Absolute scale

An absolute scale is a system of measurement that begins at a minimum, or zero point, and progresses in only one direction. An absolute scale differs from an arbitrary, or "relative," scale, which begins at some point selected by a person and can progress in both directions. An absolute scale begins at a natural minimum, leaving only one direction in which to progress.

An absolute scale can only be applied to measurements in which a true minimum is known to exist. Time, for example, which does not have a clearly known beginning, is measured on a relative scale, with an arbitrary zero-point such as the conventional date of the birth of Jesus of Nazareth or the accession of an emperor. Temperature, on the other hand, has a known minimum, absolute zero (where all vibrational motion of atoms ceases), and therefore, can be measured either in absolute terms (kelvins or degrees Rankine), or relative to a reference temperature such as the freezing point of water at a specified pressure (Celsius and Reaumur) or the lowest temperature attainable in 1724 (Fahrenheit).

Pressure is a force that can be measured absolutely, because the natural minimum of pressure is total vacuum. Pressure is frequently measured with reference to atmospheric pressure rather than on any absolute scale, relative to complete and perfect vacuum; it is technologically simpler and cheaper. It may also be more convenient to use relative scales, because, with things like pneumatics and hydraulics, the amount of energy transferred is reduced by the relative "backpressure" of the atmosphere. (e.g.: 15 psi of air in a tank at sea level will become 30 psi in the vacuum of space.) Therefore, with measurements of things like blood pressure or tire pressure, a measurement relative to air pressure is a better indication of "burst pressure" (damage threshold) than an absolute scale. Absolute scales are typically used in science, deep vacuum measurements (where the fluctuating pressure of the atmosphere becomes a nuisance), aeronautics (where precise measurements of the atmosphere are needed to determine altitude), or lighting construction (where the relative pressure of the atmosphere is inconsequential), and are measured in units of "atmospheres" or torr. Barometers do measure absolute pressure by holding a vacuum at the top of the mercury column or one side of a diaphragm, but that vacuum is awkward to achieve and maintain. Thus, while the general public may be familiar with measurements of absolute pressure from weather forecasts, most pressures such as tire pressures and water pressures are measured relative to atmospheric pressure using cheaper and simpler pressure gauges. For this reason, the pressure relative to atmospheric pressure is called gauge pressure and measurements given in units like pounds per square inch (abbreviated lbf/in2 or psi) are often shown as psig (the "g" standing for gauge) or psia ("a" for absolute).

Absolute scales are used when precise values are needed in comparison to a natural, unchanging zero point. Measurements of length, area and volume are inherently absolute, although measurements of distance are often based on an arbitrary starting point. Measurements of weight can be absolute, such as atomic weight, but more often they are measurements of the relationship between two masses, while measurements of speed are relative to an arbitrary reference frame. (Unlike many other measurements without a known, absolute minimum, speed has a known maximum and can be measured from a purely relative scale.) Absolute scales can be used for measuring a variety of things, from the flatness of an optical flat to neuroscientific tests.[1][2][3]


  1. ^ Measurement: Its Concepts, Theories and Problems by Karel Berka -- D. Reidel Publishing 1983 Page 87--91
  2. ^ The Scientific Foundation of Neuropsychological Assessment by Elbert Russell -- Elsevier 2012 Page 98--101
  3. ^ Modern Engineering Thermodynamics - Textbook with Tables Booklet by Robert T. Balmer -- Elsevier 2011 Page 40
16 mm scale

16 mm to 1 foot or 1:19.05 is a popular scale of model railway in the UK which represents narrow gauge prototypes. The most common gauge for such railways is 32 mm (1.26 in), representing 2 ft (610 mm) gauge prototypes. This scale/gauge combination is sometimes referred to as "SM32" (terminology popularised by Peco, one of the principal manufacturers of appropriate track) and is often used for model railways that run in gardens, being large enough to easily accommodate live steam models. The next most common gauge is 45 mm (1.772 in), which represents the theoretical non-existent gauge 2 feet 9 3⁄4 inches (857 mm). This gauge is commonly used to portray prototypes between 2 ft 6 in (762 mm) and 3 ft (914 mm) gauge.

There are a number of commercial manufacturers of 16 mm scale models as well as many enthusiastic amateurs who build their own rolling stock. Because real 2 ft (610 mm) railways were most commonly found in the UK, many of the models are of British prototypes. European and North American narrow gauge railways are also modeled in this scale, mainly with scratch-built or kit-built models.

