The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in  or one mile in . It depends strongly on temperature as well as the medium through which a sound wave is propagating. At , the speed of sound in air is about . More simply, the speed of sound is how fast vibrations travel.

The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior.
In colloquial speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids. For example, while sound travels at  in air, it travels at  in water (almost 4.3 times as fast) and at  in iron (almost 15 times as fast). In an exceptionally stiff material such as diamond, sound travels at , about 35 times its speed in air and about the fastest it can travel under normal conditions.
In theory, the speed of sound is actually the speed of vibrations.
Sound waves in solids are composed of compression waves (just as in gases and liquids) and a different type of sound wave called a shear wave, which occurs only in solids. Shear waves in solids usually travel at different speeds than compression waves, as exhibited in seismology. The speed of compression waves in solids is determined by the medium's compressibility, shear modulus, and density. The speed of shear waves is determined only by the solid material's shear modulus and density.

In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure for the speed of an object moving through the medium. The ratio of the speed of an object to the speed of sound (in the same medium) is called the object's Mach number. Objects moving at speeds greater than the speed of sound () are said to be traveling at supersonic speeds.

History

Sir Isaac Newton's 1687 Principia includes a computation of the speed of sound in air as . This is too low by about 15%. The discrepancy is due primarily to neglecting the (then unknown) effect of rapidly-fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiabatic process, not an isothermal process). This error was later rectified by Laplace.

During the 17th century there were several attempts to measure the speed of sound accurately, including attempts by Marin Mersenne in 1630 (1,380 Parisian feet per second), Pierre Gassendi in 1635 (1,473 Parisian feet per second) and Robert Boyle (1,125 Parisian feet per second). In 1709, the Reverend William Derham, Rector of Upminster, published a more accurate measure of the speed of sound, at 1,072 Parisian feet per second. (The Parisian foot was 325 mm. This is longer than the standard "international foot" in common use today, which was officially defined in 1959 as 304.8 mm, making the speed of sound at  1,055 Parisian feet per second).

Derham used a telescope from the tower of the church of St. Laurence, Upminster to observe the flash of a distant shotgun being fired, and then measured the time until he heard the gunshot with a half-second pendulum. Measurements were made of gunshots from a number of local landmarks, including North Ockendon church. The distance was known by triangulation, and thus the speed that the sound had travelled was calculated.

Basic concepts
The transmission of sound can be illustrated by using a model consisting of an array of spherical objects interconnected by springs.

In real material terms, the spheres represent the material's molecules and the springs represent the bonds between them. Sound passes through the system by compressing and expanding the springs, transmitting the acoustic energy to neighboring spheres. This helps transmit the energy in-turn to the neighboring sphere's springs (bonds), and so on.

The speed of sound through the model depends on the stiffness/rigidity of the springs, and the mass of the spheres. As long as the spacing of the spheres remains constant, stiffer springs/bonds transmit energy more quickly, while more massive spheres transmit energy more slowly.

In a real material, the stiffness of the springs is known as the "elastic modulus", and the mass corresponds to the material density. Sound will travel more slowly in spongy materials and faster in stiffer ones. Effects like dispersion and reflection can also be understood using this model.

For instance, sound will travel 1.59 times faster in nickel than in bronze, due to the greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen (protium) gas than in heavy hydrogen (deuterium) gas, since deuterium has similar properties but twice the density. At the same time, "compression-type" sound will travel faster in solids than in liquids, and faster in liquids than in gases, because the solids are more difficult to compress than liquids, while liquids, in turn, are more difficult to compress than gases.

Some textbooks mistakenly state that the speed of sound increases with density. This notion is illustrated by presenting data for three materials, such as air, water, and steel and noting that the speed of sound is higher in the denser materials.  But the example fails to take into account that the materials have vastly different compressibility, which more than makes up for the differences in density, which would slow wave speeds in the denser materials.  An illustrative example of the two effects is that sound travels only 4.3 times faster in water than air, despite enormous differences in compressibility of the two media. The reason is that the greater density of water, which works to slow sound in water relative to the air, nearly makes up for the compressibility differences in the two media.

A practical example can be observed in Edinburgh when the "One o'Clock Gun" is fired at the eastern end of Edinburgh Castle. Standing at the base of the western end of the Castle Rock, the sound of the Gun can be heard through the rock, slightly before it arrives by the air route, partly delayed by the slightly longer route. It is particularly effective if a multi-gun salute such as for "The Queen's Birthday" is being fired.

Compression and shear waves

In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression waves are supported in gases and liquids. An additional type of wave, the transverse wave, also called a shear wave, occurs only in solids because only solids support elastic deformations. It is due to elastic deformation of the medium perpendicular to the direction of wave travel; the direction of shear-deformation is called the "polarization" of this type of wave. In general, transverse waves occur as a pair of orthogonal polarizations.

These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake, where sharp compression waves arrive first and rocking transverse waves seconds later.

The speed of a compression wave in a fluid is determined by the medium's compressibility and density. In solids, the compression waves are analogous to those in fluids, depending on compressibility and density, but with the additional factor of shear modulus which affects compression waves due to off-axis elastic energies which are able to influence effective tension and relaxation in a compression. The speed of shear waves, which can occur only in solids, is determined simply by the solid material's shear modulus and density.

Equations
The speed of sound in mathematical notation is conventionally represented by c, from the Latin celeritas meaning "velocity".

For fluids in general, the speed of sound c is given by the Newton–Laplace equation:

where
  is a coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases);
  is the density.

Note that , where  is the pressure and the derivative is taken isentropically, that is, at constant entropy s. This is because a sound wave travels so fast that its propagation can be approximated as an adiabatic process.

Thus, the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material and decreases with an increase in density. For ideal gases, the bulk modulus K is simply the gas pressure multiplied by the dimensionless adiabatic index, which is about 1.4 for air under normal conditions of pressure and temperature.

For general equations of state, if classical mechanics is used, the speed of sound c can be derived as follows:

Consider the sound wave propagating at speed  through a pipe aligned with the  axis and with a cross-sectional area of . In time interval  it moves length . In steady state, the mass flow rate  must be the same at the two ends of the tube, therefore the mass flux  is constant and . Per Newton's second law, the pressure-gradient force provides the acceleration:

And therefore:

If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations.

In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO2 which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies ().

In a dispersive medium, the speed of sound is a function of sound frequency, through the dispersion relation. Each frequency component propagates at its own speed, called the phase velocity, while the energy of the disturbance propagates at the group velocity. The same phenomenon occurs with light waves; see optical dispersion for a description.

Dependence on the properties of the medium
The speed of sound is variable and depends on the properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with the addition of a dependence on compressibility.

In fluids, only the medium's compressibility and density are the important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrated in the hot chocolate effect.

In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to the temperature and molecular weight, thus making only the completely independent properties of temperature and molecular structure important (heat capacity ratio may be determined by temperature and molecular structure, but simple molecular weight is not sufficient to determine it).

Sound propagates faster in low molecular weight gases such as helium than it does in heavier gases such as xenon. For monatomic gases, the speed of sound is about 75% of the mean speed that the atoms move in that gas.

For a given ideal gas the molecular composition is fixed, and thus the speed of sound depends only on its temperature. At a constant temperature, the gas pressure has no effect on the speed of sound, since the density will increase, and since pressure and density (also proportional to pressure) have equal but opposite effects on the speed of sound, and the two contributions cancel out exactly. In a similar way, compression waves in solids depend both on compressibility and density—just as in liquids—but in gases the density contributes to the compressibility in such a way that some part of each attribute factors out, leaving only a dependence on temperature, molecular weight, and heat capacity ratio which can be independently derived from temperature and molecular composition (see derivations below). Thus, for a single given gas (assuming the molecular weight does not change) and over a small temperature range (for which the heat capacity is relatively constant), the speed of sound becomes dependent on only the temperature of the gas.

In non-ideal gas behavior regimen, for which the Van der Waals gas equation would be used, the proportionality is not exact, and there is a slight dependence of sound velocity on the gas pressure.

Humidity has a small but measurable effect on the speed of sound (causing it to increase by about 0.1%–0.6%), because oxygen and nitrogen molecules of the air are replaced by lighter molecules of water. This is a simple mixing effect.

Altitude variation and implications for atmospheric acoustics

In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see  below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature.

Since temperature (and thus the speed of sound) decreases with increasing altitude up to , sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. The decrease of the speed of sound with height is referred to as a negative sound speed gradient.

However, there are variations in this trend above . In particular, in the stratosphere above about , the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer. This produces a positive speed of sound gradient in this region. Still another region of positive gradient occurs at very high altitudes, in the thermosphere above .

Details

Speed of sound in ideal gases and air

For an ideal gas, K (the bulk modulus in equations above, equivalent to C, the coefficient of stiffness in solids) is given by

Thus, from the Newton–Laplace equation above, the speed of sound in an ideal gas is given by

where
 γ is the adiabatic index also known as the isentropic expansion factor. It is the ratio of the specific heat of a gas at constant pressure to that of a gas at constant volume () and arises because a classical sound wave induces an adiabatic compression, in which the heat of the compression does not have enough time to escape the pressure pulse, and thus contributes to the pressure induced by the compression;
 p is the pressure;
 ρ is the density.

