In physics, mass (from Greek μᾶζα "barley cake, lump (of dough)"), more specifically inertial mass, can be defined as a quantitative measure of an object's resistance to the change of its speed. In addition to this, gravitational mass can be described as a measure of magnitude of the gravitational force which is

1. exerted by an object (active gravitational mass), or
2. experienced by an object (passive gravitational force)

when interacting with a second object. The SI unit of mass is the kilogram (kg).

In everyday usage, mass is often referred to as weight, the units of which are often taken to be kilograms (for instance, a person may state that their weight is 75 kg). In scientific use, however, the term weight refers to a different, yet related, property of matter. Weight is the gravitational force acting on a given body—which differs depending on the gravitational pull of the opposing body (e.g. a person's weight on Earth vs on the Moon) — while mass is an intrinsic property of that body that never changes. In other words, an object's weight depends on its environment, while its mass does not. On the surface of the Earth, an object with a mass of 50 kilograms weighs 491 Newtons; on the surface of the Moon, the same object still has a mass of 50 kilograms but weighs only 81.5 Newtons. Restated in mathematical terms, on the surface of the Earth, the weight W of an object is related to its mass m by W = mg, where g is the Earth's gravitational field strength, equal to about 9.81 m/s².

The inertial mass of an object determines its acceleration in the presence of an applied force. According to Newton's second law of motion, if a body of fixed mass M is subjected to a force F, its acceleration α is given by F/M. A body's mass also determines the degree to which it generates or is affected by a gravitational field. If a first body of mass M_A is placed at a distance r from a second body of mass M_B, each body experiences an attractive force F_G whose magnitude is F_G = GM_AM_B/r², where G is the universal constant of gravitation, equal to 6.67×10⁻¹¹ N·m²·kg⁻². This is sometimes referred to as gravitational mass.^{[note 1]} Repeated experiments since the 17th century have demonstrated that inertial and gravitational mass are equivalent; since 1915, this observation has been entailed a priori in the equivalence principle of general relativity.

Special relativity shows that rest mass (or invariant mass) and rest energy are essentially equivalent, via the well-known relationship (E = mc²). This same equation also connects relativistic mass and "relativistic energy" (total system energy). The latter two "relativistic" mass and energy are concepts that are related to their "rest" counterparts, but they do not have the same value as their rest counterparts in systems where there is a net momentum. In order to deduce any of these four quantities from any of the others, in any system which has a net momentum, an equation that takes momentum into account is needed. Mass (so long as the type and definition of mass is agreed upon) is a conserved quantity over time. From the viewpoint of any single unaccelerated observer, mass can neither be created or destroyed, and special relativity does not change this understanding. All unaccelerated observers agree on the amount of invariant mass in closed systems at all times, and although different observers may not agree with each other on how much relativistic mass is present in any such system, all agree that the amount does not change over time.

Macroscopically, mass is associated with matter— although matter, unlike mass, is poorly defined in science. On the sub-atomic scale, not only fermions, the particles often associated with matter, but also some bosons, the particles that act as force carriers, have rest mass. Another problem for easy definition is that much of the rest mass of ordinary matter derives from the invariant mass contributed to matter by particles and kinetic energies which have no rest mass themselves (only 1% of the rest mass of matter is accounted for by the rest mass of its fermionic quarks and electrons). From a fundamental physics perspective, mass is the number describing under which the representation of the little group of the Poincaré group a particle transforms. In the Standard Model of particle physics, this symmetry is described as arising as a consequence of a coupling of particles with rest mass to a postulated additional field, known as the Higgs field.

The total mass of the observable universe is estimated at between 10⁵² kg and 10⁵³ kg, corresponding to the rest mass of between 10⁷⁹ and 10⁸⁰ protons.

Units of mass[link]

The kilogram is one of the seven SI base units; among these, it is one of three (besides the second and the Kelvin) which is defined ad hoc, without reference to another base unit, since 1889 by means of the international prototype kilogram.^{[note 2]}

Balance scales allow to directly compare gravitational mass within a gravitational field. Such devices have been in use since at least the Middle Bronze Age (shown is a balance for weighing tobacco dating to the mid-19th century).

In the International System of Units (SI), mass is measured in kilograms (kg). The gram (g) is ¹⁄₁₀₀₀ of a kilogram. The gram was first introduced in 1795, with a definition based on the density of water (so that at the temperature of melting ice, one cubic centimeter of water would have a mass of one gram; while the meter at the time was defined as the 10,000,000th part of the distance from the Earth's equator to the North Pole). Since 1889, the kilogram has been defined as the mass of the international prototype kilogram, and as such is independent of the meter, or the properties of water. In October 2011, the 24th General Conference on Weights and Measures resolved to "take note of the intention" to redefine the kilogram in terms of the Planck constant, scheduled for 2014.

Other units are accepted for use in SI:

• The tonne (t) is equal to 1000 kg.
• The electronvolt (eV) is primarily a unit of energy, but because of the mass–energy equivalence it can also function as a unit of mass. In this context it is denoted eV/c², or simply as eV. The electronvolt is common in particle physics.
• The atomic mass unit (u) is defined so that a single carbon-12 atom has a mass of 12 u; 1 u is approximately 1.66×10⁻²⁷ kg.^{[note 3]} The atomic mass unit is convenient for expressing the masses of atoms and molecules.

Outside the SI system, a variety of different mass units are used, depending on context, such as the slug (sl), the pound (lb), the Planck mass (m_P), and the solar mass.

In normal situations, the weight of an object is proportional to its mass, which usually makes it unproblematic to use the same unit for both concepts. However, the distinction between mass and weight becomes important for measurements with a precision better than a few percent (because of slight differences in the strength of the Earth's gravitational field at different places), and for places far from the surface of the Earth, such as in space or on other planets.

A mass can sometimes be expressed in terms of length. The mass of a very small particle may be identified with its inverse Compton wavelength (1 cm⁻¹ ≈ 3.52×10⁻⁴¹ kg). The mass of a very large star or black hole may be identified with its Schwarzschild radius (1 cm ≈ 6.73×10²⁴ kg).

Summary of mass concepts and formalisms[link]

In classical mechanics, mass has a central role in determining the behavior of bodies. Newton's second law relates the force F exerted in a body of mass M to the body's acceleration α:

Failed to parse (Missing texvc executable; please see math/README to configure.): \mathbf{F}=M\boldsymbol{\alpha}\

. Additionally, mass relates a body's momentum p to its velocity v:

Failed to parse (Missing texvc executable; please see math/README to configure.): \mathbf{p}=M\mathbf{v}\

, and the body's kinetic energy K to its velocity:

Failed to parse (Missing texvc executable; please see math/README to configure.): \mathbf{K}=\tfrac{1}{2}Mv^2\

.

In special relativity, relativistic mass is a formalism which accounts for relativistic effects by having the mass increase with velocity.

Failed to parse (Missing texvc executable; please see math/README to configure.): M=\gamma m_0\!

Failed to parse (Missing texvc executable; please see math/README to configure.): E=Mc^2\!

Since energy is dependent on reference frame (upon the observer) it is convenient to formulate the equations of physics in a way such that mass values are invariant (do not change) between observers, and so the equations are independent of the observer. For a single particle, this quantity is the rest mass; for a system of bound or unbound particles, this quantity is the invariant mass. The invariant mass M of a body is related to its energy E and the magnitude of its momentum p by

Failed to parse (Missing texvc executable; please see math/README to configure.): Mc^2=\sqrt{E^2-(pc)^2},\!

where c is the speed of light.

Summary of mass related phenomena[link]

The relation between properties of mass and their associated physical constants. Every massive object is believed to exhibit all five properties. However, due to extremely large or extremely small constants, it is generally impossible to verify more than two or three properties for any object.

• The Schwarzschild radius (r_s) represents the ability of mass to cause curvature in space and time.
• The standard gravitational parameter (μ) represents the ability of a massive body to exert Newtonian gravitational forces on other bodies.
• Inertial mass (m) represents the Newtonian response of mass to forces.
• Rest energy (E₀) represents the ability of mass to be converted into other forms of energy.
• The Compton wavelength (λ) represents the quantum response of mass to local geometry.

In physical science, one may distinguish conceptually between at least seven attributes of mass, or seven physical phenomena that can be explained using the concept of mass:^[1]

• The amount of matter in certain types of samples can be exactly determined through electrodeposition^{[clarification needed]} or other precise processes. The mass of an exact sample is determined in part by the number and type of atoms or molecules it contains, and in part by the energy involved in binding it together (which contributes a negative "missing mass," or mass deficit).

• Inertial mass is a measure of an object's resistance to changing its state of motion when a force is applied. It is determined by applying a force to an object and measuring the acceleration that results from that force. An object with small inertial mass will accelerate more than an object with large inertial mass when acted upon by the same force. One says the body of greater mass has greater inertia.

• Active gravitational mass is a measure of the strength of an object’s gravitational flux (gravitational flux is equal to the surface integral of gravitational field over an enclosing surface). Gravitational field can be measured by allowing a small ‘test object’ to freely fall and measuring its free-fall acceleration. For example, an object in free-fall near the Moon will experience less gravitational field, and hence accelerate slower than the same object would if it were in free-fall near the Earth. The gravitational field near the Moon is weaker because the Moon has less active gravitational mass.

• Passive gravitational mass is a measure of the strength of an object's interaction with a gravitational field. Passive gravitational mass is determined by dividing an object’s weight by its free-fall acceleration. Two objects within the same gravitational field will experience the same acceleration; however, the object with a smaller passive gravitational mass will experience a smaller force (less weight) than the object with a larger passive gravitational mass.

• Energy also has mass according to the principle of mass–energy equivalence. This equivalence is exemplified in a large number of physical processes including pair production, nuclear fusion, and the gravitational bending of light. Pair production and nuclear fusion are processes through which measurable amounts of mass and energy are converted into each other. In the gravitational bending of light, photons of pure energy are shown to exhibit a behavior similar to passive gravitational mass.

• Curvature of spacetime is a relativistic manifestation of the existence of mass. Curvature is extremely weak and difficult to measure. For this reason, curvature wasn’t discovered until after it was predicted by Einstein’s theory of general relativity. Extremely precise atomic clocks on the surface of the earth, for example, are found to measure less time (run slower) than similar clocks in space. This difference in elapsed time is a form of curvature called gravitational time dilation. Other forms of curvature have been measured using the Gravity Probe B satellite.

• Quantum mass manifests itself as a difference between an object’s quantum frequency and its wave number. The quantum mass of an electron, the Compton wavelength, can be determined through various forms of spectroscopy and is closely related to the Rydberg constant, the Bohr radius, and the classical electron radius. The quantum mass of larger objects can be directly measured using a watt balance.

