Heinrich Rudolf Hertz
22 February 1857
|Died||1 January 1894 36) (aged|
|Alma mater|| University of Munich |
University of Berlin
|Known for|| Contact mechanics |
Hertzian dipole antenna
Hertz's principle of least curvature
|Awards|| Matteucci Medal (1888)|
Rumford Medal (1890)
|Institutions|| University of Kiel |
University of Karlsruhe
University of Bonn
|Doctoral advisor||Hermann von Helmholtz|
|Doctoral students||Vilhelm Bjerknes|
Heinrich Rudolf Hertz ( // ; German: [ˈhaɪ̯nʁɪç ˈhɛɐ̯ts] ; 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.
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 causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.
James Clerk Maxwell was a Scottish scientist in the field of mathematical physics. His most notable achievement was to formulate the classical theory of electromagnetic radiation, bringing together for the first time electricity, magnetism, and light as different manifestations of the same phenomenon. Maxwell's equations for electromagnetism have been called the "second great unification in physics" after the first one realised by Isaac Newton.
Maxwell's equations are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits. The equations provide a mathematical model for electric, optical, and radio technologies, such as power generation, electric motors, wireless communication, lenses, radar etc. Maxwell's equations describe how electric and magnetic fields are generated by charges, currents, and changes of the fields. An important consequence of the equations is that they demonstrate how fluctuating electric and magnetic fields propagate at a constant speed (c) in a vacuum. Known as electromagnetic radiation, these waves may occur at various wavelengths to produce a spectrum of light from radio waves to γ-rays. The equations are named after the physicist and mathematician James Clerk Maxwell, who between 1861 and 1862 published an early form of the equations that included the Lorentz force law. Maxwell first used the equations to propose that light is an electromagnetic phenomenon.
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.His mother was Anna Elisabeth Pfefferkorn.
Hamburg, officially the Free and Hanseatic City of Hamburg, is the second-largest city in Germany after Berlin and 8th largest city in the European Union with a population of over 1.8 million.
The German Confederation was an association of 39 German-speaking states in Central Europe, created by the Congress of Vienna in 1815 to coordinate the economies of separate German-speaking countries and to replace the former Holy Roman Empire, which had been dissolved in 1806. The German Confederation excluded German-speaking lands in the eastern portion of the Kingdom of Prussia, the German cantons of Switzerland, and the French region of Alsace, which was predominantly German speaking.
Gustav Ferdinand Hertz was a German lawyer and senator of the Free Imperial City of Hamburg. He was the father of the pioneering physicist Heinrich Hertz.
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, Munich and 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.
The Gelehrtenschule des Johanneums is a Gymnasium in Hamburg, Germany. It is Hamburg's oldest school and was founded in 1529 by Johannes Bugenhagen. The school´s focus is on the teaching of Latin and ancient Greek. It is proud of having educated some of Germany's political leaders as well as some of Germany's notable scientists. The school is operated and financed by the city of Hamburg.
Sanskrit is a language of ancient India with a 3,500-year history. It is the primary liturgical language of Hinduism and the predominant language of most works of Hindu philosophy as well as some of the principal texts of Buddhism and Jainism. Sanskrit, in its variants and numerous dialects, was the lingua franca of ancient and medieval India. In the early 1st millennium CE, along with Buddhism and Hinduism, Sanskrit migrated to Southeast Asia, parts of East Asia and Central Asia, emerging as a language of high culture and of local ruling elites in these regions.
Dresden is the capital city of the German state of Saxony, and with around 550,000 inhabitants, it is the state's second most populous city after Leipzig. It is the 12th most populous city of Germany, the fourth largest by area after Berlin, Hamburg and Cologne, as well as the third most populous city in the area of former East Germany, after (East) Berlin and Leipzig. Dresden is contiguous with Freital, Pirna, Radebeul, Meissen and Coswig, and its urban area has around 780,000 inhabitants, making it the largest in Saxony.
In 1886, Hertz married Elisabeth Doll, the daughter of Dr. Max Doll, a lecturer in geometry at Karlsruhe. They had two daughters: Johanna, born on 20 October 1887 and 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.
Mathilde Carmen Hertz was a biologist, and was one of the first influential women scientists in the field of biology and a pioneer in the field of comparative psychology. Working in Germany, her career started to unravel in 1933 due to her Jewish ancestry. She was the younger daughter of the famous physicist Heinrich Rudolf Hertz.
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.