Using the ideal gas law to replace p with nRT/V, and replacing ρ with nM/V, the equation for an ideal gas becomes

where
 cideal is the speed of sound in an ideal gas;
 R is the molar gas constant;
 k is the Boltzmann constant;
 γ (gamma) is the adiabatic index. At room temperature, where thermal energy is fully partitioned into rotation (rotations are fully excited) but quantum effects prevent excitation of vibrational modes, the value is  for diatomic gases (such as oxygen and nitrogen), according to kinetic theory. Gamma is actually experimentally measured over a range from 1.3991 to 1.403 at , for air. Gamma is exactly  for monatomic gases (such as argon) and it is  for triatomic molecule gases that, like , are not co-linear (a co-linear triatomic gas such as  is equivalent to a diatomic gas for our purposes here);
 T is the absolute temperature;
 M is the molar mass of the gas. The mean molar mass for dry air is about ;
 n is the number of moles;
 m is the mass of a single molecule.

This equation applies only when the sound wave is a small perturbation on the ambient condition, and the certain other noted conditions are fulfilled, as noted below. Calculated values for cair have been found to vary slightly from experimentally determined values.

Newton famously considered the speed of sound before most of the development of thermodynamics and so incorrectly used isothermal calculations instead of adiabatic. His result was missing the factor of γ but was otherwise correct.

Numerical substitution of the above values gives the ideal gas approximation of sound velocity for gases, which is accurate at relatively low gas pressures and densities (for air, this includes standard Earth sea-level conditions). Also, for diatomic gases the use of  requires that the gas exists in a temperature range high enough that rotational heat capacity is fully excited (i.e., molecular rotation is fully used as a heat energy "partition" or reservoir); but at the same time the temperature must be low enough that molecular vibrational modes contribute no heat capacity (i.e., insignificant heat goes into vibration, as all vibrational quantum modes above the minimum-energy-mode have energies that are too high to be populated by a significant number of molecules at this temperature). For air, these conditions are fulfilled at room temperature, and also temperatures considerably below room temperature (see tables below). See the section on gases in specific heat capacity for a more complete discussion of this phenomenon.

For air, we introduce the shorthand

In addition, we switch to the Celsius temperature , which is useful to calculate air speed in the region near 0 °C (273 K). Then, for dry air,

Substituting numerical values

and using the ideal diatomic gas value of , we have

Finally, Taylor expansion of the remaining square root in  yields

A graph comparing results of the two equations is to the right, using the slightly more accurate value of  for the speed of sound at .

Effects due to wind shear
The speed of sound varies with temperature. Since temperature and sound velocity normally decrease with increasing altitude, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. Wind shear of 4 m/(s · km) can produce refraction equal to a typical temperature lapse rate of . Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind. This downwind refraction effect occurs because there is a wind gradient; the fact that sound is carried along by the wind is not important.

For sound propagation, the exponential variation of wind speed with height can be defined as follows:

where
 U(h) is the speed of the wind at height h;
 ζ is the exponential coefficient based on ground surface roughness, typically between 0.08 and 0.52;
 dU/dH(h) is the expected wind gradient at height h.

In the 1862 American Civil War Battle of Iuka, an acoustic shadow, believed to have been enhanced by a northeast wind, kept two divisions of Union soldiers out of the battle, because they could not hear the sounds of battle only  (six miles) downwind.

Tables
In the standard atmosphere:
 T0 is  (= ), giving a theoretical value of  (=  =  =  = ). Values ranging from 331.3 to 331.6 m/s may be found in reference literature, however;
 T20 is  (=  = ), giving a value of  (=  =  =  = );
 T25 is  (=  = ), giving a value of  (=  =  =  = ).

In fact, assuming an ideal gas, the speed of sound c depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the speed of sound using the standard atmosphere—actual conditions may vary.

Given normal atmospheric conditions, the temperature, and thus speed of sound, varies with altitude:

Effect of frequency and gas composition

General physical considerations
The medium in which a sound wave is travelling does not always respond adiabatically, and as a result, the speed of sound can vary with frequency.

The limitations of the concept of speed of sound due to extreme attenuation are also of concern. The attenuation which exists at sea level for high frequencies applies to successively lower frequencies as atmospheric pressure decreases, or as the mean free path increases. For this reason, the concept of speed of sound (except for frequencies approaching zero) progressively loses its range of applicability at high altitudes. The standard equations for the speed of sound apply with reasonable accuracy only to situations in which the wavelength of the sound wave is considerably longer than the mean free path of molecules in a gas.

The molecular composition of the gas contributes both as the mass (M) of the molecules, and their heat capacities, and so both have an influence on speed of sound. In general, at the same molecular mass, monatomic gases have slightly higher speed of sound (over 9% higher) because they have a higher γ (...) than diatomics do (). Thus, at the same molecular mass, the speed of sound of a monatomic gas goes up by a factor of

This gives the 9% difference, and would be a typical ratio for speeds of sound at room temperature in helium vs. deuterium, each with a molecular weight of 4. Sound travels faster in helium than deuterium because adiabatic compression heats helium more since the helium molecules can store heat energy from compression only in translation, but not rotation. Thus helium molecules (monatomic molecules) travel faster in a sound wave and transmit sound faster. (Sound travels at about 70% of the mean molecular speed in gases; the figure is 75% in monatomic gases and 68% in diatomic gases).

Note that in this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas give the gas additional ways to store heat which do not affect temperature, and thus do not affect molecular velocity and sound velocity. Thus, the effect of higher temperatures and vibrational heat capacity acts to increase the difference between the speed of sound in monatomic vs. polyatomic molecules, with the speed remaining greater in monatomics.

Practical application to air
By far, the most important factor influencing the speed of sound in air is temperature. The speed is proportional to the square root of the absolute temperature, giving an increase of about  per degree Celsius. For this reason, the pitch of a musical wind instrument increases as its temperature increases.

The speed of sound is raised by humidity. The difference between 0% and 100% humidity is about  at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature.

The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about  as the frequency rises from  to . For audible frequencies above  it is relatively constant. Standard values of the speed of sound are quoted in the limit of low frequencies, where the wavelength is large compared to the mean free path.

As shown above, the approximate value 1000/3 = 333.33... m/s is exact a little below 5 °C and is a good approximation for all "usual" outside temperatures (in temperate climates, at least), hence the usual rule of thumb to determine how far lightning has struck: count the seconds from the start of the lightning flash to the start of the corresponding roll of thunder and divide by 3: the result is the distance in kilometers to the nearest point of the lightning bolt.

Mach number

Mach number, a useful quantity in aerodynamics, is the ratio of air speed to the local speed of sound. At altitude, for reasons explained, Mach number is a function of temperature.
Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. The assumption is that a particular pressure represents a particular altitude and, therefore, a standard temperature. Aircraft flight instruments need to operate this way because the stagnation pressure sensed by a Pitot tube is dependent on altitude as well as speed.

Experimental methods
A range of different methods exist for the measurement of sound in air.

The earliest reasonably accurate estimate of the speed of sound in air was made by William Derham and acknowledged by Isaac Newton. Derham had a telescope at the top of the tower of the Church of St Laurence in Upminster, England. On a calm day, a synchronized pocket watch would be given to an assistant who would fire a shotgun at a pre-determined time from a conspicuous point some miles away, across the countryside. This could be confirmed by telescope. He then measured the interval between seeing gunsmoke and arrival of the sound using a half-second pendulum. The distance from where the gun was fired was found by triangulation, and simple division (distance/time) provided velocity. Lastly, by making many observations, using a range of different distances, the inaccuracy of the half-second pendulum could be averaged out, giving his final estimate of the speed of sound. Modern stopwatches enable this method to be used today over distances as short as 200–400 metres, and not needing something as loud as a shotgun.

Single-shot timing methods
The simplest concept is the measurement made using two microphones and a fast recording device such as a digital storage scope. This method uses the following idea.

If a sound source and two microphones are arranged in a straight line, with the sound source at one end, then the following can be measured:
 The distance between the microphones (), called microphone basis.
 The time of arrival between the signals (delay) reaching the different microphones ().

Then .

Other methods
In these methods, the time measurement has been replaced by a measurement of the inverse of time (frequency).

Kundt's tube is an example of an experiment which can be used to measure the speed of sound in a small volume. It has the advantage of being able to measure the speed of sound in any gas. This method uses a powder to make the nodes and antinodes visible to the human eye. This is an example of a compact experimental setup.

A tuning fork can be held near the mouth of a long pipe which is dipping into a barrel of water. In this system it is the case that the pipe can be brought to resonance if the length of the air column in the pipe is equal to  where n is an integer. As the antinodal point for the pipe at the open end is slightly outside the mouth of the pipe it is best to find two or more points of resonance and then measure half a wavelength between these.

Here it is the case that v = fλ.

High-precision measurements in air
The effect of impurities can be significant when making high-precision measurements. Chemical desiccants can be used to dry the air, but will, in turn, contaminate the sample. The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high-precision measurements are performed with air free of carbon dioxide rather than with natural air. A 2002 review found that a 1963 measurement by Smith and Harlow using a cylindrical resonator gave "the most probable value of the standard speed of sound to date." The experiment was done with air from which the carbon dioxide had been removed, but the result was then corrected for this effect so as to be applicable to real air. The experiments were done at  but corrected for temperature in order to report them at . The result was  for dry air at STP, for frequencies from  to .

Non-gaseous media

Speed of sound in solids

Three-dimensional solids
In a solid, there is a non-zero stiffness both for volumetric deformations and shear deformations. Hence, it is possible to generate sound waves with different velocities dependent
on the deformation mode. Sound waves generating volumetric deformations (compression) and shear deformations (shearing) are called pressure waves (longitudinal waves) and shear waves (transverse waves), respectively. In earthquakes, the corresponding seismic waves are called P-waves (primary waves) and S-waves (secondary waves), respectively. The sound velocities of these two types of waves propagating in a homogeneous 3-dimensional solid are respectively given by

where
 K is the bulk modulus of the elastic materials;
 G is the shear modulus of the elastic materials;
 E is the Young's modulus;
 ρ is the density;
 ν is Poisson's ratio.

