Lights flash at frequency f = 0.5 Hz (Hz = hertz), 1.0 Hz and 2.0 Hz, where Failed to parse (Missing texvc executable; please see math/README to configure.): x

Hz means Failed to parse (Missing texvc executable; please see math/README to configure.): x
flashes per second. T is the period and T = Failed to parse (Missing texvc executable; please see math/README to configure.): y
s (s = second) means that Failed to parse (Missing texvc executable; please see math/README to configure.): y

is the number of seconds per flash. T and f are each other's reciprocal: f = 1/T and T = 1/f.

The hertz (symbol Hz) is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon.^[1] One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications. The word "hertz" is named for Heinrich Rudolf Hertz, who was the first to conclusively prove the existence of electromagnetic waves.

Definition[link]

The hertz is equivalent to cycles per second.^[2] In defining the second, the CIPM declared that "the standard to be employed is the transition between the hyperfine levels F = 4, M =  0 and F = 3, M = 0 of the ground state 2S_1/2 of the cesium 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9 192 631 770 hertz"^[3] thereby effectively defining the hertz and the second simultaneously.

In English, hertz is used as a plural.^[4] As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10³ Hz), MHz (megahertz, 10⁶ Hz), GHz (gigahertz, 10⁹ Hz) and THz (terahertz, 10¹² Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. The "frequency" (activity) of aperiodic or stochastic events, such as radioactive decay, is expressed in becquerels.

Even though angular velocity, angular frequency and hertz all have the dimensions of 1/s, angular velocity and angular frequency are not expressed in hertz,^[5] but rather in an appropriate angular unit such as radians per second. Thus a disc rotating at 60 revolutions per minute (rpm) is said to be rotating at either 2π rad/s or 1 Hz, where the former measures the angular velocity and the latter reflects the number of complete revolutions per second. The conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second are:

Failed to parse (Missing texvc executable; please see math/README to configure.): \omega = 2\pi f \,

and Failed to parse (Missing texvc executable; please see math/README to configure.): f = \frac{\omega}{2\pi} \, 

. This SI unit is named after Heinrich Hertz. As with every International System of Units (SI) unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (Hz). When an SI unit is spelled out in English, it should always begin with a lower case letter (hertz), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.

History[link]

The hertz is named after the German physicist Heinrich Hertz who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1930.^[6] It was adopted by the General Conference on Weights and Measures (CGPM) (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples, primarily kilocycles per second (kc/s) and megacycles per second (Mc/s), and occasionally kilomegacycles per second (kMc/s). The term cycles per second was largely replaced by hertz by the 1970s.

The term "gigahertz", most commonly used in computer processor clock rates and radio frequency (RF) applications, can be pronounced either /ˈɡɪɡəhɜrts/, with a hard /ɡ/ sound, or /ˈdʒɪɡəhɜrts/, with a soft /dʒ/^[7] (see giga-#Pronunciation). The prefix "giga-" is derived directly from the Greek "γιγας" ("giant").

Applications[link]

Sine waves of different frequency.

Details of a heartbeat as an example of a non-sinusoidal periodic phenomenon that can be described in terms of hertz. Two complete cycles are illustrated.

Vibration[link]

Sound is a traveling wave which is an oscillation of pressure. Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz; the average adult human can hear sounds between 20 Hz and 16,000 Hz.^[8] The range of ultrasound, high-intensity infrasound and other physical vibrations such as molecular vibrations extends into the megahertz range and well beyond.

Electromagnetic radiation[link]

Electromagnetic radiation is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz.

Radio frequency radiation is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz. Electromagnetic radiation with frequencies in the low terahertz range, (intermediate between those of the highest normally usable radio frequencies and long-wave infrared light), is often called terahertz radiation. Even higher frequencies exist, such as that of gamma rays, which can be measured in exahertz. (For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)

Computing[link]

In computing, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz or gigahertz (10⁶ or 10⁹ hertz, respectively). This number refers to the frequency of the CPU's master clock signal ("clock rate"). This signal is simply an electrical voltage which changes from low to high and back again at regular intervals. This signal is a square wave. Hertz has become the primary unit of measurement accepted by the general populace to determine the performance of a CPU, but many experts have criticized this approach, which they claim is an easily manipulable benchmark.^[9] For home-based personal computers, the CPU has ranged from approximately 1 megahertz in the late 1970s (Atari, Commodore, Apple computers) to up to 6 GHz in the present (IBM POWER processors) and up to 8 GHz overclocked (AMD FX processors).^[10]

Various computer buses, such as the front-side bus connecting the CPU and northbridge, also operate at different frequencies in the megahertz range

[edit] SI multiples

Frequencies not expressed in hertz[link]

Even higher frequencies are believed to occur naturally, in the frequencies of the quantum-mechanical wave functions of high-energy (or, equivalently, massive) particles, although these are not directly observable, and must be inferred from their interactions with other phenomena. For practical reasons, these are typically not expressed in hertz, but in terms of the equivalent quantum energy, which is proportional to the frequency by the factor of Planck's constant.