The Federal City of Bonn is a city on the banks of the Rhine in the German state of North Rhine-Westphalia, with a population of over 300,000. About 24 km (15 mi) south-southeast of Cologne, Bonn is in the southernmost part of the Rhine-Ruhr region, Germany's largest metropolitan area, with over 11 million inhabitants. It is famously known as the birthplace of Ludwig van Beethoven in 1770. Beethoven spent his childhood and teenage years in Bonn.
In 1892, Hertz was diagnosed with an infection (after a bout of severe migraines) and underwent operations to treat the illness. He died of granulomatosis with polyangiitis at the age of 36 in Bonn, Germany in 1894, and was buried in the Ohlsdorf Cemetery in Hamburg.
Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis (WG), is a long-term systemic disorder that involves the formation of granulomas and inflammation of blood vessels. It is a form of vasculitis that affects small- and medium-size vessels in many organs but most commonly affects the upper respiratory tract and the kidneys. Therefore, the signs and symptoms of GPA are highly varied and reflect which organs are supplied by the affected blood vessels. Typical signs and symptoms include nosebleeds, stuffy nose and crustiness of nasal secretions, and inflammation of the uveal layer of the eye. Damage to the heart, lungs and kidneys can be fatal.
Ohlsdorf Cemetery in the Ohlsdorf quarter of the city of Hamburg, Germany, is the biggest rural cemetery in the world and the fourth-largest cemetery in the world. Most of the people buried at the cemetery are civilians, but there is also a large number of victims of war from various nations. The cemetery notably includes the Old Hamburg Memorial Cemetery with the graves of many notable Hamburg citizens.
Hertz's wife, Elisabeth Hertz née Doll (1864–1941), did not remarry. Hertz left two daughters, Johanna (1887–1967) and Mathilde (1891–1975). Hertz's daughters never married and he has no descendants.
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 and magnetic fields 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.
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.Helmholtz was sure Hertz was the most likely candidate to win it. 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.
After Hertz received his professorship at Karlsruhe he was experimenting with a pair of Riess spirals in the autumn of 1886 when he noticed that discharging a Leyden jar into one of these coils would produce 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).He used a Ruhmkorff coil-driven spark gap and one-meter wire pair as a radiator. Capacity spheres were present at the ends for circuit resonance adjustments. His receiver was a simple half-wave dipole antenna with a micrometer spark gap between the elements. This experiment produced and received what are now called radio waves in the very high frequency range.
Between 1886 and 1889 Hertz would conduct 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 would send 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.In the apparatus Hertz used, the electric and magnetic fields would radiate away from the wires as transverse waves. Hertz had positioned the oscillator about 12 meters from a zinc reflecting plate to produce standing waves. Each wave was about 4 meters long. Using the ring detector, he recorded how the wave's 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 and 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 did not realize the practical importance of his radio wave experiments. He stated that,
Asked about the applications of his discoveries, Hertz replied,
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". [ citation needed ]Today radio is an essential technology in global telecommunication networks, and the transmission medium underlying modern wireless devices.
In 1892, Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). Philipp Lenard, a student of Heinrich Hertz, further researched this "ray effect". He developed a version of the cathode tube and studied the penetration by X-rays of various materials. Philipp Lenard, though, did not realize that he was producing X-rays. Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before 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.
Hertz helped establish the photoelectric effect (which was later explained by Albert Einstein) when he noticed that a 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 electrons 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.
In 1886–1889, Hertz published two articles 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 loading, he obtained results based upon the classical theory of elasticity and continuum mechanics. The most significant failure 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 in that age as there were no experimental methods of testing for it.
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. K. 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.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 rather 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. So Hertz's research from his days as a lecturer, preceding his great work on electromagnetism, which he himself considered with his characteristic soberness to be trivial, has come down to the age of nanotechnology.
Hertz also described the "Hertzian cone", a type of fracture mode in brittle solids caused by the transmission of stress waves.
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, a new kind of hygrometer, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.
Heinrich Hertz was a Lutheran throughout his life and would not have considered himself Jewish, as his father's family had all converted to Lutheranismwhen his father was still in his childhood (aged seven) in 1834.
Nevertheless, when the Nazi regime gained power decades after Hertz's death, his portrait was removed by them from its prominent position of honor in Hamburg's City Hall (Rathaus) because of his partly Jewish ethnic ancestry. (The painting has since been returned to public display.)
Hertz's widow and daughters left Germany in the 1930s and went to England.
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.
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).
In 1928 the Heinrich-Hertz Institute for Oscillation Research was founded in Berlin. Today known as the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, HHI.