The last quantity is not an independent one, as . Note that the speed of pressure waves depends both on the pressure and shear resistance properties of the material, while the speed of shear waves depends on the shear properties only.

Typically, pressure waves travel faster in materials than do shear waves, and in earthquakes this is the reason that the onset of an earthquake is often preceded by a quick upward-downward shock, before arrival of waves that produce a side-to-side motion. For example, for a typical steel alloy, ,  and , yielding a compressional speed csolid,p of . This is in reasonable agreement with csolid,p measured experimentally at  for a (possibly different) type of steel. The shear speed csolid,s is estimated at  using the same numbers.

Speed of sound in semiconductor solids can be very sensitive to the amount of electronic dopant in them.

One-dimensional solids
The speed of sound for pressure waves in stiff materials such as metals is sometimes given for "long rods" of the material in question, in which the speed is easier to measure. In rods where their diameter is shorter than a wavelength, the speed of pure pressure waves may be simplified and is given by:

where  is Young's modulus. This is similar to the expression for shear waves, save that Young's modulus replaces the shear modulus. This speed of sound for pressure waves in long rods will always be slightly less than the same speed in homogeneous 3-dimensional solids, and the ratio of the speeds in the two different types of objects depends on Poisson's ratio for the material.

Speed of sound in liquids

In a fluid, the only non-zero stiffness is to volumetric deformation (a fluid does not sustain shear forces).

Hence the speed of sound in a fluid is given by

where  is the bulk modulus of the fluid.

Water
In fresh water, sound travels at about  at  (see the External Links section below for online calculators). Applications of underwater sound can be found in sonar, acoustic communication and acoustical oceanography.

Seawater

In salt water that is free of air bubbles or suspended sediment, sound travels at about  ( at , 10°C and 3% salinity by one method). The speed of sound in seawater depends on pressure (hence depth), temperature (a change of  ~ ), and salinity (a change of 1‰ ~ ), and empirical equations have been derived to accurately calculate the speed of sound from these variables. Other factors affecting the speed of sound are minor. Since in most ocean regions temperature decreases with depth, the profile of the speed of sound with depth decreases to a minimum at a depth of several hundred metres. Below the minimum, sound speed increases again, as the effect of increasing pressure overcomes the effect of decreasing temperature (right). For more information see Dushaw et al.

An empirical equation for the speed of sound in sea water is provided by Mackenzie:

where
 T is the temperature in degrees Celsius;
 S is the salinity in parts per thousand;
 z is the depth in metres.

The constants a1, a2, ..., a9 are

with check value  for , , . This equation has a standard error of  for salinity between 25 and 40 ppt. See  for an online calculator.

(Note: The Sound Speed vs. Depth graph does not correlate directly to the MacKenzie formula.
This is due to the fact that the temperature and salinity varies at different depths.
When T and S are held constant, the formula itself is always increasing with depth.)

Other equations for the speed of sound in sea water are accurate over a wide range of conditions, but are far more complicated, e.g., that by V. A. Del Grosso and the Chen-Millero-Li Equation.

Speed of sound in plasma
The speed of sound in a plasma for the common case that the electrons are hotter than the ions (but not too much hotter) is given by the formula (see here)

where
 mi is the ion mass;
 μ is the ratio of ion mass to proton mass ;
 Te is the electron temperature;
 Z is the charge state;
 k is Boltzmann constant;
 γ is the adiabatic index.

In contrast to a gas, the pressure and the density are provided by separate species: the pressure by the electrons and the density by the ions. The two are coupled through a fluctuating electric field.

Mars
The speed of sound on Mars varies as a function of frequency. Higher frequencies travel faster than lower frequencies. Higher frequency sound from lasers travels at , while low frequency sound topped out at .

Gradients

When sound spreads out evenly in all directions in three dimensions, the intensity drops in proportion to the inverse square of the distance. However, in the ocean, there is a layer called the 'deep sound channel' or SOFAR channel which can confine sound waves at a particular depth.

In the SOFAR channel, the speed of sound is lower than that in the layers above and below. Just as light waves will refract towards a region of higher refractive index, sound waves will refract towards a region where their speed is reduced. The result is that sound gets confined in the layer, much the way light can be confined to a sheet of glass or optical fiber. Thus, the sound is confined in essentially two dimensions. In two dimensions the intensity drops in proportion to only the inverse of the distance. This allows waves to travel much further before being undetectably faint.

A similar effect occurs in the atmosphere. Project Mogul successfully used this effect to detect a nuclear explosion at a considerable distance.

See also
 Acoustoelastic effect
 Elastic wave
 Second sound
 Sonic boom
 Sound barrier
 Speeds of sound of the elements
 Underwater acoustics
 Vibrations

References

External links
 Speed of Sound Calculator
 Calculation: Speed of Sound in Air and the Temperature
 Speed of sound: Temperature Matters, Not Air Pressure
 Properties of the U.S. Standard Atmosphere 1976
 The Speed of Sound
 How to Measure the Speed of Sound in a Laboratory
 Did Sound Once Travel at Light Speed?
 Acoustic Properties of Various Materials Including the Speed of Sound
 Discovery of Sound in the Sea (uses of sound by humans and other animals)

Fluid dynamics
Aerodynamics
Acoustics
Sound
Sound measurements
Physical quantities
Chemical properties
Velocity
Temporal rates

Speed of sound


Swami Sadananda Das (, ; 1908–1977) was born as Ernst-Georg Schulze in Germany. He met Swami Bhakti Hridaya Bon, a disciple of Hindu spiritual reformer Bhaktisiddhanta Sarasvati Thakura. Sadananda received diksa or formal initiation into the Gaudiya Vaishnava tradition through Swami Bon from Sarasvati, and later received the name Sadananda Das by Sarasvati directly after he had joined the Gaudiya Mission in Calcutta, India. He was one of the first known individuals who was not of Asian origin to embrace the Gaudiya Vaishnava tradition.

Life of Svami Sadananda Dasa
Sadananda was born in Germany in 1908. In the early 1930s, he became a disciple of Shrila Bhaktisiddhanta Sarasvati, a prominent guru and spiritual reformer of Gaudiya Vaishnavism in the early 20th century in India. First, though, Sadananda came in contact with Swami Hridaya Bon Maharaja, a disciple of Bhaktisiddhanta, when the latter visited The State Picture Gallery in Berlin, Germany, in 1933 during his missionary activities in Europe. In 1934 Sadananda then moved to London, where the Indian monks of the Gaudiya Mission had established a centre, and where he soon, in the name of Bhaktisiddhanta Sarasvati, became initiated by Swami Hridaya Bon Maharaja and Swami Bhakti Pradip Tirtha Maharaja. In 1935, he eventually travelled with Swami Bon to India, where Sarasvati gave him his spiritual name Sadananda Das. After his guru's death in 1937, Sadananda worked independently of organizations, devoting himself to study the holy texts of the Hindus.

While travelling through India from the Himalayas to the very South and back between 1938 and 1939, Sadananda met several saints, scholars and travellers. Among those was the indologist, anthroposophist, author and Far East traveler Hans-Hasso Veltheim-Ostrau who reports their meeting 1938 in the Himalayas in his diaries from that time. In February 1939, during Sadananda's travels through South India, he met the saint Swami Ramdas in his Ashram in Kanhangad, Kerala. Ramdas mentions this meeting in his work "In the Vision of God" and describes him as follows: "Sadhu Sadananda had been, it appears a Professor in a German University and was a man of great learning and attainments. But he was found to be very simply in his nature and his ways. In fact, we loved him at first sight."

During the Second World War (1939-1945) Sadananda was held in a British internment camp in Dehra Dun, India, where he met the Austrian poet Walther Eidlitz (Vamandas), who in the course of their imprisonment became his good friend and disciple. Eidlitz recounts these events in his autobiographical work "Unknown India". In 1954, Sadananda received sannyasa, i.e. he entered the stage of a mendicant, from Swami Satyabastabya Brajabasi (Baraswami), who belonged to the Gaudiya Math in Benares, becoming Swami Sadananda Das. In 1961 Sadananda returned to Europe. There he stayed until his demise in 1977, teaching bhakti yoga to a small circle of Swedish, German and Swiss friends and translating Vaishnava texts from Sanskrit and Bengali into German. He thereby assisted his disciple Walther Eidlitz with his publications, lectures and courses. Their main common work is Walther Eidlitz' book on Krishna Caitanya for which Sadananda provided the translations from the Sanskrit and Bengali sources.

Works by Svami Sadananda Dasa

 Svami Sadananda Dasa (2014): Krishna's Damodara Lila. Rendering based on passages from the Shrimad-Bhagavatam, Gopala-Campuh and Ananda-Vrindavana-Campuh. Translated into English by Kid Samuelsson and Bengt Lundborg from Svami Sadananda Dasa's German original "Die Damodara-Lila Krishna's".
 Svami Sadananda Dasa (2015): Tender as a Flower – Hard as a Thunderbolt. Words of Truth and Love. Into English by Kid Samuelsson, Bengt Lundborg and Katrin Stamm.
 Svami Sadananda Dasa (1935): "Sunder Warumbe". The Harmonist. Vol. XXXII, No. 7, pp. 154–167.
 Svami Sadananda Dasa (1936): "Society – Community – Math". The Harmonist. Vol. XXXII. No.14, pp. 329–332.
 Svami Sadananda Dasa (1936): "Sub specie aeternitatis – Spiritual View". The Harmonist, Vol. XXXII, No. 15, pp. 343–351.
 Svami Sadananda Dasa (1936): "Buddhism – Philosophy or Religion". The Harmonist. Vol. XXXII. No. 16, pp. 361–368, 385-390.

