Blood group systems.

A complete blood type would describe a full set of 30 substances on the surface of red blood cells, and an individual's blood type is one of many possible combinations of blood-group antigens. Across the 36 blood group systems, 308 different blood-group antigens have been found. Almost always, an individual has the same blood group for life, but very rarely an individual's blood type changes through addition or suppression of an antigen in infection, malignancy, or autoimmune disease. Another more common cause of blood type change is a bone marrow transplant. Bone-marrow transplants are performed for many leukemias and lymphomas, among other diseases. If a person receives bone marrow from someone who is a different ABO type (e.g., a type A patient receives a type O bone marrow), the patient's blood type will eventually convert to the donor's type.  Some blood types are associated with inheritance of other diseases; for example, the Kell antigen is sometimes associated with McLeod syndrome. Certain blood types may affect susceptibility to infections, an example being the resistance to specific malaria species seen in individuals lacking the Duffy antigen. The Duffy antigen, presumably as a result of natural selection, is less common in population groups from areas having a high incidence of malaria.

ABO blood group system.

The ABO blood group system involves two antigens and two antibodies found in human blood. The two antigens are antigen A and antigen B. The two antibodies are antibody A and antibody B. The antigens are present on the red blood cells and the antibodies in the serum. Regarding the antigen property of the blood all human beings can be classified into 4 groups, those with antigen A (group A), those with antigen B (group B), those with both antigen A and B (group AB) and those with neither antigen (group O). The antibodies present together with the antigens are found as follows:  There is an agglutination reaction between similar antigen and antibody (for example, antigen A agglutinates the antibody A and antigen B agglutinates the antibody B). Thus, transfusion can be considered safe as long as the serum of the recipient does not contain antibodies for the blood cell antigens of the donor.  The "ABO system" is the most important blood-group system in human-blood transfusion. The associated anti-A and anti-B antibodies are usually "immunoglobulin M", abbreviated IgM, antibodies. It has been hypothesized that ABO IgM antibodies are produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses, although blood group compatibility rules are applied to newborn and infants as a matter of practice. The original terminology used by Karl Landsteiner in 1901 for the classification was A/B/C; in later publications "C" became "O". Type O is often called "0" ("zero", or "null") in other languages.

Rh blood group system.

The Rh system (Rh meaning "Rhesus") is the second most significant blood-group system in human-blood transfusion with currently 50 antigens. The most significant Rh antigen is the D antigen, because it is the most likely to provoke an immune system response of the five main Rh antigens. It is common for D-negative individuals not to have any anti-D IgG or IgM antibodies, because anti-D antibodies are not usually produced by sensitization against environmental substances. However, D-negative individuals can produce IgG anti-D antibodies following a sensitizing event: possibly a fetomaternal transfusion of blood from a fetus in pregnancy or occasionally a blood transfusion with D positive RBCs. Rh disease can develop in these cases. Rh negative blood types are much less common in Asian populations (0.3%) than they are in European populations (15%). The presence or absence of the Rh(D) antigen is signified by the + or − sign, so that, for example, the A− group is ABO type A and does not have the Rh (D) antigen.

ABO and Rh distribution by country.

As with many other genetic traits, the distribution of ABO and Rh blood groups varies significantly between populations.

Other blood group systems.

Twenty-eight blood-group systems have been identified by the International Society for Blood Transfusion in addition to the common ABO and Rh systems. Thus, in addition to the ABO antigens and Rh antigens, many other antigens are expressed on the RBC surface membrane. For example, an individual can be AB, D positive, and at the same time M and N positive (MNS system), K positive (Kell system), Le or Le negative (Lewis system), and so on, being positive or negative for each blood group system antigen. Many of the blood group systems were named after the patients in whom the corresponding antibodies were initially encountered.

Clinical significance.

Blood transfusion.

Transfusion medicine is a specialized branch of hematology that is concerned with the study of blood groups, along with the work of a blood bank to provide a transfusion service for blood and other blood products. Across the world, blood products must be prescribed by a medical doctor (licensed physician or surgeon) in a similar way as medicines.  Much of the routine work of a blood bank involves testing blood from both donors and recipients to ensure that every individual recipient is given blood that is compatible and is as safe as possible. If a unit of incompatible blood is transfused between a donor and recipient, a severe acute hemolytic reaction with hemolysis (RBC destruction), kidney failure and shock is likely to occur, and death is a possibility. Antibodies can be highly active and can attack RBCs and bind components of the complement system to cause massive hemolysis of the transfused blood.  Patients should ideally receive their own blood or type-specific blood products to minimize the chance of a transfusion reaction. It is also possible to use the patients' own blood for transfusion called autologous blood transfusion, which is always compatible with the patient. This is because patients’ own red blood cells are used. The procedure of washing patients own red blood cells goes as follows. The patients lost blood is collected and washed with a saline solution. The washing procedure yields concentrated washed red blood cells. The last step is reinfusing the packed red blood cells in the patient. There are multiple ways to wash red blood cells. The two main ways are centrifugation and filtration methods. This procedure can be performed with microfiltration devices like the Hemoclear filter. Risks can be further reduced by cross-matching blood, but this may be skipped when blood is required for an emergency. Cross-matching involves mixing a sample of the recipient's serum with a sample of the donor's red blood cells and checking if the mixture "agglutinates", or forms clumps. If agglutination is not obvious by direct vision, blood bank technicians usually check for agglutination with a microscope. If agglutination occurs, that particular donor's blood cannot be transfused to that particular recipient. In a blood bank it is vital that all blood specimens are correctly identified, so labelling has been standardized using a barcode system known as ISBT 128.  The blood group may be included on identification tags or on tattoos worn by military personnel, in case they should need an emergency blood transfusion. Frontline German Waffen-SS had blood group tattoos during World War II.  Rare blood types can cause supply problems for blood banks and hospitals. For example, Duffy-negative blood occurs much more frequently in people of African origin, and the rarity of this blood type in the rest of the population can result in a shortage of Duffy-negative blood for these patients. Similarly for RhD negative people, there is a risk associated with travelling to parts of the world where supplies of RhD negative blood are rare, particularly East Asia, where blood services may endeavor to encourage Westerners to donate blood.

Hemolytic disease of the newborn (HDN).

Pregnant women may carry a fetus with a blood type which is different from their own. In those cases, the mother can make IgG blood group antibodies. This can happen if some of the fetus' blood cells pass into the mother's blood circulation (e.g. a small fetomaternal hemorrhage at the time of childbirth or obstetric intervention), or sometimes after a therapeutic blood transfusion. This can cause Rh disease or other forms of hemolytic disease of the newborn (HDN) in the current pregnancy and/or subsequent pregnancies. Sometimes this is lethal for the fetus; in these cases it is called hydrops fetalis. If a pregnant woman is known to have anti-D antibodies, the Rh blood type of a fetus can be tested by analysis of fetal DNA in maternal plasma to assess the risk to the fetus of Rh disease. One of the major advances of twentieth century medicine was to prevent this disease by stopping the formation of Anti-D antibodies by D negative mothers with an injectable medication called Rho(D) immune globulin. Antibodies associated with some blood groups can cause severe HDN, others can only cause mild HDN and others are not known to cause HDN.

Blood products.

To provide maximum benefit from each blood donation and to extend shelf-life, blood banks fractionate some whole blood into several products. The most common of these products are packed RBCs, plasma, platelets, cryoprecipitate, and fresh frozen plasma (FFP). FFP is quick-frozen to retain the labile clotting factors V and VIII, which are usually administered to patients who have a potentially fatal clotting problem caused by a condition such as advanced liver disease, overdose of anticoagulant, or disseminated intravascular coagulation (DIC).  Units of packed red cells are made by removing as much of the plasma as possible from whole blood units.  Clotting factors synthesized by modern recombinant methods are now in routine clinical use for hemophilia, as the risks of infection transmission that occur with pooled blood products are avoided.

Red blood cell compatibility.

An Rh D-negative patient who does not have any anti-D antibodies (never being previously sensitized to D-positive RBCs) can receive a transfusion of D-positive blood once, but this would cause sensitization to the D antigen, and a female patient would become at risk for hemolytic disease of the newborn. If a D-negative patient has developed anti-D antibodies, a subsequent exposure to D-positive blood would lead to a potentially dangerous transfusion reaction. Rh D-positive blood should never be given to D-negative women of child-bearing age or to patients with D antibodies, so blood banks must conserve Rh-negative blood for these patients. In extreme circumstances, such as for a major bleed when stocks of D-negative blood units are very low at the blood bank, D-positive blood might be given to D-negative females above child-bearing age or to Rh-negative males, providing that they did not have anti-D antibodies, to conserve D-negative blood stock in the blood bank. The converse is not true; Rh D-positive patients do not react to D negative blood.  This same matching is done for other antigens of the Rh system as C, c, E and e and for other blood group systems with a known risk for immunization such as the Kell system in particular for females of child-bearing age or patients with known need for many transfusions.

Plasma compatibility.

Blood plasma compatibility is the inverse of red blood cell compatibility. Type AB plasma carries neither anti-A nor anti-B antibodies and can be transfused to individuals of any blood group; but type AB patients can only receive type AB plasma. Type O carries both antibodies, so individuals of blood group O can receive plasma from any blood group, but type O plasma can be used only by type O recipients.  Rh D antibodies are uncommon, so generally neither D negative nor D positive blood contain anti-D antibodies. If a potential donor is found to have anti-D antibodies or any strong atypical blood group antibody by antibody screening in the blood bank, they would not be accepted as a donor (or in some blood banks the blood would be drawn but the product would need to be appropriately labeled); therefore, donor blood plasma issued by a blood bank can be selected to be free of D antibodies and free of other atypical antibodies, and such donor plasma issued from a blood bank would be suitable for a recipient who may be D positive or D negative, as long as blood plasma and the recipient are ABO compatible.

