The Sun is Earth's primary source of light. About 44% of the sun's electromagnetic radiation that reaches the ground is in the visible light range.

Visible light (commonly referred to simply as light) is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight.^[1] Visible light has a wavelength in the range of about 380 nanometres to about 740 nm – between the invisible infrared, with longer wavelengths and the invisible ultraviolet, with shorter wavelengths.

Primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarisation, while its speed in a vacuum, 299,792,458 meters per second (about 300,000 kilometers per second), is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation (EMR) is experimentally found to move at exactly this same speed in vacuum.

In common with all types of EMR, visible light is emitted and absorbed in tiny "packets" called photons, and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.

In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.^[2][3] This article focuses on visible light. See the electromagnetic radiation article for the general term.

Speed of visible light[link]

The speed of light in a vacuum is defined to be exactly 299,792,458 m/s (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation are believed to move at exactly this same speed in vacuum.

Different physicists have attempted to measure the speed of light throughout history. Galileo attempted to measure the speed of light in the seventeenth century. An early experiment to measure the speed of light was conducted by Ole Rømer, a Danish physicist, in 1676. Using a telescope, Rømer observed the motions of Jupiter and one of its moons, Io. Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to traverse the diameter of Earth's orbit.^[4] Unfortunately, its size was not known at that time. If Rømer had known the diameter of the Earth's orbit, he would have calculated a speed of 227,000,000 m/s.

Another, more accurate, measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849. Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin. Fizeau found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau was able to calculate the speed of light as 313,000,000 m/s.

Léon Foucault used an experiment which used rotating mirrors to obtain a value of 298,000,000 m/s in 1862. Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mt. Wilson to Mt. San Antonio in California. The precise measurements yielded a speed of 299,796,000 m/s.

The effective velocity of light in various transparent substances containing ordinary matter, is less than in vacuum. For example the speed of light in water is about 3/4 of that in vacuum. However, the slowing process in matter is thought to result not from actual slowing of particles of light, but rather from their absorption and re-emission from charged particles in matter.

As an extreme example of the nature of light-slowing in matter, two independent teams of physicists were able to bring light to a "complete standstill" by passing it through a Bose-Einstein Condensate of the element rubidium, one team at Harvard University and the Rowland Institute for Science in Cambridge, Mass., and the other at the Harvard-Smithsonian Center for Astrophysics, also in Cambridge.^[5] However, the popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrarily later time, as stimulated by a second laser pulse. During the time it had "stopped" it had ceased to be light.

Electromagnetic spectrum and visible light[link]

Electromagnetic spectrum with light highlighted

Generally, EM radiation, or EMR (the designation 'radiation' excludes static electric and magnetic and near fields) is classified by wavelength into radio, microwave, infrared, the visible region that we perceive as light, ultraviolet, X-rays and gamma rays.

The behaviour of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. When EMR interacts with single atoms and molecules, its behaviour depends on the amount of energy per quantum it carries.

ERM in the visible light region consists of quanta (called photons) that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which lead to changes in the bonding or chemistry of the molecule. At the lower end of the visible light spectrum, EMR becomes invisible to humansinfrared because its photons no longer have enough individual energy to cause a lasting molecular change (a change in conformation) in the visual molecule retinal in the human retina. This change triggers the sensation of vision.

There exist animals that are sensitive to various types of infrared, but not by means of quantum-absorption. Infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, and this is how living animals detect it.

Above the range of visible light, ultraviolet light becomes invisible to humans mostly because it is absorbed by the tissues of the eye and in particular the lens. Humans with natural eye lenses removed, as well as many animals with eyes that do not require lenses (such as insects and shrimp) are able to directly detect ultraviolet visually, by quantum photon-absorption mechanisms, in much the same chemical way that normal humans detect visible light.

Optics[link]

The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues as to the nature of light.

Refraction[link]

An example of refraction of light. The straw appears bent, because of refraction of light as it enters liquid from air.

A cloud illuminated by sunlight

Refraction is the bending of light rays when passing through a surface between one transparent material and another. It is described by Snell's Law:

Failed to parse (Missing texvc executable; please see math/README to configure.): n_1\sin\theta_1 = n_2\sin\theta_2\ .

where Failed to parse (Missing texvc executable; please see math/README to configure.): \theta_1

is the angle between the ray and the surface normal in the first medium, Failed to parse (Missing texvc executable; please see math/README to configure.): \theta_2
is the angle between the ray and the surface normal in the second medium, and n1 and n2 are the indices of refraction, n = 1 in a vacuum and n > 1 in a transparent substance.