Footnotes

References

 Bon Maharaja, Tridandi Swami Hridaya (1933), My lectures in England and Germany. Vrindaban and Calcutta: Messers N. K. Banerjee.
 Eidlitz, Walther (1952). Unknown India. A Pilgrimage into a forgotten World. New York: Rider & Company.
 Eidlitz, Walther (1968). Krishna-Caitanya. Sein Leben und Seine Lehre. Stockholm: Almkvist & Wiksell.
 Ramdas, Swami (1940). In the Vision of God. Kanhangad: Anandashram.

 Sardella, Ferdinando (2010). Bhaktisiddhanta Sarasvati. The Context and Significance of a Modern Hindu Personalist. Gothenburg: University of Gothenburg.
 Stamm, Katrin (2017), Be Careful with Bhakti or Why the Guru withdraws: The Unconventional Life and Teachings of Svami Sadananda Dasa. Journal of Vaishnava Studies. Spring 2017, Vol 25, p. 131-150.

External links

 Facebook page led by disciples

1908 births
1977 deaths
Gaudiya religious leaders
German religious leaders
German Hindus
20th-century Hindu philosophers and theologians
Converts to Hinduism
20th-century Hindu religious leaders

Sadananda Das


Yo! MTV Raps was an American two-hour television music video program, which first aired on MTV Europe from 1987 to mid-90s and on MTV US from August 1988 to August 1995. The American version of the program (created by Ted Demme and Peter Dougherty) was the first hip hop music show on the network, and was based on the original MTV Europe show, which first aired one year before the American version. Yo! MTV Raps produced a mix of rap videos, interviews with rap stars, live in-studio performances (on Fridays), and comedy. The show also yielded a Brazilian version called Yo! MTV and broadcast by MTV Brasil from 1990 to 2005.

Hosts
The U.S. version was originally hosted by Fab 5 Freddy. Later, the show's main host was Doctor Dré and Demme's high school friend, Ed Lover who both hosted together on weekdays. Soon they were joined by Doctor Dre's Original Concept group member T Money. Fab 5 Freddy proceeded to host on weekends. The original line-up of the show, starring only Fab as the host, premiered on MTV on August 6, 1988.

On the weekday version dubbed, Yo! MTV Raps Today (which debuted on March 13, 1989), Ed Lover created his own dance called the Ed Lover Dance (which was typically featured on Wednesdays) that became somewhat popular in the 1990s. The Ed Lover Dance was performed to the track "The 900 Number" by The 45 King.

History
In 1987, French journalist and producer Sophie Bramly developed and hosted the program Yo! for the then-nascent MTV Europe, with Afrika Bambaataa as the first guest. Later N.W.A, Public Enemy, LL Cool J, Ice-T, De La Soul, Eric B. & Rakim, EPMD or Ultramagnetic MCs were invited. The year after that, Run-DMC hosted the pilot episode in the US, with DJ Jazzy Jeff & the Fresh Prince as the program's first guests and Eric B. & Rakim's video for the title track of the album Follow the Leader as the first video shown on the program. The pilot was one of the highest rated programs to ever air on MTV at that point, with only the Video Music Awards and Live Aid receiving greater ratings.

Shinehead's "Chain Gang" was the first video to be shown during a regular-season episode.  Meanwhile, Ice-T's "High Rollers" was the first video to be played during the weekday show. The classic Yo! MTV Raps logo was created by early graffiti writer, Dr. Revolt. The animated show open was produced by Nigel Cox-Hagen and animated by Beau Tardy.

Yo! MTV Raps and the spread of hip-hop
The advent of Yo! MTV Raps in the late 1980s was crucial to spreading hip-hop around the world. Through MTV Europe, MTV Asia, and MTV Latino, African-American and Latino style and sound became instantly available to millions of people across the globe, helping to create a worldwide appreciation and interest in the hip-hop scene, which is something that was celebrated on the Yo! MTV Raps 20th anniversary.

Rivalry
Although Video Music Box is often considered the first contender, in 1989, former rival BET created competition by premiering Rap City . The show was the longest-running hip-hop program because of its 19-year run (ending in 2009). While Yo! MTV Raps, which is now discontinued, generally focused on the rap scene from the East Coast and largely popular West Coast artists, Rap City also included videos from up-and-coming underground rappers from different regions of the US.

"Down With MTV"
One of the most popular artists to be featured on Yo! MTV Raps was Naughty by Nature. When MTV started its Down With MTV''' advertising campaign in 1992, Naughty by Nature's smash hit "O.P.P." was used as the basis.

Censorship and declining popularity
The ratings fell after pulling Public Enemy's video "By the Time I Get to Arizona" in 1991, claiming it was too violent. Also, Yo! MTV Raps almost declined to air the video for Cypress Hill's "How I Could Just Kill a Man." Only after Sheri Howell, Vice President of Music and Artist Development at MTV, intervened that MTV changed their minds.

By around 1992–93, MTV aired Yo! MTV Raps only once a week, for two hours, on Fridays after midnight.

The end of Yo!Yo! MTV Raps had its series finale on August 17, 1995. Numerous high-profile names in the world of hip-hop closed the show out with a freestyle rap session, including Rakim, KRS-One, Redman, Method Man, Special Ed, Erick Sermon, Chubb Rock, Craig Mack, MC Serch of 3rd Bass, and Large Professor. Salt-N-Pepa holds the distinction of appearing on the first (technically, the first episode to feature Fab 5 Freddy) and last episodes of Yo! MTV Raps.

From 1996 to 1999, MTV repackaged it as simply Yo!, which was far more stripped-down and had a weekly slate of special guest hosts. For instance, Angie Martinez and Fatman Scoop served as its hosts. By 1998, Yo! had no guest hosts and became a one-hour program airing late Friday nights at 1 a.m. or 1:30 a.m. (Eastern Standard Time).

In 2000, MTV's outlet for hip-hop videos became Direct Effect, known since 2006 as Sucker Free. It aired three times a week at around 7:00 PM (Eastern Standard Time). It is one of the few music video outlets for MTV besides its late-night/early-morning music video rotation hours, as MTV continues to focus on non-music video programming, especially reality television shows.

RevivalsYo! MTV Raps made a comeback of sorts, after an eight-year hiatus during the Jackassworld.com: 24 Hour Takeover in February 2008. It had Steve-O (alongside Sam Maccarone) promoting his new rap album, doing freestyles, and showing his new music video. The old set was carefully recreated, with Johnny Knoxville joking that Mike Judge created a brand new Beavis & Butthead episode with them critiquing Steve-O's rap video.

20th Anniversary
In April 2008, Yo! MTV Raps celebrated its 20th anniversary by making a comeback on MTV. MTV's show Sucker Free transformed into Yo! MTV Raps and featured classic hip-hop music videos as well as current hip-hop videos. Fab 5 Freddy, Doctor Dré and Ed Lover contributed to the tribute of the show. At the end of April 2008, MTV aired Yo! countdown shows and featured the top moments from the show during its airing on MTV.

30th AnniversaryYo! MTV Raps was revived for a new generation in 2018, celebrating the 30th anniversary at Brooklyn's Barclays Center on June 1, 2018.

The live show featured Big Daddy Kane and the Juice Crew, Eric B & Rakim, Doug E. Fresh, KRS-One and Boogie Down Productions, EPMD, Flavor Flav, and many more. It also featured past hosts and DJs who helped shepherd the series, like Fab 5 Freddy, Ed Lover, Doctor Dré, T Money, Skribble, Red Alert, and Chuck Chillout. Tribute videos from artists like Eminem, Method Man, and Redman also commemorated the occasion.

Yo! MTV Raps International
In Spring 2019, Viacom International Media Networks relaunched the series with local versions in the UK, Germany, South-East Asia, and pan-African versions on MTV Base and MTV Africa. The Format and editorial of the series were headed by British TV producer Darcy Thomas. This also followed with a bi-weekly spin-off show Yo! MTV Rates hosted by Snoochie Shy and Poet, which aired in the UK and was also produced by Darcy Thomas for two seasons (16 episodes).

MTV Classic
Following the launch of MTV Classic on August 1, 2016, music video blocks have consistently aired on the network under the name Yo! Hip Hop Mix. When broadcast, however, this is merely an automated playlist of rap/hip-hop videos from the 1980s to the early 2000s.

Pluto TV
A Yo! MTV Raps channel was added to Pluto TV following Viacom's purchase of the service.

Paramount+
On February 24, 2021, it was announced that Yo! MTV Raps would be revived on ViacomCBS' streaming platform Paramount+, formerly CBS All Access. On February 17, 2022, it was announced that Conceited and DJ Diamond Kuts would host the revival. On May 2, 2022, it was announced that the revival would premiere on May 24, 2022.

