Heinrich Hertz: Difference between revisions

Heinrich Hertz
Heinrich Hertz
Born	Heinrich Rudolf Hertz; 22 February 1857; Hamburg, German Confederation
Died	1 January 1894 (aged 36); Bonn, German Empire
Alma mater	University of Munich; University of Berlin
Known for	Contact mechanics; Electromagnetic radiation; Emagram; Parabolic antenna; Photoelectric effect; Hertzian cone; Hertzian dipole antenna; Hertz vector; Hertz-Knudsen equation; Hertz's principle of least curvature
Awards	Matteucci Medal (1888); Rumford Medal (1890)
	Scientific career
Fields	Electromagnetism ; Electrical engineering ; Contact mechanics
Institutions	University of Kiel; University of Karlsruhe; University of Bonn
Doctoral advisor	Hermann von Helmholtz
Doctoral students	Vilhelm Bjerknes
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Heinrich Rudolf Hertz (/hɜːrts/ HURTS; German: [ˈhaɪnʁɪç ˈhɛʁts];^[1]^[2] 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism. The unit of frequency, cycle per second, was named the "hertz" in his honor.^[3]

Biography

Heinrich Rudolf Hertz was born in 1857 in Hamburg, then a sovereign state of the German Confederation, into a prosperous and cultured Hanseatic family. His father was Gustav Ferdinand Hertz.^[4]

Death

In 1892, Hertz was diagnosed with an infection (after a bout of severe migraines) and underwent operations to treat the illness. He died after complications in surgery in attempts to fix his condition that was causing these migraines, which some consider to have been a malignant bone condition.^[5] He died at the age of 36 in Bonn, Germany, in 1894, and was buried in the Ohlsdorf Cemetery in Hamburg.^[6]^[7]^[8]

Hertz's wife, Elisabeth Hertz (née Doll; 1864–1941), did not remarry and he was survived by his daughters, Johanna (1887–1967) and Mathilde (1891–1975). Neither ever married or had children, hence Hertz has no living descendants.^[9]

Scientific work

Electromagnetic waves

Hertz's 1887 apparatus for generating and detecting radio waves: a spark-gap transmitter (left) consisting of a dipole antenna with a spark gap (S) powered by high voltage pulses from a Ruhmkorff coil (T), and a receiver (right) consisting of a loop antenna and spark gap.

One of Hertz's radio wave receivers: a loop antenna with an adjustable spark micrometer (bottom).^[10]

During Hertz's studies in 1879 Helmholtz suggested that Hertz's doctoral dissertation be on testing Maxwell's theory. Helmholtz had also proposed the "Berlin Prize" problem that year at the Prussian Academy of Sciences for anyone who could experimentally prove an electromagnetic effect in the polarization and depolarization of insulators, something predicted by Maxwell's theory.^[11]^[12] Helmholtz was sure Hertz was the most likely candidate to win it.^[12] Not seeing any way to build an apparatus to experimentally test this, Hertz thought it was too difficult, and worked on electromagnetic induction instead. Hertz did produce an analysis of Maxwell's equations during his time at Kiel, showing they did have more validity than the then prevalent "action at a distance" theories.^[13]

In the autumn of 1886, after Hertz received his professorship at Karlsruhe, he was experimenting with a pair of Riess spirals when he noticed that discharging a Leyden jar into one of these coils produced a spark in the other coil. With an idea on how to build an apparatus, Hertz now had a way to proceed with the "Berlin Prize" problem of 1879 on proving Maxwell's theory (although the actual prize had expired uncollected in 1882).^[14]^[15]

[[File:Hertz first oscillator.png|thumb|upright=3|center|Hertz's first radio transmitter: a capacitance loaded dipole resonator consisting of a pair of one meter copper wires with a 7.5 mm spark gap between them, ending in 30 cm zinc spheres.^[10]

Between 1886 and 1889 Hertz conducted a series of experiments that would prove the effects he was observing were results of Maxwell's predicted electromagnetic waves. Starting in November 1887 with his paper "On Electromagnetic Effects Produced by Electrical Disturbances in Insulators", Hertz sent a series of papers to Helmholtz at the Berlin Academy, including papers in 1888 that showed transverse free space electromagnetic waves traveling at a finite speed over a distance.^[15]^[16]

Hertz's directional spark transmitter (center), a half-wave dipole antenna made of two 13 cm brass rods with spark gap at center (closeup left) powered by a Ruhmkorff coil, on focal line of a 1.2 m x 2 m cylindrical sheet metal parabolic reflector.^[17] It radiated a beam of 66 cm waves with frequency of about 450 MHz. Receiver (right) is similar parabolic dipole antenna with micrometer spark gap.

Hertz's demonstration of polarization of radio waves: the receiver does not respond when antennas are perpendicular as shown, but as receiver is rotated the received signal grows stronger (as shown by length of sparks) until it reaches a maximum when dipoles are parallel.^[17]

Another demonstration of polarization: waves pass through polarizing filter to the receiver only when the wires are perpendicular to dipoles (A), not when parallel (B).^[17]

Demonstration of refraction: radio waves bend when passing through a prism made of pitch, similarly to light waves when passing through a glass prism.^[17]

Hertz' plot of standing waves created when radio waves are reflected from a sheet of metal

Hertz did not realize the practical importance of his radio wave experiments. He stated that,^[18]^[19]^[20]

"It's of no use whatsoever[...] this is just an experiment that proves Maestro Maxwell was right—we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there."

Asked about the applications of his discoveries, Hertz replied,^[18]^[21]

"Nothing, I guess."

Hertz's proof of the existence of airborne electromagnetic waves led to an explosion of experimentation with this new form of electromagnetic radiation, which was called "Hertzian waves" until around 1910 when the term "radio waves" became current. Within 10 years researchers such as Oliver Lodge, Ferdinand Braun, and Guglielmo Marconi employed radio waves in the first wireless telegraphy radio communication systems, leading to radio broadcasting, and later television. In 1909, Braun and Marconi received the Nobel Prize in physics for their "contributions to the development of wireless telegraphy".^[22] Today radio is an essential technology in global telecommunication networks, and the communications medium used by modern wireless devices.^[23]^[24]

Contact mechanics

[[Image:Büste von Heinrich Hertz in Karlsruhe.jpg|thumb|Memorial of Heinrich Hertz on the campus of the Karlsruhe Institute of Technology, which translates as At this site, Heinrich Hertz discovered electromagnetic waves in the years 1885–1889.]]

In 1881 and 1882, Hertz published two articles.^[25]^[26]^[27]

To develop his theory Hertz used his observation of elliptical Newton's rings formed upon placing a glass sphere upon a lens as the basis of assuming that the pressure exerted by the sphere follows an elliptical distribution. He used the formation of Newton's rings again while validating his theory with experiments in calculating the displacement which the sphere has into the lens. Kenneth L. Johnson, K. Kendall and A. D. Roberts (JKR) used this theory as a basis while calculating the theoretical displacement or indentation depth in the presence of adhesion in 1971.^[28] Hertz's theory is recovered from their formulation if the adhesion of the materials is assumed to be zero. Similar to this theory, however using different assumptions, B. V. Derjaguin, V. M. Muller and Y. P. Toporov published another theory in 1975, which came to be known as the DMT theory in the research community, which also recovered Hertz's formulations under the assumption of zero adhesion. This DMT theory proved to be premature and needed several revisions before it came to be accepted as another material contact theory in addition to the JKR theory. Both the DMT and the JKR theories form the basis of contact mechanics upon which all transition contact models are based and used in material parameter prediction in nanoindentation and atomic force microscopy. These models are central to the field of tribology and he was named as one of the 23 "Men of Tribology" by Duncan Dowson.^[29] Despite preceding his great work on electromagnetism (which he himself considered with his characteristic soberness to be trivial^[18]), Hertz's research on contact mechanics has facilitated the age of nanotechnology.