When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction.

The refractive quality of lenses is frequently used to manipulate light in order to change the apparent size of images. Magnifying glasses, spectacles, contact lenses, microscopes and refracting telescopes are all examples of this manipulation.

Light sources[link]

There are many sources of light. The most common light sources are thermal: a body at a given temperature emits a characteristic spectrum of black-body radiation. A simple thermal source is sunlight, the radiation emitted by the chromosphere of the Sun at around 6,000 Kelvin peaks in the visible region of the electromagnetic spectrum when plotted in wavelength units ^[6] and roughly 44% of sunlight energy that reaches the ground is visible.^[7] Another example is incandescent light bulbs, which emit only around 10% of their energy as visible light and the remainder as infrared. A common thermal light source in history is the glowing solid particles in flames, but these also emit most of their radiation in the infrared, and only a fraction in the visible spectrum. The peak of the blackbody spectrum is in the deep infrared, at about 10 micrometer wavelength, for relatively cool objects like human beings. As the temperature increases, the peak shifts to shorter wavelengths, producing first a red glow, then a white one, and finally a blue-white colour as the peak moves out of the visible part of the spectrum and into the ultraviolet. These colours can be seen when metal is heated to "red hot" or "white hot". Blue-white thermal emission is not often seen, except in stars (the commonly seen pure-blue colour in a gas flame or a welder's torch is in fact due to molecular emission, notably by CH radicals (emitting a wavelength band around 425 nm, and is not seen in stars or pure thermal radiation)).

Atoms emit and absorb light at characteristic energies. This produces "emission lines" in the spectrum of each atom. Emission can be spontaneous, as in light-emitting diodes, gas discharge lamps (such as neon lamps and neon signs, mercury-vapor lamps, etc.), and flames (light from the hot gas itself—so, for example, sodium in a gas flame emits characteristic yellow light). Emission can also be stimulated, as in a laser or a microwave maser.

Deceleration of a free charged particle, such as an electron, can produce visible radiation: cyclotron radiation, synchrotron radiation, and bremsstrahlung radiation are all examples of this. Particles moving through a medium faster than the speed of light in that medium can produce visible Cherenkov radiation.

Certain chemicals produce visible radiation by chemoluminescence. In living things, this process is called bioluminescence. For example, fireflies produce light by this means, and boats moving through water can disturb plankton which produce a glowing wake.

Certain substances produce light when they are illuminated by more energetic radiation, a process known as fluorescence. Some substances emit light slowly after excitation by more energetic radiation. This is known as phosphorescence.

Phosphorescent materials can also be excited by bombarding them with subatomic particles. Cathodoluminescence is one example. This mechanism is used in cathode ray tube television sets and computer monitors.

A city illuminated by artificial lighting

Certain other mechanisms can produce light:

• Bioluminescence
• Cherenkov radiation
• Electroluminescence
• Scintillation
• Sonoluminescence
• triboluminescence

When the concept of light is intended to include very-high-energy photons (gamma rays), additional generation mechanisms include:

• Particle–antiparticle annihilation
• Radioactive decay

Units and measures[link]

Light is measured with two main alternative sets of units: radiometry consists of measurements of light power at all wavelengths, while photometry measures light with wavelength weighted with respect to a standardised model of human brightness perception. Photometry is useful, for example, to quantify Illumination (lighting) intended for human use. The SI units for both systems are summarised in the following tables.

The photometry units are different from most systems of physical units in that they take into account how the human eye responds to light. The cone cells in the human eye are of three types which respond differently across the visible spectrum, and the cumulative response peaks at a wavelength of around 555 nm. Therefore, two sources of light which produce the same intensity (W/m²) of visible light do not necessarily appear equally bright. The photometry units are designed to take this into account, and therefore are a better representation of how "bright" a light appears to be than raw intensity. They relate to raw power by a quantity called luminous efficacy, and are used for purposes like determining how to best achieve sufficient illumination for various tasks in indoor and outdoor settings. The illumination measured by a photocell sensor does not necessarily correspond to what is perceived by the human eye, and without filters which may be costly, photocells and charge-coupled devices (CCD) tend to respond to some infrared, ultraviolet or both.

