The erg is a unit of energy and work equal to 10−7 joules. It originated in the centimetre–gram–second (CGS) system of units. It has the symbol erg. The erg is not an SI unit. Its name is derived from ergon (ἔργον), a Greek word meaning work or task.[1]

An erg is the amount of work done by a force of one dyne exerted for a distance of one centimeter. In the CGS base units, it is equal to one gram centimeter-squared per second-squared (g·cm2/s2). It is thus equal to 10−7 joules or 100 nanojoules (nJ) in SI units. An erg is approximately the amount of work done (or energy consumed) by one common house fly performing one "push up," the leg-bending dip that brings its mouth to the surface on which it stands and back up.[2]

1 erg = 10−7 J = 100 nJ
1 erg = 10−10sn·m = 100 psn·m = 100 picosthène-metres
1 erg = 624.15 GeV = 6.2415×1011 eV
1 erg = 1 dyne cm = 1 g·cm2/s2


In 1864, Rudolf Clausius proposed the Greek word (ἐργον) ergon for the unit of energy, work and heat.[3][4] In 1873, a committee of the British Association for the Advancement of Science, including British physicists James Clerk Maxwell and William Thomson recommended the general adoption of the centimetre, the gramme, and the second as fundamental units (C.G.S. System of Units). To distinguish derived units, they recommended using the prefix "C.G.S. unit of ..." and requested that the word erg or ergon be strictly limited to refer to the C.G.S. unit of energy.[5]

In 1922, chemist William Draper Harkins proposed the name micri-erg as a convenient unit to measure the surface energy of molecules[6] in surface chemistry.[7][8] It would equate to 10−14 erg,[6][9][10][11][12] the equivalent to 10−21 joule.

The erg has not been a valid unit since 1 January 1978[13] when the EEC ratified a directive of 1971 which implemented the International System (SI) as agreed by the General Conference of Weights and Measures.[14] It is still widely used in astrophysics[15] and sometimes in mechanics.

See also


  1. ^ Oxford English Dictionary
  2. ^ Filippenko, Alex, Understanding the Universe (of The Great Courses, on DVD), Lecture 44, time 24:30, The Teaching Company, Chantilly, VA, USA, 2007
  3. ^ Clausius, Rudolf (1867). "Appendices to Sixth Memoir [1864]. Appendix A. On Terminology.". In Hirst, T. Archer. The Mechanical Theory of Heat, With Its Applications to the Steam-engine and to the Physical Properties of Bodies. London: J. Van Voorst. p. 253. Retrieved 2014-03-17.
  4. ^ Howard, Irmgard K. (2001). "S is for Entropy. U is for Energy. What Was Clausius Thinking?" (PDF). Journal of Chemical Education. 78 (4): 505. Bibcode:2001JChEd..78..505H. doi:10.1021/ed078p505. Retrieved 2014-03-17.
  5. ^ Thomson, Sir W; Foster, Professor GC; Maxwell, Professor JC; Stoney, Mr GJ; Jenkin, Professor Fleeming; Siemens, Dr; Bramwell, Mr FJ (September 1873). Everett, Professor, ed. First Report of the Committee for the Selection and Nomenclature of Dynamical and Electrical Units. Forty-third Meeting of the British Association for the Advancement of Science. Bradford: John Murray. p. 224. Retrieved 2014-03-17.
  6. ^ a b Jerrard, H.G.; McNeill, D.B. (2012-06-12) [1963]. A Dictionary of Scientific Units - Including dimensionless numbers and scales (5 ed.). Chapman and Hall Ltd., reprint: Springer Science & Business Media. ISBN 9400941110. 9789400941113. Retrieved 2015-02-15.
  7. ^ Cardarelli, François (1999) [1966]. Scientific unit conversion: A practical guide to metrication (2 ed.). Springer-Verlag London Limited. doi:10.1007/978-1-4471-0805-4. ISBN 978-1-85233-043-9. 1447108051, 9781447108054. Retrieved 2015-08-25.
  8. ^ Cardarelli, François (2003). Encyclopaedia of Scientific Units, Weights and Measures. Springer-Verlag London Ltd. ISBN 978-1-4471-1122-1.
  9. ^ Roberts, Lathrop Emerson; Harkins, William Draper; Clark, George Lindenberg (2013-07-01) [1922]. The Orientation of Molecules in Surfaces, Surface Energy, Adsorption, and Surface Catalysis. V. The Adhesional Work Between Organic Liquids and Water: Vaporization in Steps as Related to Surface Formation. University of Chicago Digital Preservation Collection. University of Chicago. Retrieved 2015-08-25.
  10. ^ Holmes, Harry N. (1925). Colloid Symposium Monograph - Papers Presented at the Second National Symposium on Colloid Chemistry, Northwestern University, June, 1924. 2. The Chemical Catalog Company, Inc. Retrieved 2015-02-15.
  11. ^ Journal of the American Chemical Society - Issues for 1898-1901 include Review of American chemical research, v. 4-7; 1879-1937, the society's Proceedings. 44. American Chemical Society. 1922. p. 665. ISSN 0002-7863. Retrieved 2015-02-15.
  12. ^ Partington, James Riddick (2010-02-17) [1949]. An Advanced Treatise on Physical Chemistry: Fundamental principles. The properties of gases. 1. Longmans, Green. Retrieved 2015-08-25.
  13. ^ Neufert, Ernst; Neufert, Peter; Kister, Johannes (2012-03-26). Architects' Data. John Wiley & Sons. ISBN 9781405192538.
  14. ^ Jennings, W. A. (October 1972). "SI units in radiation measurement". The British Journal of Radiology. 45 (538): 784–785. doi:10.1259/0007-1285-45-538-784. ISSN 0007-1285.
  15. ^ "Are ergs commonly used in astrophysics? If so, is there a specific reason for it?". Physics Stack Exchange. 2016-02-12. Retrieved 2018-09-15.