Meteorology

Hertz always had a deep interest in meteorology, probably derived from his contacts with Wilhelm von Bezold (who was his professor in a laboratory course at the Munich Polytechnic in the summer of 1878). As an assistant to Helmholtz in Berlin, he contributed a few minor articles in the field, including research on the evaporation of liquids,^[30] a new kind of hygrometer, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.^[31]

Treatment by the Third Reich

Because Hertz's family converted from Judaism to Lutheranism two decades before his birth, his legacy ran afoul of the Nazi government in the 1930s, a regime that classified people by "race" instead of religious affiliation.^[32]^[33]

Hertz's name was removed from streets and institutions and there was even a movement to rename the frequency unit named in his honor (hertz) after Hermann von Helmholtz instead, keeping the symbol (Hz) unchanged.^[33]

Legacy and honors

Heinrich Hertz's nephew Gustav Ludwig Hertz was a Nobel Prize winner, and Gustav's son Carl Helmut Hertz invented medical ultrasonography. His daughter Mathilde Carmen Hertz was a well-known biologist and comparative psychologist. Hertz's grandnephew Hermann Gerhard Hertz, professor at the University of Karlsruhe, was a pioneer of NMR-spectroscopy and in 1995 published Hertz's laboratory notes.^[34]

In 1969, in East Germany, a Heinrich Hertz memorial medal^[35] was cast. The IEEE Heinrich Hertz Medal, established in 1987, is "for outstanding achievements in Hertzian waves [...] presented annually to an individual for achievements which are theoretical or experimental in nature".^{[citation needed]}

Hertz is honored by Japan with a membership in the Order of the Sacred Treasure, which has multiple layers of honor for prominent people, including scientists.^[36]

Heinrich Hertz has been honored by a number of countries around the world in their postage issues, and in post-World War II times has appeared on various German stamp issues as well.^{[citation needed]}

On his birthday in 2012, Google honored Hertz with a Google doodle, inspired by his life's work, on its home page.^[37]^[38]

Works

Ueber die Induction in rotirenden Kugeln (in German). Berlin: Schade. 1880.
Die Prinzipien der Mechanik in neuem Zusammenhange dargestellt (in German). Leipzig: Johann Ambrosius Barth. 1894.
Schriften vermischten Inhalts (in German). Leipzig: Johann Ambrosius Barth. 1895.

Ueber die Induction in rotirenden Kugeln, 1880
Schriften vermischten Inhalts, 1895

References

^ Krech, Eva-Maria; Stock, Eberhard; Hirschfeld, Ursula; Anders, Lutz Christian (2009). Deutsches Aussprachewörterbuch [German Pronunciation Dictionary] (in German). Berlin: Walter de Gruyter. pp. 575, 580. ISBN 978-3-11-018202-6.
^ Dudenredaktion; Kleiner, Stefan; Knöbl, Ralf (2015) [First published 1962]. Das Aussprachewörterbuch [The Pronunciation Dictionary] (in German) (7th ed.). Berlin: Dudenverlag. p. 440. ISBN 978-3-411-04067-4.
^ IEC History Archived 19 May 2013 at the Wayback Machine. Iec.ch.
^ "Biography: Heinrich Rudolf Hertz". MacTutor History of Mathematics archive. Retrieved 2 February 2013.
^ Robertson, O'Connor. "Heinrich Rudolf Hertz". MacTutor. University of Saint Andrews, Scotland. Retrieved 20 October 2020.
^ Hamburger Friedhöfe » Ohlsdorf » Prominente. Friedhof-hamburg.de. Retrieved 22 August 2014.
^ Plan Ohlsdorfer Friedhof (Map of Ohlsdorf Cemetery). friedhof-hamburg.de.
^ IEEE Institute, Did You Know? Historical ‘Facts’ That Are Not True Archived 10 January 2014 at the Wayback Machine
^ Susskind, Charles. (1995). Heinrich Hertz: A Short Life. San Francisco: San Francisco Press. ISBN 0-911302-74-3
^ ^a ^b Appleyard, Rollo (October 1927). "Pioneers of Electrical Communication part 5 – Heinrich Rudolph Hertz" (PDF). Electrical Communication. 6 (2). New York: International Standard Electric Corp.: 63–77. Retrieved 19 December 2015.The two images shown are p. 66, fig. 3 and p. 70 fig. 9
^ Heinrich Hertz. nndb.com. Retrieved 22 August 2014.
^ ^a ^b Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). Heinrich Hertz: Classical Physicist, Modern Philosopher. New York: Springer-Verlag. ISBN 0-7923-4653-X. p. 49
^ Heilbron, John L. (2005) The Oxford Guide to the History of Physics and Astronomy. Oxford University Press. ISBN 0195171985. p. 148
^ Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). Heinrich Hertz: Classical Physicist, Modern Philosopher. New York: Springer-Verlag. ISBN 0-7923-4653-X. p. 53
^ ^a ^b Huurdeman, Anton A. (2003) The Worldwide History of Telecommunications. Wiley. ISBN 0471205052. p. 202
^ "The most important Experiments – The most important Experiments and their Publication between 1886 and 1889". Fraunhofer Heinrich Hertz Institute. Retrieved 19 February 2016.
^ ^a ^b ^c ^d Pierce, George Washington (1910). Principles of Wireless Telegraphy. New York: McGraw-Hill Book Co. pp. 51–55.
^ ^a ^b ^c "Heinrich Rudolph Hertz". History. Institute of Chemistry, Hebrew Univ. of Jerusalem website. 2004. Archived from the original on 25 September 2009. Retrieved 6 March 2018.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
^ Capri, Anton Z. (2007) Quips, quotes, and quanta: an anecdotal history of physics. World Scientific. ISBN 9812709207. p 93.
^ Norton, Andrew (2000). Dynamic Fields and Waves. CRC Press. p. 83. ISBN 0750307196.
^ Heinrich Hertz (1893). Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space. Dover Publications. ISBN 1-4297-4036-1.
^ "The Nobel Prize in Physics 1909". Nobel Foundation. Retrieved 18 January 2019.
^ "Heinrich Hertz | German physicist". Encyclopedia Britannica. Retrieved 21 May 2021.
^ "How Radio Works". HowStuffWorks. 7 December 2000. Retrieved 14 March 2019.
^ Hertz, Heinrich (1882). "Ueber die Berührung fester elastischer Körper". Journal für die reine und angewandte Mathematik. 1882 (92): 156–171. doi:10.1515/crll.1882.92.156. S2CID 123604617.
^ Hertz, Heinrich (1882). "Über die Berührung fester elastischer Körper und über die Härte". Verhandlungen des Vereins zur Beförderung des Gewerbefleißes. 1882: 449–463. Retrieved 9 February 2022.
^ Hertz, Heinrich (1986). Miscellaneous Papers. London: Macmillan and Co, Ltd. pp. 146–183. Retrieved 13 February 2022.
^ Johnson, K. L.; Kendall, K.; Roberts, A. D. (1971). "Surface energy and contact of elastic solids" (PDF). Proceedings of the Royal Society A. 324 (1558): 301–313. Bibcode:1971RSPSA.324..301J. doi:10.1098/rspa.1971.0141. S2CID 137730057.
^ Dowson, Duncan (1 April 1979). "Men of Tribology: Heinrich Rudolph Hertz (1857–1894) and Richard Stribeck (1861–1950)". Journal of Lubrication Technology. 101 (2): 115–119. doi:10.1115/1.3453287. ISSN 0022-2305.
^ Hertz, H. (1882). "Ueber die Verdunstung der Flüssigkeiten, insbesondere des Quecksilbers, im luftleeren Raume". Annalen der Physik. 253 (10): 177–193. Bibcode:1882AnP...253..177H. doi:10.1002/andp.18822531002. ISSN 1521-3889.
^ Mulligan, J. F.; Hertz, H. G. (1997). "An unpublished lecture by Heinrich Hertz: "On the energy balance of the Earth"". American Journal of Physics. 65 (1): 36–45. Bibcode:1997AmJPh..65...36M. doi:10.1119/1.18565.
^ Koertge, Noretta. (2007). Dictionary of Scientific Biography. New York: Thomson-Gale. ISBN 0-684-31320-0. Vol. 6, p. 340.
^ ^a ^b Wolff, Stefan L. (2008-01-04) Juden wider Willen – Wie es den Nachkommen des Physikers Heinrich Hertz im NS-Wissenschaftsbetrieb erging. Jüdische Allgemeine.
^ Hertz, H.G.; Doncel, M.G. (1995). "Heinrich Hertz's Laboratory Notes of 1887". Archive for History of Exact Sciences. 49 (3): 197–270. doi:10.1007/bf00376092. S2CID 121101068.
^ Heinrich Rudolf Hertz Archived 3 June 2013 at the Wayback Machine. Highfields-arc.co.uk. Retrieved 22 August 2014.
^ L'Harmattan: List of recipients of Japanese Order of the Sacred Treasure (in French)
^ Albanesius, Chloe (22 February 2012). "Google Doodle Honors Heinrich Hertz, Electromagnetic Wave Pioneer". PC Magazine. Retrieved 22 February 2012.
^ Heinrich Rudolf Hertz's 155th Birthday. Google (22 February 2012). Retrieved 22 August 2014.

