Heinrich Rudolf Hertz
Encyclopedia
Heinrich Rudolf Hertz was a German physicist
who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell
. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect radio
waves.
, Germany
, into a prosperous and cultured Hanseatic family. His father, Gustav Ferdinand Hertz, was a writer and later a senator. His mother was the former Anna Elisabeth Pfefferkorn. His paternal grandfather David Wolff Hertz (1757-1822), fourth son of Benjamin Wolff Hertz, moved to Hamburg in 1793 where he made his living as a jeweller. He and his wife Schöne Hertz (1760-1834) were buried in the former Jewish cemetery in Ottensen. Their first son Wolff Hertz (1790-1859), was chairman of the Jewish community. His brother Hertz Hertz (1797-1862) was a respected businessman. He was married to Betty Oppenheim, the daughter of the banker Salomon Oppenheim, from Cologne
. Hertz Hertz converted from Judaism
to Christianity
and took the name Heinrich David Hertz.
While studying at the Gelehrtenschule des Johanneums
in Hamburg, he 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 remained for post-doctoral study under Hermann von Helmholtz
.
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 where he discovered electromagnetic waves.
The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus.
The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap - whose poles on either side are formed by spheres of 2 cm radius - to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil.
To prove there really was radiation emitted, it had to be detected. Hertz used a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5 cm, with a small brass sphere on one end, and the other end of the wire was pointed, with the point near the sphere. He bought a screw mechanism so that the point could be moved very close to the sphere in a controlled fashion. This "receiver" was designed so that current oscillating back and forth in the wire would have a natural period close to that of the "transmitter" described above. The presence of oscillating charge in the receiver would be signaled by sparks across the (tiny) gap between the point and the sphere (typically, this gap was hundredths of a millimeter).
In more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also showed that the nature of radio waves’ reflection and refraction was the same as those of light, and established beyond any doubt that light is a form of electromagnetic radiation obeying the Maxwell equations.
Hertz's experiments would soon trigger the invention of the wireless telegraph, radio
, and later television
. In recognition of his work, the unit of frequency - one cycle per second - is named the "hertz
".
probably derived from his contacts with Wilhelm von Bezold
(who was Hertz's professor in a laboratory course at the Munich Polytechnic in the summer of 1878). Hertz, however, did not contribute much to the field himself except some early articles as an assistant to Helmholtz in Berlin
, including research on the evaporation
of liquid
s, a new kind of hygrometer
, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.
In 1886–1889, Hertz published two articles on what was to become known as the field of contact mechanics
. Hertz is well known for his contributions to the field of electrodynamics (see below); however, most papers that look into the fundamental nature of contact cite his two papers as a source for some important ideas. 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 their landmark article "Surface energy and contact of elastic solids" published in 1971 in the Proceedings of the Royal Society (A324, 1558, 301-313). 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.
, which was a center-fed driven element for transmitting UHF
radio waves. These antennas are the simplest practical antennas from a theoretical point of view.
In 1887, Hertz experimented with radio waves in his laboratory. These actions followed Michelson's
1881 experiment (precursor to the 1887 Michelson-Morley experiment
) which did not detect the existence of aether drift
, Hertz altered the Maxwell's equations
to take this view into account for electromagnetism. Hertz 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, a precursor to the dipole antenna, was a simple half-wave dipole antenna for shortwave
s. Hertz published his work in a book titled: Electric waves: being researches on the propagation of electric action with finite velocity through space.
Through experimentation, he proved that transverse
free space electromagnetic waves can travel over some distance. This had been predicted by James Clerk Maxwell
and Michael Faraday
. With his apparatus configuration, 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 wave
s. Each wave was about 4 meters. Using the ring detector, he recorded how the magnitude
and wave's component direction vary. Hertz measured Maxwell's waves and demonstrated that the velocity of radio waves was equal to the velocity of light. The electric field intensity and polarity was also measured by Hertz. (Hertz, 1887, 1888).
The Hertzian cone
was first described by Hertz as a type of wave-front propagation through various media
. His experiments expanded the field of electromagnetic transmission and his apparatus was developed further by others in the radio. Hertz also found that radio waves could be transmitted through different types of materials, and were reflected by others, leading in the distant future to radar
.
