Hertz, Heinrich

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{{Infobox_Scientist  
 
{{Infobox_Scientist  
 
|name = Heinrich Rudolf Hertz
 
|name = Heinrich Rudolf Hertz
 
|image = Heinrich Rudolf Hertz.jpg
 
|image = Heinrich Rudolf Hertz.jpg
 
|image_width = 230px
 
|image_width = 230px
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|caption = <div style="font-size: 90%">"''I do not think that the [[wireless]] waves I have discovered will have any [[radio|practical application]].''"</div>
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|caption = <div style="font-size: 90%">"I do not think that the [[wireless]] waves I have discovered will have any [[radio|practical application]]."</div>
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|birth_date = [[February 22]], [[1857]]
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|birth_date = February 22, 1857
 
|birth_place = [[Hamburg, Germany]]
 
|birth_place = [[Hamburg, Germany]]
 
|residence = [[Image:Flag_of_Germany.svg|20px|]] [[Germany]]  
 
|residence = [[Image:Flag_of_Germany.svg|20px|]] [[Germany]]  
 
|nationality = [[Image:Flag_of_Germany.svg|20px|]] [[Germany|German]]   
 
|nationality = [[Image:Flag_of_Germany.svg|20px|]] [[Germany|German]]   
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|death_date = [[January 1]], [[1894]]
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|death_date = January 1, 1894
 
|death_place = [[Bonn, Germany]]
 
|death_place = [[Bonn, Germany]]
 
|field = [[Physicist]] and [[Electronic Engineering|Electronic Engineer]]
 
|field = [[Physicist]] and [[Electronic Engineering|Electronic Engineer]]
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|work_institution = [[University of Kiel]]</br>[[University of Karlsruhe]]</br>[[University of Bonn]]
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|work_institution = [[University of Kiel]]<br/>[[University of Karlsruhe]]<br/>[[University of Bonn]]
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|alma_mater = [[University of Munich]]</br> [[University of Berlin]]
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|alma_mater = [[University of Munich]]<br/> [[University of Berlin]]
 
|doctoral_advisor = [[Hermann von Helmholtz]]
 
|doctoral_advisor = [[Hermann von Helmholtz]]
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|doctoral_students = <!-- please inseret—>
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|doctoral_students = <!-- please insert—>
 
|known_for  = [[Electromagnetic radiation]]
 
|known_for  = [[Electromagnetic radiation]]
 
|prizes =  
 
|prizes =  
 
|footnotes =  
 
|footnotes =  
 
}}
 
}}
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'''Heinrich Rudolf Hertz''' ([[February 22]], [[1857]] - [[January 1]], [[1894]]) was the [[Germans|German]] [[physicist]] and [[mechanician]] for whom the [[hertz]], an [[SI]] unit, is named. In [[1888]], he was the first to satisfactorily demonstrate the existence of [[electromagnetic radiation]] by building an apparatus to produce and detect [[Ultra high frequency|UHF]] [[radio]] waves.  
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'''Heinrich Rudolf Hertz''' (February 22, 1857 - January 1, 1894) was a [[Germans|German]] [[physicist]] who was the first to satisfactorily demonstrate the existence of [[electromagnetic radiation]] waves by building an apparatus to produce and detect them. His discovery was a key step  on the path to the use of [[radio wave]]s in [[communications]] and [[broadcasting]] and the use of all the many invisible octaves of the electromagnetic spectrum to the service of humanity.
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{{toc}}
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As a pioneer opening the window onto the invisible but very real world of electromagnetism, Hertz had no foundation for even imagining the multitude of uses to which these electromagnetic waves could be put. That task would fall to others benefiting from his discovery.  
  
 
==Biography==
 
==Biography==
 
===Early years===
 
===Early years===
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Heinrich Rudolf Hertz was born in [[Hamburg]], [[Germany]] on February 22, 1857, to Gustav Ferdinand Hertz, whose father converted from Judaism to Lutheranism and married into a Lutheran family, and Anna Elisabeth Pfefferkorn, herself a Lutheran. His father was an advisor in [[Hamburg]], his mother the daughter of a doctor. While going to school at the University of Hamburg, he showed an aptitude for sciences as well as languages, learning [[Arabic language|Arabic]] and [[Sanskrit]]. He studied sciences and engineering in the German cities of [[Dresden]], [[Munich]] and [[Berlin]]. He was a student of [[Gustav R. Kirchhoff]] and [[Hermann von Helmholtz]]. He obtained his [[PhD]] in [[1880]], and remained a pupil of Helmholtz until 1883 when he took a post as a lecturer in theoretical physics at the [[University of Kiel]]. In 1885 he became a full professor at the [[University of Karlsruhe]] where he discovered electromagnetic waves.
 