Universal donors and universal recipients.

In transfusions of packed red blood cells, individuals with type O Rh D negative blood are often called universal donors. Those with type AB Rh D positive blood are called universal recipients. However, these terms are only generally true with respect to possible reactions of the recipient's anti-A and anti-B antibodies to transfused red blood cells, and also possible sensitization to Rh D antigens. One exception is individuals with hh antigen system (also known as the Bombay phenotype) who can only receive blood safely from other hh donors, because they form antibodies against the H antigen present on all red blood cells.  Blood donors with exceptionally strong anti-A, anti-B or any atypical blood group antibody may be excluded from blood donation. In general, while the plasma fraction of a blood transfusion may carry donor antibodies not found in the recipient, a significant reaction is unlikely because of dilution.  Additionally, red blood cell surface antigens other than A, B and Rh D, might cause adverse reactions and sensitization, if they can bind to the corresponding antibodies to generate an immune response. Transfusions are further complicated because platelets and white blood cells (WBCs) have their own systems of surface antigens, and sensitization to platelet or WBC antigens can occur as a result of transfusion.  For transfusions of plasma, this situation is reversed. Type O plasma, containing both anti-A and anti-B antibodies, can only be given to O recipients. The antibodies will attack the antigens on any other blood type. Conversely, AB plasma can be given to patients of any ABO blood group, because it does not contain any anti-A or anti-B antibodies.

Blood typing.

Typically, blood type tests are performed through addition of a blood sample to a solution containing antibodies corresponding to each antigen. The presence of an antigen on the surface of the blood cells is indicated by agglutination. An alternative system for blood type determination involving no antibodies was developed in 2017 at Imperial College London which makes use of paramagnetic molecularly imprinted polymer nanoparticles with affinity for specific blood antigens. In these tests, rather than agglutination, a positive result is indicated by decolorization as red blood cells which bind to the nanoparticles are pulled toward a magnet and removed from solution.

Blood group genotyping.

In addition to the current practice of serologic testing of blood types, the progress in molecular diagnostics allows the increasing use of blood group genotyping. In contrast to serologic tests reporting a direct blood type phenotype, genotyping allows the prediction of a phenotype based on the knowledge of the molecular basis of the currently known antigens. This allows a more detailed determination of the blood type and therefore a better match for transfusion, which can be crucial in particular for patients with needs for many transfusions to prevent allo-immunization.

History.

Blood types were first discovered by an Austrian physician, Karl Landsteiner, working at the Pathological-Anatomical Institute of the University of Vienna (now Medical University of Vienna). In 1900, he found that blood sera from different persons would clump together (agglutinate) when mixed in test tubes, and not only that, some human blood also agglutinated with animal blood. He wrote a two-sentence footnote:  This was the first evidence that blood variation exists in humans. The next year, in 1901, he made a definitive observation that blood serum of an individual would agglutinate with only those of certain individuals. Based on this he classified human bloods into three groups, namely group A, group B, and group C. He defined that group A blood agglutinates with group B, but never with its own type. Similarly, group B blood agglutinates with group A. Group C blood is different in that it agglutinates with both A and B. This was the discovery of blood groups for which Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930. (C was later renamed to O after the German "Ohne", meaning without, or zero, or null.) The group AB was discovered a year later by Landsteiner's students Adriano Sturli and Alfred von Decastello.  In 1927, Landsteiner, with Philip Levine, discovered the MN blood group system, and the P system. Development of the Coombs test in 1945, the advent of transfusion medicine, and the understanding of ABO hemolytic disease of the newborn led to discovery of more blood groups., the International Society of Blood Transfusion (ISBT) recognizes 346 blood group antigens which are assigned to 36 blood groups.

Society and culture.

A popular pseudoscientific belief in Japan (known as ""ketsueki-gata"") (血液型)and South Korea is that a person's ABO blood type is predictive of their personality, character, and compatibility with others. Researchers have established no scientific basis exists for blood type personality categorization, and studies have found no "significant relationship between personality and blood type, rendering the theory 'obsolete' and concluding that no basis exists to assume that personality is anything more than randomly associated with blood type."

A blood type (also known as a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele (or an alternative version of a gene) and collectively form a blood group system.

Eine Blutgruppe ist eine Beschreibung der individuellen Zusammensetzung der Oberfläche der roten Blutkörperchen (Erythrozyten) von Wirbeltieren. Die Oberflächen unterscheiden sich durch verschiedene Glykolipide oder Proteine, die als Antigene wirken und somit zu einer Immunreaktion führen können. Eine besondere Bedeutung kommt den Blutgruppen in der Transfusionsmedizin zu. Wird nämlich einem Patienten Blut einer ungeeigneten Blutgruppe transfundiert, so kommt es zu einer Immunreaktion, die wiederum zur Verklumpung (Agglutination) des Blutes und damit zum Tod führen kann. Blutgruppen sind erblich und können verwendet werden, um Verwandtschaftsverhältnisse auszuschließen (siehe auch Artikel Abstammungsgutachten).


History.

Early theorizing.

The objects now called "brown dwarfs" were theorized to exist in the 1960s by Shiv S. Kumar and were originally called black dwarfs, a classification for dark substellar objects floating freely in space that were not massive enough to sustain hydrogen fusion. However: (a) the term black dwarf was already in use to refer to a cold white dwarf; (b) red dwarfs fuse hydrogen; and (c) these objects may be luminous at visible wavelengths early in their lives. Because of this, alternative names for these objects were proposed, including planetar and substar. In 1975, Jill Tarter

Deuterium fusion.

The discovery of deuterium burning down to 0.012 solar masses and the impact of dust formation in the cool outer atmospheres of brown dwarfs in the late 1980s brought these theories into question. However, such objects were hard to find because they emit almost no visible

GD 165B and class "L".

For many years, efforts to discover brown dwarfs were fruitless. In 1988, however, a faint companion to a star known as GD 165 was found in an infrared search of white dwarfs. The spectrum of the companion GD 165B was very red and enigmatic, showing none of the features expected of a low-mass red dwarf. It became clear that GD 165B would need to be classified as a much cooler object than the latest M dwarfs then known. GD 165B remained unique for almost a decade until the advent of the Two Micron All-Sky Survey (2MASS) which discovered many objects

Gliese 229B and class "T" – the methane dwarfs.

The first Brown Dwarf was discovered in 1994 by Caltech astronomers Kulkarni, Tadashi Nakajima, Keith Matthews, and Rebecca Oppenheimer, and Johns Hopkins scientists Sam Durrance and David Golimowski. It was confirmed in 1995 as a substellar companion to Gliese 229. Gliese 229b is one of the first two instances of clear evidence for a brown dwarf, along with Teide 1. Confirmed in 1995, both

Teide 1 – the first class "M" brown dwarf.

The first confirmed brown dwarf was discovered by Spanish astrophysicists (head of team), María Rosa Zapatero Osorio, and Eduardo Martín in 1994. This object, found in the Pleiades open cluster, received the name Teide 1. The discovery article was submitted to "Nature" in May 1995, and published on 14 September 1995. "Nature" highlighted "Brown dwarfs discovered, official" in the front page of that issue.  Teide 1 was discovered in images collected by the IAC team on 6 January 1994 using the 80 cm telescope (IAC 80) at Teide Observatory and its spectrum was first recorded in December 1994 using the 4.2 m William Herschel Telescope at Roque de los Muchachos Observatory (La Palma). The distance, chemical composition, and age of Teide 1 could be established because of its membership in the young Pleiades star cluster. Using the most advanced stellar and

Theory.

The standard mechanism for star birth is through the gravitational collapse of a cold interstellar cloud of gas and dust. As the cloud contracts it heats due to the Kelvin–Helmholtz mechanism. Early in the process the contracting gas quickly radiates away much of the energy, allowing the collapse to continue. Eventually, the central region becomes sufficiently dense to trap radiation. Consequently, the central temperature and density of the collapsed cloud increases dramatically with time, slowing the contraction, until the conditions are hot and dense enough for thermonuclear reactions to occur in the core of the protostar. For most stars, gas and radiation pressure generated by the thermonuclear fusion reactions within the core of the star will support it against any further gravitational contraction. Hydrostatic equilibrium is reached and the star will spend most of its lifetime fusing hydrogen into helium as a main-sequence star.  If, however, the mass of the protostar is less than about, normal hydrogen thermonuclear fusion reactions will not ignite in the core. Gravitational contraction does not heat the small protostar very effectively, and before the temperature in the core can increase enough to trigger fusion, the density reaches the point where electrons become closely packed enough to create quantum electron degeneracy pressure. According to the brown dwarf interior models, typical conditions in the core for density, temperature and pressure are expected to be the following:  This means that the protostar is not massive enough and not dense enough to ever reach the conditions needed to sustain hydrogen fusion. The infalling matter is prevented, by electron degeneracy pressure, from reaching the densities and pressures needed.  Further gravitational contraction is prevented and the result is a "failed star", or brown dwarf that simply cools off by radiating away its internal thermal energy.

High-mass brown dwarfs versus low-mass stars.

Lithium is generally present in brown dwarfs and not in low-mass stars. Stars, which reach the high temperature necessary for fusing hydrogen, rapidly deplete their lithium. Fusion of lithium-7 and a proton occurs producing two helium-4 nuclei. The temperature necessary for this reaction is just below that necessary for hydrogen fusion. Convection in low-mass stars ensures that lithium in the whole volume of the star is eventually depleted. Therefore, the presence of the lithium spectral line in a candidate brown dwarf is a strong indicator that it is indeed a substellar object.