Light pressure[link]

Light exerts physical pressure on objects in its path, a phenomenon which can be deduced by Maxwell's equations, but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c, the speed of light.  Due to the magnitude of c, the effect of light pressure is negligible for everyday objects.  For example, a one-milliwatt laser pointer exerts a force of about 3.3 piconewtons on the object being illuminated; thus, one could lift a U. S. penny with laser pointers, but doing so would require about 30 billion 1-mW laser pointers.^[8]  However, in nanometer-scale applications such as NEMS, the effect of light pressure is more significant, and exploiting light pressure to drive NEMS mechanisms and to flip nanometer-scale physical switches in integrated circuits is an active area of research.^[9]

At larger scales, light pressure can cause asteroids to spin faster,^[10] acting on their irregular shapes as on the vanes of a windmill.  The possibility to make solar sails that would accelerate spaceships in space is also under investigation.^[11][12]

Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation is incorrect; the characteristic Crookes rotation is the result of a partial vacuum.^[13] This should not be confused with the Nichols radiometer, in which the (slight) motion caused by torque (though not enough for full rotation against friction) is directly caused by light pressure.^[14]

Historical theories about light, in chronological order[link]

Classical Greece and Hellenism[link]

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In the fifth century BC, Empedocles postulated that everything was composed of four elements; fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun.

In about 300 BC, Euclid wrote Optica, in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one's eyes, then opens them at night. Of course if the beam from the eye travels infinitely fast this is not a problem.

In 55 BC, Lucretius, a Roman who carried on the ideas of earlier Greek atomists, wrote:

"The light & heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove." – On the nature of the Universe

Despite being similar to later particle theories, Lucretius's views were not generally accepted.

Ptolemy (c. 2nd century) wrote about the refraction of light in his book Optics.^[15]

Classical India[link]

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In ancient India, the Hindu schools of Samkhya and Vaisheshika, from around the early centuries CE developed theories on light. According to the Samkhya school, light is one of the five fundamental "subtle" elements (tanmatra) out of which emerge the gross elements. The atomicity of these elements is not specifically mentioned and it appears that they were actually taken to be continuous.

On the other hand, the Vaisheshika school gives an atomic theory of the physical world on the non-atomic ground of ether, space and time. (See Indian atomism.) The basic atoms are those of earth (prthivi), water (pani), fire (agni), and air (vayu) Light rays are taken to be a stream of high velocity of tejas (fire) atoms. The particles of light can exhibit different characteristics depending on the speed and the arrangements of the tejas atoms.^{[citation needed]} The Vishnu Purana refers to sunlight as "the seven rays of the sun".^{[citation needed]}

The Indian Buddhists, such as Dignāga in the 5th century and Dharmakirti in the 7th century, developed a type of atomism that is a philosophy about reality being composed of atomic entities that are momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy.^{[citation needed]}

Descartes[link]

René Descartes (1596–1650) held that light was a mechanical property of the luminous body, rejecting the "forms" of Ibn al-Haytham and Witelo as well as the "species" of Bacon, Grosseteste, and Kepler.^[16] In 1637 he published a theory of the refraction of light that assumed, incorrectly, that light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves.^{[citation needed]} Although Descartes was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media.

Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes' theory of light is regarded as the start of modern physical optics.^[17]

Particle theory[link]

Pierre Gassendi.

Pierre Gassendi (1592–1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age, and preferred his view to Descartes' theory of the plenum. He stated in his Hypothesis of Light of 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from a source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the diffraction of light (which had been observed by Francesco Grimaldi) by allowing that a light particle could create a localised wave in the aether.

Newton's theory could be used to predict the reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium because the gravitational pull was greater. Newton published the final version of his theory in his Opticks of 1704. His reputation helped the particle theory of light to hold sway during the 18th century. The particle theory of light led Laplace to argue that a body could be so massive that light could not escape from it. In other words it would become what is now called a black hole. Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light (as has been explained, neither a particle or wave theory is fully correct). A translation of Newton's essay on light appears in The large scale structure of space-time, by Stephen Hawking and George F. R. Ellis.

Wave theory[link]

In the 1660s, Robert Hooke published a wave theory of light. Christiaan Huygens worked out his own wave theory of light in 1678, and published it in his Treatise on light in 1690. He proposed that light was emitted in all directions as a series of waves in a medium called the Luminiferous ether. As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium.

Thomas Young's sketch of the two-slit experiment showing the diffraction of light. Young's experiments supported the theory that light consists of waves.