See also[link]

References[link]

External links[link]

• BIPM Cesium ion f_Cs definition
• National Research Council of Canada: Generation of the Hz
• National Research Council of Canada: Cesium fountain clock
• National Physical Laboratory: Trapped ion optical frequency standards
• National Research Council of Canada: Optical frequency standard based on a single trapped ion
• National Research Council of Canada: Optical frequency comb
• One Hertz in Radians per Second (Google). Note, as of 06 May 2009 there is an error of 2Failed to parse (Missing texvc executable; please see math/README to configure.): \pi

.

v t e SI units Base units Ampere · Candela · Kelvin · Kilogram · Metre · Mole · Second Derived units Becquerel · Coulomb · Degree Celsius · Farad · Gray · Henry · Hertz · Joule · Katal · Lumen · Lux · Newton · Ohm · Pascal · Radian · Siemens · Sievert · Steradian · Tesla · Volt · Watt · Weber Accepted for use with SI Dalton (Atomic mass unit) · Astronomical unit · Day · Decibel · Degree Celsius · Degree of arc · Electronvolt · Hectare · Hour · Litre · Minute · Minute of arc · Neper · Second of arc · Tonne Atomic units · Natural units See also SI prefixes · Systems of measurement · Conversion of units · New SI definitions · History of the metric system Book:International System of Units  · Category:SI base units

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2009)

The Crystal Method
The Crystal Method performing at SXSW 2009.
Background information
Origin	Los Angeles, California, United States
Genres	Alternative dance, chemical breaks, big beat, breakbeat, EDM
Years active	1993–present
Labels	Outpost, Geffen, V2, Tiny E
Website	TheCrystalMethod.com
Members
Scott Heisler Kirkland Ken B. Jordan

The Crystal Method is an American electronic music duo that was created in Las Vegas, Nevada by Ken Jordan and Scott Kirkland in the early 1990s. The Crystal Method's music has appeared in numerous TV shows, films, video games, and advertisements. Their best-selling album, Vegas, was certified platinum in 2007.

Biography[link]

The Crystal Method is made up of two members, Ken Jordan and Scott Kirkland. Before The Crystal Method was formed, Ken and Scott started working on music while working at the grocery store and while Ken was a local DJ in Las Vegas as well as the college radio program director at UNLV. Ken taught Scott how to DJ, and when Ken moved to L.A. to work for a producer, Scott took over his job DJ'ing at the local club. Scott would follow Ken out to L.A., and they formed The Crystal Method in 1993.

Early days (1993–1995)[link]

By the early '90s, both Ken and Scott had moved from Las Vegas to Los Angeles. Ken Jordan and Scott Kirkland bought a house together, in Glendale, California, which had a small underground shelter beneath the front lawn. Originally intending to turn the shelter into a studio, it proved to be an unrealistic idea and the duo set up a studio in their house (which was located under a Los Angeles Overpass. They subsequently named their studio The Bomb Shelter.The Crystal Method (interview) (1999). Better Living Through Circuitry (Motion picture). United States: Cleopatra Pictures. http://us.imdb.com/title/tt0207998/. 

After The Bomb Shelter was built, a tape of The Crystal Method's music found its way to a British DJ named Justin King. King was interested in starting a record label that would showcase American electronic dance acts. King teamed up with Scottish Steve Melrose to form the record label City of Angels. The first official release from the City of Angels label was The Crystal Method's "Now is the Time". The Crystal Method were signed to Outpost Recordings in 1996.

[edit] Vegas (1996–1998)

After the band signed with Outpost, they began working on their debut album. The group's second (and last) single on City of Angels was "Keep Hope Alive". Their next release was on the Mortal Kombat: More Kombat soundtrack, "Come2gether".