The lithium test.

The use of lithium to distinguish candidate brown dwarfs from low-mass stars is commonly referred to as the lithium test, and was pioneered by, Eduardo Martín and Antonio Magazzu. However, lithium is also seen in very young stars, which have not yet had enough time to burn it all.  Heavier stars, like the Sun, can also retain lithium in

Atmospheric methane.

Unlike stars, older brown dwarfs are sometimes cool enough that, over very long periods of

Iron rain.

Main-sequence stars cool, but eventually reach a minimum bolometric luminosity that they can sustain through steady fusion. This varies from star to star, but is generally at least 0.01% that of the Sun. Brown dwarfs cool and darken steadily over their lifetimes: sufficiently old brown dwarfs will be too faint to be detectable.  Iron rain as part of atmospheric convection processes is possible only in brown dwarfs, and not in small stars. The spectroscopy research into iron rain is still ongoing, but not all brown dwarfs will always have this atmospheric anomaly. In 2013, a heterogeneous iron-containing atmosphere was imaged around the B component in the close Luhman 16 system.

Low-mass brown dwarfs versus high-mass planets.

Like stars, brown dwarfs form independently, but, unlike stars, lack sufficient mass to "ignite". Like all stars, they can occur singly or in close proximity to other stars. Some orbit stars and can, like planets, have eccentric orbits.

Size and fuel-burning ambiguities.

Brown dwarfs are all roughly the same radius as Jupiter. At the high end of their mass range (), the volume of a brown dwarf is governed primarily by electron-degeneracy pressure, as it is in white dwarfs; at the low end of the range (), their volume is

Heat spectrum.

X-ray and infrared spectra are telltale signs of brown dwarfs. Some emit X-rays; and all "warm" dwarfs continue to glow tellingly in the red and infrared spectra until they cool to planet-like temperatures (under 1000 K).  Gas giants have some of the characteristics of brown

Current IAU standard.

Currently, the International Astronomical Union considers an object above (the limiting mass for thermonuclear fusion of deuterium) to be a brown dwarf, whereas an object under that mass (and orbiting a star or stellar remnant) is considered a planet.  The 13 Jupiter-mass cutoff is a rule of thumb rather than something of precise physical significance. Larger objects will

Sub-brown dwarf.

Objects below, called sub-brown dwarf or planetary-mass brown dwarf, form in the same manner as stars and brown dwarfs (i.e. through the collapse of a gas cloud) but have a mass below the limiting mass for thermonuclear fusion of deuterium.  Some researchers call them free-floating planets, whereas others call them planetary-mass brown dwarfs.

Role of other physical properties in the mass estimate.

While spectroscopic features can help to distinguish between low mass stars and brown dwarfs, it is often necessary to estimate the mass to come to a conclusion. The theory behind the mass estimate is that brown dwarfs with a similar mass form in a similar way and are hot when they form. Some have spectral types that are similar to low-mass stars, such as 2M1101AB. As they cool down the brown dwarfs should retain a range of luminosities depending on the mass. Without the age and luminosity a mass estimate is difficult; for example, an L-type brown dwarf could be an old brown dwarf with a high mass (possibly a low-mass star) or a young brown dwarf with a very low mass. For Y-dwarfs this is less of a problem as they remain low mass objects near the sub-brown dwarf limit, even for relative high age

Observations.

Classification of brown dwarfs.

Spectral class M.

These are brown dwarfs with a spectral class of M6.5 or later; they are also called late-M dwarfs.

Spectral class L.

The defining characteristic of spectral class M, the coolest type in the long-standing classical stellar sequence, is an optical spectrum dominated by absorption bands of titanium(II) oxide (TiO) and vanadium(II) oxide (VO) molecules. However, GD 165B, the cool companion to the white dwarf GD 165, had none of the hallmark TiO features of M dwarfs. The subsequent identification of many objects like GD 165B ultimately led to the definition of a

Spectral class T.

As GD 165B is the prototype of the L dwarfs, Gliese 229B is the prototype of a second new spectral class, the T dwarfs. Whereas near-infrared (NIR) spectra of L dwarfs show strong absorption bands of HO and carbon monoxide (CO), the NIR spectrum of Gliese 229B is dominated by absorption bands from methane (CH), features that were only found in the giant planets of the Solar System and Titan. CH, HO, and molecular hydrogen (H) collision-induced absorption (CIA) give Gliese 229B blue near-infrared colors. Its steeply sloped red optical spectrum also lacks the FeH

Spectral class Y.

There is some doubt as to what, if anything, should be included in the class Y dwarfs. They are expected to be much cooler than T-dwarfs. They have been modelled, though there is no well-defined spectral sequence yet with prototypes.  In 2009, the coolest known brown dwarfs had estimated effective temperatures between 500 and 600 K, and have been assigned the spectral class T9. Three examples are the brown dwarfs CFBDS J005910.90-011401.3, ULAS J133553.45+113005.2, and ULAS J003402.77−005206.7. The spectra of these objects have absorption peaks around 1.55 micrometres. Delorme et al. have suggested that this

Secondary features.

Young brown dwarfs have low surface gravities because they have larger radii and lower masses compared to the field stars of similar spectral type. These sources are marked by a letter beta (β) for intermediate surface gravity and gamma (γ) for low surface gravity. Indication for low surface gravity are weak CaH, K I and Na I lines, as well as strong VO line. Alpha (α) stands for normal surface gravity and is usually dropped. Sometimes an extremely low surface gravity is denoted by a delta (δ). The

Spectral and atmospheric properties of brown dwarfs.

The majority of flux emitted by L and T dwarfs is in the 1 to 2.5 micrometre near-infrared range. Low and decreasing temperatures through the late M-, L-, and T-dwarf sequence result in a rich near-infrared spectrum containing a wide variety of features, from relatively narrow lines of neutral atomic species to broad molecular bands, all of which have different dependencies on temperature, gravity, and metallicity. Furthermore, these low temperature conditions favor condensation out of the gas state and the formation of grains.  Typical atmospheres of known brown dwarfs range in temperature from 2200 down to 750 K. Compared to stars, which warm themselves with steady internal fusion, brown dwarfs cool quickly over time; more massive dwarfs cool more slowly than less massive ones.  Observations of known brown dwarf candidates have revealed

Observational techniques.

Coronagraphs have recently been used to detect faint objects orbiting bright visible stars, including Gliese 229B.  Sensitive telescopes equipped with charge-coupled devices (CCDs) have been used to search distant star clusters for faint objects, including Teide 1.  Wide-field searches have identified individual faint objects, such as Kelu-1 (30 ly away).  Brown dwarfs are often discovered in surveys to

Brown dwarf as an X-ray source.

X-ray flares detected from brown dwarfs since 1999 suggest changing magnetic fields within them, similar to those in very-low-mass stars.  With no strong central nuclear energy source, the interior of a brown dwarf is in a rapid boiling, or convective state. When combined with the rapid rotation that most brown dwarfs exhibit, convection sets up conditions for the development of a strong, tangled magnetic field near the surface. The flare observed by Chandra from LP 944-20 could have its origin in the turbulent magnetized hot material beneath the brown dwarf's surface. A sub-surface flare could conduct heat to the atmosphere, allowing electric currents to flow and produce an X-ray flare, like a stroke

Brown dwarfs as radio sources.

The first brown dwarf that was discovered to emit radio signals was LP 944-20, which was observed based on its X-ray emission. Approximately 5–10% of brown dwarfs appear to have strong magnetic fields and emit radio waves, and there may be as many as 40 magnetic brown dwarfs within 25 pc of the Sun based on Monte Carlo modeling and their average spatial density. The power of the radio emissions of brown dwarfs is roughly constant despite variations

Binary brown dwarfs.

Observations of the orbit of binary systems containing brown dwarfs can be used to measure the mass of the brown dwarf. In the case of 2MASSW J0746425+2000321, the secondary weighs 6% of the solar mass. This measurement is called a dynamical mass. The brown dwarf system closest to our solar system is the binary Luhman 16. It was attempted to search for planets around this system with a similar method, but none were found.  The wide binary system 2M1101AB was the first binary with a separation greater than 20 au. The discovery of the system gave definitive insights to the formation of brown dwarfs. It was previously thought that wide binary brown dwarfs are not formed or at least are disrupted at ages of 1-10 Myrs. The existence of this system is also inconsistent with the ejection hypothesis. The ejection hypothesis was a proposed hypothesis in which brown dwarfs form in a multiple system, but are ejected before they gain enough mass to burn hydrogen.  More recently the wide binary W2150AB was discovered. It has a similar mass ratio and binding energy as

Recent developments.

Estimates of brown dwarf populations in the solar neighbourhood estimated that there may be as many as six stars for every brown dwarf. A more recent estimate from 2017 using the young massive star cluster RCW 38 found that the Milky Way galaxy contains between 25 and 100

Formation and evolution.

Brown dwarfs form similar to stars and are surrounded by protoplanetary disks, such as Cha 110913-773444. As of 2017 there is only one known proto-brown dwarf that is connected with a large Herbig-Haro object. This is the brown dwarf Mayrit 1701117, which is surrounded by a pseudo-disk and a Keplerian disk. Mayrit 1701117 launches the 0.7 light-year long jet H 1165, mostly seen in ionized sulfur.  Disks around brown dwarfs have been found to have many of the same features as disks around stars; therefore, it is expected that there will be accretion-formed planets around brown dwarfs. Given the small mass

Planets around brown dwarfs.