The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young), and that light could be polarised, if it were a transverse wave. Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light, and explained colour vision in terms of three-coloured receptors in the eye.

Another supporter of the wave theory was Leonhard Euler. He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory.

Later, Augustin-Jean Fresnel independently worked out his own wave theory of light, and presented it to the Académie des Sciences in 1817. Simeon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favour of the wave theory, helping to overturn Newton's corpuscular theory. By the year 1821, Fresnel was able to show via mathematical methods that polarisation could be explained only by the wave theory of light and only if light was entirely transverse, with no longitudinal vibration whatsoever.

The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. A hypothetical substance called the luminiferous aether was proposed, but its existence was cast into strong doubt in the late nineteenth century by the Michelson-Morley experiment.

Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Léon Foucault, in 1850.^[18] His result supported the wave theory, and the classical particle theory was finally abandoned, only to partly re-emerge in the 20th century.

Quantum theory[link]

In 1900 Max Planck, attempting to explain black body radiation suggested that although light was a wave, these waves could gain or lose energy only in finite amounts related to their frequency. Planck called these "lumps" of light energy "quanta" (from a Latin word for "how much." In 1905, Albert Einstein used the idea of light quanta to explain the photoelectric effect, and suggested that these light quanta had a "real" existence. These light particles were named photons in In 1923 Arthur Holly Compton showed that the wavelength shift seen when low intensity X-rays scattered from electrons (so called Compton scattering) could be explained by a particle-theory of X-rays but not a wave theory. In 1926 Gilbert N. Lewis named these liqht quanta photons.

Eventually the modern theory of quantum quantum mechanics came to picture light as (in some sense) both a particle and a wave, and (in another sense), as a phenomenon which is neither a particle or a wave (which actually are macroscopic phenomena, such as baseballs or ocean waves). Instead, modern physics sees light as something that can be described sometimes with mathematics appropriate to one type of macroscopic metaphor (particles), and sometimes another macroscopic metaphor (water waves), but is actually something that cannot be fully imagined. As in the case for radio waves and the X-rays involved in Compton scattering, physicists have noted that electromagnetic radiation tends to behave more like a classical wave at lower frequencies, but more like a classical particle at higher frequencies, but never completely loses all qualities of one or the other. Visible light, which occupies a middle ground in frequency, can easily be shown in experiments to be describable using either a wave or particle model, or sometimes both.

Electromagnetic theory as explanation for all types of visible light and all EM radiation[link]

A linearly polarised light wave frozen in time and showing the two oscillating components of light; an electric field and a magnetic field perpendicular to each other and to the direction of motion (a transverse wave).

In 1845, Michael Faraday discovered that the plane of polarisation of linearly polarised light is rotated when the light rays travel along the magnetic field direction in the presence of a transparent dielectric, an effect now known as Faraday rotation.^[19] This was the first evidence that light was related to electromagnetism. In 1846 he speculated that light might be some form of disturbance propagating along magnetic field lines.^[20] Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.

Faraday's work inspired James Clerk Maxwell to study electromagnetic radiation and light. Maxwell discovered that self-propagating electromagnetic waves would travel through space at a constant speed, which happened to be equal to the previously measured speed of light. From this, Maxwell concluded that light was a form of electromagnetic radiation: he first stated this result in 1862 in On Physical Lines of Force. In 1873, he published A Treatise on Electricity and Magnetism, which contained a full mathematical description of the behaviour of electric and magnetic fields, still known as Maxwell's equations. Soon after, Heinrich Hertz confirmed Maxwell's theory experimentally by generating and detecting radio waves in the laboratory, and demonstrating that these waves behaved exactly like visible light, exhibiting properties such as reflection, refraction, diffraction, and interference. Maxwell's theory and Hertz's experiments led directly to the development of modern radio, radar, television, electromagnetic imaging, and wireless communications.

In the quantum theory, photons are seen as wave packets of the waves described in the classical theory of Maxwell. The quantum theory was needed to explain effects even with visual light that Maxwell's classical theory could not (such as spectral lines).

See also[link]

Wikimedia Commons has media related to: Light

Look up light in Wiktionary, the free dictionary.