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 light. 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
, whereupon 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 ultraviolet radiation 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.
Hertz did not realize the practical importance of his experiments. He stated that,
Asked about the ramifications of his discoveries, Hertz replied,
His discoveries would later be more fully understood by others and be part of the new "wireless age
". In bulk, Hertz' experiments explain reflection, refraction
, polarization, interference, and velocity
of electric waves.
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.
at the age of 36 in Bonn
, Germany in 1894, and was buried in Ohlsdorf, Hamburg at the Jewish cemetery.
Hertz's wife, Elizabeth Hertz (maiden name: Elizabeth Doll), did not remarry. Heinrich Hertz left two daughters, Joanna and Mathilde. Subsequently, all three women left Germany in the 1930s to England, after the rise of Adolf Hitler
. Charles Susskind interviewed Mathilde Hertz in the 1960s and he later published a book on Heinrich Hertz. Heinrich Hertz's daughters never married and he does not have any descendants, according to the book by Susskind.
was a Nobel Prize
winner, and Gustav's son Carl Hellmuth Hertz
invented medical ultrasonography
.
The SI unit hertz
(Hz) was established in his honor by the IEC in 1930 for frequency
, a measurement of the number of times that a repeated event occurs per second (also called "cycles per sec" (cps)). It was adopted by the CGPM (Conférence générale des poids et mesures) in 1964.
In 1969 (East Germany), there was cast a Heinrich Hertz memorial medal. 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".
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 radioelectronics 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 was 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.
Lists and histories
Electromagnetic radiation
Other
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
waves.
Early years
Hertz was born in HamburgHamburg
-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...
, Germany
German Confederation
The German Confederation was the loose association of Central European states created by the Congress of Vienna in 1815 to coordinate the economies of separate German-speaking countries. It acted as a buffer between the powerful states of Austria and Prussia...
, into a prosperous and cultured Hanseatic family. His father, Gustav Ferdinand Hertz, was a writer and later a senator. His mother was the former Anna Elisabeth Pfefferkorn. His paternal grandfather David Wolff Hertz (1757-1822), fourth son of Benjamin Wolff Hertz, moved to Hamburg in 1793 where he made his living as a jeweller. He and his wife Schöne Hertz (1760-1834) were buried in the former Jewish cemetery in Ottensen. Their first son Wolff Hertz (1790-1859), was chairman of the Jewish community. His brother Hertz Hertz (1797-1862) was a respected businessman. He was married to Betty Oppenheim, the daughter of the banker Salomon Oppenheim, from Cologne
Cologne
Cologne is Germany's fourth-largest city , and is the largest city both in the Germany Federal State of North Rhine-Westphalia and within the Rhine-Ruhr Metropolitan Area, one of the major European metropolitan areas with more than ten million inhabitants.Cologne is located on both sides of the...
. Hertz Hertz converted from Judaism
Judaism
Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...
to Christianity
Christianity
Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...
and took the name Heinrich David Hertz.
While studying at the Gelehrtenschule des Johanneums
Gelehrtenschule des Johanneums
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 motto is The Future needs a Heritage...
in Hamburg, he showed an aptitude for sciences as well as languages, learning Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
and Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...
. He studied sciences and engineering in the German cities of Dresden
Dresden
Dresden is the capital city of the Free State of Saxony in Germany. It is situated in a valley on the River Elbe, near the Czech border. The Dresden conurbation is part of the Saxon Triangle metropolitan area....
, Munich
Technical University of Munich
The Technische Universität München is a research university with campuses in Munich, Garching, and Weihenstephan...
and Berlin
Humboldt University of Berlin
The Humboldt University of Berlin is Berlin's oldest university, founded in 1810 as the University of Berlin by the liberal Prussian educational reformer and linguist Wilhelm von Humboldt, whose university model has strongly influenced other European and Western universities...
, where he studied under Gustav R. Kirchhoff and Hermann von Helmholtz
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
.