  
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===Meteorology===
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Heinrich Rudolf Hertz was born in [[Hamburg]], [[Germany]], on February 22, 1857, the oldest of the five children of Gustav Ferdinand Hertz and Anna Elisabeth Pfefferkorn. Hertz's paternal grandfather converted from [[Judaism]] to [[Lutheranism]] and married into a Lutheran family. His father was an attorney who belonged to the Hamburg senate, his mother was the daughter of a doctor. Both Hertz's father and mother were Lutheran.
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Hertz had always had a deep interest in [[meteorology]] probably derived from his contacts with [[Willhelm von Bezold]] (he 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 for 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. <ref> J. F. Mulligan and H. G. Hertz, "''On the energy balance of the Earth''", American Journal of Physics, vol. 65, pp 36-45</ref>
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In his youth, Hertz showed an advanced aptitude for mathematics, and took extra geometry lessons on Sundays. He more often than not ranked first in his class. He also had a strong affinity for languages, quickly learning Latin, Greek, [[Arabic language|Arabic]], and [[Sanskrit]]. At the same time, he showed a facility for the practical in drawing, sculpture, and handicraft. To combine these interests, he at first pursued a career in engineering construction.
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===University training===
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In 1875, Hertz spent a year in a construction department in Frankfort. He then attended the [[polytechnic]] in Dresden, and was particularly fond of the mathematical lectures given there, but also took a keen interest in history and philosophy. After only a semester in Dresden, he joined the military and spent one year on active duty. In 1877, he enrolled at the polytechnic in Munich, changing his major to physics. During this time, encouraged by his teachers, he studied the original works of famous physicists such as [[Isaac Newton]], [[Gottfried Leibniz]], [[Joseph Lagrange]], and [[Pierre-Simon Laplace]].
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Hertz was dissatisfied with the level of physics education in Munich, so he moved to Berlin. There, he studied in the laboratory of [[Hermann von Helmholtz]] and won a prize for the investigation of inertia in electric currents. Hertz was able to show that the inertia of a current was small or nonexistent; this result dovetailed with theoretical research Helmholtz was doing on electromagnetic theory. During this period, he attended lectures by [[Gustav Kirchhoff]] on mechanics. Although he would become famous for his electrical researches, Hertz's works on [[mechanics]] were also substantial.
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In 1879, he considered, but turned down, a proposal by Helmholtz to determine the existence of an electric current in a [[dielectric]], the insulating material between two conductors used to store electric charge. James Clerk Maxwell had predicted the existence of such currents. But Hertz convinced Helmholtz that the study would take longer than it was worth.
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Hertz obtained his Ph.D. in 1880, and continued to work in Helmholtz's laboratory until 1883. As an assistant to Helmholtz in [[Berlin]], Hertz submitted memoirs on the [[evaporation]] of [[liquid]]s, a new kind of [[hygrometer]], and  a graphical means of determining the properties of moist air.<ref>J. F. Mulligan and H. G. Hertz, "On the energy balance of the Earth," ''American Journal of Physics'' 65:36-45.</ref>
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He also published articles on what was to become known as the field of contact mechanics. Hertz analyzed the mechanical deformations of two colliding elastic spheres, and from this arrived at a new definition of hardness he hoped would be of some use to mineralogists.
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In 1883, Hertz accepted a post as a lecturer in theoretical physics at the [[University of Kiel]]. In 1885, he became a full professor at the [[University of Karlsruhe]] where he discovered electromagnetic waves. On July 31, of the same year he married [[Elizabeth Doll]], the daughter of [[Max Doll]], a lecturer in geometry.
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===Photoelectric effect===
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In 1886, Hertz began a series of experiments to clarify some of the theoretical predictions of Maxwell's electromagnetic theory. At this time, he discovered the utility of a spark gap, and realized that its regular effects would enable him to investigate the questions left unanswered when he turned down Helmholtz's research idea. While undertaking these experiments, he noticed what was at first an unwanted side effect: That a spark gap discharged more easily when another spark gap was activated. Hertz traced this effect to the presence of ultraviolet light waves generated from the second spark gap, which, when they reached the first, promoted current flow, thus making the discharge easier. After solving this problem, Hertz returned to the original purpose of his research. This phenomenon was later called the [[photoelectric effect]], and became the topic of a famous paper by [[Albert Einstein]] which won him a [[Nobel Prize]].
  