Wikiquote has a collection of quotations related to: Light

• Automotive lighting
• Ballistic photon
• Color temperature
• Electromagnetic spectrum
• Fermat's principle
• Huygens' principle
• International Commission on Illumination
• Journal of Luminescence
• Light beam – in particular about light beams visible from the side
• Light Fantastic (TV series)
• Light mill
• Light pollution
• Light therapy
• Lighting
• Luminescence: The Journal of Biological and Chemical Luminescence
• Photic sneeze reflex
• Photometry
• Photon
• Rights of Light
• Risks and benefits of sun exposure
• Spectroscopy
• Visible spectrum
• Wave–particle duality

Notes[link]

References[link]

John Mayer
Mayer at the Mile High Music Festival on July 20, 2008
Background information
Birth name	John Clayton Mayer
Born	(1977-10-16) October 16, 1977 (age 34) Bridgeport, Connecticut United States
Genres	Pop rock, blues rock, acoustic rock, blue-eyed soul
Occupations	Musician, songwriter, record producer, columnist, graphic designer, photographer, comedian, television host
Instruments	Guitar, vocals, omnichord, piano, vibraphone, harmonica, percussion, clarinet, violin
Years active	1998 (1998)–present
Labels	Arista, Aware, Columbia
Associated acts	John Mayer Trio, Fall Out Boy
Website	johnmayer.com
Notable instruments
Fender Stratocaster Martin Guitars Gibson Guitars

John Clayton Mayer ( /ˈmeɪ.ər/ MAY-ər;^[1] (born October 16, 1977) is an American pop and blues rock musician, singer-songwriter, recording artist, and music producer.^[2] Born in Bridgeport, Connecticut and raised in Fairfield, Connecticut, he attended Berklee College of Music in Boston. He moved to Atlanta in 1997, where he refined his skills and gained a following, and he now lives in New York City.^[3][4] His first two studio albums, Room for Squares and Heavier Things, did well commercially, achieving multi-platinum status. In 2003, he won a Grammy Award for Best Male Pop Vocal Performance for "Your Body Is a Wonderland."^[5]

Mayer began his career performing mainly acoustic rock, but gradually began a transition towards the blues genre in 2005 by collaborating with renowned blues artists such as B. B. King, Buddy Guy, and Eric Clapton, and by forming the John Mayer Trio. The blues influence can be heard throughout his 2005 live album Try! with the John Mayer Trio and his third studio album Continuum, released in September 2006. At the 49th Annual Grammy Awards in 2007 Mayer won Best Pop Vocal Album for Continuum and Best Male Pop Vocal Performance for "Waiting on the World to Change". He released his fourth studio album, Battle Studies, in November 2009. His fifth album, Born and Raised, was released on May 22, 2012. He has sold over 10 million albums in the U.S. and 20 million albums worldwide.

Early life[link]

John Clayton Mayer was born on October 16, 1977 in Bridgeport, Connecticut to Margaret, an English teacher, and Richard, a high school principal.^[6] He grew up in Fairfield, Connecticut, the second of three children.^[7] His father is Jewish, and Mayer has said that he "relat[es] to Judaism".^[8] He attended Fairfield High School in Fairfield^[9] although he was enrolled in the Center for Global Studies at Brien McMahon High School in Norwalk for his junior year (then known as the Center for Japanese Studies Abroad, it is a magnet program for students wanting to learn Japanese).^[10]

After watching Michael J. Fox's guitar performance as Marty McFly in Back to the Future, Mayer became fascinated with the instrument, and when he turned 13, his father rented one for him.^[11][12] A neighbor gave Mayer a Stevie Ray Vaughan cassette, which cultivated Mayer's love of blues music.^[13]a[›] Mayer started taking lessons from a local guitar-shop owner, Al Ferrante, and soon became consumed with playing the instrument.^[3][14] His singular focus concerned his parents, and they took him twice to see a psychiatrist—but Mayer was determined to be fine.^[3][14] Mayer says that the contentious nature of his parents' marriage led him to "disappear and create my own world I could believe in".^[3] After two years of practice, he started playing at blues bars and other venues in the area, while he was still in high school.^[10][12] In addition to performing solo, he was a member of a band called Villanova Junction (named for a Jimi Hendrix song) with Tim Procaccini, Joe Beleznay, and Rich Wolf.^[3][15] Mayer considered skipping college to pursue his music, but the disapproval of his parents dissuaded him from doing so.^[3]