Inertial mass, gravitational mass, and the various other mass-related phenomena are conceptually distinct. However, every experiment to date has shown these values to be proportional, and this proportionality gives rise to the abstract concept of mass. If, in some future experiment, one of the mass-related phenomena is shown to not be proportional to the others, then that specific phenomenon will no longer be considered a part of the abstract concept of mass.

Weight and amount[link]

A depiction of early balance scales in the Papyrus of Hunefer (dated to the 19th dynasty, ca. 1285 BC). The scene shows Anubis weighing the heart of Hunefer.

Weight, by definition, is a measure of the force which must be applied to support an object (i.e. hold it at rest) in a gravitational field. The Earth’s gravitational field causes items near the Earth to have weight. Typically, gravitational fields change only slightly over short distances, and the Earth’s field is nearly uniform at all locations on the Earth’s surface; therefore, an object’s weight changes only slightly when it is moved from one location to another, and these small changes went unnoticed through much of history. This may have given early humans the impression that weight is an unchanging, fundamental property of objects in the material world.

In the Egyptian religious illustration to the right, Anubis is using a balance scale to weigh the heart of Hunefer. A balance scale balances the force of one object’s weight against the force of another object’s weight. The two sides of a balance scale are close enough that the objects experience similar gravitational fields. Hence, if they have similar masses then their weights will also be similar. This allows the scale, by comparing weights, to also compare masses, and gives it the distinction of being one of the oldest known devices capable of measuring mass.

The concept of amount is very old and predates recorded history, so any description of the early development of this concept is speculative in nature. However, one might reasonably assume that humans, at some early era, realized that the weight of a collection of similar objects was directly proportional to the number of objects in the collection:

Failed to parse (Missing texvc executable; please see math/README to configure.): w_n \propto n

,

where w is the weight of the collection of similar objects and n is the number of objects in the collection. Proportionality, by definition, implies that two values have a constant ratio:

Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{w_n}{n} = \frac{w_m}{m}

, or equivalently Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{w_n}{w_m} = \frac{n}{m} .

Consequently, historical weight standards were often defined in terms of amounts. The Romans, for example, used the carob seed (carat or siliqua) as a measurement standard. If an object’s weight was equivalent to 1728 carob seeds, then the object was said to weigh one Roman pound. If, on the other hand, the object’s weight was equivalent to 144 carob seeds then the object was said to weigh one Roman ounce (uncia). The Roman pound and ounce were both defined in terms of different sized collections of the same common mass standard, the carob seed. The ratio of a Roman ounce (144 carob seeds) to a Roman pound (1728 carob seeds) was:

Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{ounce}{pound} = \frac{w_{144}}{w_{1728}} = \frac{144}{1728} = \frac{1}{12}

.

This example illustrates a common occurrence in physical science: when values are related through simple fractions, there is a good possibility that the values stem from a common source.

Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808).

The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The philosophical concept that matter might be composed of discrete units that cannot be further divided has been around for millennia. However, empirical proof and the universal acceptance of the existence of atoms didn’t occur until the early 20th century.

As the science of chemistry matured, experimental evidence for the existence of atoms came from the law of multiple proportions. When two or more elements combined to form a compound, their masses are always in a fixed and definite ratio. For example, the mass ratio of nitrogen to oxygen in nitric oxide is seven eights. Ammonia has a hydrogen to nitrogen mass ratio of three fourteenths. The fact that elemental masses combined in simple fractions implies that all elemental mass stems from a common source. In principle, the atomic mass situation is analogous to the above example of Roman mass units. The Roman pound and ounce were both defined in terms of different sized collections of carob seeds, and consequently, the two mass units were related to each other through a simple fraction. Comparatively, since all of the atomic masses are related to each other through simple fractions, then perhaps the atomic masses are just different sized collections of some common fundamental mass unit.

In 1805, the chemist John Dalton published his first table of relative atomic weights, listing six elements, hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, and assigning hydrogen an atomic weight of 1. And in 1815, the chemist William Prout concluded that the hydrogen atom was in fact the fundamental mass unit from which all other atomic masses were derived.

Carbon atoms in graphite (image obtained with a Scanning tunneling microscope)

If Prout's hypothesis had proven accurate, then the abstract concept of mass, as we now know it, might never have evolved, since mass could always be defined in terms of amounts of the hydrogen atomic mass. Prout’s hypothesis; however, was found to be inaccurate in two major respects. First, further scientific advancements revealed the existence of smaller particles, such as electrons and quarks, whose masses are not related through simple fractions. And second, the elemental masses themselves were found to not be exact multiples of the hydrogen atom mass, but rather, they were near multiples. Einstein’s theory of relativity explained that when protons and neutrons come together to form an atomic nucleus, some of the mass of the nucleus is released in the form of binding energy. The more tightly bound the nucleus, the more energy is lost during formation and this binding energy loss causes the elemental masses to not be related through simple fractions.

Hydrogen, for example, with a single proton, has an atomic weight of 1.007825 u. The most abundant isotope of iron has 26 protons and 30 neutrons, so one might expect its atomic weight to be 56 times that of the hydrogen atom, but in fact, its atomic weight is only 55.9383 u, which is clearly not an integer multiple of 1.007825. Prout’s hypothesis was proven inaccurate in many respects, but the abstract concepts of atomic mass and amount continue to play an influential role in chemistry, and the atomic mass unit continues to be the unit of choice for very small mass measurements.

Weights as in a box with weights

When the French invented the metric system in the late 18th century, they used an amount to define their mass unit. The kilogram was originally defined to be equal in mass to the amount of pure water contained in a one-liter container. This definition, however, was inadequate for the precision requirements of modern technology, and the metric kilogram was redefined in terms of a man-made platinum-iridium bar known as the international prototype kilogram.

Gravitational mass[link]

Active gravitational mass is a property of the mass of an object that produces a gravitational field in the space surrounding the object, and these gravitational fields govern large-scale structures in the Universe. Gravitational fields hold the galaxies together. They cause clouds of gas and dust to coalesce into stars and planets. They provide the necessary pressure for nuclear fusion to occur within stars. And they determine the orbits of various objects within the Solar System. Since gravitational effects are all around us, it is impossible to pin down the exact date when humans first discovered gravitational mass. However, it is possible to identify some of the significant steps towards our modern understanding of gravitational mass and its relationship to the other mass phenomena. Some terms associated with gravitational mass and its effects are the Gaussian gravitational constant, the standard gravitational parameter and the Schwarzschild radius.

Keplerian gravitational mass[link]

Johannes Kepler 1610.

Johannes Kepler was the first to give an accurate description of the orbits of the planets, and by doing so; he was the first to describe gravitational mass. In 1600 AD, Kepler sought employment with Tycho Brahe and consequently gained access to astronomical data of a higher precision than any previously available. Using Brahe’s precise observations of the planet Mars, Kepler realized that the traditional astronomical methods were inaccurate in their predictions, and he spent the next five years developing his own method for characterizing planetary motion.

In Kepler’s final planetary model, he successfully described planetary orbits as following elliptical paths with the Sun at a focal point of the ellipse. The concept of active gravitational mass is an immediate consequence of Kepler's third law of planetary motion. Kepler discovered that the square of the orbital period of each planet is directly proportional to the cube of the semi-major axis of its orbit, or equivalently, that the ratio of these two values is constant for all planets in the Solar System. This constant ratio is a direct measure of the Sun's active gravitational mass, it has units of distance cubed per time squared, and is known as the standard gravitational parameter:

Failed to parse (Missing texvc executable; please see math/README to configure.): \mu = 4 \pi^2 \frac{Distance^3}{Time^2} \propto Gravitational \, Mass

In 1609, Johannes Kepler published his three rules known as Kepler's laws of planetary motion, explaining how the planets follow elliptical orbits under the influence of the Sun. On 25 August of that same year, Galileo Galilei demonstrated his first telescope to a group of Venetian merchants, and in early January of 1610, Galileo observed four dim objects near Jupiter, which he mistook for stars. However, after a few days of observation, Galileo realized that these "stars" were in fact orbiting Jupiter. These four objects (later named the Galilean moons in honor of their discoverer) were the first celestial bodies observed to orbit something other than the Earth or Sun. Galileo continued to observe these moons over the next eighteen months, and by the middle of 1611 he had obtained remarkably accurate estimates for their periods. Later, the semi-major axis of each moon was also estimated, thus allowing the gravitational mass of Jupiter to be determined from the orbits of its moons. The gravitational mass of Jupiter was found to be approximately a thousandth of the gravitational mass of the Sun.

Galilean gravitational field[link]

Galileo Galilei 1636.

The distance traveled by a freely falling ball is proportional to the square of the elapsed time.

Sometime prior to 1638, Galileo turned his attention to the phenomenon of objects falling under the influence of Earth’s gravity, and he was actively attempting to characterize these motions. Galileo was not the first to investigate Earth’s gravitational field, nor was he the first to accurately describe its fundamental characteristics. However, Galileo’s reliance on scientific experimentation to establish physical principles would have a profound effect on future generations of scientists. Galileo used a number of scientific experiments to characterize free fall motion. It is unclear if these were just hypothetical experiments used to illustrate a concept, or if they were real experiments performed by Galileo,^[2] but the results obtained from these experiments were both realistic and compelling. A biography by Galileo's pupil Vincenzo Viviani stated that Galileo had dropped balls of the same material, but different masses, from the Leaning Tower of Pisa to demonstrate that their time of descent was independent of their mass.^{[note 4]} In support of this conclusion, Galileo had advanced the following theoretical argument: He asked if two bodies of different masses and different rates of fall are tied by a string, does the combined system fall faster because it is now more massive, or does the lighter body in its slower fall hold back the heavier body? The only convincing resolution to this question is that all bodies must fall at the same rate.^[3]

A later experiment was described in Galileo’s Two New Sciences published in 1638. One of Galileo’s fictional characters, Salviati, describes an experiment using a bronze ball and a wooden ramp. The wooden ramp was "12 cubits long, half a cubit wide and three finger-breadths thick" with a straight, smooth, polished groove. The groove was lined with "parchment, also smooth and polished as possible". And into this groove was placed "a hard, smooth and very round bronze ball". The ramp was inclined at various angles to slow the acceleration enough so that the elapsed time could be measured. The ball was allowed to roll a known distance down the ramp, and the time taken for the ball to move the known distance was measured. The time was measured using a water clock described as follows:

"a large vessel of water placed in an elevated position; to the bottom of this vessel was soldered a pipe of small diameter giving a thin jet of water, which we collected in a small glass during the time of each descent, whether for the whole length of the channel or for a part of its length; the water thus collected was weighed, after each descent, on a very accurate balance; the differences and ratios of these weights gave us the differences and ratios of the times, and this with such accuracy that although the operation was repeated many, many times, there was no appreciable discrepancy in the results.".^[4]

Galileo found that for an object in free fall, the distance that the object has fallen is always proportional to the square of the elapsed time:

Failed to parse (Missing texvc executable; please see math/README to configure.): g = \frac{Distance}{Time^2} \propto Gravitational \, field

Galileo Galilei died in Arcetri, Italy (near Florence), on 8 January 1642. Galileo had shown that objects in free fall under the influence of the Earth’s gravitational field have a constant acceleration, and Galileo’s contemporary, Johannes Kepler, had shown that the planets follow elliptical paths under the influence of the Sun’s gravitational mass. However, the relationship between Galileo’s gravitational field and Kepler’s gravitational mass wasn’t comprehended during Galileo’s lifetime.