External links

Quotations related to Heinrich Hertz at Wikiquote
"Hertz, Heinrich Rudolf" . Encyclopædia Britannica. Vol. 13 (11th ed.). 1911. pp. 400–401.
Newspaper clippings about Heinrich Hertz in the 20th Century Press Archives of the ZBW

[1] Krech, Eva-Maria; Stock, Eberhard; Hirschfeld, Ursula; Anders, Lutz Christian (2009). Deutsches Aussprachewörterbuch [German Pronunciation Dictionary] (in German). Berlin: Walter de Gruyter. pp. 575, 580. ISBN 978-3-11-018202-6.

[2] Dudenredaktion; Kleiner, Stefan; Knöbl, Ralf (2015) [First published 1962]. Das Aussprachewörterbuch [The Pronunciation Dictionary] (in German) (7th ed.). Berlin: Dudenverlag. p. 440. ISBN 978-3-411-04067-4.

[hertzunit-3] IEC History Archived 19 May 2013 at the Wayback Machine. Iec.ch.

[st-andrews-4] "Biography: Heinrich Rudolf Hertz". MacTutor History of Mathematics archive. Retrieved 2 February 2013.

[5] Robertson, O'Connor. "Heinrich Rudolf Hertz". MacTutor. University of Saint Andrews, Scotland. Retrieved 20 October 2020.

[Friedhof_Hamburg-6] Hamburger Friedhöfe » Ohlsdorf » Prominente. Friedhof-hamburg.de. Retrieved 22 August 2014.

[7] Plan Ohlsdorfer Friedhof (Map of Ohlsdorf Cemetery). friedhof-hamburg.de.

[IEEE_Did_you_know-8] IEEE Institute, Did You Know? Historical ‘Facts’ That Are Not True Archived 10 January 2014 at the Wayback Machine

[Susskind_1995-9] Susskind, Charles. (1995). Heinrich Hertz: A Short Life. San Francisco: San Francisco Press. ISBN 0-911302-74-3

[Appleyard-10] Appleyard, Rollo (October 1927). "Pioneers of Electrical Communication part 5 – Heinrich Rudolph Hertz" (PDF). Electrical Communication. 6 (2). New York: International Standard Electric Corp.: 63–77. Retrieved 19 December 2015.The two images shown are p. 66, fig. 3 and p. 70 fig. 9

[11] Heinrich Hertz. nndb.com. Retrieved 22 August 2014.

[autogenerated49-12] Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). Heinrich Hertz: Classical Physicist, Modern Philosopher. New York: Springer-Verlag. ISBN 0-7923-4653-X. p. 49

[13] Heilbron, John L. (2005) The Oxford Guide to the History of Physics and Astronomy. Oxford University Press. ISBN 0195171985. p. 148

[14] Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). Heinrich Hertz: Classical Physicist, Modern Philosopher. New York: Springer-Verlag. ISBN 0-7923-4653-X. p. 53

[h202-15] Huurdeman, Anton A. (2003) The Worldwide History of Telecommunications. Wiley. ISBN 0471205052. p. 202

[16] "The most important Experiments – The most important Experiments and their Publication between 1886 and 1889". Fraunhofer Heinrich Hertz Institute. Retrieved 19 February 2016.

[Pierce-17] Pierce, George Washington (1910). Principles of Wireless Telegraphy. New York: McGraw-Hill Book Co. pp. 51–55.

[UnivOfJerusalem-18] "Heinrich Rudolph Hertz". History. Institute of Chemistry, Hebrew Univ. of Jerusalem website. 2004. Archived from the original on 25 September 2009. Retrieved 6 March 2018.{{cite web}}: CS1 maint: bot: original URL status unknown (link)

[19] Capri, Anton Z. (2007) Quips, quotes, and quanta: an anecdotal history of physics. World Scientific. ISBN 9812709207. p 93.

[Norton-20] Norton, Andrew (2000). Dynamic Fields and Waves. CRC Press. p. 83. ISBN 0750307196.

[Hertz1893-21] Heinrich Hertz (1893). Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space. Dover Publications. ISBN 1-4297-4036-1.

[Nobel1909-22] "The Nobel Prize in Physics 1909". Nobel Foundation. Retrieved 18 January 2019.

[23] "Heinrich Hertz | German physicist". Encyclopedia Britannica. Retrieved 21 May 2021.

[24] "How Radio Works". HowStuffWorks. 7 December 2000. Retrieved 14 March 2019.

[25] Hertz, Heinrich (1882). "Ueber die Berührung fester elastischer Körper". Journal für die reine und angewandte Mathematik. 1882 (92): 156–171. doi:10.1515/crll.1882.92.156. S2CID 123604617.

[26] Hertz, Heinrich (1882). "Über die Berührung fester elastischer Körper und über die Härte". Verhandlungen des Vereins zur Beförderung des Gewerbefleißes. 1882: 449–463. Retrieved 9 February 2022.

[27] Hertz, Heinrich (1986). Miscellaneous Papers. London: Macmillan and Co, Ltd. pp. 146–183. Retrieved 13 February 2022.