When Mayer was seventeen, he was stricken with cardiac dysrhythmia and was hospitalized for a weekend. Reflecting on the incident, Mayer said, "That was the moment the songwriter in me was born," and he penned his first lyrics the night he got home from the hospital.^[4] Shortly thereafter, he began suffering from panic attacks, and lived with the fear of having to enter a mental institution.^[3] He continues to manage such episodes with Xanax, an anti-anxiety drug.^[4][16] After graduation, he worked for fifteen months at a gas station until he saved enough money to buy a 1996 Stevie Ray Vaughan signature Stratocaster.^[17]

Career[link]

Early career[link]

Mayer enrolled in the Berklee College of Music in Boston, Massachusetts, aged 19.^[7] However, at the urging of his college friend an Atlanta, Georgia native, Clay Cook, he left school after two semesters and moved with Cook to Atlanta.^[18] In Atlanta they formed a two-man band called LoFi Masters and began performing in local coffee houses and club venues such as Eddie's Attic.^[12] According to Cook, they began to experience musical differences due to Mayer’s desire to move more towards pop music.^[19] As a result, the two parted ways, and Mayer embarked on a solo career.^[18]

With the help of local producer and engineer Glenn Matullo, Mayer recorded the independent EP Inside Wants Out. Cook co-wrote many of the songs from the EP including Mayer's first commercial single release, "No Such Thing".^[19] The EP includes eight songs with Mayer on lead vocals and guitars. However, Cook's only contribution was backing vocals on the song "Comfortable". For the opening track, "Back To You", a full band was enlisted, including the EP’s co-producer David "DeLa" LaBruyere on bass guitars.^[20] Mayer and LaBruyere then began to perform throughout Georgia and nearby states.

Major label success[link]

	"City Love" excerpt noicon From the album Room for Squares.
Problems listening to this file? See media help.

Mayer’s reputation began to build, and a March 2000 appearance at South by Southwest brought him to the attention of "launch" label, Aware Records.^[14][21][22] After including him in the Aware Festival concerts and having his songs included on Aware compilations, in early 2001, Aware released Mayer's internet-only album titled, Room for Squares. During this time, Aware inked a deal with Columbia Records that gave Columbia first pick in signing Aware artists, and so in September of the same year, Columbia remixed and re-released Room for Squares.^[23] As part of the major label "debut", the album's artwork was updated, and the track "3x5" was added. The re-release also included reworked studio versions of the first four songs from his indie album, Inside Wants Out.^[24]

By the end of 2002, Room for Squares had spawned several radio hits, including "No Such Thing," "Your Body Is a Wonderland", and ultimately, "Why Georgia". In 2003, Mayer won a Grammy for Best Male Pop Vocal Performance for "Your Body Is a Wonderland." In his acceptance speech he remarked, "This is very, very fast, and I promise to catch up."^[25] He also figuratively referred to himself as being sixteen, a remark that many mistook to mean that he was only sixteen years old at the time.^[26]

In 2003, Mayer released a live CD and DVD of a concert in Birmingham, Alabama titled Any Given Thursday. The concert featured songs previously not recorded, such as "Man on the Side" (co-written with Cook) and "Something's Missing", which later appeared on Heavier Things. The concert also included "Covered In Rain". According to the accompanying DVD documentary, this song is "part two" of the song "City Love", which features the line "covered in rain". Commercially, the album quickly peaked at number seventeen on the Billboard 200 chart. The CD/DVD received conservative, although consistent, praise, with critics torn between his pop-idol image, and (at the time) emerging guitar prowess. Erik Crawford (of Allmusic) asked "Is he the consummate guitar hero exemplified when he plays a cover of Stevie Ray Vaughan's 'Lenny', or is he the teen idol that the pubescent girls shriek for after he plays 'Your Body Is a Wonderland?'"^[27][28]

Heavier Things, Mayer's second album, was released in 2003 to generally favorable reviews. Rolling Stone, Allmusic and Blender all gave positive, although reserved, feedback. PopMatters said that it "doesn't have as many drawbacks as one might assume".^[29] The album was commercially successful, and while it did not sell as well as Room for Squares, it peaked at number one on the US Billboard 200 chart. Mayer earned his first number one single with the song "Daughters" as well as a 2005 Grammy for Song of the Year, beating out fellow contenders Alicia Keys and Kanye West. He dedicated the award to his grandmother, Annie Hoffman, who died in May 2004. He also won Best Male Pop Vocal Performance, beating Elvis Costello, Prince, and Seal for the award. In a February 9, 2009 interview on The Ellen DeGeneres Show, Mayer said that he thought he should not have won the Grammy for Song of the year because he thought that Alicia Keys' If I Ain't Got You was the better song. Because of this, he removed the top half of the Grammy and gave it to Keys, and kept the bottom part for himself. At the 37th Annual Songwriters Hall of Fame Induction Ceremony in 2006, Mayer was honored with the Hal David Starlight Award.^[30]