The super-Jupiter planetary-mass objects 2M1207b and 2MASS J044144 that are orbiting brown dwarfs at large orbital distances may have formed by cloud collapse rather than accretion and so may be sub-brown dwarfs rather than planets, which is inferred from relatively large masses and large orbits. The first discovery of a low-mass companion orbiting a brown dwarf (ChaHα8) at a small orbital distance using the radial velocity technique paved the way for the detection of planets around brown dwarfs on orbits of a few AU or smaller. However, with a mass ratio between the companion and primary in ChaHα8 of about 0.3, this system rather resembles a binary star. Then, in 2008, the first planetary-mass companion in a relatively small orbit (MOA-2007-BLG-192Lb) was discovered orbiting a brown dwarf. Planets around brown dwarfs are likely to be carbon planets depleted of water.  A 2017 study, based upon observations with Spitzer estimates that 175 brown dwarfs need to be monitored in order to guarantee (95%) at least one detection of a planet.

Habitability.

Habitability for hypothetical planets orbiting brown dwarfs has been studied. Computer models suggesting conditions for these bodies to have habitable planets are very stringent, the habitable zone being narrow

A brown dwarf is a type of substellar object that has a mass between those of the heaviest gas giant planets and the least massive stars, i.e., approximately 13 to 75–80 times that of Jupiter (), or approximately to about. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the least massive red dwarfs. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.

Braune Zwerge sind Himmelskörper, die eine Sonderstellung zwischen Sternen und Planeten einnehmen. Ihre Massen reichen mit unter 75 Jupitermassen nicht aus, um wie in den leichtesten Sternen, den Roten Zwergen, eine Wasserstofffusion in ihrem Inneren in Gang zu setzen. Andererseits sind sie mit mindestens 13 Jupitermassen (d. h. massereicher als planetare Gasriesen) schwer genug für den Beginn der Deuteriumfusion.


Non-verbal communication.

Nonverbal communication describes the processes of conveying a type of information in a form of non-linguistic representations. Examples of nonverbal communication include haptic communication, chronemic communication, gestures, body language, facial expressions, eye contact etc. Nonverbal communication also relates to the intent of a message. Examples of intent are voluntary, intentional movements like shaking a hand or winking, as well as involuntary, such as sweating. Speech also contains nonverbal elements known as paralanguage, e.g. rhythm, intonation, tempo, and stress. It affects communication most at the subconscious level and establishes trust. Likewise, written texts include nonverbal elements such as handwriting style, the spatial arrangement of words and the use of emoticons to convey emotion.  Nonverbal communication demonstrates one of Paul Watzlawick's laws: you cannot not communicate. Once proximity has formed awareness, living creatures begin interpreting any signals received. Some of the functions of nonverbal communication in humans are to complement and illustrate, to reinforce and emphasize, to replace and substitute, to control and regulate, and to contradict the denotative message.  Nonverbal cues are heavily relied on to express communication and to interpret others' communication and can replace or substitute verbal messages. However, non-verbal communication is ambiguous. When verbal messages contradict non-verbal messages, observation of non-verbal behaviour is relied on to judge another's attitudes and feelings, rather than assuming the truth of the verbal message alone.  There are several reasons as to why non-verbal communication plays a vital role in communication:  "Non-verbal communication is omnipresent." They are included in every single communication act. To have total communication, all non-verbal channels such as the body, face, voice, appearance, touch, distance, timing, and other environmental forces must be engaged during face-to-face interaction. Written communication can also have non-verbal attributes. E-mails, web chats, and the social media have options to change text font colours, stationary, add emoticons, capitalization, and pictures in order to capture non-verbal cues into a verbal medium.  "Non-verbal behaviours are multifunctional." Many different non-verbal channels are engaged at the same time in communication acts and allow the chance for simultaneous messages to be sent and received.  "Non-verbal behaviours may form a universal language system." Smiling, crying, pointing, caressing, and glaring are non-verbal behaviours that are used and understood by people regardless of nationality. Such non-verbal signals allow the most basic form of communication when verbal communication is not effective due to language barriers.

Verbal communication.

Verbal communication is the spoken or written conveyance of a message. Human language can be defined as a system of symbols (sometimes known as lexemes) and the grammars (rules) by which the symbols are manipulated. The word "language" also refers to common properties of languages. Language learning normally occurs most intensively during human childhood. Most of the large number of human languages use patterns of sound or gesture for symbols which enable communication with others around them. Languages tend to share certain properties, although there are exceptions. There is no defined line between a language and a dialect. Constructed languages such as Esperanto, programming languages, and various mathematical formalisms are not necessarily restricted to the properties shared by human languages.  As previously mentioned, language can be characterized as symbolic. Charles Ogden and I.A Richards developed The Triangle of Meaning model to explain the symbol (the relationship between a word), the referent (the thing it describes), and the meaning (the thought associated with the word and the thing).  The properties of language are governed by rules. Language follows phonological rules (sounds that appear in a language), syntactic rules (arrangement of words and punctuation in a sentence), semantic rules (the agreed upon meaning of words), and pragmatic rules (meaning derived upon context).  The meanings that are attached to words can be literal, or otherwise known as denotative; relating to the topic being discussed, or, the meanings take context and relationships into account, otherwise known as connotative; relating to the feelings, history, and power dynamics of the communicators.  Contrary to popular belief, signed languages of the world (e.g., American Sign Language) are considered to be verbal communication because their sign vocabulary, grammar, and other linguistic structures abide by all the necessary classifications as spoken languages. There are however, nonverbal elements to signed languages, such as the speed, intensity, and size of signs that are made. A signer might sign "yes" in response to a question, or they might sign a sarcastic-large slow yes to convey a different nonverbal meaning. The sign yes is the verbal message while the other movements add nonverbal meaning to the message.

Written communication and its historical development.

Over time the forms of and ideas about communication have evolved through the continuing progression of technology. Advances include communications psychology and media psychology, an emerging field of study.  The progression of written communication can be divided into three "information communication revolutions":  Communication is thus a process by which meaning is assigned and conveyed in an attempt to create shared understanding. Gregory Bateson called it "the replication of tautologies in the universe. This process, which requires a vast repertoire of skills in interpersonal processing, listening, observing, speaking, questioning, analyzing, gestures, and evaluating enables collaboration and cooperation.

Business/Corporate.

Business communication is used for a wide variety of activities including, but not limited to: strategic communications planning, media relations, internal communications, public relations (which can include social media, broadcast and written communications, and more), brand management, reputation management, speech-writing, customer-client relations, and internal/employee communications.  Companies with limited resources may choose to engage in only a few of these activities, while larger organizations may employ a full spectrum of communications. Since it is relatively difficult to develop such a broad range of skills, communications professionals often specialize in one or two of these areas but usually have at least a working knowledge of most of them. By far, the most important qualifications communications professionals must possess are excellent writing ability, good 'people' skills, and the capacity to think critically and strategically.  Business communication could also refer to the style of communication within a given corporate entity, i.e. email conversation styles, or internal communication styles.

Political.

Communication is one of the most relevant tools in political strategies, including persuasion and propaganda. In mass media research and online media research, the effort of the strategist is that of getting a precise decoding, avoiding "message reactance", that is, message refusal. The reaction to a message is referred also in terms of approach to a message, as follows: Holistic approaches are used by communication campaign leaders and communication strategists in order to examine all the options, "actors" and channels that can generate change in the semiotic landscape, that is, change in perceptions, change in credibility, change in the "memetic background", change in the image of movements, of candidates, players and managers as perceived by key influencers that can have a role in generating the desired "end-state".  The modern political communication field is highly influenced by the framework and practices of "information operations" doctrines that derive their nature from strategic and military studies. According to this view, what is really relevant is the concept of acting on the Information Environment. The information environment is the aggregate of individuals, organizations, and systems that collect, process, disseminate, or act on information. This environment consists of three interrelated dimensions, which continuously interact with individuals, organizations, and systems. These dimensions are known as physical, informational, and cognitive.

Family.

Family communication is the study of the communication perspective in a broadly defined family, with intimacy and trusting relationship. The main goal of family communication is to understand the interactions of family and the pattern of behaviors of family members in different circumstances. Open and honest communication creates an atmosphere that allows family members to express their differences as well as love and admiration for one another. It also helps to understand the feelings of one another.  Family communication study looks at topics such as family rules, family roles or family dialectics and how those factors could affect the communication between family members. Researchers develop theories to understand communication behaviors. Family communication study also digs deep into certain time periods of family life such as marriage, parenthood or divorce and how communication stands in those situations. It is important for family members to understand communication as a trusted way which leads to a well constructed family.

Interpersonal.

In simple terms, interpersonal communication is the communication between one person and another (or others). It is often referred to as face-to-face communication between two (or more) people. Both verbal and nonverbal communication, or body language, play a part in how one person understands another. In verbal interpersonal communication there are two types of messages being sent: a content message and a relational message. Content messages are messages about the topic at hand and relational messages are messages about the relationship itself. This means that relational messages come across in "how" one says something and it demonstrates a person's feelings, whether positive or negative, towards the individual they are talking to, indicating not only how they feel about the topic at hand, but also how they feel about their relationship with the other individual.  There are many different aspects of interpersonal communication including:

Barriers to effectiveness.

Barriers to effective communication can retard or distort the message or intention of the message being conveyed. This may result in failure of the communication process or cause an effect that is undesirable. These include filtering, selective perception, information overload, emotions, language, silence, communication apprehension, gender differences and political correctness.  This also includes a lack of expressing "knowledge-appropriate" communication, which occurs when a person uses ambiguous or complex legal words, medical jargon, or descriptions of a situation or environment that is not understood by the recipient.

Cultural aspects.

