematical Society in 1996. He was a member of the National Academy of Sciences and of the American Philosophical Society, and held the Hollis Chair of Mathematics and Natural Philosophy at Harvard.

He was fond of saying that math­e­mat­ic­al proofs "really aren't there to convince you that something is true‍—‌they're there to show you why it is true." The Notices of the American Mathematical Society called him "one of the quiet giants of twentieth-century mathematics, the consummate professor dedicated to scholarship, teaching, and service in equal measure."

Atmosphere of Mars

The atmosphere of the planet Mars is composed mostly of carbon dioxide. The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi; 6.0 mbar), about 0.6% of Earth's mean sea level pressure of 101.3 kilopascals (14.69 psi; 1.013 bar). It ranges from a low of 30 pascals (0.0044 psi; 0.30 mbar) on Olympus Mons's peak to over 1,155 pascals (0.1675 psi; 11.55 mbar) in the depths of Hellas Planitia. This pressure is well below the Armstrong limit for the unprotected human body. Mars's atmospheric mass of 25 teratonnes compares to Earth's 5148 teratonnes; Mars has a scale height of 11.1 kilometres (6.9 mi) versus Earth's 8.5 kilometres (5.3 mi).The Martian atmosphere consists of approximately 96% carbon dioxide, 1.9% argon, 1.9% nitrogen, and traces of free oxygen, carbon monoxide, water and methane, among other gases, for a mean molar mass of 43.34 g/mol. There has been renewed interest in its composition since the detection of traces of methane in 2003 that may indicate life but may also be produced by a geochemical process, volcanic or hydrothermal activity.The atmosphere is quite dusty, giving the Martian sky a light brown or orange-red color when seen from the surface; data from the Mars Exploration Rovers indicate suspended particles of roughly 1.5 micrometres in diameter.On 16 December 2014, NASA reported detecting an unusual increase, then decrease, in the amounts of methane in the atmosphere of the planet Mars. Organic chemicals have been detected in powder drilled from a rock by the Curiosity rover. Based on deuterium to hydrogen ratio studies, much of the water at Gale Crater on Mars was found to have been lost during ancient times, before the lakebed in the crater was formed; afterwards, large amounts of water continued to be lost.On 18 March 2015, NASA reported the detection of an aurora that is not fully understood and an unexplained dust cloud in the atmosphere of Mars.On 4 April 2015, NASA reported studies, based on measurements by the Sample Analysis at Mars (SAM) instrument on the Curiosity rover, of the Martian atmosphere using xenon and argon isotopes. Results provided support for a "vigorous" loss of atmosphere early in the history of Mars and were consistent with an atmospheric signature found in bits of atmosphere captured in some Martian meteorites found on Earth. This was further supported by results from the MAVEN orbiter circling Mars, that the solar wind is responsible for stripping away the atmosphere of Mars over the years.In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled, and were associated with an aurora 25 times brighter than any observed earlier due to a massive, and unexpected, solar storm in the middle of the month.On 1 June 2018, NASA scientists detected signs of a dust storm (see image) on the planet Mars which may affect the survivability of the solar-powered Opportunity rover since the dust may block the sunlight (see image) needed to operate; as of 12 June, the storm is the worst ever recorded at the surface of the planet, and spanned an area about the size of North America and Russia combined (about a quarter of the planet); as of 13 June, Opportunity was reported to be experiencing serious communication problem(s) due to the dust storm; a NASA teleconference about the dust storm was presented on 13 June 2018 at 01:30 pm/et/usa and is available for replay. In July 2018, researchers reported that the largest single source of dust on the planet Mars comes from the Medusae Fossae Formation.On 7 June 2018, NASA announced a cyclical seasonal variation in atmospheric methane.

Felix Ziegel

Felix Yurievich Ziegel (Russian: Феликс Юрьевич Зигель, March 20, 1920 - November 20, 1988) was a Soviet researcher, Doctor of Science and docent of Cosmology at the Moscow Aviation Institute, author of more than forty popular books on astronomy and space exploration, generally regarded as a founder of Russian ufology. Ziegel, the co-founder of the first officially approved Soviet UFO research group, became an overnight sensation when, on November 10, 1967, speaking on the Soviet central television, he made an extensive report on the UFO sightings registered in the USSR and encouraged viewers to send him and his colleagues first-hand accounts of their observations, which resulted in barrage of letters and reports. He died in November 1988, leaving 17 volumes of the unpublished research documents for his daughter to keep.

Henry Norris Russell

Prof Henry Norris Russell ForMemRS HFRSE FRAS (October 25, 1877 – February 18, 1957) was an American astronomer who, along with Ejnar Hertzsprung, developed the Hertzsprung–Russell diagram (1910). In 1923, working with Frederick Saunders, he developed Russell–Saunders coupling, which is also known as LS coupling.

Levelland UFO case

The Levelland UFO case occurred on November 2–3, 1957, in and around the small town of Levelland, Texas. Levelland, which in 1957 had a population of about 10,000, is located west of Lubbock on the flat prairie of the Texas South Plains. The case is considered by ufologists to be one of the most impressive in UFO history, mainly because of the large number of witnesses involved over a relatively short period of time. However, both the US Air Force and UFO skeptics have described the incident as being caused by either ball lightning or a severe electrical storm.

List of people with craters of the Moon named after them

The following is a list of people whose names were given to craters of the Moon. The list of approved names in the Gazetteer of Planetary Nomenclature maintained by the International Astronomical Union includes the person the crater is named for.