Mayer again recorded live concerts across seven nights of his U.S. tour in 2004. These recordings were released to the iTunes Store under the title As/Is, indicating that the errors were included along with the good moments. A few months later, a "best of" CD was compiled from the As/Is nights. The album included a previously unreleased cover of Marvin Gaye's song "Inner City Blues (Make Me Wanna Holler)", featuring a solo from Mayer's support act, jazz and blues turntablist DJ Logic. All the album covers of the As/Is releases feature drawings of anthropomorphic bunnies.^[31]

January 2005, left to right: David Ryan Harris, John Mayer and Steve Jobs at Macworld 11, SF Moscone Center.

With increased exposure, Mayer's talent came into demand in other areas. Steve Jobs invited Mayer to perform during the keynote address of Apple's annual Macworld Conference & Expo, in January 2004, as Jobs introduced the software application GarageBand.^[32] The gig led to Mayer becoming a fixture of the event. He rejoined Jobs on stage for a solo performance at Macworld 2007, following the announcement of the iPhone.^[33] Mayer has also done endorsements, such as a Volkswagen commercial for the Beetle's guitar outlet and for the BlackBerry Curve.^[34]

Change in musical direction[link]

Mayer began to collaborate extensively, often working with artists outside of his own genre. He appeared on Common's song "Go!" and on Kanye West's "Bittersweet Poetry".^b[›] Following these collaborations, Mayer received praise from rap heavyweights Jay-Z and Nelly.^[35] When asked about his presence in the hip hop community, Mayer said, "It's not music out there right now. That's why, to me, hip-hop is where rock used to be."^[36]

	"Go!" excerpt noicon From the album Be. In 2004, after the three saw the movie Ray together, Kanye West and Mayer joined Common back in the studio. Mayer came up with the song's concept—fantasies—and his vocals were sampled for the track.[37]
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It was around this time that Mayer began hinting a change in his musical interests, announcing that he was "closing up shop on acoustic sensitivity."^[36] In 2005, he began a string of collaborations with various blues artists, including Buddy Guy, B.B. King, Eric Clapton, as well as jazz artist John Scofield. He also went on tour with legendary jazz pianist Herbie Hancock, which included a show at the Bonnaroo Music Festival in Manchester, Tennessee. These collaborations led to recordings with several of these artists, namely, Clapton (Back Home, Crossroads Guitar Festival), Guy (Bring 'Em In), Scofield (That's What I Say), and King (80). Although Mayer has maintained a reputation for being a sensitive singer-songwriter, he has also gained distinction as an accomplished guitarist, influenced by the likes of the above artists, as well as Eric Johnson, Jimi Hendrix, Stevie Ray Vaughan, Eric Clapton, Robert Cray, and Freddie King.^[38]

John Mayer Trio[link]

	"Who Did You Think I Was?" noicon From the album Try! The first single, "Who Did You Think I Was?," lyrically underscores Mayer's decision to move away from acoustic pop music and towards blues, with lines such as, "Got a brand new blues that I can't explain."[39] This sample features an extended electric guitar solo.
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In the spring of 2005, Mayer formed the John Mayer Trio with bassist Pino Palladino and drummer Steve Jordan, both of whom he had met through previous studio sessions. The trio played a combination of blues and rock music. In October 2005, the Trio opened for The Rolling Stones during a sold-out club tour of their own,^[40] and that November, released a live album called Try! The band took a break in mid-2006. In September 2006, Mayer announced plans for the Trio to begin work on a future studio album.^[41]

[edit] Continuum

Mayer's third studio album, titled Continuum, was released on September 12, 2006, and was produced by Mayer and Steve Jordan. Mayer suggested the album was intended to combine his signature pop music with the feel, sound, groove, and sensibilities of the blues. In that vein, two of the tracks from his Trio release Try!—"Vultures" and "Gravity"—also were included on Continuum.^[7]

The first single from Continuum was "Waiting on the World to Change", which debuted on The Ron and Fez Show. The song was the third most downloaded song of the week on the iTunes Store following its release on July 11, 2006, and debuted at #25 on the Billboard Hot 100 Chart.

