Sebastian Rudolf Karl von Hoerner (15 April 1919 – 7 January 2003) was a German astrophysicist and

radio astronomer Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming ...

. He was born in

Görlitz Görlitz (; pl, Zgorzelec, hsb, Zhorjelc, cz, Zhořelec, East Lusatian dialect: ''Gerlz'', ''Gerltz'', ''Gerltsch'') is a town in the German state of Saxony. It is located on the Lusatian Neisse River, and is the largest town in Upper Lus ...

Lower Silesia Lower Silesia ( pl, Dolny Śląsk; cz, Dolní Slezsko; german: Niederschlesien; szl, Dolny Ślōnsk; hsb, Delnja Šleska; dsb, Dolna Šlazyńska; Silesian German: ''Niederschläsing''; la, Silesia Inferior) is the northwestern part of the ...

. After the end of

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 studied physics at

University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen, (german: Georg-August-Universität Göttingen, known informally as Georgia Augusta) is a public research university in the city of Göttingen, Germany. Founded ...

. He obtained his doctorate at the same university in 1951 as Carl Friedrich von Weizsäcker. Together they conducted simulations that studied the formation of

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s and

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

s. He continued this work at

Astronomical Calculation Institute (University of Heidelberg) The Astronomical Calculation Institute (german: Astronomisches Rechen-Institut; ARI) is a research institute in Heidelberg, Germany, dating from the 1700s. Beginning in 2005, the ARI became part of the Center for Astronomy at Heidelberg Unive ...

with Walter Fricke. He obtained his habilitation in 1959 at the University of Heidelberg. In 1962 he moved to

National Radio Astronomy Observatory The National Radio Astronomy Observatory (NRAO) is a federally funded research and development center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc. for the purpose of radio a ...

(

Green Bank, West Virginia Green Bank is a census-designated place in Pocahontas County in West Virginia's Potomac Highlands inside the Allegheny Mountain Range. Green Bank is located along WV 28. Green Bank is home to the Green Bank Observatory and is also close to the ...

), where he collaborated, inter alia, with

Frank Drake Frank Donald Drake (May 28, 1930 – September 2, 2022) was an American astrophysicist and astrobiologist. He began his career as a radio astronomer, studying the planets of the Solar System and later pulsars. Drake expanded his interests ...

. He worked there, among others on the analysis of work and technical optimization of

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

s. His research led to the development of a new method for the construction of radio telescopes, later used in the construction of many of them. During this time, he was actively involved in discussions on

SETI The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other pl ...

, the number of advanced

civilization A civilization (or civilisation) is any complex society characterized by the development of a state, social stratification, urbanization, and symbolic systems of communication beyond natural spoken language (namely, a writing system). ...

s in the

galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System ...

, and the possibilities

interstellar travel Interstellar travel is the hypothetical travel of spacecraft from one star system, solitary star, or planetary system to another. Interstellar travel is expected to prove much more difficult than interplanetary spaceflight due to the vast diffe ...

s. He was skeptical on these issues. In 1961, he published an article in which he was not optimistic about the survival time of species using machines. At the outset, he noted that the current state of mind (primacy of

science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...

, developing

technology Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, scien ...

, searching for interstellar communication) is just one of many possibilities and in the future it can be replaced by other interests. Moreover, according to him, the progress of science and technology on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

was driven by two factors – the struggle for domination and the desire for an easy life. The former leads to complete destruction, the latter to biological or psychical degeneration. Von Hoerner assumed that any civilization must disappear after some time and listed 4 possible causes of such a catastrophe: # total destruction of life on the planet # destroying only intelligent beings # mental or physical degeneration # loss of scientific and research interests (related to cause 3.) He estimated the average duration of civilization at 6,500 years. He suggested the succession of technological species on a given

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

over a time distance of hundreds of millions of years, and each habitable planet (one in 3 million stars) during its existence "produces" an average of 4 technological species. With these assumptions, the average distance between civilizations in the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

is 1,000

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distance, astronomical distances and is equivalent to about 9.46 Orders of magnitude (numbers)#1012, trillion kilometers (), or 5.88 ...

s. Von Hoerner's calculations also show that the probability of establishing first contact with a civilization in the same phase of development as the earthly one is 0.5%. The most likely such contact is with a civilization that will be 12,000 years old and with a 75% probability that it will not be the first civilization on this planet. Hoerner died in

Esslingen am Neckar Esslingen am Neckar (Swabian: ''Esslenga am Neckor'') is a town in the Stuttgart Region of Baden-Württemberg in southern Germany, seat of the District of Esslingen as well as the largest town in the district. Within Baden-Württemberg it is th ...

Baden-Württemberg Baden-Württemberg (; ), commonly shortened to BW or BaWü, is a German state () in Southwest Germany, east of the Rhine, which forms the southern part of Germany's western border with France. With more than 11.07 million inhabitants across a ...

, at age 83. His daughter,

Hanna von Hoerner Hanna von Hoerner (14 November 1942 – 4 July 2014) was a German astrophysicist. She founded the company von Hoerner & Sulger which produces scientific instruments, notably cosmic dust analyzers used on space missions by European Space Agency ...

, was also an astrophysicist.

References

External links

Biography at David Darling's Encyclopedia of Science

Vita of Sebastian von Hoerner at von Hoerner & Sulger website

Publications

* von Hoerner S., 1960, Z. Astrophys. 50, 184 * von Hoerner S., 1963, Z. Astrophys. 57, 47 {{DEFAULTSORT:Hoerner, Sebastian Von 1919 births 2003 deaths 20th-century German astronomers 20th-century German physicists Radio astronomers People from Görlitz People from the Province of Lower Silesia Search for extraterrestrial intelligence