Newtonian gravitational mass[link]

Isaac Newton 1689.

 = Failed to parse (Missing texvc executable; please see math/README to configure.): 398 600 \frac{km^3}{s^2}

Robert Hooke published his concept of gravitational forces in 1674, stating that: “all Cœlestial Bodies whatsoever, have an attraction or gravitating power towards their own Centers" [and] "they do also attract all the other Cœlestial Bodies that are within the sphere of their activity”. He further states that gravitational attraction increases “by how much the nearer the body wrought upon is to their own center.^[5] In a correspondence of 1679–1680 between Robert Hooke and Isaac Newton, Hooke conjectures that gravitational forces might decrease according to the double of the distance between the two bodies.^[6] Hooke urged Newton, who was a pioneer in the development of calculus, to work through the mathematical details of Keplerian orbits to determine if Hooke’s hypothesis was correct. Newton’s own investigations verified that Hooke was correct, but due to personal differences between the two men, Newton chose not to reveal this to Hooke. Isaac Newton kept quiet about his discoveries until 1684, at which time he told a friend, Edmond Halley, that he had solved the problem of gravitational orbits, but had misplaced the solution in his office.^[7] After being encouraged by Halley, Newton decided to develop his ideas about gravity and publish all of his findings. In November 1684, Isaac Newton sent a document to Edmund Halley, now lost but presumed to have been titled De motu corporum in gyrum (Latin: "On the motion of bodies in an orbit").^[8] Halley presented Newton’s findings to the Royal Society of London, with a promise that a fuller presentation would follow. Newton later recorded his ideas in a three book set, entitled Philosophiæ Naturalis Principia Mathematica (Latin: "Mathematical Principles of Natural Philosophy"). The first was received by the Royal Society on 28 April 1685–6, the second on 2 March 1686–7, and the third on 6 April 1686–7. The Royal Society published Newton’s entire collection at their own expense in May 1686–7.^[9]

Isaac Newton had bridged the gap between Kepler’s gravitational mass and Galileo’s gravitational acceleration, and proved the following relationship:

Failed to parse (Missing texvc executable; please see math/README to configure.): g = \frac{\mu}{r^2}

, where g is the apparent acceleration of a body as it passes through a region of space where gravitational fields exist, μ is the gravitational mass (standard gravitational parameter) of the body causing gravitational fields, and r is the radial coordinate (the distance between the centers of the two bodies).

By finding the exact relationship between a body's gravitational mass and its gravitational field, Newton provided a second method for measuring gravitational mass. The mass of the Earth can be determined using Kepler’s method (from the orbit of Earth’s Moon), or it can be determined by measuring the gravitational acceleration on the Earth’s surface, and multiplying that by the square of the Earth’s radius. The mass of the Earth is approximately three millionths of the mass of the Sun. To date, no other accurate method for measuring gravitational mass has been discovered.^[10]

Newton's cannonball[link]

Newton's cannonball was a thought experiment used to bridge the gap between Galileo’s gravitational acceleration and Kepler’s elliptical orbits. It appeared in Newton's 1728 book A Treatise of the System of the World. According to Galileo’s concept of gravitation, a dropped stone falls with constant acceleration down towards the Earth. However, Newton explains that when a stone is thrown horizontally (meaning sideways or perpendicular to Earth’s gravity) it follows a curved path. “For a stone projected is by the pressure of its own weight forced out of the rectilinear path, which by the projection alone it should have pursued, and made to describe a curve line in the air; and through that crooked way is at last brought down to the ground. And the greater the velocity is with which it is projected, the farther it goes before it falls to the Earth.”^[11]

Newton further reasons that if an object were “projected in an horizontal direction from the top of a high mountain” with sufficient velocity, “it would reach at last quite beyond the circumference of the Earth, and return to the mountain from which it was projected.” Newton’s thought experiment is illustrated in the image to the right. A cannon on top of a very high mountain shoots a cannon ball in a horizontal direction. If the speed is low, it simply falls back on Earth (paths A and B). However, if the speed is equal to or higher than some threshold (orbital velocity), but not high enough to leave Earth altogether (escape velocity), it will continue revolving around Earth along an elliptical orbit (C and D).

Universal gravitational mass and amount[link]

Newton's cannonball illustrated the relationship between the Earth’s gravitational mass and its gravitational field; however, a number of other ambiguities still remained. Robert Hooke had asserted in 1674 that: "all Celestial Bodies whatsoever, have an attraction or gravitating power towards their own Centers", but Hooke had neither explained why this gravitating attraction was unique to celestial bodies, nor had he explained why the attraction was directed towards the center of a celestial body.

An apple experiences gravitational fields directed towards every part of the Earth; however, the sum total of these many fields produces a single powerful gravitational field directed towards the Earth’s center.

To answer these questions, Newton introduced the entirely new concept that gravitational mass is “universal”: meaning that every object has gravitational mass, and therefore, every object generates a gravitational field. Newton further assumed that the strength of each object’s gravitational field would decrease according to the square of the distance to that object. With these assumptions in mind, Newton calculated what the overall gravitational field would be if a large collection of small objects were formed into a giant spherical body. Newton found that a giant spherical body (like the Earth or Sun, with roughly uniform density at each given radius), would have a gravitational field which was proportional to the total mass of the body,^[12] and inversely proportional to the square of the distance to the body’s center.^[13]

Newton's concept of universal gravitational mass is illustrated in the image to the left. Every piece of the Earth has gravitational mass and every piece creates a gravitational field directed towards that piece. However, the overall effect of these many fields is equivalent to a single powerful field directed towards the center of the Earth. The apple behaves as if a single powerful gravitational field were accelerating it towards the Earth’s center.

Newton’s concept of universal gravitational mass puts gravitational mass on an equal footing with the traditional concepts of weight and amount. For example, the ancient Romans had used the carob seed as a weight standard. The Romans could place an object with an unknown weight on one side of a balance scale and place carob seeds on the other side of the scale, increasing the number of seeds until the scale was balanced. If an object’s weight was equivalent to 1728 carob seeds, then the object was said to weigh one Roman pound.

According to Newton’s theory of universal gravitation, each carob seed produces gravitational fields. Therefore, if one were to gather an immense number of carob seeds and form them into an enormous sphere, then the gravitational field of the sphere would be proportional to the number of carob seeds in the sphere. Hence, it should be theoretically possible to determine the exact number of carob seeds that would be required to produce a gravitational field similar to that of the Earth or Sun. And since the Roman weight units were all defined in terms of carob seeds, then knowing the Earth’s, or Sun's “carob seed mass” would allow one to calculate the mass in Roman pounds, or Roman ounces, or any other Roman unit.

Vertical section drawing of Cavendish's torsion balance instrument including the building in which it was housed. The large balls were hung from a frame so they could be rotated into position next to the small balls by a pulley from outside. Figure 1 of Cavendish's paper.

This possibility extends beyond Roman units and the carob seed. The British avoirdupois pound, for example, was originally defined to be equal to 7,000 barley grains. Therefore, if one could determine the Earth’s “barley grain mass” (the number of barley grains required to produce a gravitational field similar to that of the Earth), then this would allow one to calculate the Earth’s mass in avoirdupois pounds. Also, the original kilogram was defined to be equal in mass to a liter of pure water (the modern kilogram is defined by the man-made international prototype kilogram). Thus, the mass of the Earth in kilograms could theoretically be determined by ascertaining how many liters of pure water (or international prototype kilograms) would be required to produce gravitational fields similar to those of the Earth. In fact, it is a simple matter of abstraction to realize that any traditional mass unit can theoretically be used to measure gravitational mass.

Measuring gravitational mass in terms of traditional mass units is simple in principle, but extremely difficult in practice. According to Newton’s theory all objects produce gravitational fields and it is theoretically possible to collect an immense number of small objects and form them into an enormous gravitating sphere. However, from a practical standpoint, the gravitational fields of small objects are extremely weak and difficult to measure. And if one were to collect an immense number of objects, the resulting sphere would probably be too large to construct on the surface of the Earth, and too expensive to construct in space. Newton’s books on universal gravitation were published in the 1680s, but the first successful measurement of the Earth’s mass in terms of traditional mass units, the Cavendish experiment, didn’t occur until 1797, over a hundred years later. Cavendish found that the Earth's density was 5.448 ± 0.033 times that of water. As of 2009, the Earth’s mass in kilograms is only known to around five digits of accuracy, whereas its gravitational mass is known to over nine significant figures.

Inertial and gravitational mass[link]

Although inertial mass, passive gravitational mass and active gravitational mass are conceptually distinct, no experiment has ever unambiguously demonstrated any difference between them. In classical mechanics, Newton's third law implies that active and passive gravitational mass must always be identical (or at least proportional), but the classical theory offers no compelling reason why the gravitational mass has to equal the inertial mass. That it does is merely an empirical fact.

Albert Einstein developed his general theory of relativity starting from the assumption that this correspondence between inertial and (passive) gravitational mass is not accidental: that no experiment will ever detect a difference between them (the weak version of the equivalence principle). However, in the resulting theory, gravitation is not a force and thus not subject to Newton's third law, so "the equality of inertial and active gravitational mass [...] remains as puzzling as ever".^[14]

Inertial mass[link]

Inertial mass is the mass of an object measured by its resistance to acceleration.

To understand what the inertial mass of a body is, one begins with classical mechanics and Newton's Laws of Motion. Later on, we will see how our classical definition of mass must be altered if we take into consideration the theory of special relativity, which is more accurate than classical mechanics. However, the implications of special relativity will not change the meaning of "mass" in any essential way.

According to Newton's second law, we say that a body has a mass m if, at any instant of time, it obeys the equation of motion

Failed to parse (Missing texvc executable; please see math/README to configure.): F=m\alpha\!