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===Contact mechanics===
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===Electromagnetic waves===
  
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In 1881–1882, Hertz published two articles on what was to become known as the field of contact mechanics. Hertz is generally 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. 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. But it was natural to neglect adhesion in that age as there were no experimental methods by which they could test for adhesion. 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 in the Journal of Colloid and Interface Science 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.
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Hertz wanted to show that the speed of electromagnetic waves was finite in air and in a vacuum, thus concluding that air and dielectric insulators act in the same manner. He at first noticed that he obtained a much greater reaction at his second spark gap than would be allowed by the normal laws of the propagation of force, which generally predict a diminished action with distance. From this, he realized that he was producing electromagnetic waves, which were retaining their power of action over longer distances. Not only was he able to produce and detect these waves, but he also determined their properties, such as reflection and refraction. His results, which he published in 1887, were quickly accepted by the scientific community. When publicized by others, such as physicists [[Oliver Lodge]] and [[George Fitzgerald]], who were working in the same field, his results soon launched an all-out effort to use the phenomena for the purposes of communication, resulting in the invention of radio at the end of the next decade. One of Hertz's students, [[Philipp Lenard]], continued Hertz's electrical researches into cathode rays.
  
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===Electromagnetic research===
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After his work on electromagnetic waves, Hertz turned to one of his original fields of interest, mechanics. He wrote an important work, ''The Principles of Mechanics Presented in a New Form,'' that attempted to remove ambiguity and confusion in the various presentations up to that time.
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Hertz helped establish the [[photoelectric effect]] (which was later explained by others) when he noticed that a [[electric charge|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 in order to see the spark better; he observed, however, 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.
 
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[[Image:Hertz schematic0.PNG|right|333px|thumb|1887 experimental setup of Hertz's apparatus.]]
 
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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.  
 
 
   
 
   
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Earlier in 1886, Hertz developed a [[dipole antenna]]. This antenna is a center-fed driven element for transmitting or receiving radio frequency energy. 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 [[Albert Abraham Michelson|Michelson's]] [[1881]] experiment (precursor to the [[1887]] [[Michelson-Morley experiment]]) which did not detect the existence of [[luminiferous aether|aether drift]], Hertz altered the [[Maxwell's equations]] to take this view into account for electromagnetism. Hertz used a [[Induction coil|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.  
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In 1892, an infection was diagnosed (after a bout of severe [[migraine]]s) and Hertz underwent some operations to correct the illness. He died of [[blood poisoning]] at the age of 36 in [[Bonn]], Germany.
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His nephew [[Gustav Ludwig Hertz]] was a [[Nobel Prize]] winner, and Gustav's son [[Carl Hellmuth Hertz]] invented [[medical ultrasonography]].
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==Discoveries==
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In 1887, Hertz made observations of the photoelectric effect and of the production and reception of electromagnetic waves, which he published in the journal ''[[Annalen der Physik]].'' His receiver was a coil with a voltage difference maintained across a [[spark gap]], which would issue a spark in the presence of electromagnetic waves (which were produced by a transmitter spark coil). He placed the apparatus with the receiving spark gap in a darkened box in order to see the spark better and observed instead, that the maximum spark length was less when in the box. Putting a glass panel between the source of the waves and the receiving spark gap also caused a weakening of the spark.
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When the intervening glass panel was removed, the spark length would increase; but if instead of glass a quartz panel were put in the path of the waves, Hertz observed no decrease in spark length. Knowing already that a spark is accompanied by the production of ultraviolet light, Hertz concluded that this radiation was responsible for the increase in conductivity of the second spark gap, and submitted a memoir on the subject. He did not investigate this effect further, since it was not the main focus of his research, nor did he make any attempt at explaining how the observed phenomenon was brought about. His experiments did, however, generate a tremendous amount of interest among scientists.
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===Radio waves===
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[[Image:Hertz schematic0.PNG|right|333px|thumb|1887 experimental setup of Hertz's apparatus.]]In 1887, Hertz experimented with radio waves in his laboratory. Hertz used a [[Induction coil|Ruhmkorff coil]]-driven spark gap and one meter wire pair as a radiator. Metallic spheres were present at the ends to adjust the electrical properties of the circuit. His receiver was not much more than a curved wire with a spark gap.
  
 
[[Image:TransverseEMwave.PNG|center|Theoretical results from the 1887 experiment.]]
 
[[Image:TransverseEMwave.PNG|center|Theoretical results from the 1887 experiment.]]
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Through experimentation, he proved that [[transverse wave|transverse]] [[free space]] [[electromagnetic wave]]s 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 traverse waves. Hertz had positioned the oscillator about 12 meters from a [[zinc]] reflecting plate to produce [[standing wave]]s. Each wave was about four [[meter]]s. Using the ring detector, he recorded how the [[amplitude|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 (physics)|polarity]] was also measured by Hertz.
 