On August 23, 2006, Mayer debuted the entire album on the Los Angeles radio station Star 98.7, giving commentary on each track.^[42] A subsequent version was released the next day on the Clear Channel Music website as a streaming sneak preview. On September 21, 2006, Mayer appeared on CSI: Crime Scene Investigation, playing "Waiting on the World to Change" and "Slow Dancing in a Burning Room." The song "Gravity" was featured on the television series House, in the episode "Cane & Able", and Numb3rs. He recorded a session for the British program Live from Abbey Road at Abbey Road Studios on October 22, 2006.

On December 7, 2006, Mayer was nominated for five 2007 Grammy Awards, including Album of the Year. The John Mayer Trio also received a nomination for their album, Try!. He won two: Best Pop Song with Vocal for "Waiting on the World to Change" and Best Pop Album for Continuum. Mayer remixed an acoustic version of his single "Waiting on the World to Change" with vocal additions from fellow musician Ben Harper. In preparation for recording Continuum, Mayer had booked the Village Recorder in Los Angeles to record five demo acoustic versions of his songs with veteran musician Robbie McIntosh. These recordings became The Village Sessions, an EP released on December 12, 2006. As usual, Mayer oversaw the artwork of the release.^[43]

Mayer was featured on the cover of Rolling Stone (#1020) in February 2007, along with John Frusciante and Derek Trucks. He was named as one of the "New Guitar Gods," and the cover nicknamed him "Slowhand, Jr.," a reference to Eric Clapton.^[38] Additionally, he was selected by the editors of Time magazine as one of the 100 Most Influential People of 2007 and was listed among artists and entertainers.^[44]

On November 20, 2007, the re-issue of Continuum became available online and in stores. The release contains a bonus disc of six live songs from his 2007 tour: five from Continuum and a cover of the Ray Charles song "I Don't Need No Doctor".^[45] His new single, "Say", also became available through iTunes. On December 6, 2007, "Belief" was nominated for Best Male Pop Vocal for the 50th Annual Grammy Awards. He accompanied Alicia Keys on guitar on her song "No One" at the ceremony.

In February 2008, Mayer hosted a three-day Caribbean cruise event that included performances with various musicians including David Ryan Harris, Brett Dennen, Colbie Caillat and Dave Barnes, among others. The event was called "The Mayercraft Carrier" and was held aboard the cruise ship known as the Carnival Victory.^[46] A follow up cruise titled "Mayercraft Carrier 2" set sail from Long Beach, California from March 27–31, 2009 on the Carnival Splendor.

On July 1, 2008, Mayer released Where the Light Is, a live concert film of Mayer's performance at the Nokia Theatre L.A. Live on December 8, 2007. The film was directed by Danny Clinch. It features an acoustic set and a set with the John Mayer Trio, followed by a set with John's band from the Continuum album. The DVD and Blu-ray bonus material includes footage of Mayer backstage and playing outside on Mulholland Drive.^[47]

Australian artist Guy Sebastian invited Mayer to collaborate on three songs from his 2009 album Like It Like That.^[48] Mayer also played guitar on the title track of Crosby Loggins' debut LP, Time to Move, released on July 10, 2009.^[49]

On July 7, 2009, Mayer performed an instrumental guitar version of Michael Jackson's "Human Nature" at Jackson's televised memorial service.^[50]

[edit] Battle Studies

On November 17, 2009, Mayer's fourth studio album, Battle Studies, was released and debuted at number one on the U.S. Billboard 200 album chart.^[51] The album consists of 11 tracks with a total time of 45 minutes. The first single from the album, "Who Says", was released on September 24, 2009 in advance of album, and was followed on October 19 by the single "Heartbreak Warfare" and the single "Half of My Heart" released on June 21, 2010. Despite the album's commercial success, critics were mixed with their praise; while some reviews were glowing, calling it his "most adventurous",^[52][53] others called the album "safe" and noted that "Mayer the singer-songwriter and Mayer the man about town sometimes seem disconnected, like they don’t even belong in the same body."^{[3][54][55][56]}

Mayer admitted to Rolling Stone that he thought Battle Studies was not his best album.^[57][58]

[edit] Born and Raised

Early reports indicated that the follow-up to Battle Studies would be called Born and Raised, and would be released in October 2011.^[59]