Aoukar or Erg Aoukar is a geological depression area of south eastern Mauritania. It is located between Kiffa and Néma, south of the Tagant Plateau.

The Aoukar basin is a dry natural region of sand dunes and salt pans fringed by escarpments on its northern and eastern sides.

Arase (satellite)

Arase, formerly known as Exploration of energization and Radiation in Geospace (ERG), is a scientific satellite to study the Van Allen belts. It was developed by the Institute of Space and Astronautical Science of JAXA.

It was launched aboard Epsilon launch vehicle at 11:00:00, 20 December 2016 UTC into apogee height 32250 km, perigee 214 km orbit. Subsequent perigee-up operation moved its orbit to apogee 32110 km, perigee 460 km of 565 minutes period.


In physical geography, a dune is a hill of loose sand built by aeolian processes (wind) or the flow of water. Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter "slip face" in the lee side. The valley or trough between dunes is called a slack. A "dune field" or erg is an area covered by extensive dunes.

Dunes occur in some deserts and along some coasts. Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds. Dunes can form under the action of water flow (fluvial processes), and on sand or gravel beds of rivers, estuaries and the sea-bed.

The modern word "dune" came into English from French c. 1790, which in turn came from Middle Dutch dūne.

ERG (gene)

ERG (ETS-related gene) is an oncogene. ERG is a member of the ETS (erythroblast transformation-specific) family of transcription factors. The ERG gene encodes for a protein, also called ERG, that functions as a transcriptional regulator. Genes in the ETS family regulate embryonic development, cell proliferation, differentiation, angiogenesis, inflammation, and apoptosis.


Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors (rods and cones), inner retinal cells (bipolar and amacrine cells), and the ganglion cells. Electrodes (DTL silver/nylon fiber string) are usually placed on the surface of the cornea for Full Field/Global/Multifocal ERG's and brass/copper electrodes are placed on the skin near the eye for EOG type testing. During a recording, the patient's eyes are exposed to standardized stimuli and the resulting signal is displayed showing the time course of the signal's amplitude (voltage). Signals are very small, and typically are measured in microvolts or nanovolts. The ERG is composed of electrical potentials contributed by different cell types within the retina, and the stimulus conditions (flash or pattern stimulus, whether a background light is present, and the colors of the stimulus and background) can elicit stronger response from certain components.

If a dim flash ERG is performed on a dark-adapted eye, the response is primarily from the rod system. Flash ERGs performed on a light adapted eye will reflect the activity of the cone system. Sufficiently bright flashes will elicit ERGs containing an a-wave (initial negative deflection) followed by a b-wave (positive deflection). The leading edge of the a-wave is produced by the photoreceptors, while the remainder of the wave is produced by a mixture of cells including photoreceptors, bipolar, amacrine, and Muller cells or Muller glia. The pattern ERG (PERG), evoked by an alternating checkerboard stimulus, primarily reflects activity of retinal ganglion cells.

Clinically used mainly by ophthalmologists and optometrists, the electroretinogram (ERG) is used for the diagnosis of various retinal diseases.Inherited retinal degenerations in which the ERG can be useful include:

Retinitis pigmentosa and related hereditary degenerations

Retinitis punctata albescens

Leber's congenital amaurosis


Gyrate atrophy of the retina and choroid

Goldman-Favre syndrome

Congenital stationary night blindness - normal a-wave indicates normal photoreceptors; absent b-wave indicates abnormality in the bipolar cell region.