  
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The [[Hertzian cone]] was first described by Hertz as a type of wave-front propagation through various [[Transmission medium|media]]. His experiments help expand the field of electromagnetism transmission and his apparatus was developed further by others in the [[history of radio]]. Hertz also found that radio waves could be transmitted through different types of materials, and were reflected by others. This was key to [[radar]] and was investigated and exploited later by others. Hertz did not understand the practical importance of his experiments. He stated that,  
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Through experimentation, he proved that electromagnetic waves can travel over some distance through the air. 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 waves. Hertz had positioned the oscillator about 12 meters from a [[zinc]] reflecting plate to produce [[standing wave]]s, similar to the way a musical note is produced by sound waves reverberating in a tube of a set length. Each wave was about four [[meter]]s long. Using the ring detector, he recorded how the [[amplitude|magnitude]] and direction of the waves varied. Hertz failed, however, to conclusively measure the speed of the waves. At first he thought the speed was infinite; another series of measurements showed a large discrepancy between the velocity of waves in a wire and through air. Later investigators resolved these differences, and showed that the waves move at the speed of light.
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: "''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.''" <ref name="katz"> Eugenii Katz, "''[http://chem.ch.huji.ac.il/~eugeniik/history/hertz.htm Heinrich Rudolf Hertz]''". Biographies of Famous Electrochemists and Physicists Contributed to Understanding of Electricity,  Biosensors & Bioelectronics.</ref>
 
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Asked about the ramifications of his discoveries, Hertz replied,  
 
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: "''Nothing, I guess''." <ref name="katz"/>
 
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His discoveries would later be more fully understood by others and be part of the new "[[wireless|wireless age]]". In bulk, Hertz' experiment explain [[Reflection (electrical)|reflection]], [[refraction]], [[polarization]], [[interference]], and [[velocity]] of [[electric wave]]s.  
 
  
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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 "[[X-rays|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 [[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.
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==Legacy==
  
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===Death and afterwards===
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Like many of the scientists of his time, Hertz did not understand the wide-ranging potential applications of his production and detection of electromagnetic radiation. His original purpose was to demonstrate certain principles contained in Maxwell's theory. Had not others, such as Lodge and Fitzgerald, been working in the same field, his work and its applications might not have been well understood.
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[[Image:Autograph of Heinrich Hertz.png|right|thumb|200px|Hertz's autograph]]
 
  
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In [[1892]], an infection was diagnosed (after a bout of severe [[migraine]]s) and Hertz underwent some operations to correct the illness. He died of [[blood poisoning]] at the age of 36 in [[Bonn]], Germany. His nephew [[Gustav Ludwig Hertz]] was a [[Nobel Prize]] winner, and Gustav's son [[Carl Hellmuth Hertz]] invented [[medical ultrasonography]].  
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Of his discovery, he said:
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<blockquote>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.<ref>Eugenii Katz, Heinrich Rudolf Hertz. Biographies of Famous Electrochemists and Physicists Contributed to Understanding of Electricity, Biosensors & Bioelectronics. </ref></blockquote>
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Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess."
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His discoveries would later be more fully understood by others and be part of the new "[[wireless|wireless age]]."
  
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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 unit of time (also called "cycles per sec" (cps)). 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''". It was adopted by the CGPM (Conférence générale des poids et mesures) in 1964. 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]].
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It took more practical people like [[Nikola Tesla]] and [[Guglielmo Marconi]] to understand the practical advantage of using the waves to send messages over long distances. Hertz did not live long enough to see the blossoming of the new technology based on his discoveries.
  
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== See also ==
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==Honors==
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{| style="text-align: left; width: 75%;" border="0" cellspacing="2" cellpadding="2"
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[[Image:Autograph of Heinrich Hertz.png|right|thumb|200px|Hertz's signature]]
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| style="vertical-align: top;" |
 
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''People''
 
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* [[Hans Christian Ørsted]]
 
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* [[David E. Hughes|David Edward Hughes]]
 
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* [[Reginald Aubrey Fessenden]]
 
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* [[Guglielmo Marconi]]
 
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* [[Gustav Ludwig Hertz]]
 
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* [[Hermann von Helmholtz]]
 
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* [[James Clerk Maxwell]]
 
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* [[Nikola Tesla]]
 
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* [[Wilhelm Röntgen]]  
 