[28] Johnson, K. L.; Kendall, K.; Roberts, A. D. (1971). "Surface energy and contact of elastic solids" (PDF). Proceedings of the Royal Society A. 324 (1558): 301–313. Bibcode:1971RSPSA.324..301J. doi:10.1098/rspa.1971.0141. S2CID 137730057.

[29] Dowson, Duncan (1 April 1979). "Men of Tribology: Heinrich Rudolph Hertz (1857–1894) and Richard Stribeck (1861–1950)". Journal of Lubrication Technology. 101 (2): 115–119. doi:10.1115/1.3453287. ISSN 0022-2305.

[30] Hertz, H. (1882). "Ueber die Verdunstung der Flüssigkeiten, insbesondere des Quecksilbers, im luftleeren Raume". Annalen der Physik. 253 (10): 177–193. Bibcode:1882AnP...253..177H. doi:10.1002/andp.18822531002. ISSN 1521-3889.

[31] Mulligan, J. F.; Hertz, H. G. (1997). "An unpublished lecture by Heinrich Hertz: "On the energy balance of the Earth"". American Journal of Physics. 65 (1): 36–45. Bibcode:1997AmJPh..65...36M. doi:10.1119/1.18565.

[DSB340-32] Koertge, Noretta. (2007). Dictionary of Scientific Biography. New York: Thomson-Gale. ISBN 0-684-31320-0. Vol. 6, p. 340.

[Wolff_2008-33] Wolff, Stefan L. (2008-01-04) Juden wider Willen – Wie es den Nachkommen des Physikers Heinrich Hertz im NS-Wissenschaftsbetrieb erging. Jüdische Allgemeine.

[34] Hertz, H.G.; Doncel, M.G. (1995). "Heinrich Hertz's Laboratory Notes of 1887". Archive for History of Exact Sciences. 49 (3): 197–270. doi:10.1007/bf00376092. S2CID 121101068.

[35] Heinrich Rudolf Hertz Archived 3 June 2013 at the Wayback Machine. Highfields-arc.co.uk. Retrieved 22 August 2014.

[36] L'Harmattan: List of recipients of Japanese Order of the Sacred Treasure (in French)

[37] Albanesius, Chloe (22 February 2012). "Google Doodle Honors Heinrich Hertz, Electromagnetic Wave Pioneer". PC Magazine. Retrieved 22 February 2012.

[38] Heinrich Rudolf Hertz's 155th Birthday. Google (22 February 2012). Retrieved 22 August 2014.