In 1880, Hertz obtained his PhD
PHD
PHD may refer to:*Ph.D., a doctorate of philosophy*Ph.D. , a 1980s British group*PHD finger, a protein sequence*PHD Mountain Software, an outdoor clothing and equipment company*PhD Docbook renderer, an XML renderer...
from the University of Berlin; and remained for post-doctoral study under Hermann von Helmholtz
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
.
In 1883, Hertz took a post as a lecturer in theoretical physics at the University of Kiel
University of Kiel
The University of Kiel is a university in the city of Kiel, Germany. It was founded in 1665 as the Academia Holsatorum Chiloniensis by Christian Albert, Duke of Holstein-Gottorp and has approximately 23,000 students today...
.
In 1885, Hertz became a full professor at the University of Karlsruhe where he discovered electromagnetic waves.
The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus.
The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap - whose poles on either side are formed by spheres of 2 cm radius - to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil.
To prove there really was radiation emitted, it had to be detected. Hertz used a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5 cm, with a small brass sphere on one end, and the other end of the wire was pointed, with the point near the sphere. He bought a screw mechanism so that the point could be moved very close to the sphere in a controlled fashion. This "receiver" was designed so that current oscillating back and forth in the wire would have a natural period close to that of the "transmitter" described above. The presence of oscillating charge in the receiver would be signaled by sparks across the (tiny) gap between the point and the sphere (typically, this gap was hundredths of a millimeter).
In more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also showed that the nature of radio waves’ reflection and refraction was the same as those of light, and established beyond any doubt that light is a form of electromagnetic radiation obeying the Maxwell equations.
Hertz's experiments would soon trigger the invention of the wireless telegraph, radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
, and later television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
. In recognition of his work, the unit of frequency - one cycle per second - is named the "hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
".
Meteorology
He always had a deep interest in meteorologyMeteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
probably derived from his contacts with Wilhelm von Bezold
Wilhelm von Bezold
Johann Friedrich Wilhelm von Bezold was a German physicist and meteorologist born in Munich, Kingdom of Bavaria....
(who was Hertz's professor in a laboratory course at the Munich Polytechnic in the summer of 1878). Hertz, however, did not contribute much to the field himself except some early articles as an assistant to Helmholtz in Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, including research on the evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
of liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
s, a new kind of hygrometer
Hygrometer
A hygrometer is an instrument used for measuring the moisture content in the environmental air, or humidity. Most measurement devices usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed...
, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.
Contact mechanics
Contact mechanics
Contact mechanics is the study of the deformation of solids that touch each other at one or more points. The physical and mathematical formulation of the subject is built upon the mechanics of materials and continuum mechanics and focuses on computations involving elastic, viscoelastic, and plastic...
. Hertz is well known for his contributions to the field of electrodynamics (see below); however, most papers that look into the fundamental nature of contact cite his two papers as a source for some important ideas. 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
Newton's rings
The phenomenon of Newton's rings, named after Isaac Newton who first studied them in 1717, is an interference pattern caused by the reflection of light between two surfaces - a spherical surface and an adjacent flat surface...
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 their landmark article "Surface energy and contact of elastic solids" published in 1971 in the Proceedings of the Royal Society (A324, 1558, 301-313). 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
Boris Derjaguin
Professor Boris Vladimirovich Derjaguin was one of the renowned Soviet/Russian chemists of the twentieth century. As a member of the Russian Academy of Sciences he laid the foundation of the modern science of colloids and surfaces...
, 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.
Electromagnetic research
In 1886, Hertz developed the Hertz antenna receiver. This is a set of terminals which is not electrically grounded for its operation. He also developed a transmitting type of dipole antennaDipole antenna
A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other , with a small space between them. The radio frequency voltage is applied to the antenna at...
, which was a center-fed driven element for transmitting UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
radio waves. These antennas are the simplest practical antennas from a theoretical point of view.
In 1887, Hertz experimented with radio waves in his laboratory. These actions followed Michelson's
Albert Abraham Michelson
Albert Abraham Michelson was an American physicist known for his work on the measurement of the speed of light and especially for the Michelson-Morley experiment. In 1907 he received the Nobel Prize in Physics...