,

where F is the force acting on the body and α is the acceleration of the body.^{[note 5]} For the moment, we will put aside the question of what "force acting on the body" actually means.

This equation illustrates how mass relates to the inertia of a body. Consider two objects with different masses. If we apply an identical force to each, the object with a bigger mass will experience a smaller acceleration, and the object with a smaller mass will experience a bigger acceleration. We might say that the larger mass exerts a greater "resistance" to changing its state of motion in response to the force.

However, this notion of applying "identical" forces to different objects brings us back to the fact that we have not really defined what a force is. We can sidestep this difficulty with the help of Newton's third law, which states that if one object exerts a force on a second object, it will experience an equal and opposite force. To be precise, suppose we have two objects A and B, with constant inertial masses m_X and m_Y. We isolate the two objects from all other physical influences, so that the only forces present are the force exerted on X by Y, which we denote F_XY, and the force exerted on Y by X, which we denote F_YX. Newton's second law states that

Failed to parse (Missing texvc executable; please see math/README to configure.): \!F_{XY}=m_X\alpha_X

,

Failed to parse (Missing texvc executable; please see math/README to configure.): \!F_{YX}=m_Y\alpha_Y

, where α_X and α_Y are the accelerations of X and Y, respectively. Suppose that these accelerations are non-zero, so that the forces between the two objects are non-zero. This occurs, for example, if the two objects are in the process of colliding with one another. Newton's third law then states that

Failed to parse (Missing texvc executable; please see math/README to configure.): F_{XY}=-F_{YX}\!

and thus

Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{m_X}{m_Y}=-\frac{\alpha_Y}{\alpha_X}\!

.

Note that our requirement that α_X be non-zero ensures that the fraction is well-defined.

This is, in principle, how we would measure the inertial mass of an object. We choose a "reference" object and define its mass m_Y as (say) 1 kilogram. Then we can measure the mass of any other object in the universe by colliding it with the reference object and measuring the accelerations.

Newtonian gravitational mass[link]

The Newtonian concept of gravitational mass rests on Newton's law of gravitation. Let us suppose we have two objects A and B, separated by a distance r_AB. The law of gravitation states that if A and B have gravitational masses M_A and M_B respectively, then each object exerts a gravitational force on the other, of magnitude

Failed to parse (Missing texvc executable; please see math/README to configure.): F=\frac{GM_AM_B}{r_{\mathrm{AB}}^2}\!

, where G is the universal gravitational constant. The above statement may be reformulated in the following way: if g is the magnitude at a given location in a gravitational field, then the gravitational force on an object with gravitational mass M is

Failed to parse (Missing texvc executable; please see math/README to configure.): F=Mg\!

. This is the basis by which masses are determined by weighing. In simple spring scales, for example, the force F is proportional to the displacement of the spring beneath the weighing pan, as per Hooke's law, and the scales are calibrated to take g into account, allowing the mass M to be read off. A balance measures gravitational mass; only the spring scale measures weight.

Equivalence of inertial and gravitational masses[link]

The equivalence of inertial and gravitational masses is sometimes referred to as the Galilean equivalence principle or weak equivalence principle. The most important consequence of this equivalence principle applies to freely falling objects. Suppose we have an object with inertial and gravitational masses m and M respectively. If the only force acting on the object comes from a gravitational field g, combining Newton's second law and the gravitational law yields the acceleration

Failed to parse (Missing texvc executable; please see math/README to configure.): a = \frac{M}{m} g.

This says that the ratio of gravitational to inertial mass of any object is equal to some constant K if and only if all objects fall at the same rate in a given gravitational field. This phenomenon is referred to as the 'universality of free-fall'. (In addition, the constant K can be taken to be 1 by defining our units appropriately.)

The first experiments demonstrating the universality of free-fall were conducted by Galileo. It is commonly stated that Galileo obtained his results by dropping objects from the Leaning Tower of Pisa, but this is most likely apocryphal; actually, he performed his experiments with balls rolling down inclined planes. Increasingly precise experiments have been performed, such as those performed by Loránd Eötvös,^[15] using the torsion balance pendulum, in 1889. As of 2008^[update], no deviation from universality, and thus from Galilean equivalence, has ever been found, at least to the precision 10⁻¹². More precise experimental efforts are still being carried out.

The universality of free-fall only applies to systems in which gravity is the only acting force. All other forces, especially friction and air resistance, must be absent or at least negligible. For example, if a hammer and a feather are dropped from the same height through the air on Earth, the feather will take much longer to reach the ground; the feather is not really in free-fall because the force of air resistance upwards against the feather is comparable to the downward force of gravity. On the other hand, if the experiment is performed in a vacuum, in which there is no air resistance, the hammer and the feather should hit the ground at exactly the same time (assuming the acceleration of both objects towards each other, and of the ground towards both objects, for its own part, is negligible). This can easily be done in a high school laboratory by dropping the objects in transparent tubes that have the air removed with a vacuum pump. It is even more dramatic when done in an environment that naturally has a vacuum, as David Scott did on the surface of the Moon during Apollo 15.

A stronger version of the equivalence principle, known as the Einstein equivalence principle or the strong equivalence principle, lies at the heart of the general theory of relativity. Einstein's equivalence principle states that within sufficiently small regions of space-time, it is impossible to distinguish between a uniform acceleration and a uniform gravitational field. Thus, the theory postulates that the force acting on a massive object caused by a gravitational field is a result of the object's tendency to move in a straight line (in other words its inertia) and should therefore be a function of its inertial mass and the strength of the gravitational field.

Mass and energy in special relativity[link]

The term mass in special relativity usually refers to the rest mass of the object, which is the Newtonian mass as measured by an observer moving along with the object. The invariant mass is another name for the rest mass of single particles. However, the more general invariant mass (calculated with a more complicated formula) may also be applied to systems of particles in relative motion, and because of this, is usually reserved for systems which consist of widely separated high-energy particles. The invariant mass of systems is the same for all observers and inertial frames, and cannot be destroyed, and is thus conserved, so long as the system is closed. In this case, "closure" implies that an idealized boundary is drawn around the system, and no mass/energy is allowed across it.

In as much as energy is conserved in closed systems in relativity, the mass of a system is also a quantity which is conserved: this means it does not change over time, even as some types of particles are converted to others. For any given observer, the mass of any system is separately conserved and cannot change over time, just as energy is separately conserved and cannot change over time. The incorrect popular idea that mass may be converted to (massless) energy in relativity is because some matter particles may in some cases be converted to types of energy which are not matter (such as light, kinetic energy, and the potential energy in magnetic, electric, and other fields). However, this confuses "matter" (a non-conserved and ill-defined thing) with mass (which is well-defined and is conserved). Even if not considered "matter," all types of energy still continue to exhibit mass in relativity. Thus, mass and energy do not change into one another in relativity; rather, both are names for the same thing, and neither mass nor energy appear without the other. "Matter" particles may not be conserved in reactions in relativity, but closed-system mass always is.

For example, a nuclear bomb in an idealized super-strong box, sitting on a scale, would in theory show no change in mass when detonated (although the inside of the box would become much hotter). In such a system, the mass of the box would change only if energy were allowed to escape from the box as light or heat. However, in that case, the removed energy would take its associated mass with it. Letting heat out of such a system is simply a way to remove mass. Thus, mass, like energy, cannot be destroyed, but only moved from one place to another.^[16]

In bound systems, the binding energy must (often) be subtracted from the mass of the unbound system, simply because this energy has mass, and this mass is subtracted from the system when it is given off, at the time it is bound. Mass is not conserved in this process because the system is not closed during the binding process. A familiar example is the binding energy of atomic nuclei, which appears as other types of energy (such as gamma rays) when the nuclei are formed, and (after being given off) results in nuclides which have less mass than the free particles (nucleons) of which they are composed.

The term relativistic mass is also used, and this is the total quantity of energy in a body or system (divided by c²). The relativistic mass (of a body or system of bodies) includes a contribution from the kinetic energy of the body, and is larger the faster the body moves, so unlike the invariant mass, the relativistic mass depends on the observer's frame of reference. However, for given single frames of reference and for closed systems, the relativistic mass is also a conserved quantity.

Because the relativistic mass is proportional to the energy, it has gradually fallen into disuse among physicists.^[17] There is disagreement over whether the concept remains pedagogically useful.^[18][19][20]

Mass in general relativity[link]

In general relativity, the equivalence principle is any of several related concepts dealing with the equivalence of gravitational and inertial mass. At the core of this assertion is Albert Einstein's idea that the gravitational force as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

However, it turns out that it is impossible to find an objective general definition for the concept of invariant mass in general relativity. At the core of the problem is the non-linearity of the Einstein field equations, which makes it impossible to write the gravitational field energy as part of the Stress–energy tensor in a way that is invariant for all observers. For a given observer, this can be achieved by the Stress–energy–momentum pseudotensor.^[21]

Mass in quantum physics[link]

In classical mechanics, the inert mass of a particle appears in the Euler–Lagrange equation as a parameter m,

Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{\mathrm{d}}{\mathrm{d}t} \ \left( \, \frac{\partial L}{\partial \dot{x}_i} \, \right) \ = \ m \, \ddot{x}_i

. After quantization, replacing the position vector x with a wave function, the parameter m appears in the kinetic energy operator,

Failed to parse (Missing texvc executable; please see math/README to configure.): i\hbar\frac{\partial}{\partial t} \Psi(\mathbf{r},\,t) = \left(-\frac{\hbar^2}{2m}\nabla^2 + V(\mathbf{r})\right)\Psi(\mathbf{r},\,t)

. In the ostensibly covariant^{[disambiguation needed ]} (relativistically invariant) Dirac equation, and in natural units, this becomes

Failed to parse (Missing texvc executable; please see math/README to configure.): (-i\gamma^\mu\partial_\mu + m) \psi = 0\,

Where the "mass" parameter m is now simply a constant associated with the quantum described by the wave function ψ.

In the Standard Model of particle physics as developed in the 1960s, there is the proposal that this term arises from the coupling of the field ψ to an additional field Φ, the so-called Higgs field. In the case of fermions, the Higgs mechanism results in the replacement of the term mψ in the Lagrangian with Failed to parse (Missing texvc executable; please see math/README to configure.): G_{\psi} \overline{\psi} \phi \psi . This shifts the explanandum of the value for the mass of each elementary particle to the value of the unknown couplings G_ψ. The discovery of a massive Higgs boson would be regarded as a strong confirmation of this theory. But there is indirect evidence for the reality of the Electroweak symmetry breaking as described by the Higgs mechanism, and the non-existence of the Higgs boson would indicate a "Higgsless" description of this mechanism.