References in popular culture
In the ABC sitcom-drama Doogie Howser, M.D. from around the same time, Doogie is frequently seen wearing a Yo! MTV Raps white T-shirt, among other colors.
A Magic: The Gathering podcast is named "Yo! MTG Taps", a reference to the "tapping" mechanic used in the game.
There was a set of Yo! MTV Raps trading cards which featured the various hosts of the show and many of the artists whose videos were featured on the show.
In the Ice Cube song "It Was a Good Day", the show is referenced in the lyrics "Went to Short Dog's house, they was watchin' Yo! MTV Raps".
In the Juelz Santana song "Good Times", the show is referenced in the lyrics "'Memba them ol' "Yo! MTV Raps" man, I hope they bring Yo! MTV back".

See also
 Rap City Who's the Man?''

References

External links
 Yo! MTV Raps 20th Anniversary on MTV.com
 Jump The Shark - "Yo! MTV Raps"

 VH1 Goes Inside "Yo! MTV Raps"
 Diesel Nation: Yo! MTV Raps
 Hip-Hop's Greatest TV Moments - Yo! MTV Raps

 Yo! MTV Raps England Website

1980s American music television series
1988 American television series debuts
1990s American music television series
1995 American television series endings
2020s American music television series
2022 American television series debuts
2022 American television series endings
American television series revived after cancellation
Hip hop television
MTV original programming
MTV weekday shows
Paramount+ original programming

Yo! MTV Raps


The International (TI) is an annual esports world championship for the five-on-five video game Dota 2. Produced by the game's developer Valve, the International is the final event of the Dota Pro Circuit (DPC) and consists of 20 teams: 12 based on final results from the DPC; six from North America, South America, Southeast Asia, China, Eastern Europe, and Western Europe regional leagues; and two from last-chance qualifiers. The International was first held at Gamescom in 2011 to promote the game's release. It was then held annually in Seattle, where Valve is headquartered, until it began to be hosted internationally again starting with The International 2018.

The tournament's prize pool has been crowdfunded via a battle pass system within the game since 2013, with a quarter of all revenue from it directly going towards it. Internationals have the largest single-tournament prize pool of any esport event, with largest reaching 40 million. The most recent champion is Team Spirit, who won The International 2023. OG is the only repeat winner in the tournament's history, winning The International 2018 and 2019.
The International 2023 will be held in Seattle in October 2023. The prize pool is set at $3,058,500, representing the lowest sum since 2013, when it amounted to $2,874,380.

History

Early years

Valve announced the first edition of The International on August 1, 2011. 16 teams were invited to compete in the tournament, which would also serve as the first public viewing of Dota 2. The tournament was funded by Valve, including the 1 million grand prize, with Nvidia supplying the hardware. It took place at Gamescom in Cologne from August 17–21 the same year. The tournament started with a group stage in which the winners of each of the four groups were entered into a winner's bracket, and the other teams entered the loser's bracket. The rest of the tournament was then played as a double-elimination tournament. The final of this inaugural tournament was between Ukrainian-based Natus Vincere and Chinese-based EHOME, with Natus Vincere winning the series 3–1. EHOME won 250,000, with the rest of the 14 teams splitting the remaining $350,000.

 The International as an recurring annual event was confirmed in May 2012. The International 2012 was held at the 2,500 seat Benaroya Hall in Seattle from August 31 to September 2, with teams situated in glass booths on the main stage. The total prize pool remained at $1.6 million, with $1 million for the winning team. The previous winners, Natus Vincere, were beaten 3-1 by Chinese team Invictus Gaming in the grand finals. In November 2012, Valve released a free documentary on the event that featured interviews with the teams, and following them from the preliminary stages through to the finale.

Introduction of crowdfunding

 The International 2013 was hosted again at the Benaroya Hall in Seattle from August 7–11. Sixteen teams participated, thirteen of which received direct invitations, and the final three being decided in two qualifying tournaments and a match at the start of the tournament. In May 2013, it was announced that an in-game battle pass, known as the Compendium, would be available for purchase that allowed for the tournament's prize pool to be crowdfunded. A quarter of the total revenue from the Compendium was added to the base $1.6 million prize pool. The prize pool eventually reached over $2.8 million, making it the largest prize pool in esports history at the time. KCPQ news anchor Kaci Aitchison acted as a host at the event, providing behind-the-scenes commentary and player interviews. The International 2013 was viewed by over a million concurrent viewers at its peak, via live streaming websites such as Twitch.

The International 2014 took place from July 18–21 at the KeyArena in Seattle. For the event, eleven teams would receive direct invites, with an additional four spots determined by regional qualifiers taking place between May 12–25. The sixteenth spot would be determined by a wild card qualifier between the runners-up from the regional competitions. The tickets for the event were sold out within an hour of going on sale that April. The tournament's crowdfunded prize pool again broke esport records for being the largest in history, with it totalling over $10.9 million. As a result, eight Dota 2 players became the highest earning players in esports, surpassing the top earning player at the time, Lee "Jaedong" Jae-dong of StarCraft. The event was also broadcast on ESPN networks for the first time.

Expansion
The tournament was expanded to 18 teams for The International 2017 onwards, an increase from the previous 16. The event in 2017 was also the last time it was held in Seattle, with every International since being hosted in a new country. The International 2020 was the first International to skip a year, as it was postponed due to the COVID-19 pandemic. Ahead of the event, originally scheduled to be held in Stockholm, Sweden, the Swedish Sports Federation voted to deny recognition of esports as a sporting event, making it difficult for Valve to help international players to secure travel visas for participating there. Valve later rescheduled the event and rebranded it as The International 2021, which was held at the Arena Națională in Bucharest, Romania, in October 2021. It set a record for the largest prize pool of any single esports event at $40 million.

The International 2022 increased to 20 teams and was held in Singapore in October 2022, where it was won by Tundra Esports. It was the first International to not surpass the previous one's prize pool at $18.9 million, the lowest since The International 2015. The International 2023 was hosted at Climate Pledge Arena in Seattle, which was built at the same site as KeyArena, and ran from October 27 to 29.

List of Internationals

Format

Invitations
The International features a series of tournaments before the event, known as the Dota Pro Circuit (DPC), with the top 12 ranking teams receiving direct invitations based on their final standings. Besides the directly invited DPC teams, an additional team from the Commonwealth of Independent States (CIS), China, Europe, North America, South America, and Southeast Asia regions each earn an invite by winning regional playoffs, bringing the total number of participating teams up to 18. At the International, two separate best-of-two round robin groups consisting of nine teams each are played, with lowest placed team from both at the end of the stage being eliminated. The remaining 16 teams then move on to the double elimination main event at the hosted venue, with the top four finishing teams from both groups advancing to the upper bracket, and the bottom four advancing to the lower bracket. The first round of the lower bracket is treated as single-elimination, with the loser of each match being immediately eliminated from the tournament. Every other round of both brackets is played in a best-of-three series, with the exception being the Grand Finals, which is played between the winners of the upper and lower brackets in a best-of-five series.

Prize pool
Since The International 2013, the tournament's prize pool is primarily crowdfunded through a type of in-game battle pass called the "Compendium", which raises money from players buying them to get exclusive in-game virtual goods and other bonuses. 25% of all the revenue made from yearly Compendiums go directly to the prize pool. The contribution of players from the game community is the main source of prize pool for the International. Until 2022, each iteration of The International has surpassed the previous one's prize pool. The International 2021 had the largest prize pool, awarding $40 million (£29 million) in total to participating teams.

Trophy

The Aegis of Champions is a trophy that is awarded to the champions of an International. The reverse side of it is permanently engraved with the names of each player on the winning team. The Aegis is a shield inspired by Norse and Chinese designs, with it molded in bronze and silver by the prop studio, Weta Workshop. Miniature replicas of it are also sometimes awarded to compendium owners for having a high enough level in it.

Media coverage

The primary medium for International coverage is through the video game live streaming platform Twitch, which is done by a selection of dedicated esports organizations and personnel who provide on-site commentary, analysis, match predictions, and player interviews surrounding the event in progress, similar to traditional sporting events. Multiple streams are provided in a variety of languages, mainly in English, Russian, and Chinese. The International also sometimes provides a "newcomer stream" that is dedicated to presenting games for viewers unfamiliar with the game.

Documentaries
In 2014, Valve released a free documentary, Free to Play, which followed three players during their time at the first International in 2011. In 2016, Valve began producing an episodic-based documentary series titled True Sight, considered a spiritual successor to Free to Play. Several more episodes of it have been filmed, showcasing the 2017, 2018, 2019, and 2021 tournaments.

References

External links

Recurring sporting events established in 2011

The International (Dota 2)


The term "soft ontology", coined by Eli Hirsch in 1993, refers to the embracing or reconciling of apparent ontological differences, by means of relevant distinctions and contextual analyses.

Overview
Hirsch used the term to broaden and expand on what William James discussed in his landmark 1907 work in epistemology, Pragmatism.  James gave a now famous example of  dispute over a squirrel:

The corpus of the dispute was a squirrel--a live squirrel supposed to be clinging to one side of a tree-trunk; while over against the tree's opposite side a human being was imagined to stand. This human witness tries to get sight of the squirrel by moving rapidly round the tree, but no matter how fast he goes, the squirrel moves as fast in the opposite direction, and always keeps the tree between himself and the man, so that never a glimpse of him is caught. The resultant metaphysical problem now is this: DOES THE MAN GO ROUND THE SQUIRREL OR NOT?

James' solution was that by clarifying "pragmatically" whether "around" meant traversing north/east/south/west of something versus traversing left/right/before/behind something, the dispute was readily solvable.

Hirsch actually calls James' example a "verbal" dispute and explains, at some length, the connection between verbal and soft ontological disagreements (they are, according to Hirsch, partly but not completely overlapping sets of problems).