Although models of approximately this scale were being built as early as the 1930s, it was the founding of the Merioneth Railway Society just after the Second World War that marks the popularization of this scale. The society was famous for its rulebook, which read, in its entirety:

The Merioneth Railway Society rule book states:

Rule 1. The Society shall be known as the Merioneth Railway Society.

Rule 2. There shall be no rules.This set the light-hearted spirit of the 16 mm fraternity, where a sense of fun and whimsy often override more serious concerns. The use of live steam as the predominant motive power of the models means absolute scale reproduction is often sacrificed to the demands of steam engineering at this scale. However the realistic sound, smell and visual effects of steam-driven locomotives makes up for loss of fidelity elsewhere. Driving a live steam locomotive, even at this small scale is very different from driving an electrically powered model.

For many years there were no commercially available parts, and everything was hand-built or kit-bashed from O scale components. In the early 1970s Archangel emerged as the first commercial manufacturer on a large scale, followed by Merlin and Beck at the end of that decade. All three companies produced affordable live steam locomotives in this scale. In 1981 Mamod entered the market with a cheap if somewhat crude steam loco for the UK market. Although not perfect, the low cost opened the hobby to a much wider range of people and as a result demand for other products grew. Today, Roundhouse almost dominate the market as builders of high quality live steam locomotives. A vibrant group of professional and hobbyist makers have emerged to meet this demand.

Absolute temperature scale

Absolute temperature scale can refer to:

Kelvin scale, an absolute-temperature scale related to the Celsius scale

Planck temperature scale, an absolute-temperature scale based on absolute zero and the Planck temperature

Rankine scale, an absolute-temperature scale related to the Fahrenheit scaleFor a type of measuring system that begins at an absolute minimum (not necessarily a temperature scale) see:

Absolute scale

Cave rescue

Cave rescue is a highly specialized field of wilderness rescue in which injured, trapped or lost cave explorers are medically treated and extracted from various cave environments.

Cave rescue borrows elements from firefighting, confined space rescue, rope rescue and mountaineering techniques but has also developed its own special techniques and skills for performing work in conditions that are almost always difficult and demanding. Since cave accidents, on an absolute scale, are a very limited form of incident, and cave rescue is a very specialized skill, normal emergency staff are rarely employed in the underground elements of the rescue. Instead, this is usually undertaken by other experienced cavers who undergo regular training through their organizations and are called up at need.

Cave rescues are slow, deliberate operations that require both a high level of organized teamwork and good communication. The extremes of the cave environment (air temperature, water, vertical depth) dictate every aspect of a cave rescue. Therefore, the rescuers must adapt skills and techniques that are as dynamic as the environment they must operate in.


The Celsius scale, also known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.

From 1743, the Celsius scale is based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure. Prior to 1743, the scale was also based on the boiling and melting points of water, but the values were reversed (i.e. the boiling point was at 0 degrees and the melting point was at 100 degrees). The 1743 scale reversal was proposed by Jean-Pierre Christin.

By international agreement, since 1954 the unit degree Celsius and the Celsius scale are defined by absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW), a specially purified water. This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. The temperature of the triple point of water is defined as exactly 273.16 K (0.01 °C). This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same.On 20 May 2019, the kelvin, and along with it the degree Celsius, will be redefined so that its value will be determined by definition of the Boltzmann constant.

Chemical shift

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy such as photoemission spectroscopy.

Some atomic nuclei possess a magnetic moment (nuclear spin), which gives rise to different energy levels and resonance frequencies in a magnetic field. The total magnetic field experienced by a nucleus includes local magnetic fields induced by currents of electrons in the molecular orbitals (note that electrons have a magnetic moment themselves). The electron distribution of the same type of nucleus (e.g. 1H, 13C, 15N) usually varies according to the local geometry (binding partners, bond lengths, angles between bonds, and so on), and with it the local magnetic field at each nucleus. This is reflected in the spin energy levels (and resonance frequencies). The variations of nuclear magnetic resonance frequencies of the same kind of nucleus, due to variations in the electron distribution, is called the chemical shift. The size of the chemical shift is given with respect to a reference frequency or reference sample (see also chemical shift referencing), usually a molecule with a barely distorted electron distribution.

Conduit and Sink OFCs

Conduit OFC and Sink OFC is an empirical quantitative method of classifying corporate tax havens, offshore financial centres and tax havens.