1881 experiment (precursor to the 1887 Michelson-Morley experiment
Michelson-Morley experiment
The Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio. Its results are generally considered to be the first strong evidence against the theory of a luminiferous ether and in favor of special...
) which did not detect the existence of aether drift
Luminiferous aether
In the late 19th century, luminiferous aether or ether, meaning light-bearing aether, was the term used to describe a medium for the propagation of light....
, Hertz altered the Maxwell's equations
Maxwell's equations
Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies.Maxwell's equations...
to take this view into account for electromagnetism. Hertz used a Ruhmkorff coil
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...
-driven spark gap and one meter wire pair as a radiator. Capacity spheres were present at the ends for circuit resonance adjustments. His receiver, a precursor to the dipole antenna, was a simple half-wave dipole antenna for shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
s. Hertz published his work in a book titled: Electric waves: being researches on the propagation of electric action with finite velocity through space.
Transverse wave
A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer...
free space electromagnetic waves can travel over some distance. This had been predicted by James Clerk Maxwell
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
and Michael Faraday
Michael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
. With his apparatus configuration, 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
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
reflecting plate to produce standing wave
Standing wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
s. Each wave was about 4 meters. Using the ring detector, he recorded how the magnitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
and wave's component direction vary. Hertz measured Maxwell's waves and demonstrated that the velocity of radio waves was equal to the velocity of light. The electric field intensity and polarity was also measured by Hertz. (Hertz, 1887, 1888).
The Hertzian cone
Hertzian cone
A Hertzian cone is the cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact, eventually removing a full or partial cone. An example often occurs when a plate-glass window is struck by a small object, such as an airgun projectile...
was first described by Hertz as a type of wave-front propagation through various media
Transmission medium
A transmission medium is a material substance that can propagate energy waves...
. His experiments expanded the field of electromagnetic transmission and his apparatus was developed further by others in the radio. Hertz also found that radio waves could be transmitted through different types of materials, and were reflected by others, leading in the distant future to radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
.
Hertz helped establish the photoelectric effect (which was later explained by Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...
) when he noticed that a charged
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
object loses its charge more readily when illuminated by ultraviolet light. 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
Annalen der Physik
Annalen der Physik is one of the oldest physics journals worldwide. The journal publishes original, peer-reviewed papers in the areas of experimental, theoretical, applied and mathematical physics and related areas...
. His receiver consisted of a coil with a spark gap
Spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the gap's breakdown voltage, a spark forms,...
, whereupon 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 ultraviolet radiation that assisted the electrons in jumping across the gap.
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of 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.
Hertz did not realize the practical importance of his experiments. He stated that,
- "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 ramifications of his discoveries, Hertz replied,
- "Nothing, I guess."
His discoveries would later be more fully understood by others and be part of the new "wireless age
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
". In bulk, Hertz' experiments explain reflection, refraction
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...
, polarization, interference, and velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of electric waves.
In 1892, Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
). Philipp Lenard
Philipp Lenard
Philipp Eduard Anton von Lenard , known in Hungarian as Lénárd Fülöp Eduárd Antal, was a Hungarian - German physicist and the winner of the Nobel Prize for Physics in 1905 for his research on cathode rays and the discovery of many of their properties...
, 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
Wilhelm Conrad Röntgen
Wilhelm Conrad Röntgen was a German physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range today known as X-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901....
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.
Death at age 36
In 1892, an infection was diagnosed (after a bout of severe migraines) and Hertz underwent some operations to correct the illness. He died of Wegener's granulomatosisWegener's granulomatosis
Wegener's granulomatosis , more recently granulomatosis with polyangiitis , is an incurable form of vasculitis that affects the nose, lungs, kidneys and other organs. Due to its end-organ damage, it is life-threatening and requires long-term immunosuppression...
at the age of 36 in Bonn
Bonn
Bonn is the 19th largest city in Germany. Located in the Cologne/Bonn Region, about 25 kilometres south of Cologne on the river Rhine in the State of North Rhine-Westphalia, it was the capital of West Germany from 1949 to 1990 and the official seat of government of united Germany from 1990 to 1999....
, Germany in 1894, and was buried in Ohlsdorf, Hamburg at the Jewish cemetery.