Cultural differences exist within countries (tribal/regional differences, dialects etc.), between religious groups and in organisations or at an organisational level – where companies, teams and units may have different expectations, norms and idiolects. Families and family groups may also experience the effect of cultural barriers to communication within and between different family members or groups. For example: words, colours and symbols have different meanings in different cultures. In most parts of the world, nodding your head means agreement, shaking your head means no, except in some parts of the world.  Communication to a great extent is influenced by culture and cultural variables. Understanding "cultural aspects of communication" refers to having knowledge of different cultures in order to communicate effectively with cross culture people. Cultural aspects of communication are of great relevance in today's world which is now a global village, thanks to globalisation. Cultural aspects of communication are the cultural differences which influences communication across borders. Impact of cultural differences on communication components are explained below:  So in order to have an effective communication across the world it is desirable to have a knowledge of cultural variables effecting communication.  According to Michael Walsh and Ghil'ad Zuckermann, Western conversational interaction is typically "dyadic", between two particular people, where eye contact is important and the speaker controls the interaction; and "contained" in a relatively short, defined time frame. However, traditional Aboriginal conversational interaction is "communal", broadcast to many people, eye contact is not important, the listener controls the interaction; and "continuous", spread over a longer, indefinite time frame.

Nonhuman.

Every information exchange between living organisms — i.e. transmission of signals that involve a living sender and receiver can be considered a form of communication; and even primitive creatures such as corals are competent to communicate. Nonhuman communication also include cell signaling, cellular communication, and chemical transmissions between primitive organisms like bacteria and within the plant and fungal kingdoms.

Animals.

The broad field of animal communication encompasses most of the issues in ethology. Animal communication can be defined as any behavior of one animal that affects the current or future behavior of another animal. The study of animal communication, called "zoo semiotics" (distinguishable from anthroposemiotics, the study of human communication) has played an important part in the development of ethology, sociobiology, and the study of animal cognition. Animal communication, and indeed the understanding of the animal world in general, is a rapidly growing field, and even in the 21st century so far, a great share of prior understanding related to diverse fields such as personal symbolic name use, animal emotions, animal culture and learning, and even sexual conduct, long thought to be well understood, has been revolutionized.

Plants and fungi.

Communication is observed within the plant organism, i.e. within plant cells and between plant cells, between plants of the same or related species, and between plants and non-plant organisms, especially in the root zone. Plant roots communicate with rhizome bacteria, fungi, and insects within the soil. Recent research has shown that most of the microorganism plant communication processes are neuron-like. Plants also communicate via volatiles when exposed to herbivory attack behavior, thus warning neighboring plants. In parallel they produce other volatiles to attract parasites which attack these herbivores.  Fungi communicate to coordinate and organize their growth and development such as the formation of Marcelia and fruiting bodies. Fungi communicate with their own and related species as well as with non fungal organisms in a great variety of symbiotic interactions, especially with bacteria, unicellular eukaryote, plants and insects through biochemicals of biotic origin. The biochemicals trigger the fungal organism to react in a specific manner, while if the same chemical molecules are not part of biotic messages, they do not trigger the fungal organism to react. This implies that fungal organisms can differentiate between molecules taking part in biotic messages and similar molecules being irrelevant in the situation. So far five different primary signalling molecules are known to coordinate different behavioral patterns such as filamentation, mating, growth, and pathogenicity. Behavioral coordination and production of signaling substances is achieved through interpretation processes that enables the organism to differ between self or non-self, a biotic indicator, biotic message from similar, related, or non-related species, and even filter out "noise", i.e. similar molecules without biotic content.

Bacteria quorum sensing.

Communication is not a tool used only by humans, plants and animals, but it is also used by microorganisms like bacteria. The process is called quorum sensing. Through quorum sensing, bacteria can sense the density of cells, and regulate gene expression accordingly. This can be seen in both gram positive and gram negative bacteria. This was first observed by Fuqua "et al." in marine microorganisms like "V. harveyi" and "V. fischeri".

Models.

The first major model for communication was introduced by Claude Shannon and Warren Weaver for Bell Laboratories in 1949 The original model was designed to mirror the functioning of radio and telephone technologies. Their initial model consisted of three primary parts: sender, channel, and receiver. The sender was the part of a telephone a person spoke into, the channel was the telephone itself, and the receiver was the part of the phone where one could hear the other person. Shannon and Weaver also recognized that often there is static that interferes with one listening to a telephone conversation, which they deemed noise.  In a simple model, often referred to as the transmission model or standard view of communication, information or content (e.g. a message in natural language) is sent in some form (as spoken language) from an emitter ("emisor" in the picture)/sender/encoder to a destination/receiver/decoder. This common conception of communication simply views communication as a means of sending and receiving information. The strengths of this model are simplicity, generality, and quantifiability. Claude Shannon and Warren Weaver structured this model based on the following elements:  Shannon and Weaver argued that there were three levels of problems for communication within this theory.  Daniel Chandler critiques the transmission model by stating:  In 1960, David Berlo expanded on Shannon and Weaver's (1949) linear model of communication and created the SMCR Model of Communication. The Sender-Message-Channel-Receiver Model of communication separated the model into clear parts and has been expanded upon by other scholars.  Communication is usually described along a few major dimensions: message (what type of things are communicated), source/emisor/sender/encoder (from whom), form (in which form), channel (through which medium), destination/receiver/target/decoder (to whom). Wilbur Schram (1954) also indicated that we should also examine the impact that a message has (both desired and undesired) on the target of the message. Between parties, communication includes acts that confer knowledge and experiences, give advice and commands, and ask questions. These acts may take many forms, in one of the various manners of communication. The form depends on the abilities of the group communicating. Together, communication content and form make messages that are sent towards a destination. The target can be oneself, another person or being, another entity (such as a corporation or group of beings).  Communication can be seen as processes of information transmission with three levels of semiotic rules:  Therefore, communication is social interaction where at least two interacting agents share a common set of signs and a common set of semiotic rules. This commonly held rule in some sense ignores autocommunication, including intrapersonal communication via diaries or self-talk, both secondary phenomena that followed the primary acquisition of communicative competences within social interactions.  In light of these weaknesses, Barnlund (2008) proposed a transactional model of communication. The basic premise of the transactional model of communication is that individuals are simultaneously engaging in the sending and receiving of messages.  In a slightly more complex form a sender and a receiver are linked reciprocally. This second attitude of communication, referred to as the constitutive model or constructionist view, focuses on how an individual communicates as the determining factor of the way the message will be interpreted. Communication is viewed as a conduit; a passage in which information travels from one individual to another and this information becomes separate from the communication itself. A particular instance of communication is called a speech act. The sender's personal filters and the receiver's personal filters may vary depending upon different regional traditions, cultures, or gender; which may alter the intended meaning of message contents. In the presence of "communication noise" on the transmission channel (air, in this case), reception and decoding of content may be faulty, and thus the speech act may not achieve the desired effect. One problem with this encode-transmit-receive-decode model is that the processes of encoding and decoding imply that the sender and receiver each possess something that functions as a codebook, and that these two code books are, at the very least, similar if not identical. Although something like code books is implied by the model, they are nowhere represented in the model, which creates many conceptual difficulties.  Theories of coregulation describe communication as a creative and dynamic continuous process, rather than a discrete exchange of information. Canadian media scholar Harold Innis had the theory that people use different types of media to communicate and which one they choose to use will offer different possibilities for the shape and durability of society. His famous example of this is using ancient Egypt and looking at the ways they built themselves out of media with very different properties stone and papyrus. Papyrus is what he called 'Space Binding'. it made possible the transmission of written orders across space, empires and enables the waging of distant military campaigns and colonial administration. The other is stone and 'Time Binding', through the construction of temples and the pyramids can sustain their authority generation to generation, through this media they can change and shape communication in their society.

Noise.

In any communication model, noise is interference with the decoding of messages sent over the channel by an encoder. There are many examples of noise: To face communication noise, redundancy and acknowledgement must often be used. Acknowledgements are messages from the addressee informing the originator that his/her communication has been received and is understood. Message repetition and feedback about message received are necessary in the presence of noise to reduce the probability of misunderstanding. The act of disambiguation regards the attempt of reducing noise and wrong interpretations, when the semantic value or meaning of a sign can be subject to noise, or in presence of multiple meanings, which makes the sense-making difficult. Disambiguation attempts to decrease the likelihood of misunderstanding. This is also a fundamental skill in communication processes activated by counselors, psychotherapists, interpreters, and in coaching sessions based on colloquium. In Information Technology, the disambiguation process and the automatic disambiguation of meanings of words and sentences has also been an interest and concern since the earliest days of computer treatment of language.

As academic discipline.

The academic discipline that deals with processes of human communication is communication studies. The discipline encompasses a range of topics, from face-to-face conversation to mass media outlets such as television broadcasting. Communication studies also examines how messages are interpreted through the political, cultural, economic, semiotic, hermeneutic, and social dimensions of their contexts. Statistics, as a quantitative approach to communication science, has also been incorporated into research on communication science in order to help substantiate claims.

Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

Chemie ([]; mittel- und norddeutsch auch []; süddeutsch: []) ist diejenige Naturwissenschaft, die sich mit dem Aufbau, den Eigenschaften und der Umwandlung von chemischen Stoffen beschäftigt. Ein Stoff besteht aus Atomen, Molekülen oder beidem. Er kann außerdem Ionen enthalten. Die chemischen Reaktionen sind Vorgänge in den Elektronenhüllen der Atome, Moleküle und Ionen. Zentrale Begriffe der Chemie sind chemische Reaktionen und chemische Bindungen. Durch chemische Reaktionen werden chemische Bindungen gebildet oder gebrochen. Dabei verändert sich die Elektronenaufenthaltswahrscheinlichkeit in den Elektronenhüllen der beteiligten Stoffe und damit deren Eigenschaften. Die Herstellung von Stoffen ("Synthese") mit von der Menschheit benötigten Eigenschaften ist heute das zentrale Anliegen der Chemie.