Rather than analyzing taxation and legal structures, called base erosion and profit shifting (BEPS) tools, to identify and classify potential tax havens (the preferred EU, IMF, and OECD route), this approach analyses the ownership chains of 98 million global companies (a purely empirical, or outcomes–based, route), relative to the size of countries of their incorporation. The technique gives both a method of classification and a method of understanding the relative scale – but not absolute scale – of corporate tax havens/offshore financial centers.

The results were formally published by the University of Amsterdam's CORPNET Group in July 2017, and identify two major classifications:

24 global Sink OFCs: jurisdictions in which a disproportional amount of value disappears from the economic system (i.e. the traditional tax havens).(See the table below for the list of Sinks)

5 global Conduit OFCs: jurisdictions through which a disproportional amount of value moves toward sink OFCs (i.e. modern corporate tax havens).(Conduits are: Netherlands, United Kingdom, Switzerland, Singapore and Ireland)Our findings debunk the myth of tax havens as exotic far–flung islands that are difficult, if not impossible, to regulate. Many offshore financial centers are highly developed countries with strong regulatory environments.

The CORPNET report has been praised, and in March 2017, the EU has adopted its approach into some of their policy frameworks. Research by Gabriel Zucman (et alia) published in June 2018, showed using Orbis database connections, underestimates Ireland, which the Zucman–Tørsløv–Wier 2018 list shows is the largest corporate Conduit OFC in the world. However, CORPNET's Conduits and Sinks, still reconcile closely with the world's top ten tax havens.

Gay-Lussac's law

Gay-Lussac's law can refer to several discoveries made by French chemist Joseph Louis Gay-Lussac (1778–1850) and other scientists in the late 18th and early 19th centuries pertaining to thermal expansion of gases and the relationship between temperature, volume, and pressure.

It states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.Mathematically, it can be written as: P/T=constant,

Gay-Lussac is most often recognized for the Pressure Law which established that the pressure of an enclosed gas is directly proportional to its temperature and which he was the first to formulate (c. 1808). He is also sometimes credited, rightfully according to many modern scholars, with being the first to publish convincing evidence that shows the relationship between the pressure and temperature of a fixed mass of gas kept at a constant volume.

These laws are also known variously as the Pressure Law or Amontons's law and Dalton's law respectively.

Glossary of physics

This glossary of physics is a list of definitions of terms and concepts relevant to physics, its sub-disciplines, and related fields, including mechanics, materials science, nuclear physics, particle physics, and thermodynamics.

For more inclusive glossaries concerning related fields of science and technology, see Glossary of chemistry terms, Glossary of astronomy, Glossary of areas of mathematics, and Glossary of engineering.

Joseph Louis Gay-Lussac

Joseph Louis Gay-Lussac (; French: [ʒɔzɛf lwi ɡɛlysak]; 6 December 1778 – 9 May 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen (with Alexander von Humboldt), for two laws related to gases, and for his work on alcohol-water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries.


The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin (symbol: K) is the base unit of temperature in the International System of Units (SI).

Until 2018, the kelvin was defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). In other words, it was defined such that the triple point of water is exactly 273.16 K.

On 16 November 2018, a new definition was adopted, in terms of a fixed value of the Boltzmann constant. For legal metrology purposes, the new definition will officially come into force on 20 May 2019 (the 130th anniversary of the Metre Convention).The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or written as a degree. The kelvin is the primary unit of temperature measurement in the physical sciences, but is often used in conjunction with the degree Celsius, which has the same magnitude. The definition implies that absolute zero (0 K) is equivalent to −273.15 °C (−459.67 °F).


Loudness, K-weighted, relative to full scale (LKFS) is a loudness standard designed to enable normalization of audio levels for delivery of broadcast TV and other video. Loudness units relative to full scale (LUFS) is a synonym for LKFS that was introduced in EBU R128. Loudness units (LU) is an additional unit used in EBU R128. It describes Lk without direct absolute reference and therefore describes loudness level differences.

LKFS is standardized in ITU-R BS.1770. In March 2011, the ITU introduced a loudness gate in the second revision of the recommendation, ITU-R BS.1770-2. In August 2012, the ITU released the third revision of this recommendation ITU-R BS.1770-3. In October 2015, the ITU released the fourth revision of this recommendation ITU-R BS.1770-4.The EBU has suggested that the ITU should change the unit to LUFS, as LKFS does not comply with scientific naming conventions and is not in line with the standard set out in ISO 80000-8. Furthermore, they suggest the symbol for 'Loudness level, k-weighted' should be Lk, which would make Lk and LUFS equivalent when LUFS indicates the value of Lk with reference to digital full scale.LKFS and LUFS are identical in that they are both measured in absolute scale and both equal to one decibel (dB).


Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.


Nitroethane is an organic compound having the chemical formula C2H5NO2. Similar in many regards to nitromethane, nitroethane is an oily liquid at standard temperature and pressure. Pure nitroethane is colorless and has a fruity odor.

Pressure measurement

Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure gauges or vacuum gauges. A manometer (not to be confused with nanometer) is a good example, as it uses a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge.

A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: −15 psig or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very accurate readings, especially at very low pressures, a gauge that uses total vacuum as the zero point may be used, giving pressure readings in an absolute scale.

Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system (telemetry).

Rankine scale

The Rankine scale () is an absolute scale of thermodynamic temperature named after the Glasgow University engineer and physicist William John Macquorn Rankine, who proposed it in 1859. (The Kelvin scale was first proposed in 1848.) It may be used in engineering systems where heat computations are done using degrees Fahrenheit.

The symbol for degrees Rankine is °R (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales). By analogy with kelvin, some authors term the unit rankine, omitting the degree symbol. Zero on both the Kelvin and Rankine scales is absolute zero, but a temperature difference of one Rankine degree is defined as equal to one Fahrenheit degree, rather than the Celsius degree used on the Kelvin scale. Thus, a temperature of 0 K (−273.15 °C; −459.67 °F) is equal to 0 °R, and a temperature of −458.67 °F equal to 1 °R.

The US National Institute of Standards and Technology recommends against using the degree symbol when using Rankine in NIST publications.Some important temperatures relating the Rankine scale to other temperature scales are shown in the table below.

Safety testing of explosives

The safety testing of explosives involves the determination of various properties of the different energetic materials that are used in commercial, mining, and military applications. It is highly desirable to measure the conditions under which explosives can be set off for several reasons, including: safety in handling, safety in storage, and

safety in use.

It would be very difficult to provide an absolute scale for sensitivity with respect to the different properties of explosives. Therefore, it is generally required that one or more compounds be considered a standard for comparison to those compounds being tested. For example, PETN is considered to be a primary explosive by some individuals, and a secondary explosive by others. As a general rule, PETN is considered to be either a relatively insensitive primary explosive, or one of the most sensitive secondary explosives. PETN may be detonated by striking with a hammer on a hard steel surface (a very dangerous thing to do), and is generally considered the least sensitive explosive with which this may be done. For these facts and other reasons, PETN is considered one standard by which other explosives are gauged.

Another explosive that is used as a calibration standard is TNT, which was afforded the arbitrary Figure of Insensitivity of 100. Other explosives could then be compared against this standard.


Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales. The most commonly used scales are the Celsius scale (formerly called centigrade) (denoted °C), Fahrenheit scale (denoted °F), and Kelvin scale (denoted K). The kelvin (the word is spelled with a lower-case k) is the unit of temperature in the International System of Units (SI), in which temperature is one of the seven fundamental base quantities. The Kelvin scale is widely used in science and technology.

Theoretically, the coldest a system can be is when its temperature is absolute zero, at which point the thermal motion in matter would be zero. However, an actual physical system or object can never attain a temperature of absolute zero. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit scale.

For an ideal gas, temperature is proportional to the average kinetic energy of the random microscopic motions of the constituent microscopic particles.

Temperature is important in all fields of natural science, including physics, chemistry, Earth science, medicine, and biology, as well as most aspects of daily life.


The torr (symbol: Torr) is a unit of pressure based on an absolute scale, now defined as exactly 1/760 of a standard atmosphere (101325 Pa). Thus one torr is exactly 101325/760 pascals (≈ 133.32 Pa).

Historically, one torr was intended to be the same as one "millimeter of mercury". However, subsequent redefinitions of the two units made them slightly different (by less than 0.000015%). The torr is not part of the International System of Units (SI), but it is often combined with the metric prefix milli to name one millitorr (mTorr) or 0.001 Torr.

The unit was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644.

Vaginal photoplethysmograph

Vaginal photoplethysmography (VPG, VPP) is a technique using light to measure the amount of blood in the walls of the vagina. The device that is used is called a vaginal photometer.

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