On September 8, 1997, The Crystal Method released their best-selling album, Vegas. Vegas peaked at number 92 on the Billboard 200.^[1] It was certified gold by the RIAA in 1998, then platinum in 2007.^[2]

Five of the album's ten tracks were released as singles: "Trip Like I Do", "Busy Child", "High Roller", "Comin' Back", and "Keep Hope Alive".

[edit] Tweekend (1999–2002)

In 1999, the band went into the studio to record their next studio album, Tweekend, which featured more guest artists than Vegas had. The album was released in July 2001, and peaked at number 32 on the Billboard 200,^[1] which is still the group's highest album chart position.

Featured guests from the album include Rage Against the Machine guitarist Tom Morello, Stone Temple Pilots vocalist Scott Weiland, and others, like Doug Grean, DJ Swamp, Ryan "Ryu" Maginn, and Julie Gallios. Four singles were released from Tweekend: "Wild, Sweet and Cool", "Murder", "Blowout", "Name of the Game".

[edit] Community Service

Jordan and Kirkland used to have a radio show called "Community Service" which aired Friday nights on radio station Indie 103.1, in California.^{[citation needed]} They played electronic music and hosted guests, like Death in Vegas and UNKLE. Their show came back on air in 2011 and airs weekly on Sirius XMs Channel 52.

A year after the release of Tweekend, The Crystal Method released a continuous mix album based on their radio show, titled Community Service. The album does not feature any new studio material from The Crystal Method, but is composed of remixes of bands like P.O.D., Rage Against the Machine, and Garbage, plus remixes of songs from Tweekend. Their remix of P.O.D.'s "Boom" from this album, also appeared in the video game Amplitude.

Community Service peaked at number 160 on the Billboard 200, number five on the Top Electronic Albums chart, and number 15 on the Top Independent Albums chart.^[1]

[edit] Legion of Boom (2003–2005)

After the release of Community Service, The Crystal Method went back into the studio to record their third album, Legion of Boom. During the recording, they used the house as their recording studio instead of The Bomb Shelter.^{[citation needed]}

In December 2003, the single "Born Too Slow", with vocals from John Garcia and guitar by Wes Borland was released. Legion of Boom was released on January 13, 2004, and peaked at number 36 on the Billboard 200.^[1] It sold over 25,000 copies in its first week.^[3] The track was also part of the soundtrack of the very popular racing game Need for Speed: Underground, used prominently especially in its demo.

The other single released from Legion of Boom, "Starting Over", featured vocals from Rahzel from The Roots. No other singles were released but other songs, including "Weapons of Mass Distortion", "Bound Too Long" and "Realizer", appeared in various movies and TV shows. "I Know It's You" appeared in the trailer for the film Resident Evil: Extinction, and includes vocals by the movie's star, Milla Jovovich.

In 2005, the album was nominated for the Best Electronic/Dance Album Grammy,^[4] the first year that category existed. It lost to Kish Kash by Basement Jaxx.^[5]

It is also around this time that Jordan and Kirkland formed their own record label, called Tiny e Recordings.^[3]

[edit] Community Service II

On April 5, 2005, The Crystal Method released their sequel to Community Service, called Community Service II, another continuous mix of electronica songs and remixes of music by artists including The Doors, Unkle, New Order and Smashing Pumpkins. The album peaked at number 31 on the Top Independent Albums chart and number 8 on the Top Electronic albums chart.^[1]

A 5-track EP, Community Service II Exclusives, was also released through the iTunes Store. It included one new track, "Badass", and full versions of four tracks from Community Service II. It was removed from the iTunes store not long after it was released.^[3]

[edit] Drive, London, and Vegas re-release (2006–2008)

The group composed and performed the score for the film London, which was released in February 2006. The soundtrack album included excerpts from the score, two Crystal Method vocal tracks—"Smoked" and "Glass Breaker", which were also released as a single—and songs by artists like Evil Nine, The Out Crowd, and The Perishers.

Shortly after the release of the London soundtrack, The Crystal Method was approached by Nike to take part in a series of music releases specifically designed to be listened to while running. The group's contribution, Drive: Nike + Original Run—the first in the series^[6]—was initially released digitally, in June 2006, with the physical release following a year later. Drive peaked at number 23 on the Top Electronic Albums chart.^[1] The album, a 45 minute continuous mix, starts off slow, increases in tempo, and slows at the end, following the arc of a typical distance run.^[3] In 2006 the track Robogirl released by the duo appeared on Dance Dance Revolution: SuperNOVA as well. ^[7]

In 2007, ten years after its original release, the group's debut album, Vegas was certified platinum by the RIAA.^[2] One month later, a special edition of the album was released, with a second disc including remixes and video.