Hertz's wife, Elizabeth Hertz (maiden name: Elizabeth Doll), did not remarry. Heinrich Hertz left two daughters, Joanna and Mathilde. Subsequently, all three women left Germany in the 1930s to England, after the rise of Adolf Hitler
Adolf Hitler
Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party , commonly referred to as the Nazi Party). He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945...
. Charles Susskind interviewed Mathilde Hertz in the 1960s and he later published a book on Heinrich Hertz. Heinrich Hertz's daughters never married and he does not have any descendants, according to the book by Susskind.
Legacy and honors
His nephew Gustav Ludwig HertzGustav Ludwig Hertz
Gustav Ludwig Hertz was a German experimental physicist and Nobel Prize winner, and a nephew of Heinrich Rudolf Hertz.-Biography:...
was a Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...
winner, and Gustav's son Carl Hellmuth Hertz
Carl Hellmuth Hertz
For the Stage Magician, see Carl Hertz.Carl Hellmuth Hertz was the son of Gustav Ludwig Hertz.During the World War II he served as a soldier for Nazi Germany. He was captured by USA troops and brought overseas...
invented medical ultrasonography
Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
.
The SI unit hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
(Hz) was established in his honor by the IEC in 1930 for frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, a measurement of the number of times that a repeated event occurs per second (also called "cycles per sec" (cps)). It was adopted by the CGPM (Conférence générale des poids et mesures) in 1964.
In 1969 (East Germany), there was cast a Heinrich Hertz memorial medal. 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".
A crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
that lies on the far side of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, just behind the eastern limb, is named in his honor
Hertz (crater)
Hertz is a lunar crater that lies on the far side of the Moon, just behind the eastern limb. Due to libration this feature can sometimes be observed from the Earth under favorable lighting conditions. It is located to the west-southwest of the larger crater Fleming, and north-northeast of the...
. The Hertz market for radioelectronics products in Nizhny Novgorod
Nizhny Novgorod
Nizhny Novgorod , colloquially shortened to Nizhny, is, with the population of 1,250,615, the fifth largest city in Russia, ranking after Moscow, St. Petersburg, Novosibirsk, and Yekaterinburg...
, Russia, is named after him. The Heinrich-Hertz-Turm
Heinrich-Hertz-Turm
The Heinrich-Hertz-Turm is a radio telecommunication tower and a famous landmark of Hamburg, Germany....
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
Order of the Sacred Treasure
The is a Japanese Order, established on January 4, 1888 by Emperor Meiji of Japan as the Order of Meiji. It is awarded in eight classes . It is generally awarded for long and/or meritorious service and considered to be the lowest of the Japanese orders of merit...
, which has multiple layers of honor for prominent people, including scientists.
Heinrich Hertz was 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.
Nazi revisionism
Although Hertz would not have considered himself Jewish, his "Jewish" portrait was removed by the Nazis from its prominent position of honor in Hamburg's City Hall (Rathaus) because of his partly "Jewish ancestry." Hertz was a Lutheran; and although his father’s family had been Jewish, his father had converted to Catholicism before marrying. The painting has since been returned to public display.See also
People- Berend Wilhelm FeddersenBerend Wilhelm FeddersenBerend Wilhelm Feddersen was a German physicist.-Biography:Feddersen lived from 1858 as a private scholar in Leipzig. In 1859 he succeeded in experiments with the Leyden jar to prove that every single electric spark discharge composed of oscillations...
- Hans Christian ØrstedHans Christian ØrstedHans Christian Ørsted was a Danish physicist and chemist who discovered that electric currents create magnetic fields, an important aspect of electromagnetism...
- David Edward HughesDavid E. HughesDavid Edward Hughes , was a British scientist and musician. Hughes was co-inventor of the microphone, a harpist and a professor of music.-Biography:...
- Reginald Aubrey Fessenden
- Guglielmo MarconiGuglielmo MarconiGuglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...
- Nikola TeslaNikola TeslaNikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
- Wilhelm Röntgen
Lists and histories
- Electromagnetism timelineTimeline of electromagnetism and classical opticsTimeline of electromagnetism and classical optics*424 BC Aristophanes "lens" is a glass globe filled with water....