  
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''Lists and histories''  
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* The ''hertz'' (Hz) was established in Hertz's honor in 1930 as a unit of measurement for [[frequency]], a measurement of the number of times that a repeated event occurs per unit of time (also called "cycles per sec").
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* [[Timeline of electromagnetism and classical optics|Electromagnetism timeline]]  
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* In 1969 ([[East Germany]]), there was cast a [[Heinrich Hertz memorial medal]].
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* [[Timeline of quantum mechanics, molecular physics, atomic physics, nuclear physics, and particle physics|Timeline of mechanics and physics]]  
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* The [[IEEE Heinrich Hertz Medal]], established in 1987, is for outstanding achievements in Hertzian waves presented annually to an individual for theoretical achievements.
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* [[List of physicists]]  
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* 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]].
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* [[History of radio|Radio history]]  
 
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* [[Wireless telegraphy]]  
 
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* [[List of people on stamps of Germany]]  
 
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* [[List of physics topics]]
 
  
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| style="vertical-align: top;" | <br>
 
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| style="vertical-align: top;" | 
 
  
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''[[Electromagnetic radiation]]''
 
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* [[Microwave]]
 
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* [[Luminiferous aether]]
 
  
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''Other''
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== Notes ==
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* [[University of Bonn]]
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<references/>
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* [[University of Karlsruhe]]
 
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* [[Radio]]
 
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|}
 
  
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== Further reading ==
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== References ==
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* Appleyard, Rollo, "''Pioneers of electrical communication''". London, Macmillan and co., limited, 1930. LCCN 30011090 //r87  ( ''ed''. memoirs were published in Electrical communication.)
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* Bodanis, David. 2005. ''Electric Universe: How Electricity Switched on the Modern World.''  New York: Three Rivers Press. ISBN 0307335984
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* Bodanis, David. ''Electric Universe: How Electricity Switched on the Modern World.''  New York: Three Rivers Press, 2005. ISBN 0-307-33598-4
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* 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: Institute of Electrical and Electronics Engineers. ISBN 0879427108
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* Buchwald, Jed Z., "''The creation of scientific effects : Heinrich Hertz and electric waves''". Chicago : University of Chicago Press, c1994. ISBN 0-226-07887-6 (alk. paper) ISBN 0-226-07888-4 (pbk.; alk. paper) LCCN 93041783
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* Buchwald, Jed Z. 1994. ''The Creation of Scientific Effects: Heinrich Hertz and Electric Waves.'' Chicago: University of Chicago Press. ISBN 0226078876
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* Susskind, Charles, "''Heinrich Hertz : a short life''". San Francisco, CA : San Francisco Press, c1995. ISBN 0-911302-74-3
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* Dahl, P.F. 1997. ''Flash of the Cathode Rays: A History of J.J. Thomson's Electron.'' Bristol: Institute of Physics Pub. ISBN 0750304537
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* Lodge, Oliver, "''The work of Hertz and his successors : being a description of signalling across space without wires by electric waves'', "The Electrician" series. Signalling without wires.  London : "The Electrician" Printing and Pub. Co., [1897?], 2nd ed.
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* Lützen, Jesper. 2005. ''Mechanistic Images In Geometric Form: Heinrich Hertz's Principles of Mechanics.'' New York: Oxford University Press. 50-62. ISBN 0198567375
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* Bryant, John H., "''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 : Institute of Electrical and Electronics Engineers ; Piscataway, NJ : IEEE Service Center, Single Publication Sales Dept. [distributor], c1988. ISBN 0-87942-710-8 LCCN 88176362 (''ed''. 1988 IEEE/MTT-S Hertz Centennial Celebration exhibition at the 1988 MTT-S International Microwave Symposium)
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* Susskind, Charles. 1995. ''Heinrich Hertz: A Short Life.'' San Francisco: San Francisco Press. ISBN 0911302743
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* Baird, Davis. (ed.), Hughes, R. I. G. (ed.), and Nordmann, Alfred,  (ed.), "''Heinrich Hertz : classical physicist, modern philosopher''". Boston studies in the philosophy of science. v. 198, Dordrecht ; Boston : Kluwer Academic Publishers, c1998. ISBN 0-7923-4653-X (hardcover; alk. paper) LCCN 97023406
 
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* Ducretet, E., "''La télégraphie hertzienne sans fils : expériences de Henri Hertz''" (Tr., ''Hertzian telegraphy without wire: experiments of Henri Hertz''). Guise (Aisne) : s.n., 1898 (Baré)
 
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* Maugis, D., "''Contact, Adhesion and Rupture of Elastic Solids''". ISBN 3-540-66113-1, (Springer-Verlag)
 
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== References, external links, and other articles ==
 
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;Citations
 
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<references/>
 
  
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;Websites
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== External links ==
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{{Commons}}
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All links retrieved December 13, 2017.
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* Kim Breitfelder (Program Manager) and Mike Geselowitz, (Director), "''[http://www.ieee-virtual-museum.org/collection/people.php?taid=&id=1234576&lid=1 Heinrich Hertz]''".  IEEE History Center, IEEE 2006.
 