In late 2008, the group remixed their song "Now Is the Time". Where the original version featured samples of Jesse Jackson, this "Vote '08 Remix" used samples of Barack Obama, marking the presidential election.

[edit] Divided by Night (2009–present)

Following the release of Legion of Boom, The Crystal Method began construction of a new, full-sized recording studio in Los Angeles—Crystalwerks. When it was finished, they began work on their next album, Divided by Night.

On April 14, 2009, The Crystal Method released the digital single "Drown in the Now". A second single, "Black Rainbows", was released via Beatport two weeks later.

The Divided by Night tour started in Boston on May 6, and the album was released the following week. It peaked at number 38 on the Billboard 200, number two on the Top Electronic Albums chart, and number four on the Top Independent Albums chart,^[1] and also granted the duo another Grammy nomination. The album features guest artists including Peter Hook (of New Order), Matisyahu, Meiko, Justin Warfield, Emily Haines (of Metric), and Jason Lytle.

X Games 3D: The Movie, released in August 2009, included a number of Crystal Method songs and remixes,^[8] including "Drown in the Now" and "Now Is the Time".

"Re:Generation Music Project 2012"[link]

The Crystal Method's most recent track "I'm Not Leaving," featured a collaboration with Motown's Martha Reeves for the Re:Generation Music Project documentary. The film followed five DJ/producers who each collaborated with one of five singers, each from a different genre of music.

Instruments[link]

The Crystal Method use a wide array of equipment, with the Clavia Nord Lead being most closely associated with their style and sound. It was the primary source of sound for their first album Vegas.^{[citation needed]}

Discography[link]

• Vegas (1997)
• Tweekend (2001)
• Legion of Boom (2004)
• Divided by Night (2009)

References[link]

External links[link]

• Official website
• The Crystal Method at Allmusic
• The Crystal Method at the Internet Movie Database

This biographical article needs additional citations for verification. Please help by adding reliable sources. Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful. (January 2008)

Kevin Farley
Farley at the June 2009 premiere for The Proposal
Born	Kevin Peter Farley (1965-06-08) June 8, 1965 (age 47) Madison, Wisconsin, U.S.
Occupation	Actor
Years active	1995–present

Kevin Peter Farley (born June 8, 1965) is an American actor, production designer, singer, dancer, occasional composer and aspiring stand-up comic.^[1]

Early life[link]

Farley was born in Madison, Wisconsin, the son of Mary Anne (née Crosby), a homemaker, and Thomas Farley, who owned an oil company, Farley Oil.^[2][3] He was raised in an Irish Catholic family.^[4] He is the younger brother of late comedian and actor Chris Farley and older brother of actor John P. Farley. Like his brother Chris, Kevin Farley attended and graduated from Marquette University.^[5]

Career[link]

Farley is best known for portraying "Doug Linus" in the fictional boy band 2ge+her. The Farley brothers do routines together and receive roles from many of Chris Farley's Saturday Night Live castmates, such as David Spade and Adam Sandler, appearing in The Waterboy and Dirty Work.

Farley appeared on the HBO series, Curb Your Enthusiasm as an exterminator in the episode, "The Rat Dog." Farley was also in a Dairy Queen commercial^[6] advertising the Kit-Kat Blizzard, commercials for Hertz Rent-A-Car, and portrayed Felix the limo driver on Disney's That's So Raven. He also starred in the parody movie An American Carol in 2008. Farley appeared on The View (September 30, 2008) to promote the movie.

In 2007, Farley was featured in the web serial, Two Guys Drinking at a Bar.^[7]

Farley appeared at the 2008 Republican National Convention, and during an interview with 97.1 FM Talk's Jamie Allman he identified his politics as mostly conservative.

Farley appeared as the kidnapped beer truck driver in the music video for "This Afternoon" by Nickelback.

In May 2010, Farley appeared as a guest on Tom Green's House Tonight where he performed a section of his new standup routine.^[1]

References[link]

External links[link]

• Kevin Farley at the Internet Movie Database
• The Farley brothers' official site.