Notes[link]

References[link]

Bibliography[link]

• Sir Isaac Newton; N. W. Chittenden (1848). Newton's Principia: The mathematical principles of natural philosophy. D. Adee. http://books.google.com/books?id=KaAIAAAAIAAJ&pg=PA31. Retrieved 12 March 2011. 

External links[link]

• Stanford Encyclopedia of Philosophy: "The Equivalence of Mass and Energy" by Francisco Flores.
• "The Mysteries of Mass," Scientific American, July 2005.
• Usenet Physics FAQ by John Baez:
  • "Does mass change with velocity?"
  • "What is the mass of a photon?"
• "The Origin of Mass and the Feebleness of Gravity." Video of lecture by the Nobel Laureate Frank Wilczek.
• Okun, L. B., "Photons, Clocks, Gravity and the Concept of Mass." Slides for a talk.
• The Apollo 15 Hammer-Feather Drop.
• Online mass units conversion.

Bee Gees
The Bee Gees performing on Dutch television in 1968. From left to right: Barry, Robin, and Maurice Gibb
Background information
Genres	Pop, pop rock, disco, blue-eyed soul, soft rock
Years active	1958–2003 2009–2012
Labels	RSO, Warner Bros., Festival, Polydor, Atco
Website	www.beegees.com
Past members
Barry Gibb Robin Gibb Maurice Gibb Colin Petersen Vince Melouney Geoff Bridgford Alan Kendall Dennis Bryon Blue Weaver

The Bee Gees were a musical group founded in 1958. The group's line-up consisted of brothers Barry, Robin, and Maurice Gibb. The trio were successful for most of their decades of recording music, but they had two distinct periods of exceptional success: as a pop act in the late 1960s/early 1970s, and as prominent performers of the disco music era in the late 1970s.

The group sang three-part tight harmonies that were instantly recognisable; Robin's clear vibrato lead was a hallmark of their earlier hits, while Barry's R&B falsetto became their signature sound during the late 1970s and 1980s. The brothers wrote all of their own hits, as well as writing and producing several major hits for other artists.

Born in the Isle of Man to English parents, the Gibb brothers lived their first few years in Chorlton, Manchester, England, then moved in the late 1950s to Redcliffe, Queensland, Australia, where they began their musical careers.^[1] After achieving their first chart success in Australia with "Spicks and Specks" (their 12th single), they returned to the United Kingdom in January 1967 where producer Robert Stigwood began promoting them to a worldwide audience.

It has been estimated that the Bee Gees' career record sales total more than 220 million,^[2] ranking them among the best-selling music artists of all time. They were inducted into the Rock and Roll Hall of Fame in 1997;^[3] the presenter of the award to "Britain's first family of harmony" was Brian Wilson, historical leader of the Beach Boys, a "family act" also featuring three harmonising brothers.^[4] The Bee Gees' Hall of Fame citation says "Only Elvis Presley, The Beatles, Michael Jackson, Garth Brooks and Paul McCartney have outsold the Bee Gees".^[3]

Following Maurice's sudden death in January 2003, Barry and Robin Gibb retired the group's name after 45 years of activity. In 2009, however, Robin announced that he and Barry had agreed that the Bee Gees would re-form and perform again.^[5] Robin died in May 2012 after a prolonged bout of cancer.^[6]

History[link]

Early years[link]

Plaque at Maitland Terrace/Strang Road intersection in Union Mills, Isle of Man.

Barry Gibb (b. 1946) and fraternal twin brothers Robin (1949–2012) and Maurice Gibb (1949–2003) were born on the Isle of Man, but the family returned to father Hugh Gibb's home town of Chorlton-cum-Hardy, Manchester, England where they went to Oswald Road Primary School, in the early 1950s where the boys began to sing in harmony. The story is told that they were going to lip sync to a record in the local Gaumont cinema (as other children had done on previous weeks) and as they were running to the theatre, the heavy 78-RPM record broke. The brothers had to sing live and received such a positive response from the audience that they decided to pursue a singing career.^[7]

In 1958 the Gibb family, including infant brother, Andy (1958–1988), emigrated to Redcliffe in Queensland, Australia. The young brothers began performing where they could to raise pocket money. First called the Rattlesnakes, later Wee Johnny Hayes & the Bluecats, they were introduced to radio DJ Bill Gates by racetrack promoter Bill Goode (who saw them perform at Brisbane's Speedway Circuit). Gates renamed them the "Bee Gees" after his and Goode's initials – thus the name was not specifically a reference to "Brothers Gibb", despite popular belief.^[8]

By 1960 the Bee Gees were featured on television shows. In the next few years they began working regularly at resorts on the Queensland coast. For his songwriting, Barry sparked the interest of Australian star Col Joye, who helped them get a record deal with Festival Records subsidiary, Leedon Records, in 1963 under the name "Bee Gees." The three released two or three singles a year, while Barry supplied additional songs to other Australian artists. From 1963 to 1966 the Gibb family lived at 171 Bunnerong Road, Maroubra in Sydney.^[9]

A minor hit in 1965, "Wine and Women", led to the group's first LP The Bee Gees Sing and Play 14 Barry Gibb Songs. By 1966 Festival was, however, on the verge of dropping them from the Leedon roster because of their perceived lack of commercial success. It was at this time that they met American-born songwriter, producer and entrepreneur, Nat Kipner, who had just been appointed A&R manager of a new independent label, Spin Records. Kipner briefly took over as the group's manager and successfully negotiated their transfer to Spin in exchange for Festival being granted the Australian distribution rights to the group's recordings.^{[citation needed]}

Through Kipner the Bee Gees met engineer-producer, Ossie Byrne. He produced (or co-produced with Kipner) many of the earlier Spin recordings, most of which were cut at his own small self-built St Clair Studio in the Sydney suburb of Hurstville. Byrne gave the Gibb brothers virtually unlimited access to St Clair Studio over a period of several months in mid-1966. The group later acknowledged that this enabled them to greatly improve their skills as recording artists. During this productive time they recorded a large batch of original material—including the song that would become their first major hit, "Spicks and Specks" (on which Byrne played the trumpet coda) – as well as cover versions of current hits by overseas acts such as The Beatles. They regularly collaborated with other local musicians, including members of beat band Steve & The Board, led by Steve Kipner, Nat's teenage son.

Frustrated by their lack of success, the Gibbs decided to return to England in late 1966. Ossie Byrne travelled with them, and Colin Petersen, who eventually became the group's drummer, followed soon after. While at sea in January 1967, they learned that "Spicks and Specks" had been awarded Best Single of the Year by Go-Set, Australia's most popular and influential music newspaper.

Late 1960s: first international fame[link]

The Bee Gees in 1967.

Before their departure from Australia to England, Hugh Gibb sent demos to Brian Epstein who managed The Beatles and was director of NEMS, a British music store and promoter. Brian Epstein had passed the demo tapes to Robert Stigwood, who had recently joined NEMS. After an audition with Stigwood in February 1967, the Bee Gees were signed to a five-year contract whereby Polydor Records would be their record label in the United Kingdom and ATCO Records would be the United States distributor. Work quickly began on the group's first international album, and Robert Stigwood launched a promotional campaign to coincide with its release.

Stigwood proclaimed that the Bee Gees were "The Most Significant New Talent Of 1967" and thus began the immediate comparison to The Beatles.^[10] Their second British single (their first UK 45 rpm issued was "Spicks and Specks"), "New York Mining Disaster 1941", was issued to radio stations with a blank white label listing only the song title. Some DJs immediately assumed this was a new single by The Beatles and started playing the song in heavy rotation. This helped the song climb into the Top 20 in both the United Kingdom and the United States. No such chicanery was needed to boost the Bee Gees' second single, "To Love Somebody", into the US Top 20. Originally written for Otis Redding, "To Love Somebody" was a soulful ballad sung by Barry, which has since become a pop standard covered by hundreds of artists including Gram Parsons, Rod Stewart, Bonnie Tyler, Janis Joplin, The Animals, Nina Simone, Jimmy Somerville and Michael Bolton. Another single, "Holiday", was released in the United States, peaking at No. 16. The parent album, Bee Gees 1st (their first internationally), peaked at No. 7 in the United States and No. 8 in the United Kingdom.

Following the success of Bee Gees 1st, the band (which now consisted of Barry on rhythm guitar, Maurice on bass, Vince Melouney on lead guitar and Colin Petersen on drums),.^[10] began work on the act's second album. Released in late 1967, Horizontal repeated the success of their first album, featuring the No. 1 UK single "Massachusetts" (a No. 11 US hit), and the No. 7 UK single "World". The sound of the album Horizontal had a more "rock" sound than their previous release, though ballads like "And The Sun Will Shine" and "Really And Sincerely" were also prominent. The Horizontal album reached No. 12 in the US, and No. 16 in the UK promoting the record, the Bee Gees made their first appearances in America, playing live concerts and television shows such as The Ed Sullivan Show and Rowan & Martin's Laugh-In. Two more singles followed in early 1968, the ballad "Words" (No. 15 US, No. 8 UK) and the double A-sided single "Jumbo" b/w "The Singer Sang His Song". "Jumbo" was the Bee Gees' least successful single to date only reaching No. 57 in the US, and No. 25 in the UK. The Bee Gees felt that "The Singer Sang His Song" was the stronger of the two sides, an opinion shared by listeners in the Netherlands, who made it a No. 3 hit. Further Bee Gees chart singles followed: "I've Gotta Get a Message to You" (No. 8 US, No. 1 UK) and "I Started A Joke" (No. 6 US), both culled from the band's third album Idea. Idea was another Top 20 album in the US (No. 17) and the UK (No. 4). Following the tour and TV special to promote the album, Vince Melouney left the group, feeling that he wanted to play more of a blues style music than the Gibbs were writing. Melouney did achieve one feat while with the Bee Gees—his composition "Such A Shame" (from Idea) is the only song on any Bee Gees album not written by a Gibb brother.

By 1969, the cracks began to show within the group. Robin began to feel that Stigwood had been favouring Barry as the frontman. Their next album, which was to have been a concept album called Masterpeace, evolved into the double-album Odessa. Most rock critics felt this was the best Bee Gees album of the '60s, with its progressive rock feel on the title track, the country-flavoured "Marley Purt Drive" and "Give Your Best", and signature ballads such as "Melody Fair" and "First of May"; the last of which became the only single from the album, and was a minor hit. Feeling that the flipside, "Lamplight" should have been the A-side, Robin quit the group in mid-1969 and launched a solo career. Robin Gibb saw brief success in Europe with the No. 2 hit "Saved By The Bell" and the album Robin's Reign. Barry and Maurice continued as the Bee Gees, even recruiting their sister Lesley to appear with them on stage.

