Cubic metreThe cubic metre (in Commonwealth English and international spelling as used by the International Bureau of Weights and Measures) or cubic meter (in American English) is the unit of volume in the International System of Units (SI). Its symbol is m3. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure (for instance, in reference to wood). Another alternative name, no longer widely used, was the kilolitre.
Barn (unit)A barn (symbol: b) is a metric unit of area equal to e−28m2 (100 fm2). Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is also used in all fields of high-energy physics to express the cross sections of any scattering process, and is best understood as a measure of the probability of interaction between small particles. A barn is approximately the cross-sectional area of a uranium nucleus.
FaradThe farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI), equivalent to 1 coulomb per volt (C/V). It is named after the English physicist Michael Faraday (1791–1867). In SI base units 1 F = 1 kg−1⋅m−2⋅s4⋅A2. The capacitance of a capacitor is one farad when one coulomb of charge changes the potential between the plates by one volt. Equally, one farad can be described as the capacitance which stores a one-coulomb charge across a potential difference of one volt.
Unit of lengthA unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
AngstromThe angstrom (ˈæŋstrəm; ) or ångström is a metric unit of length equal to e-10 m; that is, one ten-billionth (US) of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. Its symbol is Å, a letter of the Swedish alphabet. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–1874). The angstrom is often used in the natural sciences and technology to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, and dimensions of integrated circuit parts.
International Electrotechnical CommissionThe International Electrotechnical Commission (IEC; in French: Commission électrotechnique internationale) is an international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies – collectively known as "electrotechnology". IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy, nanotechnology and marine energy as well as many others.
TorrThe torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly 1/760 of a standard atmosphere (101325Pa). Thus one torr is exactly 101325/760 pascals (≈ ). Historically, one torr was intended to be the same as one "millimeter of mercury", but 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). It is often combined with the metric prefix milli to name one millitorr (mTorr) or 0.
Grave (unit)The grave (ɡræv, ɡʁav), abbreviated gv, is the unit of mass used in the first metric system which was implemented in France in 1793. In 1795, the grave was renamed as the kilogram. The modern kilogram has its origins in the Age of Enlightenment and the French Revolution. In 1790 an influential proposal by Talleyrand called for a new system of units, including a unit of length derived from an invariable length in nature, and a unit of mass (then called weight) equal to the mass of a unit volume of water.
1,000,000,0001,000,000,000 (one billion, short scale; one thousand million or one milliard, one yard, long scale) is the natural number following 999,999,999 and preceding 1,000,000,001. With a number, "billion" can be abbreviated as b, bil or bn. In standard form, it is written as 1 × 109. The metric prefix giga indicates 1,000,000,000 times the base unit. Its symbol is G. One billion years may be called an eon in astronomy or geology. Previously in British English (but not in American English), the word "billion" referred exclusively to a million millions (1,000,000,000,000).
Orders of magnitude (mass)To help compare different orders of magnitude, the following lists describe various mass levels between 10−59 kg and 1052 kg. The least massive thing listed here is a graviton, and the most massive thing is the observable universe. Typically, an object having greater mass will also have greater weight (see mass versus weight), especially if the objects are subject to the same gravitational field strength. The table at right is based on the kilogram (kg), the base unit of mass in the International System of Units (SI).