X-linked juvenile retinoschisis


Cone dystrophy

Disorders mimicking retinitis pigmentosa

Usher SyndromeOther ocular disorders in which the standard ERG provides useful information include:

Diabetic retinopathy

Other ischemic retinopathies including central retinal vein occlusion (CRVO), branch vein occlusion (BVO), and sickle cell retinopathy

Toxic retinopathies, including those caused by Plaquenil and Vigabatrin. The ERG is also used to monitor retinal toxicity in many drug trials.

Autoimmune retinopathies such as Cancer Associated Retinopathy (CAR), Melanoma Associated Retinopathy (MAR), and Acute Zonal Occult Outer Retinopathy (AZOOR)

Retinal detachment

Assessment of retinal function after trauma, especially in vitreous hemorrhage, dense cataracts, and other conditions where the fundus cannot be visualized.The ERG is also used extensively in eye research, as it provides information about the function of the retina that is not otherwise available.

Other ERG tests, such as the photopic negative response (PhNR) and pattern ERG (PERG) may be useful in assessing retinal ganglion cell function in diseases like glaucoma.

The multifocal ERG is used to record separate responses for different retinal locations.

The international body concerned with the clinical use and standardization of the ERG, EOG, and VEP is the International Society for the Clinical Electrophysiology of Vision (ISCEV).

Erbogachen Airport

Erbogachen Airport (Russian: Аэропорт Ербогачён) (IATA: ERG, ICAO: UIKE) is an airport in Russia located 1 km east of Erbogachen.

Erg (landform)

An erg (also sand sea or dune sea, or sand sheet if it lacks dunes) is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. The term takes its name from the Arabic word ʿarq (عرق), meaning "dune field". Strictly speaking, an erg is defined as a desert area that contains more than 125 km2 (48 sq mi) of aeolian or wind-blown sand and where sand covers more than 20% of the surface. Smaller areas are known as "dune fields". The largest hot desert in the world, the Sahara, covers 9 million square kilometres (3.5×10^6 sq mi) and contains several ergs, such as the Chech Erg (24.57°N 2.59°W / 24.57; -2.59) and the Issaouane Erg (31.18°N 7.93°E / 31.18; 7.93) in Algeria. Approximately 85% of all the Earth's mobile sand is found in ergs that are greater than 32,000 km2 (12,355 sq mi). Ergs are also found on other celestial bodies, such as Venus, Mars, and Saturn's moon Titan.

Erg (tug)

Erg was a vessel built and owned by Halifax Steamship Ltd. in 1915. She was used to ferry workers across the harbour to vessels under repair during the Second World War. Erg was sunk in the Halifax Harbour three times and is currently located in the Bedford Basin.

Erg Chebbi

Erg Chebbi (Arabic: عرق الشبي‎) is one of Morocco's several ergs – large seas of dunes formed by wind-blown sand. There are several other ergs such as Erg Chigaga near M'hamid. Technically all these ergs are within an area of semi-arid Pre-Saharan Steppes and not part of the Sahara desert which lies some distance to the south.

Erg Mountain Provincial Park

Erg Mountain Provincial Park is a provincial park in British Columbia, Canada.

The park is spread over an area of 1,011 hectares. In its interior parts, starting from the slopes of the valley above the Upper Fraser Trench, the park consists of cedar hemlock forests. From these forests, the park continues on to higher altitudes, reaching the sub-alpine and alpine areas near the Erg Mountain. This mountain, which is an old hiking destination, is known for the magnificent vistas it offers of the Upper Fraser Valley along with the mountain range in the vicinity. When the weather is clear, the prominent Mount Sir Alexander is visible.

Erromanga language

Erromangan, or Sie (Sye), is the primary language spoken on the island Erromango in the Tafea region of the Vanuatu islands. The other Erromanga languages are either moribund or extinct. Although the island is quite large (887 km²), the total number of speakers of Erromango is estimated at around 1900.

Hyperion Cantos

The Hyperion Cantos is a series of science fiction novels by Dan Simmons. The title was originally used for the collection of the first pair of books in the series, Hyperion and The Fall of Hyperion, and later came to refer to the overall storyline, including Endymion, The Rise of Endymion, and a number of short stories. More narrowly, inside the fictional storyline, after the first volume, the Hyperion Cantos is an epic poem written by the character Martin Silenus covering in verse form the events of the first book.Of the four novels, Hyperion received the Hugo and Locus Awards in 1990; The Fall of Hyperion won the Locus and British Science Fiction Association Awards in 1991; and The Rise of Endymion received the Locus Award in 1998. All four novels were also nominated for various science fiction awards.