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*  John D. Jenkins, "''[http://www.sparkmuseum.com/BOOK_HERTZ.HTM The Discovery of Radio Waves] - 1888; Heinrich Rudolf Hertz (1847-1894)''". sparkmuseum.com.
 
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* Francesco Errante, "''[http://www.esmartstart.com/_framed/250x/radiondistics/hertzian_radiation.htm Hertzian Radiation, (better known as radio-waves) : what it is and how it happens]''". Radiondistics.com.
 
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* Russell Naughton, "''[http://www.acmi.net.au/AIC/HERTZ_BIO.html Heinrich Rudolph (alt: Rudolf) Hertz, Dr : 1857 - 1894]''". Adventures in CyberSound.
 
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* "''[http://indykfi.atomki.hu/indyKFI/MT/hertz.htm Heinrich Rudolf Hertz]''".  Institute of Experimental Physics, University of Debrecen.
 
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* Wilhelm Mosel, "''[http://www1.uni-hamburg.de/rz3a035//bundesstrasse1.html Buildings Integral to the Former Life and/or Persecution of Jews in Hamburg - Eimsbüttel/Rotherbaum]''". Deutsch-Jüdische Gesellschaft, Hamburg. 
 
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* "''[http://www.wsone.com/fecha/hertz.htm Heinrich Hertz]''". The First Electronic Church of America.
 
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* "''[http://www.corrosion-doctors.org/Biographies/HertzBio.htm Heinrich Rudolph Hertz (1857 - 1894)]''". Corrosion-doctors.org.
 
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* Struan Robertson, "''[http://www1.uni-hamburg.de/rz3a035//rathaus.html#4 Heinrich Hertz (1857 - 1894)]''". uni-hamburg.de. (''ed''. Hertz' portrait in the Hamburg City Hall.)
 
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*[http://historical.library.cornell.edu/cgi-bin/cul.cdl/docviewer?did=cdl334&view=50&frames=0&seq=5 Electric waves: being researches on the propagation of electric action with finite velocity through space] by Heinrich Rudolph Hertz.  Cornell University Library Historical Monographs Collection. {Reprinted by} [http://www.amazon.com/dp/1429740361/ Cornell University Library Digital Collections]
 
  
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<!-- Metadata: see [[Wikipedia:Persondata]] -->
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* John D. Jenkins, "''[http://www.sparkmuseum.com/BOOK_HERTZ.HTM The Discovery of Radio Waves] - 1888; Heinrich Rudolf Hertz (1847-1894)''." sparkmuseum.com.
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{{Persondata
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* "''[http://www.corrosion-doctors.org/Biographies/HertzBio.htm Heinrich Rudolph Hertz (1857 - 1894)]''." Corrosion-doctors.org.
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|NAME= Hertz, Heinrich Rudolf
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*[http://historical.library.cornell.edu/cgi-bin/cul.cdl/docviewer?did=cdl334&view=50&frames=0&seq=5 Electric waves: being researches on the propagation of electric action with finite velocity through space] by Heinrich Rudolph Hertz. Cornell University Library Historical Monographs Collection. {Reprinted by} Cornell University Library Digital Collections.
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|SHORT DESCRIPTION= [[Physicist]] and [[Electronic Engineering|Electronic Engineer]]
 
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|DATE OF BIRTH= [[February 22]], [[1857]]
 
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|DATE OF DEATH= [[January 1]], [[1894]]
 
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Latest revision as of 15:17, 25 January 2023

Heinrich Rudolf Hertz

Heinrich Rudolf Hertz.jpg
"I do not think that the wireless waves I have discovered will have any practical application."
Born

February 22, 1857
Hamburg, Germany

Died January 1, 1894

Bonn, Germany

Residence Flag of Germany.svg Germany
Nationality Flag of Germany.svg German
Field Physicist and Electronic Engineer
Institutions University of Kiel
University of Karlsruhe
University of Bonn
Alma mater University of Munich
University of Berlin
Academic advisor  Hermann von Helmholtz
Known for Electromagnetic radiation

Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was a German physicist who was the first to satisfactorily demonstrate the existence of electromagnetic radiation waves by building an apparatus to produce and detect them. His discovery was a key step on the path to the use of radio waves in communications and broadcasting and the use of all the many invisible octaves of the electromagnetic spectrum to the service of humanity.

As a pioneer opening the window onto the invisible but very real world of electromagnetism, Hertz had no foundation for even imagining the multitude of uses to which these electromagnetic waves could be put. That task would fall to others benefiting from his discovery.