Heinrich Hertz
Born	Heinrich Rudolf Hertz (1857-02-22)22 February 1857 Hamburg, German Confederation
Died	1 January 1894(1894-01-01) (aged 36) Bonn, German Empire
Residence	Germany
Nationality	German
Fields	Physics Electronic Engineering
Institutions	University of Kiel University of Karlsruhe University of Bonn
Alma mater	University of Munich University of Berlin
Doctoral advisor	Hermann von Helmholtz
Known for	Electromagnetic radiation Photoelectric effect
Signature

Heinrich Rudolf Hertz (22 February 1857 – 1 January 1894) was a German physicist who clarified and expanded James Clerk Maxwell's electromagnetic theory of light, which was first demonstrated by David Edward Hughes using non-rigorous trial and error procedures. Hertz is distinguished from Maxwell and Hughes because he was the first to conclusively prove the existence of electromagnetic waves by engineering instruments to transmit and receive radio pulses using experimental procedures that ruled out all other known wireless phenomena.^[1] The scientific unit of frequency — cycles per second — was named the "hertz" in his honor.^[2]

Life and career[link]

Early years[link]

Hertz was born in Hamburg, then a sovereign state of the German Confederation, into a prosperous and cultured Hanseatic family. His father, David Gustav Hertz, was a writer and later a senator. His mother was the former Anna Elisabeth Pfefferkorn. His paternal great-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. Hertz' paternal grandfather, Heinrich David Hertz (1797–1862), was a respected businessman, and his paternal grandmother, Betty Oppenheim, was the daughter of the banker Salomon Oppenheim, from Cologne. Hertz's father and paternal grandparents converted from Judaism to Christianity.^[3][4] His mother's family was Lutheran.^[5]

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 successful radio transmission was made by David Edward Hughes in 1879, but it would not be conclusively proven to have been electromagnetic waves until the experiments of Heinrich Hertz in 1886. For the Hertz 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 triggered broad interest in radio research that eventually produced commercially successful wireless telegraph, audio radio, and later television. In 1930 the International Electrotechnical Commission (IEC) honored Hertz by naming the unit of frequency—one cycle per second—the "hertz".^[2]

Meteorology[link]

He always had a deep interest in meteorology 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 liquids, a new kind of hygrometer, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.^[6]

Contact mechanics[link]

Memorial of Heinrich Hertz on the campus of the Karlsruhe Institute of Technology

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.

Electromagnetic research[link]

Official English translation of Untersuchungen über die Ausbreitung der elektrischen Kraft published in 1893, a year before Hertz's death.

Theoretical results from the 1887 experiment

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 antenna, 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 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 shortwaves. Hertz published his work in a book titled: Electric waves: being researches on the propagation of electric action with finite velocity through space.^[7]

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 waves. 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, whereby a spark would be seen upon detection of EM waves. He placed the apparatus in a darkened box to see the spark better. He observed that the maximum spark length was reduced when in the box. A glass panel placed between the source of EM waves and the receiver absorbed 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,

"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."^[8][9][10]

Asked about the ramifications of his discoveries, Hertz replied,

"Nothing, I guess."^[8]

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.

Death at age 36[link]

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 granulomatosis at the age of 36 in Bonn, Germany in 1894, and was buried in Ohlsdorf, Hamburg at the Jewish cemetery.^{[citation needed]}

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 and went 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.

Legacy and honors[link]

His nephew Gustav Ludwig Hertz 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, an expression of the number of times that a repeated event occurs per second. It was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, officially replacing the previous name, the "cycle per second" (cps).

In 1969 (East Germany), a Heinrich Hertz memorial medal^[11] was cast. The IEEE Heinrich Hertz Medal, established in 1987, is "for outstanding achievements in Hertzian waves [...] presented annually to an individual for achievements which are theoretical or experimental in nature".

Heinrich Hertz

A crater that lies on the far side of the Moon, just behind the eastern limb, is named in his honor. The Hertz market for radio electronics products in Nizhny Novgorod, Russia, is named after him. The Heinrich-Hertz-Turm radio telecommunication tower in Hamburg is named after the city's famous son.

Hertz is honored by Japan with a membership in the Order of the Sacred Treasure, which has multiple layers of honor for prominent people, including scientists.^[12]

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

On his birthday in 2012, Google honored Hertz with a Google doodle, inspired by his life's work, on its home page.^[13][14]

Nazi revisionism[link]

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,^[15] his father had converted to Catholicism before marrying.^{[citation needed]} The painting has since been returned to public display.^[16]

See also[link]

Notes[link]

References[link]

Further reading[link]

External links[link]

Wikimedia Commons has media related to: Heinrich Hertz

• Quotations related to Heinrich Hertz at Wikiquote
• Hertzian radiation - better known as radio waves: what it is and how it happens
• Encyclopædia Britannica (1911): Hertz biography