An event series is being developed by Bradley Cooper, Graham King, and Todd Phillips for Syfy based on the first novel Hyperion.

Indoor rower

An indoor rower, or rowing machine, is a machine used to simulate the action of watercraft rowing for the purpose of exercise or training for rowing. Indoor rowing has become established as a sport in its own right. The term also refers to a participant in this sport.

Modern indoor rowers are often known as ergometers (colloquially erg or ergo), an ergometer being a device which measures the amount of work performed. The indoor rower is calibrated to measure the amount of energy the rower is using through their use of the equipment.

Ly Erg

The Ly Erg is a fairy from Scottish folklore, particularly associated with the area in and around the Glenmore Forest, part of the present-day Cairngorms National Park. It is dressed as a soldier, distinguishable from a real soldier only by its red right hand, said to be stained with the blood of its victims. While out walking it will stop near water, and by raising its right hand challenge passersby to fight. But anyone who engages in combat with the Ly Erg will be dead within a fortnight, win or lose.Writing in 1847, the antiquarian Joseph Robertson tells of three brothers who fought the Ly Erg, each of them dying immediately after their encounter.

Murzuq Desert

The Murzuq Desert, Idehan Murzuq, Idhan Murzuq, (also Murzaq, Murzuk, Marzuq and Murzak), is an erg in southwestern Libya with a surface of approximately 58,000 km2. It is named after the town of Murzuk in the Fezzan. Like the Idehan Ubari further north, the Idehan Murzuq is part of the greater Sahara Desert region. It is separated from the southern Sahara Desert by the Tibesti Mountains and the Tassili n'Ajjer.

Olympia Undae

Olympia Undae is a vast dune field in the north polar region of the planet Mars. It consists of a broad "sand sea" or erg that partly rings the north polar plateau (Planum Boreum) from about 120° to 240°E longitude and 78° to 83°N latitude. Stretching about 1,100 km (680 mi) across and covering an area of 470,000 km2, Olympia Undae is the largest continuous dune field on Mars. It is similar in size to the Rub' Al Khali in the Arabian Peninsula, the largest active erg on Earth.Olympia Undae lies within the informally named Borealis basin (also called the north polar basin), the largest of three topographic basins that occur in the northern lowlands of Mars. The average elevation in Olympia Undae is about 4,250 m below datum (martian "sea" level). The 19-km-diameter crater Jojutla lies near the geographic center of Olympia Undae at 81.63°N latitude and 169.65°E longitude.This crater was named by Andres Eloy Martinez Rojas, Mexican astronomer and science writer.Unda (pl. undae) is a Latin term meaning water, particularly water in motion as waves. The International Astronomical Union (IAU) adopted the term to describe "undulatory," dune-like features on other planets. Olympia Undae contains a variety of dune forms and wind-related (aeolian) depositional features, including sand sheets, transverse dunes, simple barchan dunes, mega-barchans, and complex barchanoid ridges. All of these dune types occur on Earth too.