Biography

Early years

Heinrich Rudolf Hertz was born in Hamburg, Germany, on February 22, 1857, the oldest of the five children of Gustav Ferdinand Hertz and Anna Elisabeth Pfefferkorn. Hertz's paternal grandfather converted from Judaism to Lutheranism and married into a Lutheran family. His father was an attorney who belonged to the Hamburg senate, his mother was the daughter of a doctor. Both Hertz's father and mother were Lutheran.

In his youth, Hertz showed an advanced aptitude for mathematics, and took extra geometry lessons on Sundays. He more often than not ranked first in his class. He also had a strong affinity for languages, quickly learning Latin, Greek, Arabic, and Sanskrit. At the same time, he showed a facility for the practical in drawing, sculpture, and handicraft. To combine these interests, he at first pursued a career in engineering construction.

University training

In 1875, Hertz spent a year in a construction department in Frankfort. He then attended the polytechnic in Dresden, and was particularly fond of the mathematical lectures given there, but also took a keen interest in history and philosophy. After only a semester in Dresden, he joined the military and spent one year on active duty. In 1877, he enrolled at the polytechnic in Munich, changing his major to physics. During this time, encouraged by his teachers, he studied the original works of famous physicists such as Isaac Newton, Gottfried Leibniz, Joseph Lagrange, and Pierre-Simon Laplace.

Hertz was dissatisfied with the level of physics education in Munich, so he moved to Berlin. There, he studied in the laboratory of Hermann von Helmholtz and won a prize for the investigation of inertia in electric currents. Hertz was able to show that the inertia of a current was small or nonexistent; this result dovetailed with theoretical research Helmholtz was doing on electromagnetic theory. During this period, he attended lectures by Gustav Kirchhoff on mechanics. Although he would become famous for his electrical researches, Hertz's works on mechanics were also substantial.

In 1879, he considered, but turned down, a proposal by Helmholtz to determine the existence of an electric current in a dielectric, the insulating material between two conductors used to store electric charge. James Clerk Maxwell had predicted the existence of such currents. But Hertz convinced Helmholtz that the study would take longer than it was worth.

Hertz obtained his Ph.D. in 1880, and continued to work in Helmholtz's laboratory until 1883. As an assistant to Helmholtz in Berlin, Hertz submitted memoirs on the evaporation of liquids, a new kind of hygrometer, and a graphical means of determining the properties of moist air.[1]

He also published articles on what was to become known as the field of contact mechanics. Hertz analyzed the mechanical deformations of two colliding elastic spheres, and from this arrived at a new definition of hardness he hoped would be of some use to mineralogists.

In 1883, Hertz accepted a post as a lecturer in theoretical physics at the University of Kiel. In 1885, he became a full professor at the University of Karlsruhe where he discovered electromagnetic waves. On July 31, of the same year he married Elizabeth Doll, the daughter of Max Doll, a lecturer in geometry.

Photoelectric effect

In 1886, Hertz began a series of experiments to clarify some of the theoretical predictions of Maxwell's electromagnetic theory. At this time, he discovered the utility of a spark gap, and realized that its regular effects would enable him to investigate the questions left unanswered when he turned down Helmholtz's research idea. While undertaking these experiments, he noticed what was at first an unwanted side effect: That a spark gap discharged more easily when another spark gap was activated. Hertz traced this effect to the presence of ultraviolet light waves generated from the second spark gap, which, when they reached the first, promoted current flow, thus making the discharge easier. After solving this problem, Hertz returned to the original purpose of his research. This phenomenon was later called the photoelectric effect, and became the topic of a famous paper by Albert Einstein which won him a Nobel Prize.

Electromagnetic waves

Hertz wanted to show that the speed of electromagnetic waves was finite in air and in a vacuum, thus concluding that air and dielectric insulators act in the same manner. He at first noticed that he obtained a much greater reaction at his second spark gap than would be allowed by the normal laws of the propagation of force, which generally predict a diminished action with distance. From this, he realized that he was producing electromagnetic waves, which were retaining their power of action over longer distances. Not only was he able to produce and detect these waves, but he also determined their properties, such as reflection and refraction. His results, which he published in 1887, were quickly accepted by the scientific community. When publicized by others, such as physicists Oliver Lodge and George Fitzgerald, who were working in the same field, his results soon launched an all-out effort to use the phenomena for the purposes of communication, resulting in the invention of radio at the end of the next decade. One of Hertz's students, Philipp Lenard, continued Hertz's electrical researches into cathode rays.

After his work on electromagnetic waves, Hertz turned to one of his original fields of interest, mechanics. He wrote an important work, The Principles of Mechanics Presented in a New Form, that attempted to remove ambiguity and confusion in the various presentations up to that time.