Soft ontological dilemmas are contrasted with hard ones—those which would not admit of translation, reconciliation, or overlap, and would instead require a systematic or paradigmatic shift of one's ontology.  One can choose to construct a hard or soft ontology, depending on the flexibility one intends to obtain.

Other related terms in philosophy and in cognitive science include "ontological relativity" (as in Quine) and "cognitive relativism" (as in Jack Meiland).

Computer science (unrelated terminology)
Soft ontology, as proposed in computer science circles by Aviles et al. (2003), is a definition of a domain in terms of a flexible set of ontological dimensions. It can be regarded as a subclass of ontologies as they are conceived of in computer science, in Gruber's terms (1993) as definitions of conceptualization. Unlike standard ontologies, the approach allows the number of its constitutive concepts to increase or decrease dynamically, any subsets of the ontology to be taken into account at a time, or the order their mutual weight or priority to vary in a graded manner so as to allow different ontological perspectives.
Where conventional ontologies describe or interpret the conceptualization of a domain from a prioritized perspective, the soft ontology approach transfers the task of interpretation to the observer, user or learner, depending on the context. (see Weak ontology)

Application areas in the information sciences
The approach is particularly applicable for expert practices that intend to present raw content or data without presenting any authoritative taxonomy or categorization. It also serves to support neutrality for domains such as ethics, politics, aesthetics or philosophy, in which there may not exist a single authorized conceptualization or truth, or it may be instrumental to present a range of perspectives to the domain.
Soft ontologies also result inherently from user-defined ontology practices, such as folksonomies or tagging practices ("tagsonomies"), characteristic of many contemporary user-driven media genres.

References

Ontology (information science)

Soft ontology


Harry Gordon Selfridge, Sr. (11 January 1858 – 8 May 1947) was an American-British business owner. He founded the London-based department store Selfridges. He was one of the most respected and wealthy retail businessmen in the United Kingdom.

Early life

Selfridge was born in Ripon, Wisconsin. Selfridge was raised in Jackson, Michigan. Selfridge's parents were Robert Oliver Selfridge and his wife Lois. They had three sons. His father fought in the American Civil War. He was a major in the Union Army. After he was discharged, he did not come back to the family.

Both of Selfridge's brothers died young. His mother taught school. From the age of 10, Harry began working. He sold newspapers to help his mother. Later he stocked shelves at a dry goods store.

Career
When he was 21, Selfridge went to Chicago. He worked for Field, Leiter and Company. This later became Marshall Field's & Co. He worked there for 25 years. Selfridge started the idea of a bargain basement in a department store. Selfridge's ideas added to the success of Marshall Field & Company. When he asked Marshall Field to let him become a partner, Field was surprised, but he agreed. Field even lent him the money needed to become a partner.

After visiting England, Selfridge decided to open his own department store in London. In 1909, his store opened on Oxford Street. It brought about many changes in shopping. It is still a big store today. In fact, Selfridges & Co. was named the Best Department Store in the World in 2010 and 2012. and 2014.

Personal life
In 1890, Selfridge married Rose Buckingham. Her family was wealthy and influential. Rose was a property developer when she married. She died of the Spanish flu in 1918. Harry never married again, even though he had several girlfriends.

Death
Selfridge died of pneumonia in Putney, London, aged 89.

Writings
Selfridge wrote the book The Romance of Commerce. He used a ghostwriter to help him write it. The book was published in 1918.

References

Other websites
Selfridges
Gordon Selfridge: The Gambler
Biography from the DNB

1858 births
1947 deaths
British businesspeople
Businesspeople from Michigan
Businesspeople from Wisconsin
Deaths from pneumonia
Infectious disease deaths in England

Harry Gordon Selfridge


Robert Donald Murphy (born January 18, 1977) is a former professional gridiron football offensive lineman. He most recently played for the Toronto Argonauts of the Canadian Football League (CFL).  He played college football for Ohio State University, and was recognized as an All-American.  He was originally signed by the Kansas City Chiefs as an undrafted free agent in 2000, and has played professionally for the Frankfurt Galaxy, Chicago Enforcers, Indianapolis Colts, San Francisco 49ers and BC Lions.

Early years
Murphy was born in Buffalo, New York.  He attended Moeller High School in Cincinnati, Ohio, and played football, ice hockey, and wrestled for the Moeller Crusaders.

College career
Murphy attended Ohio State University, and was a three-year starter for the Ohio State Buckeyes football team.  He participated in the 1997 Rose Bowl and the 1998 Sugar Bowl.  He was a first-team All-American selection in 1997 and a consensus first-team All-American in 1998, and twice received first-team All-Big Ten honours.

Professional career
Murphy signed with the Cincinnati Bengals in 1999, was on the practice squad and was picked up by the Kansas City Chiefs in the last week of the 1999 season and signed to the active roster. He was allocated by the Chiefs to NFL Europe and played and started 10 games with the Frankfurt Galaxy in 2000.

He was put on the injured reserve by the Kansas City Chiefs in 2000 and was released at the end of the season. Murphy was drafted 184th overall by the Chicago Enforcers in the 2001 XFL Draft and started 11 games including their playoff game.

At the end of the XFL season Murphy signed a free agent contract with the Indianapolis Colts. Signed to active roster in week 3. But did not see any action. In 2002, he played in 10 games and 1 playoff game against the NY Jets and was also used as a short yardage tight end. He was released in August 2003 and immediately signed with the San Francisco 49ers. He played in 2 games in 2003. In 2004 Murphy played in 14 games at the guard position.

In Spring of 2005 he was released and signed by the Detroit Lions. He was released at the end of training camp but was signed back at the halfway point in the season. He went unsigned in the NFL after the end of the 2005 season.

Canadian Football League
The BC Lions signed Murphy as a free agent prior to the 2006 CFL season and made an immediate impact winning the CFL's Most Outstanding Offensive Lineman Award, was selected to the CFL All-Star team, and helped the Lions win the 94th Grey Cup; all in his first CFL season. With such success, Murphy was able to renegotiate a significant salary increase for the option year on his contract.

Murphy continued his success in the 2007 CFL season. He was again named the CFL's Most Outstanding Offensive Lineman and selected for the CFL All-Star team. He was named Gladiator of the Game during Friday Night Football against Edmonton Eskimos and, at the conclusion of the season, named a 2007 Walby Warrior.

In 2008, he was again named a CFL All Star.

He became a free agent on February 16, 2009, and the Argonauts signed him the same day for a two-year deal worth $400,000 plus incentives.

He started all 18 games at Left Tackle.

In 2010 Murphy had a resurgence from the 2009 season. He was voted team captain and was again named a CFL and Divisional All Star for the 4th year of his five years in the CFL. He was nominated as the Argonauts Most Outstanding Lineman. Murphy was named "Nastiest Player" in the CFL according to a TSN players poll at the end of the season. He currently hosts a weekly radio show on TSN 1050 with Cybulski and Company called Murphy's Law. He is heard frequently as well as a fill in co-host on TSN 1050. He is known for his quick wit and shoot straight from the hip attitude as his on-air persona.

On May 23, 2012, Murphy announced his retirement from professional football.

Personal life
Murphy has joint-custody of their three children with ex-wife, Amy. The triplets were born July 1, 2008. His daughter is named Rowan, and the two boys are Grey and Maddox. Murphy is now a Firefighter in St. Augustine, FL.

References

External links
Toronto Argonauts bio

1977 births
Living people
All-American college football players
American football offensive linemen
American players of Canadian football
BC Lions players
Chicago Enforcers players
Frankfurt Galaxy players
Indianapolis Colts players
Ohio State Buckeyes football players
Players of American football from Buffalo, New York
Sportspeople from Buffalo, New York
San Francisco 49ers players
Toronto Argonauts players

Rob Murphy (gridiron football)


Edward LeRoy Hart (December 28, 1916 – March 9, 2008) was a Latter-day Saint poet.  He wrote the words to "Our Savior's Love" which is #113 in the current LDS hymnbook.  He was also an English professor at Brigham Young University (BYU) and wrote many poems.

Early life
Hart was born in Bloomington, Idaho.  He received a bachelor's degree from the University of Utah, where he initially studied economics, but decided to change his major even though his close advisor Lowell L. Bennion urged him to let writing be just a free time activity.  Hart was also on the track team at the University of Utah.

Education
Hart then went on to receive a master's degree from the University of Michigan, receiving that degree in 1941.  He was then a Rhodes scholar at the University of Oxford, starting in 1945.  Originally Hart would have gone to Oxford in 1939 but the outbreak of World War II postponed those plans.

Hart was a United States Naval intelligence officer during World War II.

Career
Hart began his career as a professor at the University of Washington and then joined the BYU faculty in 1952. Besides his long career at BYU, Hart also taught for a time at the University of California, Berkeley.  Although he retired in 1982, Hart continued to teach one honors class a year at BYU until 1995.

Hart's earliest poem "A Lesson In Praise" dates to 1954.  He published a collection of poems on the occasion of the 150th anniversary of the founding of the LDS Church.  Hart edited Minor Lives: A Collection of Biographies that was published in 1971 by Harvard University Press.  He also wrote a hymn entitled "The Fullness of Times" on that occasion.  He also edited the journals and published them along with a biography of James H. Hart and published works in BYU Studies and the Mormon Letters Annual of the Association for Mormon Letters.

Among Hart's callings in the LDS Church he served from 1980-1988 as a bishop of a student ward at BYU.