Barchans are isolated, crescent-shaped dunes with horns that point downwind. They occur is areas where sand supply is moderate to low. Small simple barchan dunes and large mega-barchans are common at the margins of Olympia Undae and in areas where the sand cover is thin. Barchanoid ridges are broad linear to sinuous sand accumulations. They form through the lateral coalition of individual barchans and indicate increasing sand supply. Where sand is abundant, transverse dunes occur; they are commonly defined as long barchaoid ridges with fairly straight segments that are perpendicular to the wind direction. The majority of dunes in Olympia Undae are transverse dunes. Their spacing ranges from 200 to 800 m apart crest to crest, and comparison to terrestrial dunes with similar spacing indicates that they are 10 to 25 m high.On Earth, dunes are produced by saltating grains of sand. The requirement that dunes are produced by saltation allows scientists to determine the likely grain size for the particles making up the dunes in Olympia Undae and other martian dune fields. On Mars, the particle size most easily moved by wind is about 100 μm in diameter (fine sand). The sand in Olympia Undae is extremely dark in color and probably consists of basaltic rock fragments. The surface of Olympia Undae has a strong TES Type 2 spectral signature, indicating that the surface materials consist of basaltic andesite or weathered basalt and/or basaltic glass.In 2005, the OMEGA instrument on the Mars Express orbiter detected high concentrations of gypsum in the eastern portion of Olympia Undae (centered at 244.5°E, 80.2°N). CRISM data from the Mars Reconnaissance Orbiter (MRO) suggests that the gypsum is more concentrated along the crests of dunes than in the interdune hollows. The source of the gypsum is uncertain. Gypsum is an evaporitic mineral that precipitates from saline water; thus, its presence may indicate conditions different from today’s martian environment. The mineral may have formed through the melting of acidic snow, or the melting and discharge of sulfur-rich water from the base of the polar ice cap. However, the presence of gypsum does not necessarily require large surface water bodies (e.g., playa lakes). The mineral could have formed in volcanically heated groundwater in the shallow subsurface and later been exposed and concentrated by wind erosion and winnowing ("eolian mining").The term Olympia Undae can be the source of some confusion among Mars researchers. The term is used to describe 1) the geographical area described above and the type area for 2) a stratigraphic or geologic map unit (e.g. formation) called the Olympia Undae unit. As a stratigraphic unit, Olympia Undae describes materials that make up the geographic Olympia Undae as well as other sand sheets and dune fields encircling Planum Boreum (e.g., Abalos Undae). The Olympia Undae unit is Amazonian in age. To address some of this confusion, the stratigraphic term Olympia Undae unit has recently been renamed to simply "undae unit," since it encompasses other named dune fields (undae) around Planum Boreum. Another possible source of confusion is the distinction between Olympia Undae and Olympia Planum (formerly, Olympia Planitia). As a geographic area, Olympia Undae refers to the erg that covers a large fraction of Olympia Planum between longitude 120° and 240°E. Olympia Undae and Olympia Planum are not interchangeable terms. Olympia Planum is a broad, plain (and topographic bench) adjacent to Planum Boreum. It is half-domed shaped in profile (cross-section) and slopes southward into the Vastitas Borealis. The Olympia Undae erg covers both the bulk of southern Olympia Planum and part of the northern Vastitas Borealis.

Polar effect

The polar effect or electronic effect in chemistry is the effect exerted by a substituent on modifying electrostatic forces operating on a nearby reaction center. The main contributors to the polar effect are the inductive effect, mesomeric effect and the through-space electronic field effect.

An electron withdrawing group or EWG draws electrons away from a reaction center. When this center is an electron rich carbanion or an alkoxide anion, the presence of the electron-withdrawing substituent has a stabilizing effect.

Examples of electron withdrawing groups are

halogens (F, Cl);

nitriles CN;

carbonyls RCOR';

nitro groups NO2.An electron releasing group or ERG (may also be called electron donating groups or EDG's) releases electrons into a reaction center and as such stabilizes electron deficient carbocations. An ERG can essentially promote groups into have a higher effect. These higher effects are defined as steric effects to a degree, however other effects include observations to changes in polarity, which can thus produce an entirely different molecule. This entirely different molecule is the ERG, plus whatever substituent was left behind. This is partially true but in truth the entirely different molecule is composed of parts and can be further differentiated and stabilized as separate molecules as well, although this can prove difficult for the beginner. Different steric effects can produce different molecules as well, and these essentially allow certain molecular formations to take themselves apart, and if this is done, then the ERG can be recognized as a separate molecule. This is difficult but can prove that ERGs form themselves not due to some type of separation but due to the fact that the presence of weak electronic sources, that an ERG must form. If it does not then the electron weak reaction center will fall apart, and return to its original formation, and thus the separation must occur due to the steric effect itself, and not the fact that the alcohols donate electrons, but due to the change in electrons that allows the center to remain stable without the need for the other molecules to be present (Examples).

Examples of electron releasing groups are

alkyl groups;

alcohol groups;

amino groups.The total substituent effect is the combination of the polar effect and the combined steric effects.

In electrophilic aromatic substitution and nucleophilic aromatic substitution substituents are divided into activating groups and deactivating groups where the direction of activation or deactivation is also taken into account.

Roller Hockey Bundesliga

Rollhockey Bundesliga is the biggest Roller Hockey Clubs Championship in Germany. Since 2011-12 season, the Dutch club Valkenswaardse RC takes part in Bundesliga.

The Champion in the last edition of Bundesliga was ERG Iserlohn.


The Ténéré (Berber: Tiniri, literally: desert, wilderness) is a desert region in the south central Sahara. It comprises a vast plain of sand stretching from northeastern Niger into western Chad, occupying an area of over 400,000 square kilometres (150,000 sq mi). The Ténéré's boundaries are said to be the Aïr Mountains in the west, the Hoggar Mountains in the north, the Djado Plateau in the northeast, the Tibesti Mountains in the east, and the basin of Lake Chad in the south. The central part of the desert, the Erg du Bilma, is centred at approximately 17°35′N 10°55′E. It is the locus of the Neolithic Tenerian culture.

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