Early life.

Babbage's birthplace is disputed, but according to the "Oxford Dictionary of National Biography" he was most likely born at 44 Crosby Row, Walworth Road, London, England. A blue plaque on the junction of Larcom Street and Walworth Road commemorates the event.  His date of birth was given in his obituary in "The Times" as 26 December 1792; but then a nephew wrote to say that Babbage was born one year earlier, in 1791. The parish register of St. Mary's, Newington, London, shows that Babbage was baptised on 6 January 1792, supporting a birth year of 1791. Babbage was one of four children of Benjamin Babbage and Betsy Plumleigh Teape. His father was a banking partner of William

At the University of Cambridge.

Babbage arrived at Trinity College, Cambridge, in October 1810. He was already self-taught in some parts of contemporary mathematics; he had read in Robert Woodhouse, Joseph Louis Lagrange, and Marie Agnesi. As a result, he was disappointed in the standard mathematical instruction available at the university.  Babbage, John Herschel, George Peacock, and several other friends formed the Analytical Society in 1812; they were also close to

After Cambridge.

Considering his reputation, Babbage quickly made progress. He lectured to the Royal Institution on astronomy in 1815, and was elected a Fellow of the Royal Society in 1816. After graduation, on the other hand, he applied for positions unsuccessfully, and had little in the way of career. In 1816 he was a candidate for a teaching job at Haileybury College; he had recommendations from James Ivory and John Playfair, but lost out to Henry Walter. In 1819, Babbage and Herschel visited Paris and the Society of Arcueil, meeting leading French mathematicians and physicists. That year Babbage applied to be professor at the University of Edinburgh, with the recommendation of Pierre Simon Laplace; the post went to William Wallace.  With Herschel, Babbage worked on the electrodynamics of Arago's rotations, publishing in 1825. Their explanations were only transitional, being picked up and broadened by Michael Faraday. The phenomena are now part of the theory of eddy currents, and Babbage and Herschel missed some of the clues to unification of electromagnetic theory, staying close to Ampère's force law.  Babbage purchased the actuarial tables of George Barrett, who died in 1821 leaving unpublished work, and surveyed the field in 1826 in "Comparative View of the Various Institutions for the Assurance of Lives". This interest followed a project to set up an insurance company, prompted by Francis Baily and mooted in 1824, but not carried out. Babbage did calculate actuarial tables for that scheme, using Equitable Society mortality data from 1762 onwards.  During this whole period Babbage depended awkwardly on his father's support, given his father's attitude to his early marriage, of 1814: he and Edward Ryan wedded the Whitmore sisters. He made a home in Marylebone in London, and founded a large family. On his father's death in 1827, Babbage inherited a large estate (value around £100,000, equivalent to £ or $ today), making him independently wealthy. After his wife's death in the same year he spent time travelling. In Italy he met Leopold II, Grand Duke of Tuscany, foreshadowing a later visit to Piedmont. In April 1828 he was in Rome, and relying on Herschel to manage the difference engine project, when he heard that he had become professor at Cambridge, a position he had three times failed to obtain (in 1820, 1823 and 1826).

Royal Astronomical Society.

Babbage was instrumental in founding the Royal Astronomical Society in 1820, initially known as the Astronomical Society of London. Its original aims were to reduce astronomical calculations to a more standard form, and to circulate data. These directions were closely connected with Babbage's ideas on computation, and in 1824 he won its Gold Medal, cited "for his invention of an engine for calculating mathematical and astronomical tables".  Babbage's motivation to overcome errors in tables by mechanisation had been a commonplace since Dionysius Lardner wrote about it in 1834 in the "Edinburgh Review" (under Babbage's guidance). The context of these developments is still debated. Babbage's own account of the origin of the difference engine

British Lagrangian School.

The Analytical Society had initially been no more than an undergraduate provocation. During this period it had some more substantial achievements. In 1816 Babbage, Herschel and Peacock published a translation from French of the lectures of Sylvestre Lacroix, which was then the state-of-the-art calculus textbook.  Reference to Lagrange in calculus terms marks out the application of what are now called formal power series. British mathematicians had used them from about 1730 to 1760. As re-introduced, they were not simply applied as notations in differential calculus. They opened up the fields of functional equations (including the difference equations fundamental to the difference engine) and operator (D-module) methods for differential equations. The analogy of difference and differential equations was notationally changing Δ to D, as a "finite" difference becomes "infinitesimal". These symbolic directions became popular,

Academic.

From 1828 to 1839 Babbage was Lucasian Professor of Mathematics at Cambridge. Not a conventional resident don, and inattentive to his teaching responsibilities, he wrote three topical books during this period of his life. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1832. Babbage was out of sympathy with colleagues: George Biddell Airy, his predecessor as Lucasian Professor of Mathematics at Trinity College, Cambridge, thought an issue should be made of his lack of interest in lecturing. Babbage planned to lecture in 1831 on political economy. Babbage's reforming direction looked to see university education more inclusive, universities doing more for research, a broader syllabus and more interest in applications; but William Whewell found the programme unacceptable. A controversy Babbage had with Richard Jones lasted for six years. He never did give a lecture.  It was during this period that Babbage tried to enter politics. Simon Schaffer writes that his views of the 1830s included disestablishment of the Church of England, a broader political franchise, and inclusion of manufacturers as stakeholders. He twice stood for Parliament as a candidate for the borough of Finsbury. In 1832 he came in third among five candidates, missing out by some 500 votes in the two-member constituency when two other reformist candidates, Thomas Wakley and Christopher Temple, split the vote. In his memoirs Babbage related how this election brought him the friendship of Samuel Rogers: his brother Henry Rogers wished to support Babbage again, but died within days. In 1834 Babbage finished last among four. In 1832, Babbage, Herschel and Ivory were appointed Knights of the Royal Guelphic Order, however they were not subsequently made knights bachelor to entitle them to the prefix "Sir", which often came with appointments to that foreign order (though Herschel was later created a baronet).

"Declinarians", learned societies and the BAAS.

Babbage now emerged as a polemicist. One of his biographers notes that all his books contain a "campaigning element". His "Reflections on the Decline of Science and some of its Causes" (1830) stands out, however, for its sharp attacks. It aimed to improve British science, and more particularly to oust Davies Gilbert as President of the Royal Society, which Babbage wished to reform. It was written out of pique, when Babbage hoped to become the junior secretary of the Royal Society, as Herschel was the senior, but failed because of his antagonism to Humphry Davy. Michael Faraday had a reply written, by Gerrit Moll, as "On the Alleged Decline of Science in

"On the Economy of Machinery and Manufactures".

Babbage published "On the Economy of Machinery and Manufactures" (1832), on the organisation of industrial production. It was an influential early work of operational research. John Rennie the Younger in addressing the Institution of Civil Engineers on manufacturing in 1846 mentioned mostly surveys in encyclopaedias, and Babbage's book was first an article in the "Encyclopædia Metropolitana", the form in which Rennie noted it, in the company of related works by John Farey, Jr., Peter Barlow and Andrew Ure. From "An essay on the general

"Babbage principle".

In "Economy of Machinery" was described what is now called the "Babbage principle". It pointed out commercial advantages available with more careful division of labour. As Babbage himself noted, it had already appeared in the work of Melchiorre Gioia in 1815. The term was introduced in 1974 by Harry Braverman. Related formulations are the "principle of multiples" of Philip Sargant Florence, and the "balance of processes".

Publishing.

Another aspect of the work was its detailed breakdown of the cost structure of book publishing. Babbage took the unpopular line, from the publishers' perspective, of

Influence.

It has been written that "what Arthur Young was to agriculture, Charles Babbage was to the factory visit and machinery". Babbage's theories are said to have influenced the layout of the 1851 Great Exhibition, and his views had a strong effect on his contemporary George Julius Poulett Scrope. Karl Marx argued that the source of the productivity of the factory system was exactly the combination of the division of labour with machinery, building on Adam Smith, Babbage and Ure. Where Marx picked up on Babbage and disagreed with Smith was on the motivation for division of labour by the manufacturer: as Babbage did, he wrote that it was for the sake of profitability, rather than productivity, and identified an impact on the concept of a trade.  John Ruskin went further, to oppose completely what manufacturing in Babbage's sense stood for. Babbage also affected the economic

Natural theology.

In 1837, responding to the series of eight "Bridgewater Treatises", Babbage published his "Ninth Bridgewater Treatise", under the title "On the Power, Wisdom and Goodness of God, as manifested in the Creation". In this work Babbage weighed in on the side of uniformitarianism in a current debate. He preferred the conception of creation in which a God-given natural law dominated, removing the need for continuous "contrivance".  The book is a work of natural theology, and incorporates extracts from related correspondence of Herschel with Charles Lyell. Babbage put forward the thesis that God had the omnipotence and foresight to create as a divine legislator. In this book, Babbage dealt with relating interpretations between science and religion; on the one hand, he insisted that ""there exists no fatal collision between the words of Scripture and the facts of nature;"" on the one hand, he wrote the Book of Genesis was not meant to

Religious views.

Babbage was raised in the Protestant form of the Christian faith, his family having inculcated in him an orthodox form of worship. He explained:  Rejecting the Athanasian Creed as a "direct contradiction in terms", in his youth he looked to Samuel Clarke's works on religion, of which "Being and Attributes of God" (1704) exerted a particularly strong influence on him. Later in life, Babbage concluded that "the true value of the Christian religion rested, not on speculative [theology]... but... upon those doctrines of kindness and benevolence which that religion claims and enforces, not merely in favour of man himself but of every creature susceptible of pain or of happiness."  In his autobiography (1864), Babbage wrote a whole chapter on the topic of religion, where he identified three sources of divine knowledge:

Later life.