In 1892, an infection was diagnosed (after a bout of severe migraines) and Hertz underwent some operations to correct the illness. He died of blood poisoning at the age of 36 in Bonn, Germany.

His nephew Gustav Ludwig Hertz was a Nobel Prize winner, and Gustav's son Carl Hellmuth Hertz invented medical ultrasonography.

Discoveries

In 1887, Hertz made observations of the photoelectric effect and of the production and reception of electromagnetic waves, which he published in the journal Annalen der Physik. His receiver was a coil with a voltage difference maintained across a spark gap, which would issue a spark in the presence of electromagnetic waves (which were produced by a transmitter spark coil). He placed the apparatus with the receiving spark gap in a darkened box in order to see the spark better and observed instead, that the maximum spark length was less when in the box. Putting a glass panel between the source of the waves and the receiving spark gap also caused a weakening of the spark.

When the intervening glass panel was removed, the spark length would increase; but if instead of glass a quartz panel were put in the path of the waves, Hertz observed no decrease in spark length. Knowing already that a spark is accompanied by the production of ultraviolet light, Hertz concluded that this radiation was responsible for the increase in conductivity of the second spark gap, and submitted a memoir on the subject. He did not investigate this effect further, since it was not the main focus of his research, nor did he make any attempt at explaining how the observed phenomenon was brought about. His experiments did, however, generate a tremendous amount of interest among scientists.

Radio waves

1887 experimental setup of Hertz's apparatus.

In 1887, Hertz experimented with radio waves in his laboratory. Hertz used a Ruhmkorff coil-driven spark gap and one meter wire pair as a radiator. Metallic spheres were present at the ends to adjust the electrical properties of the circuit. His receiver was not much more than a curved wire with a spark gap.

Theoretical results from the 1887 experiment.

Through experimentation, he proved that electromagnetic waves can travel over some distance through the air. 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 waves. Hertz had positioned the oscillator about 12 meters from a zinc reflecting plate to produce standing waves, similar to the way a musical note is produced by sound waves reverberating in a tube of a set length. Each wave was about four meters long. Using the ring detector, he recorded how the magnitude and direction of the waves varied. Hertz failed, however, to conclusively measure the speed of the waves. At first he thought the speed was infinite; another series of measurements showed a large discrepancy between the velocity of waves in a wire and through air. Later investigators resolved these differences, and showed that the waves move at the speed of light.

Legacy

Like many of the scientists of his time, Hertz did not understand the wide-ranging potential applications of his production and detection of electromagnetic radiation. His original purpose was to demonstrate certain principles contained in Maxwell's theory. Had not others, such as Lodge and Fitzgerald, been working in the same field, his work and its applications might not have been well understood.

Of his discovery, he said:

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.[2]

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."

It took more practical people like Nikola Tesla and Guglielmo Marconi to understand the practical advantage of using the waves to send messages over long distances. Hertz did not live long enough to see the blossoming of the new technology based on his discoveries.

Honors

Hertz's signature
  • The hertz (Hz) was established in Hertz's honor in 1930 as a unit of measurement for frequency, a measurement of the number of times that a repeated event occurs per unit of time (also called "cycles per sec").
  • 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 theoretical achievements.
  • A crater that lies on the far side of the Moon, just behind the eastern limb, is named in his honor.


Notes

  1. ↑ J. F. Mulligan and H. G. Hertz, "On the energy balance of the Earth," American Journal of Physics 65:36-45.
  2. ↑ Eugenii Katz, Heinrich Rudolf Hertz. Biographies of Famous Electrochemists and Physicists Contributed to Understanding of Electricity, Biosensors & Bioelectronics.

References
ISBN links support NWE through referral fees

  • Bodanis, David. 2005. Electric Universe: How Electricity Switched on the Modern World. New York: Three Rivers Press. ISBN 0307335984
  • 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: Institute of Electrical and Electronics Engineers. ISBN 0879427108
  • Buchwald, Jed Z. 1994. The Creation of Scientific Effects: Heinrich Hertz and Electric Waves. Chicago: University of Chicago Press. ISBN 0226078876
  • Dahl, P.F. 1997. Flash of the Cathode Rays: A History of J.J. Thomson's Electron. Bristol: Institute of Physics Pub. ISBN 0750304537
  • Lützen, Jesper. 2005. Mechanistic Images In Geometric Form: Heinrich Hertz's Principles of Mechanics. New York: Oxford University Press. 50-62. ISBN 0198567375
  • Susskind, Charles. 1995. Heinrich Hertz: A Short Life. San Francisco: San Francisco Press. ISBN 0911302743

External links

All links retrieved December 13, 2017.

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