Personal life
In December 1944 Hart married Eleanor May Coleman in Washington, D.C., they were sealed in the Salt Lake Temple the following August.  Eleanor and their young son Richard went with Hart to Oxford, and his next son, Paul, was born while he was studying there.  Edward and Eleanor also had two daughters, Barbara and Patricia. Eleanor died in 1990.  In 1993 he married Leah Bryson née Yates. She died in 2001. In 2002 Hart married Frances Cannon Lee.

Hart died on March 9, 2008, in Provo, Utah.

Notes

References

  — Text of podcast that mentions Hart and origins of "Our Savior's Love"

External links
 Search results for Edward L. Hart from Barnes & Noble
 Open Library listing for Hart

1916 births
2008 deaths
American Latter Day Saint hymnwriters
American leaders of the Church of Jesus Christ of Latter-day Saints
United States Navy personnel of World War II
American Rhodes Scholars
Brigham Young University faculty
People from Bear Lake County, Idaho
University of California, Berkeley faculty
University of Michigan alumni
University of Utah alumni
University of Washington faculty
20th-century American musicians
Latter Day Saints from Idaho
Latter Day Saints from Michigan
Latter Day Saints from Washington (state)
Latter Day Saints from Utah
United States Navy officers
Latter Day Saint poets

Edward L. Hart


Gordon M. Dineen (born September 21, 1962) is a Canadian former professional ice hockey defenceman. As of 2019, he is an assistant coach of the Rochester Americans. He is a former head coach for the Toronto Marlies of the American Hockey League, and a longtime assistant with several other teams.

Although born in Canada, Dineen spent much of his youth in the United States, while his father Bill Dineen played and coached professionally.  He returned to Canada to play major junior hockey for the Sault Ste. Marie Greyhounds. He was drafted by the New York Islanders with the forty-second pick in the 1981 draft. His brothers Kevin and Peter were also NHL players.

Playing career

Junior
Dineen was drafted in the fifth round, 54th overall, by the Sault Ste. Marie Greyhounds of the Ontario Hockey League (OHL) in 1980. In his rookie season with the Greyhounds in 1980–81, Dineen scored four goals and 30 points, as well as 158 penalty minutes, in 68 games. In the playoffs, Dineen had a goal, eight points, and 59 penalty minutes in 19 games as the Greyhounds lost to the Kitchener Rangers in the final round.

Dineen returned to the Greyhounds for the 1981–82 season, in which he saw his offensive numbers improve. In 68 games, Dineen scored nine goals and 54 points, while earning 185 penalty minutes. In the post-season, Dineen had a goal and three points in 13 games

Professional

New York Islanders (1982–1988)
Dineen was selected by the New York Islanders in the second round, 42nd overall, in the 1981 NHL Entry Draft. Following his junior career, the Islanders assigned Dineen to the Indianapolis Checkers of the Central Hockey League (CHL) for the 1982–83 season. In 73 games with the Checkers, Dineen scored 10 goals and 57 points. Dineen was named the CHL's Most Improved Defenseman and Most Outstanding Defenseman. In 13 playoff games, Dineen had two goals and 12 points, helping the Checkers win the Adams Cup. Dineen also saw limited action with the New York Islanders, playing in two games in the 1982–83 season and did not score any points.

Dineen spent more time with the Checkers in 1983–84, as he scored four goals and 17 points in 26 games with Indianapolis. He earned a promotion to the Islanders, in which he played in 43 games, scoring a goal and 12 points. Dineen played in nine playoff games, scoring a goal and two points, as the Islanders lost to the Edmonton Oilers in the 1984 Stanley Cup Finals.

In 1984–85, Dineen spent time with the Islanders American Hockey League (AHL) affiliate, the Springfield Indians. In 25 games with Springfield, Dineen had a goal and nine points. He spent a majority of the 1984–85 season with the Islanders, playing in 48 games, scoring a goal and 13 points, as well as earning 89 penalty minutes. In 10 playoff games with New York, Dineen had no points and 26 penalty minutes. Dineen again split the 1985–86 season between Springfield and New York. In 11 games with the Indians, Dineen had two goals and five points. In 57 games with the Islanders in 1985–86, Dineen had a goal and nine points. In three playoff games, he was held with no points.

In 1986–87, Dineen remained in the NHL on a full-time basis. In 71 games with the Islanders, Dineen scored four goals and 14 points, while accumulating 110 penalty minutes. In the post-season, Dineen had four assists in seven games. His tenure with the Islanders is perhaps best known for assisting on Pat LaFontaine's series-winning goal in the fourth overtime in the 1987 Stanley Cup playoffs opening round against the Washington Capitals, known today as "The Easter Epic."

Dineen began the 1987–88 season with the Islanders, where in 57 games, Dineen scored four goals and 16 points. His career with the Islanders came to an end on March 7, 1988, as Dineen was traded to the Minnesota North Stars for Chris Pryor and a seventh round draft pick in the 1989 NHL Entry Draft.

Minnesota North Stars (1988)
His first game with the North Stars was on March 9, 1988, and was held without a point in a 6–2 loss to the Buffalo Sabres. On April 3, Dineen scored his first goal with the North Stars, against Mike Vernon of the Calgary Flames, in a 4–1 loss.

Dineen began the 1988–89 season with the North Stars, earning an assist in two games. The North Stars assigned Dineen to the Kalamazoo Wings of the International Hockey League (IHL) for 25 games with two goals and eight points. On December 17, 1988, the North Stars traded Dineen and Scott Bjugstad to the Pittsburgh Penguins for Ville Siren and Steve Gotaas.

Pittsburgh Penguins (1988–1992)
Dineen made his debut with the Pittsburgh Penguins on December 23, 1988, earning no points in a 2–2 tie against the New Jersey Devils. On December 31, Dineen earned his first point as a Penguin, an assist on a goal by Mario Lemieux in an 8–6 victory. On February 14, Dineen scored his first goal with Pittsburgh against Jacques Cloutier of the Buffalo Sabres and added an assist in a 7–3 win. With the Penguins in 1988–89, Dineen played in 38 games, scoring a goal and three points. In the playoffs, Dineen added two assists in 11 games.

In 1989–90, Dineen played in 69 games with the Penguins, scoring a goal and eight points, while earning a career-high 125 penalty minutes. Dineen played most of the 1990–91 with the Muskegon Lumberjacks of the IHL, where Dineen scored one goal and 15 points in 40 games. In five playoff games with Muskegon, Dineen had two assists. In nine games with Pittsburgh during the 1990–91 season, Dineen had no points.

The 1991–92 season was mostly spent in Muskegon. In 79 games with the Lumberjacks, Dineen had eight goals and 45 points. In the post-season, Dineen scored two goals and six points in 14 games, as Muskegon lost to the Kansas City Blades in the Turner Cup finals. Dineen also appeared in one game with the Penguins during 1991–92, getting no points.

Following the season, Dineen was granted free agency.

Ottawa Senators (1992–1994)
Dineen signed with the expansion Ottawa Senators on August 31, 1992. The Senators assigned Dineen to the San Diego Gulls of the IHL to begin the 1992–93 season. With the Gulls, Dineen had six goals and 29 points in 41 games, earning a promotion to the Senators. Dineen played in his first game with Ottawa on January 21, 1993, where he was held without a point in a 7–2 loss to the Minnesota North Stars. On February 8, Dineen earned his first two points with the Senators, both assists, in a 4–2 win over the Buffalo Sabres. On February 25, Dineen scored his first goal with the Senators against Tom Barrasso of the Pittsburgh Penguins and added an assist in a 2–1 win. In 32 games with Ottawa, Dineen had two goals and six points.

In 1993–94, Dineen returned to the Senators. With 17 games remaining in the season, the Senators named Dineen captain of the club for the rest of the year. Overall, in a career high 77 games, Dineen did not score a goal, but had 21 assists. After the season, Dineen became a free agent.

New York Islanders (1994–1995)
On July 26, 1994, Dineen returned to the New York Islanders, as a free agent. Due to the 1994–95 NHL lockout, Dineen spent a majority of the season with the Islanders IHL affiliate, the Denver Grizzlies, where he was named captain of the team. In 68 games with Denver, Dineen scored five goals and 32 points. In 17 playoff games, Dineen had a goal and seven points, as Denver won the Turner Cup. Dineen did play in nine games with the Islanders during 1994–95, earning no points.

International Hockey League (1995–2000)
With the arrival of Colorado Avalanche for the 1995–96 season, the Grizzlies relocated to Utah as the Utah Grizzlies. Dineen remained captain of the club. In the 1995–96 season, Dineen scored a goal and 18 points in 82 games. In the playoffs, Dineen earned three assists in 22 games, as the Grizzlies once again won the Turner Cup.

In 1996–97, Dineen appeared in 81 games, scoring five goals and 34 points. In seven post-season games, he earned three points. Dineen played in all 82 games for the Grizzlies in the 1997–98 season, scoring three goals and 37 points for the club. In four playoff games, Dineen had two assists. Dineen continued to be productive during the 1998–99 season with Utah as in 77 games, he had five goals and 27 points.

In the 1999–2000 season, Dineen became a player-coach with the Grizzlies. In 50 games, he had 18 points, all assists. On March 16, 2000, Dineen was traded to the Chicago Wolves. In 17 games, he had a goal and three points. In the post-season, Dineen had five assists in 16 games, helping Chicago win the Turner Cup.

Following the season, Dineen announced his retirement from playing. His number 2 is the only number retired by the Grizzlies.