List of ufologists

This is a list of notable people who are Ufologists (UFO researchers).

Mz 1

Mz 1 (Menzel 1), is a bipolar planetary nebula (PN) in the constellation Norma.

Mz 3

Mz 3 (Menzel 3) is a young bipolar planetary nebula (PN) in the constellation Norma that is composed of a bright core and four distinct high-velocity outflows that have been named lobes, columns, rays, and chakram. These nebulosities are described as: two spherical bipolar lobes, two outer large filamentary hour-glass shaped columns, two cone shaped rays, and a planar radially expanding, elliptically shaped chakram.

Mz 3 is a complex system composed of three nested pairs of bipolar lobes and an equatorial ellipse.

Its lobes all share the same axis of symmetry but each have very different morphologies and opening angles.

It is an unusual PN in that it is believed, by some researchers, to contain a symbiotic binary at its center.

One study suggests that the dense nebular gas at its center may have originated from a source different from that of its extended lobes. The working model to explain this hypothesizes that this PN is composed of a giant companion that caused a central dense gas region to form, and a white dwarf that provides ionizing photons for the PN.Mz 3 is often referred to as the Ant Nebula because it resembles the head and thorax of a garden-variety ant.

Nash-Fortenberry UFO sighting

The Nash-Fortenberry UFO sighting was an unidentified flying object sighting that occurred on July 14, 1952, when two commercial pilots (William B. Nash and William H. Fortenberry) claimed to have seen eight UFOs flying in a tight echelon formation over Chesapeake Bay in the state of Virginia.

UFOlogists say the pilots observation allowed for relatively precise measurements of the objects' motion and size when compared to known landmarks, and that the encounter was corroborated by several groups of independent ground witnesses. The case was listed in the U.S. Air Force's Project Blue Book as an "unknown."Donald Howard Menzel in his book The World of Flying Saucers (1963) suggested some possible naturalistic explanations. He suggested that the pilots may have seen lights on the ground that were distorted by haze. He later suggested they may have seen fireflies that were trapped between the panes of glass in their cockpit window.Skeptical researcher Steuart Campbell suggested the pilots UFO sighting was a mirage of Venus.

Peterson Field Guides

The Peterson Field Guides (PFG) are a popular and influential series of American field guides intended to assist the layman in identification of birds, plants, insects and other natural phenomena. The series was created and edited by renowned ornithologist Roger Tory Peterson (1908–1996). His inaugural volume was the classic 1934 book A Field Guide to the Birds, published (as were all subsequent volumes) by the Houghton Mifflin Company.

The PFG series utilized what became known as the Peterson Identification System, a practical method for field identification which highlights readily noticed visual features rather than focusing on the technical features of interest to scientists. The series both reflected and contributed to awareness of the emerging environmental movement.

Most books in this series use a section of plates of drawings (usually reduced from commissioned paintings) rather than photographs of the subject species, grouped at the center of the book. This allows for idealized portraits that highlight the identifying "field marks" of each species; such field marks are often indicated by arrows or straight lines in the plate illustrations. However, in several books in this series, the plates consist of photographs (usually without such arrows or indicators), such as in the guides for the atmosphere, coral reefs, rocks and minerals, and the (old Charles Covell 1984 guide to) Eastern moths. In many books in this series (especially older editions), a number of the plates are in black and white. For examples, older editions of the Eastern reptiles/amphibians book had many black and white plates which were colorized for the current edition, and the original 1934 Eastern bird book had only 4 color plates. At least one book (insects) was entirely in black and white. However, most newer editions are often full-color (or almost full-color) and tend to be larger. One source claims that the increased size of one of the new editions (Eastern reptiles/amphibians) was considered detrimental to its use as a field guide by its own author and was a publisher decision.In some cases, new "editions" in this series are entirely new books with completely new texts and illustrations. For example, the fourth edition of the mammals guide has an entirely new text and illustrations by new author Fiona Reid, because the author (William Burt) and illustrator (Richard Grossenheider) of previous editions are both deceased. In fact, Grossenheider died prior to the publication of the previous third edition of 1976. Also, the current Northeastern moths guide by David Beadle and Seabrooke Leckie is an entirely new book than the out-of-print 1984 Eastern moths guide by Charles Covell. The Beadle/Leckie book covers a smaller geographical area and (one author claims) covers moths in greater detail. The old Covell book has been out-of-print for many years, but is currently available through the Virginia Museum of Natural History (which purchased the rights to that book).The above situation of an old "edition" persisting alongside its intended replacement edition is not unique to the Eastern moths guide. George Petrides' 1988 Eastern trees book (PFG11B) was originally intended to replace Petrides' own 1958 Eastern tree and shrubs (PFG11A) book. However, both books remain popular and the original publisher still offers both books for sale (unlike the case of the old Eastern moths book).Differences between editions can serve to indicate changes in scientific perspective as well as changes species distribution. For example, the second edition of the freshwater fishes guide by Page and Burr (2011), published 20 years after the first edition, increased the number of species included from 768 to 909, largely due to the addition of previously unrecognized species (114), as well as increased numbers of newly established exotic species (16). It also expanded coverage of marine fish commonly found in freshwater (19).

Prabhu Lal Bhatnagar

Prabhu Lal Bhatnagar (8 August 1912 – 5 October 1976), commonly addressed as P. L. Bhatnagar, was an Indian mathematician known for his contribution to the Bhatnagar–Gross–Krook operator used in Lattice Boltzmann methods (LBM).

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