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@@ Line 2: / Line 2: @@
 {{short description|German physicist, namesake of the SI unit of frequency}}
 {{Use dmy dates|date=February 2021}}
 {{Infobox scientist
 | birth_name        = Heinrich Rudolf Hertz
@@ Line 22: / Line 21: @@
 }}
 {{electromagnetism|Scientists}}
 '''Heinrich Rudolf Hertz''' ({{IPAc-en|h|ɜr|t|s}} {{respell|HURTS}}; {{IPA-de|ˈhaɪnʁɪç ˈhɛʁts|lang}};<ref>{{Cite book |last=Krech |first=Eva-Maria |url=https://books.google.com/books?id=E-1tr_oVkW4C&q=deutsches+ausspracheworterbuch |title=Deutsches Aussprachewörterbuch |last2=Stock |first2=Eberhard |last3=Hirschfeld |first3=Ursula |last4=Anders |first4=Lutz Christian |publisher=Walter de Gruyter |year=2009 |isbn=978-3-11-018202-6 |location=Berlin |pages=575, 580 |language=de |trans-title=German Pronunciation Dictionary}}</ref><ref>{{Cite book |last=Dudenredaktion |url=https://books.google.com/books?id=T6vWCgAAQBAJ |title=Das Aussprachewörterbuch |last2=Kleiner |first2=Stefan |last3=Knöbl |first3=Ralf |publisher=Dudenverlag |year=2015 |isbn=978-3-411-04067-4 |edition=7th |location=Berlin |page=440 |language=de |trans-title=The Pronunciation Dictionary |orig-year=First published 1962}}</ref> 22 February 1857&nbsp;– 1 January 1894) was a German [[physicist]] who first conclusively proved the existence of the [[electromagnetic waves]] predicted by [[James Clerk Maxwell]]'s [[Maxwell's equations|equations of electromagnetism]]. The unit of frequency, [[cycle per second]], was named the "[[hertz]]" in his honor.<ref name="hertzunit">[http://www.iec.ch/about/history/overview/ IEC History] {{Webarchive|url=https://web.archive.org/web/20130519144600/http://www.iec.ch/about/history/overview/ |date=19 May 2013 }}. Iec.ch.</ref>
 ==Biography==
-Heinrich Rudolf Hertz was born in 1857 in [[Hamburg]], then a sovereign state of the [[German Confederation]], into a prosperous and cultured [[Hanseatic (class)|Hanseatic]] family. His father was [[Gustav Ferdinand Hertz]].<ref name="st-andrews">{{Cite web |title=Biography: Heinrich Rudolf Hertz |url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Hertz_Heinrich.html |access-date=2 February 2013 |publisher=MacTutor History of Mathematics archive}}</ref> His mother was Anna Elisabeth Pfefferkorn.{{fact|date=July 2022}}
+Heinrich Rudolf Hertz was born in 1857 in [[Hamburg]], then a sovereign state of the [[German Confederation]], into a prosperous and cultured [[Hanseatic (class)|Hanseatic]] family. His father was [[Gustav Ferdinand Hertz]].<ref name="st-andrews">{{Cite web |title=Biography: Heinrich Rudolf Hertz |url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Hertz_Heinrich.html |access-date=2 February 2013 |publisher=MacTutor History of Mathematics archive}}</ref>
-While studying at the [[Gelehrtenschule des Johanneums]] in Hamburg, Hertz showed an aptitude for sciences as well as languages, learning [[Arabic]] and [[Sanskrit]]. He studied sciences and engineering in the German cities of [[Dresden]], [[Technical University of Munich|Munich]] and [[Humboldt University of Berlin|Berlin]], where he studied under [[Gustav R. Kirchhoff]] and [[Hermann von Helmholtz]]. In 1880, Hertz obtained his PhD from the [[University of Berlin]], and for the next three years remained for post-doctoral study under Helmholtz, serving as his assistant. In 1883, Hertz took a post as a lecturer in theoretical physics at the [[University of Kiel]]. In 1885, Hertz became a full professor at the [[University of Karlsruhe]].{{fact|date=July 2022}}
-In 1886, Hertz married Elisabeth Doll, the daughter of Max Doll, a lecturer in geometry at Karlsruhe. They had two daughters: Johanna, born on 20 October 1887 and [[Mathilde Carmen Hertz|Mathilde]], born on 14 January 1891, who went on to become a notable biologist. During this time Hertz conducted his landmark research into electromagnetic waves.{{fact|date=July 2022}}
-Hertz took a position of Professor of Physics and Director of the Physics Institute in [[Bonn]] on 3 April 1889, a position he held until his death. During this time he worked on theoretical mechanics with his work published in the book ''Die Prinzipien der Mechanik in neuem Zusammenhange dargestellt'' (''The Principles of Mechanics Presented in a New Form''), published posthumously in 1894.{{fact|date=July 2022}}
 ==Death==
-In 1892, Hertz was diagnosed with an infection (after a bout of severe [[migraines]]) and underwent operations to treat the illness. He died after complications in surgery in attempts to fix his condition that was causing these migraines, which some consider to have been a malignant bone condition.<ref>{{Cite web |last=Robertson, O'Connor |title=Heinrich Rudolf Hertz |url=https://mathshistory.st-andrews.ac.uk/Biographies/Hertz_Heinrich/ |access-date=20 October 2020 |website=MacTutor |publisher=University of Saint Andrews, Scotland}}</ref> He died at the age of 36 in [[Bonn]], Germany, in 1894, and was buried in the [[Ohlsdorf Cemetery]] in Hamburg.<ref name="Friedhof_Hamburg">[http://www.friedhof-hamburg.de/ohlsdorf/prominente/h/ Hamburger Friedhöfe » Ohlsdorf » Prominente]. Friedhof-hamburg.de. Retrieved 22 August 2014.</ref><ref name="Map_of_Cemetery_Ohlsdorf">[https://web.archive.org/web/20120131202611/http://www.friedhof-hamburg.de/fileadmin/Dateien/pdf/ohlsdorf/plan_ohlsdorf_A4.pdf Plan Ohlsdorfer Friedhof (Map of Ohlsdorf Cemetery)]. friedhof-hamburg.de.</ref><ref name="IEEE_Did_you_know">IEEE Institute, [http://theinstitute.ieee.org/technology-focus/technology-history/did-you-know-historical-facts-that-are-not-true Did You Know? Historical ‘Facts’ That Are Not True] {{webarchive|url=https://web.archive.org/web/20140110200549/http://theinstitute.ieee.org/technology-focus/technology-history/did-you-know-historical-facts-that-are-not-true |date=10 January 2014 }}</ref><!-- Note: [[Ohlsdorf Cemetery]] is not the same as [[Ohlsdorf Jewish Cemetery]]. Heinrich Hertz is buried at Q24, 53-58. The map shows that this is located in the middle of the Ohlsdorf Cemetery. The Ohlsdorf Jewish Cemetery is located about a kilometer southwest of the Ohlsdorf Cemetery. -->
+In 1892, Hertz was diagnosed with an infection (after a bout of severe [[migraines]]) and underwent operations to treat the illness. He died after complications in surgery in attempts to fix his condition that was causing these migraines, which some consider to have been a malignant bone condition.<ref>{{Cite web |last=Robertson, O'Connor |title=Heinrich Rudolf Hertz |url=https://mathshistory.st-andrews.ac.uk/Biographies/Hertz_Heinrich/ |access-date=20 October 2020 |website=MacTutor |publisher=University of Saint Andrews, Scotland}}</ref> He died at the age of 36 in [[Bonn]], Germany, in 1894, and was buried in the [[Ohlsdorf Cemetery]] in Hamburg.<ref name="Friedhof_Hamburg">[http://www.friedhof-hamburg.de/ohlsdorf/prominente/h/ Hamburger Friedhöfe » Ohlsdorf » Prominente]. Friedhof-hamburg.de. Retrieved 22 August 2014.</ref><ref>[https://web.archive.org/web/20120131202611/http://www.friedhof-hamburg.de/fileadmin/Dateien/pdf/ohlsdorf/plan_ohlsdorf_A4.pdf Plan Ohlsdorfer Friedhof (Map of Ohlsdorf Cemetery)]. friedhof-hamburg.de.</ref><ref name="IEEE_Did_you_know">IEEE Institute, [http://theinstitute.ieee.org/technology-focus/technology-history/did-you-know-historical-facts-that-are-not-true Did You Know? Historical ‘Facts’ That Are Not True] {{webarchive|url=https://web.archive.org/web/20140110200549/http://theinstitute.ieee.org/technology-focus/technology-history/did-you-know-historical-facts-that-are-not-true |date=10 January 2014 }}</ref><!-- Note: [[Ohlsdorf Cemetery]] is not the same as [[Ohlsdorf Jewish Cemetery]]. Heinrich Hertz is buried at Q24, 53-58. The map shows that this is located in the middle of the Ohlsdorf Cemetery. The Ohlsdorf Jewish Cemetery is located about a kilometer southwest of the Ohlsdorf Cemetery. -->
 Hertz's wife<!-- married in 1886 -->, Elisabeth Hertz (''[[née]]'' Doll; 1864–1941), did not remarry and he was survived by his daughters, Johanna (1887–1967) and Mathilde (1891–1975). Neither ever married or had children, hence Hertz has no living descendants.<ref name="Susskind_1995">Susskind, Charles. (1995). ''Heinrich Hertz: A Short Life.'' San Francisco: San Francisco Press. {{ISBN|0-911302-74-3}}</ref>
 ==Scientific work==
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-In 1864 Scottish mathematical physicist [[James Clerk Maxwell]] proposed a comprehensive theory of electromagnetism, now called [[Maxwell's equations]].  Maxwell's theory predicted that coupled [[electric field|electric]] and [[magnetic field]]s could travel through space as an "[[electromagnetic wave]]".  Maxwell proposed that light consisted of electromagnetic waves of short wavelength, but no one had been able to prove this, or generate or detect electromagnetic waves of other wavelengths.{{fact|date=July 2022}}
 During Hertz's studies in 1879 Helmholtz suggested that Hertz's doctoral dissertation be on testing Maxwell's theory. Helmholtz had also proposed the "Berlin Prize" problem that year at the [[Prussian Academy of Sciences]] for anyone who could experimentally prove an electromagnetic effect in the polarization and depolarization of [[electrical insulator|insulators]], something predicted by Maxwell's theory.<ref>[http://www.nndb.com/people/419/000072203/ Heinrich Hertz]. nndb.com. Retrieved 22 August 2014.</ref><ref name="autogenerated49">Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). ''Heinrich Hertz: Classical Physicist, Modern Philosopher.'' New York: [[Springer-Verlag]]. {{ISBN|0-7923-4653-X}}. p. 49</ref> Helmholtz was sure Hertz was the most likely candidate to win it.<ref name="autogenerated49" /> Not seeing any way to build an apparatus to experimentally test this, Hertz thought it was too difficult, and worked on [[electromagnetic induction]] instead. Hertz did produce an analysis of Maxwell's equations during his time at Kiel, showing they did have more validity than the then prevalent "[[action at a distance]]" theories.<ref>Heilbron, John L. (2005) ''The Oxford Guide to the History of Physics and Astronomy''. Oxford University Press. {{ISBN|0195171985}}. p. 148</ref>