The first of many Bee Gees compilations, Best of Bee Gees was released, featuring the non-LP single "Words" plus the Australian hit "Spicks and Specks" The CD release replaces "Spicks and Specks" with another non-LP single "Tomorrow Tomorrow", because Polydor could no longer secure the rights to the Australian track. "Tomorrow Tomorrow" was a moderate hit in the UK reaching No. 23, but stalled at No. 54 in the US. The compilation reached the Top Ten in both the US and the UK.

While Robin was off on his own, Barry, Maurice, and Colin continued on as the Bee Gees, recording their next album, Cucumber Castle. There was also a TV special filmed to accompany the album, which aired on the BBC in 1971. Colin Petersen played drums on the tracks recorded for the album, but was fired from the group after filming began and his parts were edited out of the final cut of the film. After Colin was fired, Australian drummer Geoff Bridgford was recruited to complete the recording of songs for Cucumber Castle. The leadoff single, "Don't Forget to Remember" was a big hit in the UK reaching No. 2, but a disappointment in the US, only reaching No. 73. The next 2 singles, "I.O.I.O." and "If I Only Had My Mind on Something Else" barely scraped the charts, and following the release of the album, Barry and Maurice parted ways. It seemed that the Bee Gees were finished. Barry recorded a solo album which never saw official release, though "I'll Kiss Your Memory" was released as a single, without much interest. Meanwhile, Maurice released the single "Railroad", and starred in the West End musical Sing A Rude Song.

Early 1970s[link]

The three brothers reunited in the later part of 1970 penning a series of songs about heartache and loneliness. During this period they became a four piece band joined again by Australian drummer Geoff Bridgford who after playing on the 2 Years On album and Trafalgar album became the last non-Gibb brother to be a member of the Bee Gees. Although they had lost traction on the British charts, the Bee Gees hit No. 3 in America with "Lonely Days" (from the reunion LP 2 Years On) and had their first US No. 1 with "How Can You Mend a Broken Heart" (from Trafalgar). The trio's talents were included in the soundtrack for the 1971 film Melody as they performed several songs for the title. In 1972, they hit No. 16 in America with the single "My World" and "Run To Me" from the LP To Whom It May Concern; the latter also returned them to the British top ten for the first time in three years.

By 1973, however, the Bee Gees were in a rut. The album, Life in a Tin Can, released on RSO Records and its lead-off single, "Saw a New Morning," sold poorly with the single peaking at No. 94. This was followed by an unreleased album (known as A Kick in the Head Is Worth Eight in the Pants). A second compilation album, Best of Bee Gees, Volume 2 was released in 1973, though it did not repeat the success of Volume 1.

On the advice of Ahmet Ertegün, head of their US label Atlantic Records, Stigwood arranged for the group to record with famed soul music producer Arif Mardin. The resulting LP, Mr. Natural, included fewer ballads and foreshadowed the R&B direction of the rest of their career. But when it too failed to attract much interest, Mardin encouraged them to work with the soul music style.

The brothers attempted to assemble a live stage band that could replicate their studio sound. Lead guitarist Alan Kendall had come on board in 1971, but did not have much to do until Mr. Natural. For that album, they added drummer Dennis Bryon, and they later added ex-Strawbs keyboard player Blue Weaver, completing the late 1970s "Bee Gees band". Maurice, who had previously performed on piano, guitar, organ, mellotron, and bass guitar, as well as exotica like mandolin and Moog synthesiser, now confined himself to bass onstage.

At Eric Clapton's suggestion, the brothers relocated to Miami, Florida, early in 1975 to record. After starting off with ballads, they eventually heeded the urging of Mardin and Stigwood and crafted more rhythmic disco songs, including their second US No. 1, "Jive Talkin'", along with US No. 7 "Nights on Broadway." The band liked the resulting new sound, and this time the public agreed, sending the LP Main Course up the charts. This was their second album to have two US top-10 singles since 1968's Idea. Main Course also became their first charting R&B album. Mardin was unable to work with the group afterwards, but the Bee Gees enlisted Albhy Galuten and Karl Richardson who had worked with Mardin during the Main Course sessions. This production team would carry the Bee Gees through the rest of the 1970s.

The next album, Children of the World, was drenched in Barry's newfound falsetto and Weaver's synthesiser disco licks. Led off by the single "You Should Be Dancing," it pushed the Bee Gees to a level of stardom they had not previously achieved in the US, though their new R&B/disco sound was not as popular with some die hard fans from the 1960s. The Bee Gees' band was now closer to a rock act, with rhythm guitar and real drums behind the falsetto.

[edit] Late 1970s: Saturday Night Fever

Following a successful live album, Here at Last... Bee Gees... Live, the Bee Gees agreed with Stigwood to participate in the creation of the Saturday Night Fever soundtrack. It would be the turning point of their career. The cultural impact of both the film and the soundtrack was seismic, not only in the United States, but in the rest of the world as well, bringing the nascent disco scene mainstream.

The band's involvement in the film did not begin until post-production. As John Travolta asserted, "The Bee Gees weren't even involved in the movie in the beginning ... I was dancing to Stevie Wonder and Boz Scaggs."^[11] Producer Robert Stigwood commissioned the Bee Gees to create the songs for the film. The brothers wrote the songs "virtually in a single weekend" at France's Château d'Hérouville studio.^[11] Barry Gibb remembered the reaction when Stigwood and music supervisor Bill Oakes arrived and listened to the demos:

Bill Oakes, who supervised the soundtrack, asserts that Saturday Night Fever did not begin the disco craze; rather, it prolonged it: "Disco had run its course. These days, Fever is credited with kicking off the whole disco thing–-it really didn't. Truth is, it breathed new life into a genre that was actually dying."^[11]

Three Bee Gees singles ("How Deep Is Your Love", "Stayin' Alive", and "Night Fever") reached No. 1 in the United States and many countries around the world, launching the most popular period of the disco era. They also penned the song "If I Can't Have You" which became a No. 1 hit for Yvonne Elliman, while the Bee Gees' own version was the B-Side of "Stayin' Alive." Such was the popularity of Saturday Night Fever that two different versions of the song "More Than a Woman" received airplay, one by the Bee Gees, which was relegated to album track, and another by Tavares, which was the hit. The Gibb sound was inescapable. During an eight-month period beginning in the Christmas season of 1977, six songs written by the brothers held the No. 1 position on the US charts for 25 of 32 consecutive weeks—three of their own releases, two for brother Andy Gibb, and the Yvonne Elliman single.

Fueled by the movie's success, the soundtrack broke multiple industry records, becoming the highest-selling album in recording history to that point. With more than 40 million copies sold, Saturday Night Fever is among music's top five best selling soundtrack albums. It is currently calculated as the 4th highest-selling album worldwide.^[12]

During this era, Barry and Robin also wrote "Emotion" for an old friend, Australian vocalist Samantha Sang, who made it a Top Ten hit (the Bee Gees sang backing vocals). Barry also wrote the title song to the movie version of the Broadway musical Grease for Frankie Valli to perform, which went to No. 1. During this period, the Bee Gees' younger brother Andy followed his older siblings into a music career, and enjoyed considerable success. Produced by Barry, Andy Gibb's first three singles all topped the US charts. In March 1978, the Bee Gees held the top 2 positions on the US Charts with "Night Fever" and "Stayin' Alive", the first time this had happened since The Beatles. On the US Billboard Hot 100 chart for 25 March 1978, five songs written by the Gibbs were in the US top ten at the same time: "Night Fever", "Stayin' Alive", "If I Can't Have You", "Emotion" and "Love is Thicker Than Water". Such chart dominance hadn't been seen since April 1964, when The Beatles had all five of the top five American singles. Barry Gibb became the only songwriter to have four consecutive number one hits in the US breaking the John Lennon and Paul McCartney 1964 record. These songs were "Stayin' Alive", "Love Is Thicker Than Water", "Night Fever", "If I Can't Have You".

The Bee Gees also co-starred with Peter Frampton in the movie Sgt. Pepper's Lonely Hearts Club Band (1978) loosely inspired by the classic 1967 album by The Beatles. The film had been heavily promoted prior to release, and was expected to enjoy great commercial success. However, the disjointed film was savaged by the movie critics, and ignored by the public. Though some of its tracks charted, the soundtrack too was a high-profile flop. The single "Oh! Darling", credited to Robin Gibb, reached No. 15 in the US. Previously, the Bee Gees had recorded three Beatles covers—"Golden Slumbers/Carry That Weight", "She Came in Through the Bathroom Window" and "Sun King" – for the transitory musical documentary All This and World War II.

The Bee Gees' follow-up to Saturday Night Fever was the Spirits Having Flown album. It yielded three more No. 1 hits: "Too Much Heaven", "Tragedy", and "Love You Inside Out." This gave the act six consecutive No. 1 singles in America within a year and a half (a record surpassed only by Whitney Houston). "Too Much Heaven" ended up as the Bee Gees' musical contribution to the Music for UNICEF Concert at the United Nations General Assembly in January 1979, a benefit organised by the Bee Gees, Robert Stigwood, and David Frost for UNICEF that was broadcast worldwide. The brothers donated the royalties from the song to the charity. Up to 2007, this song has earned over $11 million for UNICEF. During the summer of 1979, the Bee Gees embarked on their largest concert tour covering the US and Canada. The Spirits Having Flown tour capitalised on Bee Gees fever that was sweeping the nation, with sold out concerts in 38 cities. The Bee Gees produced a video for the title track of "Too Much Heaven" directed by Miami-based film-maker, Martin Pitts and produced by Charles Allen. With this video, Pitts and Allen began a long association with the brothers.

The Bee Gees even had a country hit in 1979 with "Rest Your Love On Me", the flip side of their pop hit "Too Much Heaven", which made Top 40 on the country charts. In 1981, Conway Twitty's version of "Rest Your Love On Me" topped the country charts.

The Bee Gees' overwhelming success rose and fell with the disco bubble. By the end of 1979, disco was rapidly declining in popularity, and the backlash against disco put the Bee Gees' American career in a tailspin. Radio stations around America began promoting "Bee Gee Free Weekends". Following their remarkable run from 1975 to 1979, the act would have only one more top ten single in the US, and that would not come until 1989. The Bee Gees' international popularity sustained somewhat less damage. Barry Gibb considered the success of the Saturday Night Fever soundtrack both a blessing and a curse:

1980s[link]

Robin and Barry Gibb released various solo albums in the 1980s but only with sporadic and moderate chart success. The brothers had continuing success behind the scenes, however, writing and producing for several artists. In 1980 Barry Gibb worked with Barbra Streisand on her album Guilty. He co-produced and wrote or co-wrote all nine of the album's tracks (four of them written with Robin and the title track with both Robin and Maurice). Barry also appeared on the album's cover with Streisand, and duetted with her on two tracks. The album reached No.1 in both the US and the UK, as did the single "Woman in Love" (written by Barry and Robin), becoming Streisand's most successful single and album to date.