In 1969 (East Germany), a Heinrich Hertz memorial medalwas 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".
In 1980, in Italy a High School called "Istituto Tecnico Industriale Statale Heinrich Hertz" was founded in the neighborhood of Cinecittà Est, in Rome.
A crater that lies on the far side of the Moon, just behind the eastern limb, is 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.
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.
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.
On his birthday in 2012, Google honored Hertz with a Google doodle, inspired by his life's work, on its home page.
Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields, is responsible for electromagnetic radiation such as light, and is one of the four fundamental interactions in nature. The other three fundamental interactions are the strong interaction, the weak interaction, and gravitation. At high energy the weak force and electromagnetic force are unified as a single electroweak force.
The photoelectric effect is the emission of electrons or other free carriers when light hits a material. Electrons emitted in this manner can be called photoelectrons. This phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry and electrochemistry.
The early history of radio is the history of technology that produces and uses radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting.
Wilhelm Carl Werner Otto Fritz Franz Wien was a German physicist who, in 1893, used theories about heat and electromagnetism to deduce Wien's displacement law, which calculates the emission of a blackbody at any temperature from the emission at any one reference temperature.
Gustav Ludwig Hertz was a German experimental physicist and Nobel Prize winner for his work on inelastic electron collisions in gases, and a nephew of Heinrich Rudolf Hertz.
Pyotr Nikolaevich Lebedev was a Russian physicist. His name was also transliterated as Peter Lebedew and Peter Lebedev. Lebedev was a creator of first scientific school in Russia.
The history of special relativity consists of many theoretical results and empirical findings obtained by Albert A. Michelson, Hendrik Lorentz, Henri Poincaré and others. It culminated in the theory of special relativity proposed by Albert Einstein and subsequent work of Max Planck, Hermann Minkowski and others.
Paul Karl Ludwig Drude was a German physicist specializing in optics. He wrote a fundamental textbook integrating optics with Maxwell's theories of electromagnetism.
Rudolf Seeliger was a German physicist who specialized in electric discharges in gases and plasma physics.
The Annus mirabilis papers are the papers of Albert Einstein published in the Annalen der Physik scientific journal in 1905. These four articles contributed substantially to the foundation of modern physics and changed views on space, time, mass, and energy. The annus mirabilis is often called the "miracle year" in English or Wunderjahr in German.
The invention of radio communication, although generally attributed to Guglielmo Marconi in the 1890s, spanned many decades, from theoretical underpinnings, through proof of the phenomenon's existence, development of technical means, to its final use in signalling.
Johann Friedrich Wilhelm von Bezold was a German physicist and meteorologist born in Munich, Kingdom of Bavaria. He is best known for discovering the Bezold effect and the Bezold–Brücke shift.
The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history.
The history of electromagnetic theory begins with ancient measures to understand atmospheric electricity, in particular lightning. People then had little understanding of electricity, and were unable to explain the phenomena. Scientific understanding into the nature of electricity grew throughout the eighteenth and nineteenth centuries through the work of researchers such as Ampère, Coulomb, Faraday and Maxwell.
Heinrich Rubens was a German physicist. He is known for his measurements of the energy of black-body radiation which led Max Planck to the discovery of his radiation law. This was the genesis of quantum theory.
In physics, a quantum is the minimum amount of any physical entity involved in an interaction. The fundamental notion that a physical property may be "quantized" is referred to as "the hypothesis of quantization". This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum.
Otto Heinrich Wiener was a German physicist.
Peter Theophil Riess was a German physicist, known mostly for his work in electricity, particularly friction electricity, but also in the field of electromagnetic induction. In the latter work he developed two devices, the spark micrometer and the Riess spiral coils, both of which were used by Heinrich Hertz in his experiments to prove the propagation of electromagnetic waves.
The spark micrometer, also known as a Riess micrometer was a device used by 19th century physicists to measure potential in an electric circuit. It was developed principally by German physicist Peter Riess. It consisted of two electrodes very close together, one of which was attached to a micrometer screw with a calibrated dial, so by turning a knob the width of the gap could be adjusted very precisely. From Paschen's law, the distance between two electrodes when a spark just jumped across a gap was proportional to the potential difference (voltage) between the electrodes, so a spark micrometer could serve as a crude voltage measuring instrument, by widening the gap until the voltage was just able to jump across.
The 19th century in science saw the birth of science as a profession; the term scientist was coined in 1833 by William Whewell, which soon replaced the older term of (natural) philosopher.
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