-In the autumn of 1886, after Hertz received his professorship at Karlsruhe, he was experimenting with a pair of [[Riess spiral]]s  when he noticed that discharging a [[Leyden jar]] into one of these coils produced a spark in the other coil. With an idea on how to build an apparatus, Hertz now had a way to proceed with the "Berlin Prize" problem of 1879 on proving Maxwell's theory (although the actual prize had expired uncollected in 1882).<ref>Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). ''Heinrich Hertz: Classical Physicist, Modern Philosopher.'' New York: [[Springer-Verlag]]. {{ISBN|0-7923-4653-X}}. p. 53</ref><ref name="h202">Huurdeman, Anton A. (2003) ''The Worldwide History of Telecommunications''. Wiley. {{ISBN|0471205052}}. p. 202</ref> He used a [[dipole antenna]] consisting of two collinear one-meter wires with a spark gap between their inner ends, and zinc spheres attached to the outer ends for [[capacitance]], as a radiator.  The antenna was excited by pulses of high voltage of about 30 [[volt|kilovolts]] applied between the two sides from a [[Induction coil|Ruhmkorff coil]].  He received the waves with a resonant single-[[loop antenna]] with a [[spark micrometer|micrometer spark gap]] between the ends. This experiment produced and received what are now called [[radio wave]]s in the [[very high frequency]] range.
+In the autumn of 1886, after Hertz received his professorship at Karlsruhe, he was experimenting with a pair of [[Riess spiral]]s  when he noticed that discharging a [[Leyden jar]] into one of these coils produced a spark in the other coil. With an idea on how to build an apparatus, Hertz now had a way to proceed with the "Berlin Prize" problem of 1879 on proving Maxwell's theory (although the actual prize had expired uncollected in 1882).<ref>Baird, Davis, Hughes, R.I.G. and Nordmann, Alfred eds. (1998). ''Heinrich Hertz: Classical Physicist, Modern Philosopher.'' New York: [[Springer-Verlag]]. {{ISBN|0-7923-4653-X}}. p. 53</ref><ref name="h202">Huurdeman, Anton A. (2003) ''The Worldwide History of Telecommunications''. Wiley. {{ISBN|0471205052}}. p. 202</ref>
-[[File:Hertz first oscillator.png|thumb|upright=3|center|Hertz's first radio transmitter: a [[loaded dipole|capacitance loaded]] [[dipole antenna|dipole resonator]] consisting of a pair of one meter copper wires with a 7.5&nbsp;mm spark gap between them, ending in 30 cm zinc spheres.<ref name="Appleyard" /> When an [[induction coil]] applied a high voltage between the two sides, sparks across the spark gap created [[standing wave]]s of radio frequency current in the wires, which radiated [[radio wave]]s. The [[frequency]] of the waves was roughly 50 MHz, about that used in modern television transmitters.]]
+[[File:Hertz first oscillator.png|thumb|upright=3|center|Hertz's first radio transmitter: a [[loaded dipole|capacitance loaded]] [[dipole antenna|dipole resonator]] consisting of a pair of one meter copper wires with a 7.5&nbsp;mm spark gap between them, ending in 30 cm zinc spheres.<ref name="Appleyard" />
-Between 1886 and 1889 Hertz conducted a series of experiments that would prove the effects he was observing were results of Maxwell's predicted electromagnetic waves. Starting in November 1887 with his paper "On Electromagnetic Effects Produced by Electrical Disturbances in Insulators", Hertz sent a series of papers to Helmholtz at the Berlin Academy, including papers in 1888 that showed transverse [[free space]] [[electromagnetic wave]]s traveling at a finite speed over a distance.<ref name=h202/><ref>{{Cite web |title=The most important Experiments – The most important Experiments and their Publication between 1886 and 1889 |url=http://www.hhi.fraunhofer.de/fraunhofer-hhi-the-institute/about-us/history-of-hhi/the-most-important-experiments.html |access-date=19 February 2016 |publisher=Fraunhofer Heinrich Hertz Institute}}</ref> In the apparatus Hertz used, the electric and magnetic fields radiated away from the wires as [[transverse waves]]. Hertz had positioned the [[oscillator]] about 12 meters from a [[zinc]] reflecting plate to produce [[standing wave]]s. Each wave was about 4 meters long.{{citation needed|date=March 2020}} Using the ring detector, he recorded how the wave's [[amplitude|magnitude]] and component direction varied. Hertz measured Maxwell's waves and demonstrated that the [[velocity]] of these waves was equal to the velocity of light. The [[electric field intensity]], [[polarization (waves)|polarization]] and [[Reflection (electrical)|reflection]] of the waves were also measured by Hertz. These experiments established that light and these waves were both a form of electromagnetic radiation obeying the Maxwell equations.  Hertz may not have been the first to come across the phenomenon of radio waves - [[David Edward Hughes]] may have detected their existence nine years earlier but did not publish his findings.{{fact|date=July 2022}}
+Between 1886 and 1889 Hertz conducted a series of experiments that would prove the effects he was observing were results of Maxwell's predicted electromagnetic waves. Starting in November 1887 with his paper "On Electromagnetic Effects Produced by Electrical Disturbances in Insulators", Hertz sent a series of papers to Helmholtz at the Berlin Academy, including papers in 1888 that showed transverse [[free space]] [[electromagnetic wave]]s traveling at a finite speed over a distance.<ref name=h202/><ref>{{Cite web |title=The most important Experiments – The most important Experiments and their Publication between 1886 and 1889 |url=http://www.hhi.fraunhofer.de/fraunhofer-hhi-the-institute/about-us/history-of-hhi/the-most-important-experiments.html |access-date=19 February 2016 |publisher=Fraunhofer Heinrich Hertz Institute}}</ref>
 {{multiple image
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@@ Line 91: / Line 81: @@
 :"''Nothing, I guess''."
 Hertz's proof of the existence of airborne electromagnetic waves led to an explosion of experimentation with this new form of electromagnetic radiation, which was called "Hertzian waves" until around 1910 when the term "[[radio waves]]" became current.  Within 10 years researchers such as [[Oliver Lodge]], [[Ferdinand Braun]], and [[Guglielmo Marconi]] employed radio waves in the first [[wireless telegraphy]] [[radio communication]] systems, leading to [[radio broadcasting]], and later television. In 1909, Braun and Marconi received the Nobel Prize in physics for their "contributions to the development of wireless telegraphy".<ref name="Nobel1909">{{Cite web |title=The Nobel Prize in Physics 1909 |url=https://www.nobelprize.org/prizes/physics/1909/summary/ |access-date=18 January 2019 |publisher=Nobel Foundation}}</ref> Today radio is an essential technology in global telecommunication networks, and the communications medium used by modern wireless devices.<ref>{{Cite web |title=Heinrich Hertz {{!}} German physicist |url=https://www.britannica.com/biography/Heinrich-Hertz |access-date=2021-05-21 |website=Encyclopedia Britannica |language=en}}</ref><ref>{{Cite web |date=7 December 2000 |title=How Radio Works |url=https://electronics.howstuffworks.com/radio.htm |access-date=14 March 2019 |website=HowStuffWorks}}</ref>
-=== Cathode rays ===
-In 1892, Hertz began experimenting and demonstrated that [[cathode ray]]s could penetrate very thin metal foil (such as aluminium). [[Philipp Lenard]], a student of Heinrich Hertz, further researched this "[[X-rays|ray effect]]". He developed a version of the cathode tube and studied the penetration by X-rays of various materials. However, Lenard did not realize that he was producing X-rays. Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before [[Wilhelm Conrad Röntgen|Röntgen]] made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light (''Wiedmann's Annalen'', Vol. XLVIII). However, he did not work with actual X-rays.{{fact|date=July 2022}}
-=== Photoelectric effect ===
-Hertz helped establish the [[photoelectric effect]] (which was later explained by [[Albert Einstein]]) when he noticed that a [[electric charge|charged]] object loses its charge more readily when illuminated by [[ultraviolet radiation]] (UV). In 1887, he made observations of the photoelectric effect and of the production and reception of electromagnetic (EM) waves, published in the journal [[Annalen der Physik]]. His receiver consisted of a coil with a [[spark gap]], whereby a spark would be seen upon detection of EM waves. He placed the apparatus in a darkened box to see the spark better. He observed that the maximum spark length was reduced when in the box. A glass panel placed between the source of EM waves and the receiver absorbed UV that assisted the [[electron]]s in jumping across the gap. When removed, the spark length would increase. He observed no decrease in spark length when he substituted quartz for glass, as [[quartz]] does not absorb UV radiation. Hertz concluded his months of investigation and reported the results obtained. He did not further pursue investigation of this effect, nor did he make any attempt at explaining how the observed phenomenon was brought about.{{fact|date=July 2022}}
 ===Contact mechanics===
@@ Line 102: / Line 86: @@
 {{Main|Contact mechanics}}
-In 1881 and 1882, Hertz published two articles<ref>{{Cite journal |last=Hertz, Heinrich |year=1882 |title=Ueber die Berührung fester elastischer Körper |url=https://www.degruyter.com/document/doi/10.1515/crll.1882.92.156/html |journal=Journal für die reine und angewandte Mathematik |volume=1882 |issue=92 |pages=156–171 |doi=10.1515/crll.1882.92.156 |s2cid=123604617}}</ref><ref>{{Cite journal |last=Hertz |first=Heinrich |date=1882 |title=Über die Berührung fester elastischer Körper und über die Härte |url=https://d-nb.info/1138446343/34 |journal=Verhandlungen des Vereins zur Beförderung des Gewerbefleißes |volume=1882 |pages=449–463 |access-date=9 February 2022}}</ref><ref>{{Cite book |last=Hertz |first=Heinrich |url=https://www.google.com/books/edition/Miscellaneous_Papers/0wM1AQAAMAAJ?hl=en&gbpv=0 |title=Miscellaneous Papers |date=1986 |publisher=Macmillan and Co, Ltd. |location=London |pages=146–183 |access-date=13 February 2022}}</ref> on what was to become known as the field of [[contact mechanics]], which proved to be an important basis for later theories in the field. [[Joseph Valentin Boussinesq]] published some critically important observations on Hertz's work, nevertheless establishing this work on contact mechanics to be of immense importance. His work basically summarises how two [[axi-symmetric]] objects placed in contact will behave under [[Structural load|loading]], he obtained results based upon the classical theory of [[elasticity (physics)|elasticity]] and [[continuum mechanics]]. The most significant flaw of his theory was the neglect of any nature of [[adhesion]] between the two solids, which proves to be important as the materials composing the solids start to assume high elasticity. It was natural to neglect adhesion at the time, however, as there were no experimental methods of testing for it.{{fact|date=July 2022}}