In 1981 the Bee Gees released the album Living Eyes, their last release on RSO. This album was the first CD ever played in public, when it was played to viewers of the BBC show Tomorrow's World.^[13] With the disco backlash still running strong, the album failed to make the UK or US Top 40. Two singles from the album fared little better – "He's a Liar" reached No. 30 in the US and "Living Eyes" reached No. 45, breaking the Bee Gees' Top 40 streak which started in 1975 with "Jive Talkin'".

In 1982 Dionne Warwick enjoyed a UK No.2 and US Adult Contemporary No. 1 with her comeback single, "Heartbreaker", taken from her album of the same name written largely by the Bee Gees and co-produced by Barry Gibb. The album reached No.3 in the UK and the Top 30 in the US where it was certified Gold.

A year later Dolly Parton and Kenny Rogers recorded the Bee Gees-penned track "Islands in the Stream", which became a US No. 1 hit and Top 10 in the UK. Rogers' 1983 album, Eyes That See In The Dark, was written entirely by the Bee Gees and co-produced by Barry. The album was a Top 10 hit in the US and was certified Double Platinum.

The Bee Gees had greater success with the soundtrack to Staying Alive in 1983, the sequel to Saturday Night Fever. The soundtrack was certified platinum in the US, and included their Top 30 hit "The Woman in You".

Also in 1983 the band were sued by Chicago songwriter Ronald Selle, who claimed that the brothers stole melodic material from one of his songs, "Let It End", and used it in "How Deep Is Your Love". At first, the Bee Gees lost the case; one juror said that a factor in the jury's decision was the Gibbs' failure to introduce expert testimony rebutting the plaintiff's expert testimony that it was "impossible" for the two songs to have been written independently. However, the verdict was overturned a few months later.

In 1985 Diana Ross released the album Eaten Alive, written by the Bee Gees, with the title track co-written with Michael Jackson (who also performed on the track). The album was again co-produced by Barry Gibb and the single "Chain Reaction" gave Ross a UK and Australian No.1 hit.

The Bee Gees released the album E.S.P. in 1987, which sold over 3 million copies. It was their first album in six years, and their first for Warner Bros. Records. The single "You Win Again" went to No. 1 in numerous countries, including the UK,^[14] and made the Bee Gees the first group to score a UK No. 1 hit in each of three decades: the 1960s, 1970s, and 1980s.^[15] The single was a disappointment in the US, charting at No. 75, and the Bee Gees voiced their frustration over American radio stations not playing their new European hit single, an omission which the group felt led to poor sales of their current album in the States.

On 10 March 1988, younger brother Andy died, aged 30, as a result of myocarditis, an inflammation of the heart muscle due to a recent viral infection. His brothers acknowledge that Andy's past drug and alcohol use probably made his heart more susceptible to this illness. Just before Andy's death, it had been decided by the group that Andy would join them, which would have made the group a four-piece group. The Bee Gees' following album, One (1989), featured a song dedicated to Andy, "Wish You Were Here". The album also contained their first US top ten hit (No. 7) in a decade, "One". After the album's release, they embarked on their first world tour in ten years.

1990s[link]

In 1990, Polydor Records issued the box set Tales from the Brothers Gibb: A History in Song, which contained all of the group's singles (except 1981's "Living Eyes"), rare B-sides, unreleased tracks, solo material, and live performances. Many songs received new stereo mixes by Bill Inglot with some songs making their CD debut. At the time of its release, Tales was one of the first box sets issued in the music business and it was considered an honour for a group to have one. In the UK, Polydor issued a single disc hits collection from Tales called The Very Best of the Bee Gees, which contained their biggest UK hits. The album became one of their best selling albums in that country, eventually being certified Triple Platinum.

The Bee Gees in Los Angeles in 1992.

Following their next album, High Civilization (1991), which contained the UK top five hit "Secret Love", the Bee Gees went on a European tour. After the tour, Barry Gibb began to battle a serious back problem, which required surgery. In addition, he also suffered from arthritis, and at one point, it was so severe that it was doubtful that he would be able to play guitar for much longer. Also in the early 1990s, Maurice Gibb finally sought treatment for his alcoholism, which he had battled for many years, with the help of Alcoholics Anonymous.

In 1993, the group returned to the Polydor label, and released the album Size Isn't Everything, which contained the UK top five hit "For Whom the Bell Tolls". Success still eluded them in the US, however, as the first single released, "Paying the Price of Love" only managed to reach No. 74 on the Billboard Hot 100 while the parent album stalled at No. 153.

In 1997, they released the album Still Waters, which sold over four million copies, and reached No.2 in the UK (their highest album chart position there since 1979) and No.11 in the US. The album's first single, "Alone", gave them another UK Top 5 hit and a top 30 hit in the US. Still Waters would be the band's most successful US release of their post-RSO era.

At the 1997 BRIT Awards held in Earls Court, London on 24 February, the Bee Gees received the award for Outstanding Contribution to Music.^[16] On 14 November 1997, the Bee Gees performed a live concert in Las Vegas called One Night Only. The show included a performance of "Our Love (Don't Throw It All Away)" synchronised with a vocal by their deceased brother Andy and a cameo appearance by Celine Dion singing "Immortality". The CD of the performance sold over 5 million copies. The "One Night Only" name grew out of the band's declaration that, due to Barry's health issues, the Las Vegas show was to be the final live performance of their career. After the immensely positive audience response to the Vegas concert, Barry decided to continue despite the pain, and the concert expanded into their last full-blown world tour of "One Night Only" concerts.^[17] The tour included playing to 56,000 people at London's Wembley Stadium on 5 September 1998 and concluded in the newly built Olympic Stadium in Sydney, Australia on 27 March 1999 to 72,000 people.^[17]

In 1998, the group's soundtrack for Saturday Night Fever was incorporated into a stage production produced first in the West End and then on Broadway. They wrote three new songs for the adaptation. Also in 1998 the brothers recorded Ellan Vannin for Isle of Man charities. Known as the unofficial national anthem of the Isle of Man, the brothers performed the song during their world tour to reflect their pride in the place of their birth.^[18]

The Bee Gees closed the decade with what turned out to be their last full-sized concert, known as BG2K, on 31 December 1999.

2000–08: Maurice's death and hiatus[link]

In 2001, the group released what turned out to be their final album of new material as a group, This Is Where I Came In. The album was another success, reaching the Top 10 in the UK (being certified Gold), and the Top 20 in the US. The title track was also a UK Top 20 hit single. The album gave each member of the group a chance to write in his own way, as well as composing songs together. For example, Maurice's compositions and leads are the "Man in the Middle" and "Walking on Air," while Robin contributed "Déjà Vu," "Promise the Earth," and "Embrace," and Barry contributed "Loose Talk Costs Lives," "Technicolour Dreams", and "Voice in the Wilderness". The other songs are collaborative in writing and vocals. They performed many tracks from This Is Where I Came In, plus many of their biggest hits, on the live televised concert series Live by Request, shown on the A&E Network. The last concert of the Bee Gees as a trio was at the Love and Hope Ball in 2002.

Maurice, who had been the musical director of the Bee Gees during their final years as a group, died unexpectedly on 12 January 2003 at the age of 53 from a heart attack, while awaiting emergency surgery to repair a strangulated intestine.^[19] Initially, his surviving brothers announced that they intended to carry on the name "Bee Gees" in his memory. But as time passed they decided to retire the group name, leaving it to represent the three brothers together.^[20]

The same week that Maurice died, Robin's solo album Magnet was released. On 23 February 2003, the Bee Gees received the Grammy Legend Award. Barry and Robin accepted as well as Maurice's son, Adam, in a tearful ceremony.

Although there was talk of a memorial concert featuring both surviving brothers and invited guests,^[21] nothing materialised. Barry and Robin continued to work independently, and both released recordings with other artists, occasionally coming together to perform at special events.

In late 2004, Robin embarked on a solo tour of Germany, Russia and Asia. During January 2005, Barry, Robin and several legendary rock artists recorded "Grief Never Grows Old," the official tsunami relief record for the Disasters Emergency Committee. Later that year, Barry reunited with Barbra Streisand for her top-selling album Guilty Pleasures, released as Guilty Too in the UK as a sequel album to the previous Guilty. Robin continued touring in Europe. Also in 2004, Barry recorded his song "I Cannot Give You My Love" with Cliff Richard, which became a UK top 20 hit single.^[22]

In February 2006, Barry and Robin reunited on stage for a Miami charity concert to benefit the Diabetes Research Institute. It was their first public performance together since the death of brother Maurice. Barry and Robin also played at the 30th annual Prince's Trust Concert in the UK on 20 May 2006.

In October 2008, Robin performed a couple of songs in London as part of the BBC Electric Proms Saturday Night Fever performance. This involved various other performers and the BBC Concert Orchestra and was screened on the BBC and BBC interactive services.

2009–12: Return to performing and Robin's death[link]

On 1 September 2009, Barry's 63rd birthday, he, in an interview with Easy Mix radio host Tim Roxborough, mentioned on the subject of future tours that "they will be back"; but in an agreement with Warner/Rhino they would not make an announcement at that time.^[23][24] On 7 September 2009, Robin Gibb disclosed to Jonathan Agnew that he had been in touch with Barry Gibb and that they had agreed that the Bee Gees would re-form and "perform again".^[25]

Barry and Robin performed on the BBC's Strictly Come Dancing on 31 October 2009^[26] and appeared on ABC-TV's Dancing with the Stars on 17 November 2009.^[27] On 15 March 2010, Barry and Robin inducted the Swedish group ABBA into the Rock and Roll Hall of Fame.^[28] On 26 May 2010, the two made a surprise appearance on the ninth season finale of American Idol.

In October 2010, Robin Gibb was interviewed by the Daily Mail, and confirmed that the story of the Bee Gees is to be made into a Hollywood movie by Steven Spielberg. The Oscar-winning director believes the group's journey from unknowns in Manchester to worldwide fame will prove box-office gold. Robin told the Daily Mail: "The movie is going to be done by some very important people. It will be our life story. Barry and I will be involved in the technical side". One of the challenges for Spielberg will be replicating the brothers' distinctive three-part harmonies and Barry's falsetto voice. Robin said: "I'd like our original recordings to be used because it's very hard to emulate them."^[29]

On 13 February 2012, Robin joined British military trio The Soldiers for the Coming Home charity concert at the London Palladium, in support of injured servicemen. It was his first public appearance for almost five months, and his final.

