Orest Danilovich Khvolson or Chwolson (russian: Орест Данилович Хвольсон) (November 22 ( N.S. December 4), 1852 – May 11, 1934) was a Russian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

and honorary member of the

Soviet Academy of Sciences The Academy of Sciences of the Soviet Union was the highest scientific institution of the Soviet Union from 1925 to 1991, uniting the country's leading scientists, subordinated directly to the Council of Ministers of the Soviet Union (until 1946 ...

(1920). He is most noted for being one of the first to study the

gravitational lens A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer that is capable of bending the light from the source as the light travels toward the observer. This effect is known ...

effect.

Early life and education

Orest, son of the noted Orientalist

Daniel Chwolson Daniel Abramovich Chwolson or Chwolsohn or Khvolson (russian: Даниил Авраамович (Абрамович) Хвольсон; he, דניאל אברמוביץ' חבולסון) () – )) was a Russian-Jewish orientalist. Biography Chwolso ...

, was born in

Saint Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

. He graduated from

St. Petersburg University Saint Petersburg State University (SPBU; russian: Санкт-Петербургский государственный университет) is a public research university in Saint Petersburg, Russia. Founded in 1724 by a decree of Peter t ...

in 1873.

Career

Khvolson began teaching at his alma mater in 1876 and became a professor in 1891. He authored works on

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

photometry Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electro ...

, and

actinometry Actinometers are instruments used to measure the heating power of radiation. They are used in meteorology to measure solar radiation as pyranometers, pyrheliometers and net radiometers. An actinometer is a chemical system or physical device which ...

. He proposed the designs of an

actinometer Actinometers are instruments used to measure the heating power of radiation. They are used in meteorology to measure solar radiation as pyranometers, pyrheliometers and net radiometers. An actinometer is a chemical system or physical device which ...

and a

pyrheliometer A pyrheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal v ...

, which would be used by the Russian

weather station A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...

s for many years. After 1896, Khvolson was mainly engaged in compiling the five-volume ''Physics Course'' (Курс физики), which would improve immensely the teaching of

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 r ...

throughout the country and remain a principal textbook in universities for years to come. It was even translated into the

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

, French, and

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Cana ...

languages. His most noted accomplishment was in 1924, when he published about gravitational lenses in ''

Astronomische Nachrichten ''Astronomische Nachrichten'' (''Astronomical Notes''), one of the first international journals in the field of astronomy, was established in 1821 by the German astronomer Heinrich Christian Schumacher. It claims to be the oldest astronomical jour ...

'', a scientific journal on astronomy. In the article he mentioned the “halo effect” of gravitation when the source, lens, and observer are in near-perfect alignment (now referred to as the

Einstein ring An Einstein ring, also known as an Einstein–Chwolson ring or Chwolson ring (named for Orest Chwolson), is created when light from a galaxy or star passes by a massive object en route to the Earth. Due to gravitational lensing, the light is diver ...

), although he did not explicitly discuss the use of the ring as lens. The concept of gravitational lenses did not get much attention until 1936, when

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

wrote about the gravitational lens effect. The "halo" effect of a gravitational lens, where one source (sun or galaxy) produces a ring around another source is referred to as an Chwolson ring, "Today such a lens configuration is called 'Einstein-ring', although ''more correctly it should be called'' 'Chwolson-ring'." or Einstein ring. He became an honorary member of the

, awarded the

Order of the Red Banner of Labour The Order of the Red Banner of Labour (russian: Орден Трудового Красного Знамени, translit=Orden Trudovogo Krasnogo Znameni) was an order of the Soviet Union established to honour great deeds and services to th ...

. The crater Khvolson 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 of ...

is named after him.

Personal life and demise

Khvolson died in

Leningrad Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

, the same city he was born, but its name had changed.

Publications

* * * * ** ** * ** ** * * * * *

References

{{DEFAULTSORT:Khvolson, Orest Russian physicists Russian people of Jewish descent 1852 births 1934 deaths Scientists from Saint Petersburg Corresponding members of the Saint Petersburg Academy of Sciences Honorary Members of the USSR Academy of Sciences