- Timeline of mechanics and physics
- List of physicists
- Radio historyHistory of radioThe early history of radio is the history of technology that produced 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"...
- Wireless telegraphyWireless telegraphyWireless telegraphy is a historical term used today to apply to early radio telegraph communications techniques and practices, particularly those used during the first three decades of radio before the term radio came into use....
- List of people on stamps of Germany
- List of physics topics
Electromagnetic radiation
- MicrowaveMicrowaveMicrowaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
Other
- German inventors and discoverersGerman inventors and discoverersThis is a list of German inventors and discoverers. The following list comprises people from Germany or German-speaking Europe, also of people of predominantly German heritage, in alphabetical order of the surname. The main section includes existing articles, indicated by blue links, and possibly...
Further reading
- Appleyard, Rollo. (1930). Pioneers of Electrical Communication". London: Macmillan and Company. [reprinted by Ayer Company Publishers, Manchester, New Hampshire: 10-ISBN 0836-90156-8; 13-ISBN 978-0-836-90156-6 (cloth)]
- Baird, Davis, R.I.G. Hughes, and Alfred Nordmann, eds. (1998). 'Heinrich Hertz: Classical Physicist, Modern Philosopher. New York: Springer-Verlag. 10-ISBN 0-792-34653-X; 13-ISBN 978-0-792-34653-1
- Bodanis, David. (2006). Electric Universe: How Electricity Switched on the Modern World. New York: Three Rivers PressThree Rivers PressThree Rivers Press is the trade paperback imprint of the Crown Publishing Group, a division of Random House. It publishes original paperback titles as well as paperback reprints of books issued initially in hardcover by the other Crown imprints.- History :...
. 10-ISBN 0-307-33598-4; 13-ISBN 978-0-307-33598-2 - BuchwaldJed BuchwaldJed Z. Buchwald is Doris and Henry Dreyfuss Professor of History at Caltech. He was previously director of the Dibner Institute for the History of Science and Technology at MIT...
, Jed Z. (1994). The Creation of Scientific Effects : Heinrich Hertz and Electric Waves. Chicago : University of Chicago PressUniversity of Chicago PressThe University of Chicago Press is the largest university press in the United States. It is operated by the University of Chicago and publishes a wide variety of academic titles, including The Chicago Manual of Style, dozens of academic journals, including Critical Inquiry, and a wide array of...
. 10-ISBN 0-226-07887-6; 13-ISBN 978-0-226-07887-8 (cloth) 10-ISBN 0-226-07888-4; 13-ISBN 978-0-226-07888-5 (paper) - Bryant, John H. (1988). Heinrich Hertz, the Beginning of Microwaves: Discovery of Electromagnetic Waves and Opening of the Electromagnetic Spectrum by Heinrich Hertz in the Years 1886-1892. New York : IEEE (Institute of Electrical and Electronics Engineers). 10-ISBN 0-879-42710-8; 13-ISBN 978-0-879-42710-8
- http://www.acmi.net.au/aic/phd8030.htmlLodge, Oliver Joseph. (1900). Signalling Across Space without Wires by Electric Waves: Being a Description of the work of HeinrichHeinrichHeinrich is a male given name or surname of Germanic origin. Equivalents in other languages are Henry , Hendrik , Hinnerk , Enrico , Henri , Enrique , Enric , and Henrique . A pet form of Heinrich is "Heinz". The once-common Americanized nickname "Heinie" is largely obsolete...
Hertz and his Successors.] [reprinted by Arno Press, New York, 1974. 10-ISBN 0-405-06051-3 - Maugis, Daniel. (2000). Contact, Adhesion and Rupture of Elastic Solids. New York: Springer-Verlag. 10-ISBN 3-540-66113-1; 13-ISBN 978-3-54066113-9]
- Susskind, Charles. (1995).Heinrich Hertz :a Short Life. San Francisco: San Francisco Press. 10-ISBN 0-911-30274-3; 13-ISBN 978-0-911-30274-5
External links
- Hertzian radiation - better known as radio waves: what it is and how it happens
- Encyclopædia Britannica (1911): Hertz biography