On 20 November 2011 it was announced that Robin Gibb, at 61 years old, was diagnosed with liver cancer, a condition he became aware of several months earlier. He had become noticeably thinner in previous months and had to cancel several appearances due to issues with severe abdominal pain.^[30] On 14 April 2012, it was reported that Gibb had contracted pneumonia^[31] in a Chelsea hospital and was in a coma.^[32] Gibb came out of his coma on 20 April 2012.^[33] He died on 20 May 2012.^[34] With Robin's death, Barry became the last surviving Gibb brother.

Songwriting success[link]

The Bee Gees have sold in excess of 200 million records worldwide.^[35] At one point in 1978, the Gibb brothers were responsible for writing and/or performing nine of the songs in the Billboard Hot 100.^[36] In all, the Gibbs placed 13 singles onto the Hot 100 in 1978, with 12 making the Top 40. The Gibb brothers are fellows of the British Academy of Songwriters, Composers and Authors (BASCA).^[37]

At least 2,500 artists have recorded their songs.^[38] Their most popular composition is "How Deep Is Your Love", with 400 versions by other artists in existence.^[39] Among the artists who have covered their songs are Ardijah, Michael Bolton, Boyzone, Eric Clapton, Billy Corgan, Destiny's Child, Faith No More, Feist, The Flaming Lips, Al Green, Jinusean, Elton John, Tom Jones, Janis Joplin, Lulu, Elvis Presley, Nina Simone, Percy Sledge, Robert Smith, Take That, and John Frusciante (who has covered "How Deep Is Your Love" during Red Hot Chili Peppers concerts). The band's music has also been sampled by dozens of hip hop artists.

Songs written by the Gibbs, but largely better known through versions by other artists, include:

• "Ain't Nothing Gonna Keep Me From You" by Teri DeSario
• "Buried Treasure" by Kenny Rogers (backing vocals The Gatlin Brothers)
• "Chain Reaction" by Diana Ross
• "Come on Over" by Olivia Newton-John
• "Emotion" by Samantha Sang
• "Gilbert Green" by Gerry Marsden
• "Grease" by Frankie Valli
• "Guilty" and "Woman in Love" by Barbra Streisand
• "Heartbreaker" & "All the Love in the World" by Dionne Warwick
• "Hold On to My Love" by Jimmy Ruffin
• "I Will Be There" by Tina Turner
• "If I Can't Have You" by Yvonne Elliman
• "Immortality" by Celine Dion
• "Islands in the Stream" by Kenny Rogers and Dolly Parton
• "Morning of My Life" by Abi and Esther Ofarim
• "Only One Woman" by The Marbles
• "Rest Your Love on Me" by Conway Twitty
• "Sacred Trust" by One True Voice
• "Warm Ride" by Graham Bonnet

The Bee Gees' major non-UK/US breakthrough hit "Spicks and Specks"—a 1966 chart success in Australia (top five) and New Zealand (number one), and in Holland (top five) in 1967—was covered by British rock-pop band Status Quo for their 1968 debut album. And Al Green's 1972 non-single cover of the Bee Gees' massive 1971 North American number one "How Can You Mend a Broken Heart" enjoys a certainly critical and popular following, particularly in the UK.

Awards and recognition[link]

Bee Gees for the television special Billboard No. 1 Music Awards (November 1977) Top to bottom: Barry, Robin and Maurice.

Inductions[link]

• 1979 Hollywood Walk of Fame
• 1994 Songwriters Hall of Fame
• 1995 Florida's Artists Hall of Fame
• 1997 Rock and Roll Hall of Fame
• 1997 ARIA (Australian Recording Industry Association) Hall of Fame
• 2001 Vocal Group Hall of Fame
• 2004 Dance Music Hall of Fame
• 2005 London's Walk of Fame

Grammy Awards[link]

• 1978 Best Pop Vocal Performance By A Group – "How Deep Is Your Love"
• 1979 Best Pop Vocal Performance By A Duo Or Group – "Saturday Night Fever"
• 1979 Best Arrangement Of Voices – "Stayin' Alive"
• 1979 Album Of The Year – "Saturday Night Fever"
• 1979 Producer Of The Year – "Saturday Night Fever"
• 1981 Best Pop Performance By A Duo Or Group With Vocal – "Guilty" (Barry Gibb with Barbra Streisand)
• 2000 Lifetime Achievement Award
• 2003 Legend Award
• 2004 Hall Of Fame Award – "Saturday Night Fever"

World Music Awards[link]

• 1997 Legend Award

American Music Awards[link]

• 1979 Favorite Pop / Rock Band, Duo Or Group
• 1979 Favorite Soul / R&B Album – "Saturday Night Fever"
• 1980 Favorite Pop / Rock Band, Duo Or Group
• 1980 Favorite Pop / Rock Album – "Spirits Having Flown"
• 1997 International Artist Award

BRIT Awards[link]

• 1997 Outstanding Contribution To Music

BMI Awards[link]

• On 15 May 2007, the Bee Gees were named BMI Icons at the 55th annual BMI Pop Awards. Collectively, Barry, Maurice and Robin Gibb have earned 109 BMI Pop, Country and Latin Awards.^[40]

Commemorative stamps[link]

In October 1999 the Isle of Man Post Office unveiled a set of 6 stamps honouring their native sons' music. The official launch took place at the London Palladium where the stage show of Saturday Night Fever was playing. A similar launch was held in New York shortly after to coincide with the show opening across the Atlantic. The songs depicted on the stamps are "Massachusetts", "Words", "I've Gotta Get A Message To You", "Night Fever", "Stayin' Alive" and "Immortality".

Civic honours[link]

In 1978, following the success of Saturday Night Fever, and the single "Night Fever" in particular, Reubin Askew, the Governor of the US state of Florida, named the Bee Gees honorary citizens of the state, since they resided in Miami at the time.^[41]

All three brothers (including Maurice, posthumously) were appointed Commanders in the Order of the British Empire in December 2001 with the ceremony taking place at Buckingham Palace on 27 May 2004.^[42][43]

On 10 July 2009, the Isle of Man's capital bestowed the Freedom of the Borough of Douglas honour on Barry and Robin, as well as posthumously on Maurice.^[44] On 20 November 2009, Douglas Borough Council released a limited edition commemorative DVD to mark their naming as Freemen of the Borough.^[45]

Discography[link]

Studio albums[link]

Live albums[link]

Soundtrack releases[link]

Catalogue reissue[link]

The Gibbs recently gained ownership rights to their back catalogue, and set up a new distribution arrangement with Warner/Rhino/Reprise Records where they have since reissued digitally remastered versions of Saturday Night Fever, their later Bee Gees Greatest album, and a new boxed set: The Studio Albums: 1967–1968.

Additionally, more recent titles such as Still Waters and This Is Where I Came In were among the first batch of re-releases. The band's three Warner Bros. releases, E. S. P., One and High Civilisation were also made available on iTunes for the first time since the albums went out of print in North America in the mid-90s.

According to Robin Gibb's website, three more reissues were planned for the 2008 holiday season: Best of Bee Gees, Best of Bee Gees, Volume 2 and Love Songs. The double album Odessa was released on 13 January 2009 in a special 3-disc deluxe edition complete with the original red velvet cover with remastered stereo and mono versions of the album as well as alternate versions and unreleased tracks.

Since the remastered release of Odessa, Rhino has stopped reissuing original Bee Gees albums and there has not been any announcement as to when the remaining albums will be remastered.

Limited edition[link]

Ellan Vannin was recorded in 1997 as a 1,000 quantity limited edition single for Isle of Man charities. The song was featured in the Bee Gees World Tour and on ITV's "An Evening With ..." but to date has not been released generally. The single was subsequently also available as part of the 1999 Bee Gees Stamp issue.

50th anniversary collections[link]

In conjunction with the 50th anniversary of the Bee Gees (when they started calling themselves "Bee Gees" in 1959), Rhino Records have released two new collections. Mythology is a four-disc collection highlighting each brother, including Andy, with tracks personally selected by Barry, Robin, Maurice's wife Yvonne (with his children Adam and Samantha), and Andy's daughter Peta. Maurice's disc contains two unreleased tracks called "Angel Of Mercy" and "The Bridge". Andy's disc contains the unreleased track "Arrow Through The Heart". Mythology also features a scrapbook of family photos, many never-before published, along with tributes from artists such as George Martin, Brian Wilson, Elton John, Graham Nash and the band's longtime manager Robert Stigwood.

The second collection, The Ultimate Bee Gees, is a more modest two-disc 40-track collection highlighting their biggest hits and includes a bonus DVD of unreleased videos, previously unreleased television appearances, live performances, and promo videos. Each disc is themed, with the first disc being the more upbeat songs called "A Night Out" and the second disc being more ballad-focused called "A Night In".^[46]

Band instrumentalists[link]

Barry Gibb played rhythm guitar.

During the early 1970s, Robin Gibb played piano and violin occasionally, but most of the time he only sang. Although he kept on playing strings and keyboards privately, he had not played any instrument on stage since mid-'70s.

Maurice Gibb played bass guitar, rhythm and lead guitar, piano, organ, harpsichord, electric piano, mellotron, and electronic keyboards, synthesisers and drum tracks. From 1966 to 1972 he played multiple instruments on many records. During the late 1970s he played mainly bass guitar. From about 1986 onward he usually played keyboards and guitars. Maurice was credited by the brothers as being the most technologically savvy member of the band, and had built his own home studio. The bootleg CD ESP Demos allegedly includes rough versions of tracks from the album of the same name that were recorded at that studio.^{[citation needed]}

These musicians were considered members of the band:^{[citation needed]}

• Colin Petersen – drums (1967–1969)
• Vince Melouney – lead guitar (1967–1968)
• Geoff Bridgford – drums (1969–1972)
• Alan Kendall – lead guitar (1971–1980, 1987–2001)
• Dennis Bryon – drums (1974–1980)
• Blue Weaver – keyboards (1975–1980)

Filmography[link]

• 1969: Cucumber Castle
• 1978: Sgt. Pepper's Lonely Hearts Club Band
• 1979: The Bee Gees Special
• 1990: One For All Tour
• 1997: Keppel Road
• 1998: One Night Only
• 2001: This Is Where I Came In
• 2002: Live By Request
• 2010: In Our Own Time