+In 1881 and 1882, Hertz published two articles.<ref>{{Cite journal |last=Hertz, Heinrich |year=1882 |title=Ueber die Berührung fester elastischer Körper |url=https://www.degruyter.com/document/doi/10.1515/crll.1882.92.156/html |journal=Journal für die reine und angewandte Mathematik |volume=1882 |issue=92 |pages=156–171 |doi=10.1515/crll.1882.92.156 |s2cid=123604617}}</ref><ref>{{Cite journal |last=Hertz |first=Heinrich |date=1882 |title=Über die Berührung fester elastischer Körper und über die Härte |url=https://d-nb.info/1138446343/34 |journal=Verhandlungen des Vereins zur Beförderung des Gewerbefleißes |volume=1882 |pages=449–463 |access-date=9 February 2022}}</ref><ref>{{Cite book |last=Hertz |first=Heinrich |url=https://www.google.com/books/edition/Miscellaneous_Papers/0wM1AQAAMAAJ?hl=en&gbpv=0 |title=Miscellaneous Papers |date=1986 |publisher=Macmillan and Co, Ltd. |location=London |pages=146–183 |access-date=13 February 2022}}</ref>
 To develop his theory Hertz used his observation of elliptical [[Newton's rings]] formed upon placing a glass sphere upon a lens as the basis of assuming that the pressure exerted by the sphere follows an [[elliptical distribution]]. He used the formation of Newton's rings again while validating his theory with experiments in calculating the [[displacement (fluid)|displacement]] which the sphere has into the lens. [[Kenneth L. Johnson]], K. Kendall and A. D. Roberts (JKR) used this theory as a basis while calculating the theoretical displacement or ''indentation depth'' in the presence of adhesion in 1971.<ref>{{Cite journal |last=Johnson, K. L. |last2=Kendall, K. |last3=Roberts, A. D. |year=1971 |title=Surface energy and contact of elastic solids |url=http://www.ewp.rpi.edu/hartford/~ernesto/F2012/FWM/Papers/Johnson-Kendall-Roberts-1971.pdf |journal=Proceedings of the Royal Society A |volume=324 |issue=1558 |pages=301–313 |bibcode=1971RSPSA.324..301J |doi=10.1098/rspa.1971.0141 |doi-access=free |s2cid=137730057}}</ref> Hertz's theory is recovered from their formulation if the adhesion of the materials is assumed to be zero. Similar to this theory, however using different assumptions, [[Boris Derjaguin|B. V. Derjaguin]], V. M. Muller and Y. P. Toporov published another theory in 1975, which came to be known as the DMT theory in the research community, which also recovered Hertz's formulations under the assumption of zero adhesion. This DMT theory proved to be premature and needed several revisions before it came to be accepted as another material contact theory in addition to the JKR theory. Both the DMT and the JKR theories form the basis of contact mechanics upon which all transition contact models are based and used in material parameter prediction in [[nanoindentation]] and [[atomic force microscopy]]. These models are central to the field of [[tribology]] and he was named as one of the 23 "Men of Tribology" by [[Duncan Dowson]].<ref>{{Cite journal |last=Dowson |first=Duncan |date=1 April 1979 |title=Men of Tribology: Heinrich Rudolph Hertz (1857–1894) and Richard Stribeck (1861–1950) |url=https://asmedigitalcollection.asme.org/tribology/article/101/2/115/419215/Men-of-Tribology-Heinrich-Rudolph-Hertz-1857-1894 |journal=Journal of Lubrication Technology |language=en |volume=101 |issue=2 |pages=115–119 |doi=10.1115/1.3453287 |issn=0022-2305 |doi-access=free}}</ref> Despite preceding his great work on electromagnetism (which he himself considered with his characteristic soberness to be trivial<ref name="UnivOfJerusalem"/>), Hertz's research on contact mechanics has facilitated the age of [[nanotechnology]].
-Hertz also described the "[[Hertzian cone]]", a type of [[fracture mechanics|fracture mode]] in brittle solids caused by the transmission of stress waves.{{fact|date=July 2022}}
 ===Meteorology===
 Hertz always had a deep interest in [[meteorology]], probably derived from his contacts with [[Wilhelm von Bezold]] (who was his professor in a laboratory course at the Munich Polytechnic in the summer of 1878).  As an assistant to Helmholtz in [[Berlin]], he contributed a few minor articles in the field, including research on the [[evaporation]] of liquids,<ref>{{Cite journal |last=Hertz |first=H. |date=1882 |title=Ueber die Verdunstung der Flüssigkeiten, insbesondere des Quecksilbers, im luftleeren Raume |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.18822531002 |journal=Annalen der Physik |language=en |volume=253 |issue=10 |pages=177–193 |bibcode=1882AnP...253..177H |doi=10.1002/andp.18822531002 |issn=1521-3889}}</ref> a new kind of [[hygrometer]], and a graphical means of determining the properties of moist air when subjected to [[adiabatic]] changes.<ref>{{Cite journal |last=Mulligan, J. F. |last2=Hertz, H. G. |year=1997 |title=An unpublished lecture by Heinrich Hertz: "On the energy balance of the Earth" |journal=American Journal of Physics |volume=65 |issue=1 |pages=36–45 |bibcode=1997AmJPh..65...36M |doi=10.1119/1.18565}}</ref>
-==Third Reich treatment==
+==Treatment by the Third Reich==
 Because Hertz's family converted from Judaism to Lutheranism two decades before his birth, his legacy ran afoul of the [[Nazism|Nazi]] government in the 1930s, a regime that classified people by "race" instead of religious affiliation.<ref name="DSB340">Koertge, Noretta. (2007). ''Dictionary of Scientific Biography''. New York: [[Thomson-Gale]]. {{ISBN|0-684-31320-0}}. Vol. 6, p. 340.</ref><ref name="Wolff_2008">Wolff, Stefan L. (2008-01-04) [http://www.juedische-allgemeine.de/article/view/id/1394 ''Juden wider Willen – Wie es den Nachkommen des Physikers Heinrich Hertz im NS-Wissenschaftsbetrieb erging'']. Jüdische Allgemeine.<!-- Since there are several authors named Stefan Wolff, the author of the above mentioned article is this one: http://www.deutsches-museum.de/forschung/wissenschaftl-mitarbeiter/dr-stefan-wolff/ --></ref>
 Hertz's name was removed from streets and institutions and there was even a movement to rename the frequency unit named in his honor (hertz) after Hermann von Helmholtz instead, keeping the symbol (Hz) unchanged.<ref name="Wolff_2008"/>
-His family was also persecuted for their non-Aryan status. Hertz's youngest daughter, Mathilde, lost a lectureship at Berlin University after the Nazis came to power and within a few years she, her sister, and their mother left Germany and settled in England.{{fact|date=July 2022}}
 ==Legacy and honors==
 [[File:Heinrich Hertz Deutsche-200-1Kcs.jpg|thumb|right|Heinrich Hertz]]
 Heinrich Hertz's nephew [[Gustav Ludwig Hertz]] was a Nobel Prize winner, and Gustav's son [[Carl Helmut Hertz]] invented [[medical ultrasonography]]. His daughter [[Mathilde Carmen Hertz]] was a well-known biologist and comparative psychologist. Hertz's grandnephew Hermann Gerhard Hertz, professor at the [[University of Karlsruhe]], was a pioneer of NMR-spectroscopy and in 1995 published Hertz's laboratory notes.<ref>{{Cite journal |last=Hertz |first=H.G. |last2=Doncel |first2=M.G. |year=1995 |title=Heinrich Hertz's Laboratory Notes of 1887 |journal=Archive for History of Exact Sciences |volume=49 |issue=3 |pages=197–270 |doi=10.1007/bf00376092 |s2cid=121101068}}</ref>
-The SI unit ''[[hertz]]'' (Hz) was established in his honor by the [[International Electrotechnical Commission]] in 1930 for [[frequency]], an expression of the number of times that a repeated event occurs per second. It was adopted by the [[CGPM]] (Conférence générale des poids et mesures) in 1960, officially replacing the previous name, "[[cycles per second]]" (cps).{{fact|date=July 2022}}
-In 1928 the [[Fraunhofer Institute for Telecommunications|Heinrich-Hertz Institute for Oscillation Research]] was founded in Berlin. Today known as the ''Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, HHI''.{{fact|date=July 2022}}
 In 1969, in [[East Germany]], a Heinrich Hertz memorial medal<ref>[http://highfields-arc.co.uk/biogs/hrhertz.htm Heinrich Rudolf Hertz] {{webarchive|url=https://web.archive.org/web/20130603182619/http://highfields-arc.co.uk/biogs/hrhertz.htm |date=3 June 2013 }}. Highfields-arc.co.uk. Retrieved 22 August 2014.</ref> was cast. The [[IEEE]] Heinrich Hertz Medal, established in 1987, is "''for outstanding achievements in Hertzian waves ''[...]'' presented annually to an individual for achievements which are theoretical or experimental in nature''".{{fact|date=July 2022}}
-In 1980, in Italy a High School called "Istituto Tecnico Industriale Statale Heinrich Hertz" was founded in the neighborhood of Cinecittà Est, in Rome.{{fact|date=July 2022}}
-The [[Heinrich Hertz Submillimeter Telescope|Submillimeter Radio Telescope]] at Mt. Graham, Arizona, constructed in 1992 is named after him.{{fact|date=July 2022}}
-A [[Impact crater|crater]] that lies on the [[Far side (Moon)|far side]] of the [[Moon]], just behind the eastern limb, is [[Hertz (crater)|named in his honor]]. The Hertz market for radio electronics products in [[Nizhny Novgorod]], Russia, is named after him. The [[Heinrich-Hertz-Turm]] radio telecommunication tower in Hamburg is named after the city's famous son.{{fact|date=July 2022}}
 Hertz is honored by Japan with a membership in the [[Order of the Sacred Treasure]], which has multiple layers of honor for prominent people, including scientists.<ref>L'Harmattan: [http://www.editions-harmattan.fr/index.asp?navig=catalogue&obj=article&no=8245 List of recipients of Japanese Order of the Sacred Treasure (in French)]</ref>