The British Association was consciously modelled on the Deutsche Naturforscher-Versammlung, founded in 1822. It rejected romantic science as well as metaphysics, and started to entrench the divisions of science from literature, and professionals from amateurs. Belonging as he did to the "Wattite" faction in the BAAS, represented in particular by James Watt the younger, Babbage identified closely with industrialists. He wanted to go faster in the same directions, and had little time for the more gentlemanly component of its membership. Indeed, he subscribed to a version of conjectural history that placed industrial society as the culmination of human development (and shared this view with Herschel). A clash with Roderick Murchison led in 1838 to his withdrawal from further involvement. At the end of the same year he sent in his resignation as Lucasian professor, walking away also from the Cambridge struggle with Whewell. His interests became more focussed, on computation and metrology, and on international contacts.

Metrology programme.

A project announced by Babbage was to tabulate all physical constants (referred to as "constants of nature", a phrase in itself a neologism), and then to compile an encyclopaedic work of numerical information. He was a pioneer in the field of "absolute measurement". His ideas followed on from those of Johann Christian Poggendorff, and were mentioned to Brewster in 1832.

Engineer and inventor.

Through the Royal Society Babbage acquired the friendship of the engineer Marc Brunel. It was through Brunel that Babbage knew of Joseph Clement, and so came to encounter the artisans whom he observed in his work on manufactures. Babbage provided an introduction for Isambard Kingdom Brunel in 1830, for a contact with the proposed Bristol & Birmingham Railway. He carried out studies, around 1838, to show the

Cryptography.

Babbage achieved notable results in cryptography, though this was still not known a century after his death. Letter frequency was category 18 of Babbage's tabulation project. Joseph Henry later defended interest in it, in the absence of the facts, as relevant to the management of movable type.  As early as 1845, Babbage had solved a cipher that had been posed as a challenge by his nephew Henry Hollier, and in the process, he made a discovery about ciphers that were based on

Public nuisances.

Babbage involved himself in well-publicised but unpopular campaigns against public nuisances. He once counted all the broken panes of glass of a factory, publishing in 1857 a "Table of the Relative Frequency of the Causes of Breakage of Plate Glass Windows": Of 464 broken panes, 14 were caused by "drunken men, women or boys".  Babbage's distaste for commoners ("the Mob") included writing "Observations of Street Nuisances" in 1864, as well as tallying up 165 "nuisances" over a

Computing pioneer.

Babbage's machines were among the first mechanical computers. That they were not actually completed was largely because of funding problems and clashes of personality, most notably with Airy, the Astronomer Royal.  Babbage directed the building of some steam-powered machines that achieved some modest success, suggesting that calculations could be mechanised. For more than ten years he received government funding for his project, which amounted to £17,000, but eventually the Treasury lost confidence in him.  While Babbage's machines were mechanical and unwieldy, their basic architecture was similar to a modern computer. The data and program memory were separated, operation was instruction-based, the control unit could make conditional jumps, and the machine had a separate I/O unit.

Background on mathematical tables.

In Babbage's time, printed mathematical tables were calculated by human computers; in other words, by hand. They were central to navigation, science and engineering, as well as mathematics. Mistakes were known to occur in transcription as well as calculation.  At Cambridge, Babbage saw the fallibility of this process, and the opportunity of adding mechanisation into its management. His own account of his path towards mechanical computation

Difference engine.

Babbage began in 1822 with what he called the difference engine, made to compute values of polynomial functions. It was created to calculate a series of values automatically. By using the method of finite differences, it was possible to avoid the need for multiplication and division.  For a prototype difference engine, Babbage brought in Joseph Clement to implement the design, in 1823. Clement worked to high standards, but his machine tools were particularly elaborate. Under the standard terms of business of the time, he could charge for their construction, and would also own them. He and Babbage fell

Completed models.

The Science Museum has constructed two Difference Engines according to Babbage's plans for the Difference Engine No 2. One is owned by the museum. The other, owned by the technology multimillionaire Nathan Myhrvold, went on exhibition at the Computer History Museum in Mountain View, California on 10 May 2008. The two models that have been constructed are not replicas; Myhrvold's engine is the first design by Babbage, and the Science Museum's is a later model.

Analytical Engine.

After the attempt at making the first difference engine fell through, Babbage worked to design a more complex machine called the Analytical Engine. He hired C. G. Jarvis, who had previously worked for Clement as a draughtsman. The Analytical Engine marks the transition from mechanised arithmetic to fully-fledged general purpose computation. It is largely on it that Babbage's standing as computer pioneer rests.

Ada Lovelace and Italian followers.

Ada Lovelace, who corresponded with Babbage during his development of the Analytical Engine, is credited with developing an algorithm that would enable the Engine to calculate a sequence of Bernoulli numbers. Despite documentary evidence in Lovelace's own handwriting, some scholars dispute to what extent the ideas were Lovelace's own. For this achievement, she is often described as the first computer programmer; though no programming language had yet been

Swedish followers.

Per Georg Scheutz wrote about the difference engine in 1830, and experimented in automated computation. After 1834 and Lardner's "Edinburgh Review" article he

Legacy.

In 2011, researchers in Britain proposed a multimillion-pound project, "Plan 28", to construct Babbage's Analytical Engine. Since Babbage's plans were continually being refined and were never completed, they intended to engage the public in the project and crowd-source the analysis of what should be built. It would have the equivalent of 675 bytes of memory, and run at a clock speed of about 7 Hz. They hope to complete it

Family.

On 25 July 1814, Babbage married Georgiana Whitmore at St. Michael's Church in Teignmouth, Devon; her sister Louisa married Sir Edward Ryan five months later. The couple lived at Dudmaston Hall, Shropshire (where Babbage engineered the central heating system), before moving to 5 Devonshire Street, London in 1815.  Charles and Georgiana had eight children, but only four – Benjamin Herschel, Georgiana Whitmore, Dugald Bromhead and Henry

Death.

Babbage lived and worked for over 40 years at 1 Dorset Street, Marylebone, where he died, at the age of 79, on 18 October 1871; he was buried in London's Kensal Green Cemetery. According to Horsley, Babbage died "of renal inadequacy, secondary to cystitis." He had declined both a knighthood and baronetcy. He also argued against hereditary peerages, favouring life peerages instead.

Autopsy report.

In 1983 the autopsy report for Charles Babbage was discovered and later published by his great-great-grandson. A copy of the original is

Memorials.

There is a black plaque commemorating the 40 years Babbage

In fiction and film.

Babbage frequently appears in steampunk works; he has been called an iconic figure of the genre. Other works in which Babbage appears include:

Charles Babbage (; 26 December 1791 – 18 October 1871) was an English polymath. A mathematician, philosopher, inventor and mechanical engineer, Babbage originated the concept of a digital programmable computer.

Charles Babbage (* 26. Dezember 1791 in Walworth, Grafschaft Surrey, England; † 18. Oktober 1871 in London) war ein englischer Mathematiker, Philosoph, Erfinder und Politischer Ökonom.


Overview.

Often property is defined by the code of the local sovereignty, and protected wholly or more usually partially by such entity, the owner being responsible for any remainder of protection. The standards of proof concerning proofs of ownerships are also addressed by the code of the local sovereignty, and such entity plays a role accordingly, typically somewhat managerial. Some philosophers assert that property rights arise from social convention, while others find justifications for them in morality or in natural law.  Various scholarly disciplines (such as law, economics, anthropology or sociology) may treat the concept more systematically, but definitions vary, most particularly when involving contracts. Positive law defines such rights, and the judiciary can adjudicate and enforce property rights.  According to Adam Smith, the expectation of profit from "improving one's stock of capital" rests on private property rights. Capitalism has as a central assumption that property rights encourage their holders to develop the property, generate wealth, and efficiently allocate resources based on the operation of markets. From this has evolved the modern conception of property as a right enforced by positive law, in the expectation that this will produce more wealth and better standards of living. However, Smith also expressed a very critical view on the effects of property laws on inequality:  In his text "The Common Law", Oliver Wendell Holmes describes property as having two fundamental aspects. The first, possession, can be defined as control over a resource based on the practical inability of another to contradict the ends of the possessor. The second, title, is the expectation that others will recognize rights to control resource, even when it is not in possession. He elaborates the differences between these two concepts, and proposes a history of how they came to be attached to persons, as opposed to families or to entities such as the church.  Both communism and some kinds of socialism have also upheld the notion that private ownership of capital is inherently illegitimate. This argument centers mainly on the idea that private ownership of capital always benefits one class over another, giving rise to domination through the use of this privately owned capital. Communists do not oppose personal property that is "hard-won, self-acquired, self-earned" (as "The Communist Manifesto" puts it) by members of the proletariat. Both socialism and communism distinguish carefully between private ownership of capital (land, factories, resources, etc.) and private property (homes, material objects and so forth).

Related concepts.

Of the following, only

Issues in property theory.

What can be property?

The two major justifications given for original property, or the homestead principle, are effort and scarcity. John Locke emphasized effort, "mixing your labor" with an object, or clearing and cultivating virgin land. Benjamin Tucker preferred to look at the telos of property, i.e. What is the purpose of property? His answer: to solve the scarcity problem. Only when items are relatively scarce with respect to people's desires do they become property. For example, hunter-gatherers did not consider land to be property, since there was no shortage of land. Agrarian societies later made arable land property, as it was scarce. For something to be economically scarce it must necessarily have the "exclusivity property"—that use by one person excludes others from using

Who can be an owner?

Ownership laws may vary widely among countries depending on the nature of the property of interest (e.g. firearms, real property, personal property, animals). Persons can own property directly. In most societies legal entities, such as

Whether and to what extent the state may interfere with property.

