Marcel Gilles Jozef Minnaert (12 February 1893 – 26 October 1970) was a Dutch

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either o ...

of Belgian origin. He was born in

Bruges Bruges ( , nl, Brugge ) is the capital and largest city A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Scienc ...

and died in

Utrecht Utrecht ( , , ) is the fourth-largest city and a municipality of the Netherlands, capital and most populous city of the province of Utrecht. It is located in the eastern corner of the Randstad conurbation, in the very centre of mainland Nethe ...

. He is notable for his contributions to

astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

and

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which rel ...

and for a popular book on

meteorological optics Atmospheric optics is "the study of the optical characteristics of the atmosphere or products of atmospheric processes .... ncludingtemporal and spatial resolutions beyond those discernible with the naked eye". Meteorological optics is "that par ...

: ''Light and colour in the open air'', first published in English in 1940.

Biography

Minnaert obtained a

PhD PHD or PhD may refer to: * Doctor of Philosophy (PhD), an academic qualification Entertainment * '' PhD: Phantasy Degree'', a Korean comic series * ''Piled Higher and Deeper'', a web comic * Ph.D. (band), a 1980s British group ** Ph.D. (Ph.D. albu ...

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditar ...

Ghent University Ghent University ( nl, Universiteit Gent, abbreviated as UGent) is a public research university located in Ghent, Belgium. Established before the state of Belgium itself, the university was founded by the Dutch King William I in 1817, whe ...

in 1914. Later he obtained also a

from

Utrecht University Utrecht University (UU; nl, Universiteit Utrecht, formerly ''Rijksuniversiteit Utrecht'') is a public research university in Utrecht, Netherlands. Established , it is one of the oldest universities in the Netherlands. In 2018, it had an enrollm ...

, under the supervision of Leonard Ornstein. He was a supporter of the

Flemish movement The Flemish Movement ( nl, Vlaamse Beweging) is an umbrella term which encompasses various political groups in the Belgian region of Flanders and, less commonly, in French Flanders. Ideologically, it encompasses groups which have sought to prom ...

during

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

and endorsed the replacement of

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

by Dutch during the German occupation of Belgium. He worked as "lector fysica" at the new Flemish University of Ghent, which was made possible by the support of the German occupation forces, and was viewed as connivance with the enemy by the reestablished Belgian authorities. Because of this, he was sentenced after the war in absence to 15 years of forced labor. However, Minnaert had anticipated this outcome by fleeing Belgium in time. In 1918, he found a position at Utrecht University in the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

, initially to do photometric research. In

, he became interested in

, and he became a pioneer of

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

research. He specialized in

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter ...

and the study of

stellar atmosphere The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone. Overview The stellar atmosphere is divided into several regions of distinct character: * The photosphere, wh ...

s and invented the spectroscopic curve of growth. Minnaert was also interested in

bubbles Bubble, Bubbles or The Bubble may refer to: Common uses * Bubble (physics), a globule of one substance in another, usually gas in a liquid ** Soap bubble * Economic bubble, a situation where asset prices are much higher than underlying fundame ...

and musical nature of the sounds made by running water. In 1933 he published a solution for the acoustic resonance frequency of a single bubble in water, the so-called Minnaert resonance. In 1937, he was appointed director of the stellar observatory '' Sonnenborgh'' in Utrecht and full professor in astronomy at the university. In 1940, he published his famous Utrecht Atlas of the solar spectrum. In 1941, he invented the

Minnaert function The Minnaert function is a photometric function used to interpret astronomical observations and remote sensing data for the Earth. It was named after the astronomer Marcel Minnaert. This function expresses the radiance factor (RADF) as a function t ...

, which is used in optical measurements of celestial bodies. During the German occupation of the Netherlands in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

, he was imprisoned by the Germans because of his left-wing, anti-

fascist Fascism is a far-right, authoritarian, ultra-nationalist political ideology and movement,: "extreme militaristic nationalism, contempt for electoral democracy and political and cultural liberalism, a belief in natural social hierarchy and the ...

sympathies. During his incarceration, he taught

and astronomy to his fellow prisoners. After the War, he was one of the founders of the Mathematisch Centrum in Amsterdam. Minnaert was elected to the

American Academy of Arts and Sciences The American Academy of Arts and Sciences (abbreviation: AAA&S) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, ...

in 1959. In 1946 he became member of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...

. He became a member of the United States

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the Nat ...

in 1964 and the

American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communi ...

in 1969.

Publications

One of his interests was the effects of the atmosphere on light and images. His classic book on this subject, the first part of a trilogy, was originally published in Dutch in 1937 as: *''De natuurkunde van 't vrije veld. Licht en kleur in het landschap''. It was released in English translation as: *''Light and colour in the open air'' (H. M. Kremer-Priest, Trans.). London: G. Bell and Sons. An edition of this book was reprinted in 1954, as a Dover reprint: *''The Nature of Light and Color in the Open Air'', Dover, 1954, and in a new translation with color photographs as: *''Light and Color in the Outdoors'', Springer, 1993, , , .

Honors

Awards *

Gold Medal of the Royal Astronomical Society The Gold Medal of the Royal Astronomical Society is the highest award given by the Royal Astronomical Society (RAS). The RAS Council have "complete freedom as to the grounds on which it is awarded" and it can be awarded for any reason. Past awa ...

(1947) *

Bruce Medal The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was f ...

(1951) Named after him *

Asteroid An asteroid is a minor planet of the Solar System#Inner solar system, inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic o ...

1670 Minnaert *

Minnaert (crater) Minnaert is a large lunar impact crater that is located on the far side of the Moon, deep in the southern hemisphere. It is partly overlain along the southeastern side by the larger and younger crater Antoniadi. To the west-northwest lies L ...

on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

Minnaert building
of the Uithof campus of

* Minnaert resonance

References

* Molenaar, Leo. ''De rok van het universum: Marcel Minnaert, astrofysicus 1893–1970'' Balans, Amsterdam, 2003 n Dutch

External links

Biography by Leo Molenaar

* Curve of growth
Astrowww.phys.uvic.ca
{{DEFAULTSORT:Minnaert, Marcel 1893 births 1970 deaths Belgian emigrants to the Netherlands 20th-century Dutch astronomers Foreign associates of the National Academy of Sciences Ghent University alumni Members of the Royal Netherlands Academy of Arts and Sciences Scientists from Bruges Recipients of the Gold Medal of the Royal Astronomical Society Science teachers Utrecht University faculty Members of the American Philosophical Society