v t e Scientists whose names are used as units
SI base units	André-Marie Ampère (ampere) Lord Kelvin (kelvin)
SI derived units	Henri Becquerel (becquerel) Anders Celsius (degree Celsius) Charles-Augustin de Coulomb (coulomb) Michael Faraday (farad) Louis Harold Gray (gray) Joseph Henry (henry) Heinrich Hertz (hertz) James Prescott Joule (joule) Isaac Newton (newton) Georg Ohm (ohm) Blaise Pascal (pascal) Werner von Siemens (siemens) Rolf Maximilian Sievert (sievert) Nikola Tesla (tesla) Alessandro Volta (volt) James Watt (watt) Wilhelm Eduard Weber (weber)
Non-SI metric (cgs) units	Anders Jonas Ångström (angstrom) Peter Debye (debye) Loránd Eötvös (eotvos) Galileo Galilei (gal) Carl Friedrich Gauss (gauss) William Gilbert (gilbert) Heinrich Kayser (kayser) Johann Heinrich Lambert (lambert) Samuel Langley (langley) James Clerk Maxwell (maxwell) Hans Christian Ørsted (oersted) Jean Léonard Marie Poiseuille (poise) Sir George Stokes, 1st Baronet (stokes) John William Strutt, 3rd Baron Rayleigh (rayl)
Imperial and US customary units	Daniel Gabriel Fahrenheit (degree Fahrenheit) Johann Heinrich Lambert (foot-lambert) William John Macquorn Rankine (degree Rankine)
Non-systematic units	Alexander Graham Bell (bel) Marie Curie (curie) Pierre Curie (curie) John Dalton (dalton) Michael Faraday (faraday) Heinrich Mache (Mache) John Napier (neper) René Antoine Ferchault de Réaumur (degree Réaumur) Wilhelm Röntgen (roentgen) J. J. Thomson (thomson) Evangelista Torricelli (torr)
List of scientists whose names are used as units · Scientists whose names are used in physical constants · People whose names are used in chemical element names

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