In 17th-century England, the legal directive that nobody may enter a home, which in the 17th-century would typically have been male owned, unless by the owners invitation or consent, was established as common law in Sir Edward Coke’s "Institutes of the Lawes of England". "For a man's house is his castle, et domus sua cuique est tutissimum refugium [and each man's home is his safest refuge]." It is the origin of the famous dictum, “an Englishman’s home is his castle”. The ruling enshrined into law what several English writers had espoused in the 16th-century. Unlike the rest of Europe the British had a proclivity towards owning their own homes. British Prime Minister William Pitt, 1st Earl of Chatham defined the meaning of castle in 1763, "The poorest man may in his cottage bid defiance to all the forces of the crown. It may

Theories.

There exist many theories of property. One is the relatively rare first possession theory of property, where ownership of something is seen as justified simply by someone seizing something before someone else does. Perhaps one of the most popular is the natural rights definition of property rights as advanced by John Locke. Locke advanced the theory that God granted dominion over nature to man through Adam in the book of Genesis. Therefore, he theorized that when one mixes one's labor with nature, one gains a relationship with that part of nature with which the labor is mixed, subject to the limitation that there should be "enough, and as good, left in common for others." (see Lockean proviso)  From the RERUM NOVARUM, Pope Leo XIII wrote "It is surely undeniable that, when a man engages in remunerative labor, the impelling reason and motive of his work is to obtain property, and thereafter to hold it as his very own."  Anthropology studies the diverse systems of ownership, rights of use and transfer, and possession under the

Property in philosophy.

In medieval and Renaissance Europe the term "property" essentially referred to land. After much rethinking, land has come to be regarded as only a special case of the property genus. This rethinking was inspired by at least three broad features of early modern Europe: the surge of commerce, the breakdown of efforts to prohibit interest (then called "usury"), and the development of centralized national monarchies.

Ancient philosophy.

Urukagina, the king of the Sumerian city-state Lagash, established the first laws that forbade compelling the sale of property.  The Bible in Leviticus 19:11 and ibid. 19:13 states that the Israelites are not to steal.  Aristotle, in "Politics," advocates "private property." He argues that self-interest leads to neglect of the commons. "[T]hat which is common to the greatest number has the least care bestowed upon it. Every one thinks chiefly of his own, hardly at all of the common interest; and only when he is himself

Medieval philosophy.

Thomas Aquinas (13th century).

The canon law "Decretum Gratiani" maintained that mere human law creates property, repeating the phrases used by St. Augustine. St. Thomas Aquinas agreed with regard to the private consumption of property but modified patristic theory in finding that the private possession of property is necessary. Thomas Aquinas concludes that, given certain detailed provisions,

Modern philosophy.

Thomas Hobbes (17th century).

The principal writings of Thomas Hobbes appeared between 1640 and 1651—during and immediately following the war between forces loyal to King Charles I and those loyal to Parliament. In his own words, Hobbes' reflection began with the idea

James Harrington (17th century).

A contemporary of Hobbes, James Harrington, reacted to the same tumult in a different way: he considered property natural but not inevitable. The author of "Oceana", he may have been the first political theorist to postulate that political power is a consequence, not the cause, of

Robert Filmer (17th century).

Another member of the Hobbes/Harrington generation, Sir Robert Filmer, reached conclusions much like Hobbes', but through Biblical exegesis. Filmer said that the institution of kingship is analogous to

John Locke (17th century).

In the following generation, John Locke sought to answer Filmer, creating a rationale for a balanced constitution in which the monarch had a part to play, but not an overwhelming part. Since Filmer's views essentially require that the Stuart family be uniquely descended from the patriarchs of the Bible, and since even in the late 17th century that was a difficult view to uphold, Locke attacked Filmer's views in his First Treatise on Government, freeing him to set out his own views in the Second Treatise on Civil Government. Therein, Locke imagined a pre-social world, each of the unhappy residents of which are willing to create a social contract because otherwise "the enjoyment of the property he has in this state is very unsafe, very unsecure," and therefore the "great and chief end, therefore, of men's uniting into commonwealths, and putting themselves under government, is the preservation of their property." They would, he allowed, create a monarchy, but its task would be to execute the will of an elected legislature. "To this end" (to achieve the previously specified goal), he wrote, "it is that men give up all their natural power to

David Hume (18th century).

In contrast to the figures discussed in this section thus far David Hume lived a relatively quiet life that had settled down to a relatively stable social and political structure. He lived the life of a solitary writer until 1763 when, at 52 years of age, he went off to Paris to work at the British embassy.  In contrast, one might think, to his polemical works on religion and his empiricism-driven skeptical epistemology, Hume's views on law and property were quite conservative.  He did not believe in hypothetical contracts, or in the love of mankind in general, and sought to ground politics upon actual human beings

Adam Smith.

"The property which every man has in his own labour, as it is the original foundation of all other property, so it is the most sacred and inviolable. The patrimony of a poor man lies in the strength and dexterity of his hands; and to hinder him from employing this strength and dexterity in what manner he thinks proper without injury to his neighbour, is a plain violation of this most sacred property. It is a manifest encroachment upon the just liberty both of the workman, and of those who might be disposed to employ him. As it hinders the one from

Karl Marx.

Section VIII, "Primitive Accumulation" of Capital involves a critique of Liberal Theories of property rights. Marx notes that under Feudal Law, peasants were legally as entitled to their land as the aristocracy was to its manors. Marx cites several historical events in which large numbers of the

Charles Comte: legitimate origin of property.

Charles Comte, in "Traité de la propriété" (1834), attempted to justify the legitimacy of private property in response to the Bourbon Restoration. According to David Hart, Comte had three main points: "firstly, that interference by the state over the centuries in property ownership has had dire consequences for justice as well as for economic productivity; secondly, that property is legitimate when it emerges in such a way as not to harm anyone; and thirdly, that historically some, but by no means all, property which

Pierre-Joseph Proudhon: property is theft.

In his 1840 treatise "What is Property?", Pierre Proudhon answers with "Property is theft!" In natural resources, he sees two types of property, "de jure" property (legal title) and "de facto" property (physical possession), and argues that the former is illegitimate. Proudhon's conclusion is that "property, to be just and possible, must necessarily have equality for its condition."  His analysis of the product of labor upon natural resources as property (usufruct) is more nuanced. He asserts that land itself cannot

Frédéric Bastiat: property is value.

Frédéric Bastiat's main treatise on property can be found in chapter 8 of his book "Economic Harmonies" (1850). In a radical departure from traditional property theory, he defines property not as a physical object, but rather as a relationship between people with respect to an object. Thus, saying one owns a glass of water is merely verbal shorthand for "I may justly gift or trade this water to another person". In essence, what one owns is not the object but the value of the object. By "value," Bastiat apparently means "market value"; he emphasizes that this is quite different from utility. ""In our relations with one another, we are not owners of the utility of things,

Andrew J. Galambos: a precise definition of property.

Andrew J. Galambos (1924–1997) was an astrophysicist and philosopher who innovated a social structure that seeks to maximize human peace and freedom. Galambos’ concept of property was basic to his philosophy. He defined property as a man's life and all non-procreative derivatives of his life. (Because the English language is deficient in omitting the feminine form “man” when referring to humankind, it is implicit and obligatory that the feminine is included in the term “man”.)  Galambos taught that property is essential to a non-coercive social structure.

Contemporary views.

Contemporary political thinkers who believe that natural persons enjoy rights to own property and to enter into contracts espouse two views about John Locke. On the one hand, some admire Locke, such as William H. Hutt (1956), who praised Locke for laying down the "quintessence of individualism". On the other hand, those such as Richard Pipes regard Locke's arguments as weak, and think

See also.

Property-giving (legal)  Property-taking (legal)  Property-taking (illegal)

Property in the abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article, it is one or more components (rather than attributes), whether physical or incorporeal, of a person's estate; or so belonging to, as in being owned by, a person or jointly a group of people or a legal entity like a corporation or even a society. Depending on the nature of the property, an owner of property has the right to consume, alter, share, redefine, rent, mortgage, pawn, sell, exchange, transfer, give away or destroy it, or to exclude others from doing these things, as well as to perhaps abandon it; whereas regardless of the nature of the property, the owner thereof has the right to properly use it (as a durable, mean or factor, or whatever), or at the very least exclusively keep it.

Eigentum (Lehnübersetzung aus dem lat. "proprietas" zu "proprius" „eigen“) bezeichnet die umfassendste Sachherrschaft, welche die Rechtsordnung an einer Sache zulässt. Merkmale moderner Formen des Eigentums sind die rechtliche Zuordnung von Gütern zu einer natürlichen oder juristischen Person, die Anerkennung der beliebigen Verfügungsgewalt des Eigentümers und die Beschränkung des Eigentümerbeliebens durch Gesetze. Eigentum ist in den meisten Verfassungen als Grundrecht geschützt, aber nicht inhaltlich bestimmt. Der materiale Gehalt des Eigentums ergibt sich aus einer Vielzahl von Gesetzen des Privatrechts und Öffentlichen Rechts (Bodenrecht, Mietrecht, Kaufrecht, Denkmalschutz, Umweltrecht, Steuergesetze etc.; als Besonderheit: Tierschutz) oder gerichtlichen Präzedenzfällen. Man spricht daher auch von Eigentum als einem „Bündel von Rechten und Berechtigungen“, das die Beziehungen und das Handeln zwischen Personen symbolisiert. Der Gehalt des Eigentumsbegriffs ist nicht statisch und naturgegeben, sondern entwickelt sich im Laufe der Zeit durch die gewohnheitsrechtliche Praxis, Rechtsprechung und Gesetzgebung.