Coaching career
Dineen's was named as a player-coach during his final season with the Utah Grizzlies in 1999 until he was traded to the Chicago Wolves in March 2000. After retiring from playing, Dineen was named an assistant coach with the Louisville Panthers of the American Hockey League (AHL) in 2000–01. Louisville was the AHL affiliate of the Florida Panthers. Dineen worked under head coach Joe Paterson. The next season, he was named head coach and general manager of the Macon Whoopee of the East Coast Hockey League (ECHL) for the 2001–02 season. Under Dineen, the Whoopee finished with a 29–31–12 record, earning 70 points, and did not make the post-season. Following the season, the Whoopee relocated to Lexington, Kentucky, to become the Lexington Men O' War and he was not retained by the club.

In 2002, Dineen became the head coach and general manager of the ECHL's Richmond Renegades, leading the team to a 35–31–6 record and 76 points. The club failed to make the playoffs and folded at the end of the season.

Dineen was then hired by the Phoenix Coyotes as an assistant coach for their AHL affiliate, the Springfield Falcons of the AHL, for the 2003–04 season. The next season, the Coyotes changed their AHL affiliation to Utah Grizzlies, which had since joined the AHL after the IHL dissolved, and Dineen was retained by the organization as an assistant coach under Pat Conacher in the 2004–05 season. The Grizzlies suspended operations in 2005 and Dineen was moved to the Coyotes' new AHL affiliate, the San Antonio Rampage in the same role from 2005 to 2007. The Coyotes released the entire Rampage coaching staff the end of the season.

Dineen was hired by the Anaheim Ducks in the 2007–08 season to join the coaching staff of their affiliate, the Portland Pirates, where he worked under head coach and younger brother Kevin Dineen. Following the season, the Ducks affiliated with the Iowa Chops. The Ducks named him head coach of the Chops for the 2008–09 season, his first AHL head coaching job. The Chops finished the season with a 33–33–4–10 record, earning 80 points, and missed the playoffs. After the season, the Ducks dropped the Chops as their affiliate, leading to the team having their franchise revoked and the team suspended. The Ducks did not have an AHL affiliate for the 2009–10 season and Dineen was not retained by the Ducks.

In 2009–10, Dineen was hired as an assistant coach with the Toronto Marlies, the AHL affiliate of the Toronto Maple Leafs. He remained with the Marlies as an assistant under head coach Dallas Eakins from 2009 to 2013 and under Steve Spott in 2013–14. Dineen was promoted to head coach of the Marlies for the 2014–15 season, earning a record of 40–27–9–0 for 89 points, finishing second in the North Division. In the post-season, the Marlies lost to the Grand Rapids Griffins in the first round. The Maple Leafs then hired Sheldon Keefe as head coach of the Marlies for the 2015–16 season, deemed and up and coming coach, and Dineen was moved back to the assistant coaching position. Following the 2016–17 season, Dineen was not retained by the Marlies.

Dineen then joined the Rochester Americans of the AHL as an assistant to head coach Chris Taylor in 2017. Days before the start of the 2019–20 AHL season, Taylor was called up to the Americans' NHL parent team, the Buffalo Sabres, and Dineen was named the Americans' interim head coach. After Taylor returned from Buffalo, Dineen went back to his role as assistant coach.

Awards
1982–83: Bobby Orr Trophy
1982–83: Bob Gassoff Trophy

Career statistics

Head coaching statistics

See also
Notable families in the NHL

References

External links

Hockey Draft Central

1962 births
Canadian ice hockey defencemen
Chicago Wolves (IHL) players
Denver Grizzlies players
Ice hockey people from Ontario
Indianapolis Checkers (CHL) players
Kalamazoo Wings (1974–2000) players
Living people
Minnesota North Stars players
Muskegon Lumberjacks players
New York Islanders draft picks
New York Islanders players
Ottawa Senators players
Sportspeople from Seattle
Pittsburgh Penguins players
San Diego Gulls (IHL) players
Sault Ste. Marie Greyhounds players
Springfield Indians players
Stanley Cup champions
Utah Grizzlies (IHL) players
Toronto Marlies coaches
Canadian expatriate ice hockey players in the United States
Canadian ice hockey coaches

Gord Dineen


The goatfishes are perciform fish of the family Mullidae. The family is also sometimes referred to as the red mullets, which also refers more narrowly to the genus Mullus.

The family name and the English common name mullet derived from Latin mullus, the red mullet; other than the red mullet and the striped red mullet or surmullet, the English word "mullet" generally refers to a different family of fish, the Mugilidae or gray mullets.

Description
Goatfish are characterized by two chin barbels (or goatee),  which contain chemosensory organs and are used to probe the sand or holes in the reef for food. Their bodies are deep and elongated, with forked tails and widely separated dorsal fins. The first dorsal fin has 6-8 spines; the second dorsal has one spine and 8-9 soft rays, shorter than anal fin. Spines in anal fin 1 or 2, with 5-8 soft rays. They have 24 vertebrae.

Many goatfish are brightly colored. The largest species, the dash-and-dot goatfish (Parupeneus barberinus), grows to  in length; most species are less than half this size.
Within the family are six genera and about 86 species.

Genera
These genera are classified as belonging to the Mullidae:

 Mulloidichthys Whitley, 1929
 Mullus Linnaeus, 1758
 Parupeneus Bleeker, 1863
 Pseudupeneus Bleeker, 1862
 Upeneichthys Bleeker, 1853
 Upeneus Cuvier, 1829

Distribution and habitat
Goatfish are distributed worldwide in tropical, subtropical, and temperate waters, in a range of habitats. Most species are associated with the bottom of the littoral, but some species of Upeneus can be deep; for example, the goatfish Upeneus davidaromi can be found at depths of . Tropical goatfish live in association with coral reefs. Some species, such as the freckled goatfish (Upeneus tragula), enter estuaries and rivers, although not to any great extent.

Ecology
Goatfish are benthic feeders, using a pair of long chemosensory barbels (whiskers) protruding from their chins to feel through the sediments in search of prey. They feed on worms, crustaceans, molluscs and other small invertebrates. Other fish shadow the active goatfish, waiting patiently for any overlooked prey. For example, in Indonesia large schools of the goldsaddle goatfish (Parupeneus cyclostomus) and moray eels hunt together. This behavior is known as shadow feeding or cooperative hunting.
By day, many goatfish will form large schools of inactive (nonfeeding) fish; these aggregates may contain both conspecifics and heterospecifics. For example, the yellowfin goatfish (Mulloidichthys vanicolensis) is often seen congregating with bluestripe snappers (Lutjanus kasmira).
All goatfish have the ability to change their coloration depending on their current activity. One notable example, the diurnal goldsaddle goatfish (Parupeneus cyclostomus) can change from a lemon-yellow to a pale cream whilst feeding.

Mimicry
Goatfish have the ability to rapidly change color, and many species adopt a pale coloration when resting on the sand to blend with the background and become less visible to predators. These changes in color are reversible phenotypic changes and happen within seconds, many times during the lifespan of an individual.

Two species, the mimic goatfish (Mulloidichthys mimicus) and Ayliffe's goatfish (Mulloidichthys ayliffe) have evolved to mimic the blue-striped snapper (Lutjanus kasmira), with which they often form schools. These are slow, genetic changes that have occurred during their evolution over many generations.

Reproduction and life cycle
Goatfish are pelagic spawners; they release many buoyant eggs into the water, which become part of the plankton. The eggs float freely with the currents until hatching.
The larvae drift in oceanic waters or in the outer shelf for a period of 4–8 weeks until they metamorphose and develop barbels. Soon thereafter, most species take on a bottom-feeding lifestyle, although other species remain in the open water as juveniles or feed on plankton.
Juvenile goatfish often prefer soft bottoms, in seagrass beds to mangroves. They change habitat preference as they develop, coinciding with changes in feeding habits, social behavior, and the formation of association with other species. Most species reach reproductive maturity after 1–2 years.

Economic importance
Goatfish species are an important fishery in many areas of the world and some species are economically important.
In ancient Rome until the end of the second century BCE, two species of goatfish (Mullus barbatus and Mullus surmuletus) were highly sought-after and expensive, not as a delicacy, but for aesthetic pleasure, since the fish assume a variety of colors and shades also during death. Therefore, it was paramount to serve the fish live and let them die before the eyes of the guests.

Timeline

Gallery

References

Percoidei
Taxa named by Constantine Samuel Rafinesque

Goatfish


WorldTracer is a SITA / IATA service provided for the tracking of lost or delayed baggage. It has been in operation for many years and is used by all airlines that are members of IATA. Most of the low-cost carriers that are based in Europe such as Norwegian Air Shuttle, Wizz Air also use WorldTracer.

Operation
WorldTracer operates globally and can exchange information with 2800+ member airports. It tracks and follows baggage for up to 100 days and collaborates with other services. The World Tracer internet interface allows passengers to track their bags by entering a transaction number.

Whenever baggage is found without an owner, it can be registered as on-hand baggage. It is then automatically matched with various missing-baggage files (called AHLs). Whenever an on-hand produces a likely match, the station that registered the missing bag file receives an alert. The bag is matched based on its routing number, tag number, passenger's surname, type of baggage and content. When a handling agent finds an on-hand which matches one of AHLs, he/she can request the on-hand by sending a message to the station that registered it.

Tracking numbers
The tracking number format is AAABBNNNNN, where AAA is the airport's IATA code, BB is the airline's IATA code and NNNNN is a 5-digit tracking number. For example, the tracking number PHLDL19676 is from Philadelphia International Airport, flew on Delta Air Lines, and has the tracking number of 19676.

References

External links

 Portal for travelers

Airline trade associations
International Air Transport Association
Organizations established in 1945
Organizations based in Montreal

WorldTracer