text stringlengths 26 3.6k | page_title stringlengths 1 71 | source stringclasses 1
value | token_count int64 10 512 | id stringlengths 2 8 | url stringlengths 31 117 | topic stringclasses 4
values | section stringlengths 4 49 ⌀ | sublist stringclasses 9
values |
|---|---|---|---|---|---|---|---|---|
Human blood is typical of that of mammals, although the precise details concerning cell numbers, size, protein structure, and so on, vary somewhat between species. In non-mammalian vertebrates, however, there are some key differences:
Red blood cells of non-mammalian vertebrates are flattened and ovoid in form, and retain their cell nuclei.
There is considerable variation in the types and proportions of white blood cells; for example, acidophils are generally more common than in humans.
Platelets are unique to mammals; in other vertebrates, small nucleated, spindle cells called thrombocytes are responsible for blood clotting instead.
Physiology
Circulatory system
Blood is circulated around the body through blood vessels by the pumping action of the heart. In humans, blood is pumped from the strong left ventricle of the heart through arteries to peripheral tissues and returns to the right atrium of the heart through veins. It then enters the right ventricle and is pumped through the pulmonary artery to the lungs and returns to the left atrium through the pulmonary veins. Blood then enters the left ventricle to be circulated again. Arterial blood carries oxygen from inhaled air to all of the cells of the body, and venous blood carries carbon dioxide, a waste product of metabolism by cells, to the lungs to be exhaled. However, one exception includes pulmonary arteries, which contain the most deoxygenated blood in the body, while the pulmonary veins contain oxygenated blood.
Additional return flow may be generated by the movement of skeletal muscles, which can compress veins and push blood through the valves in veins toward the right atrium.
The blood circulation was famously described by William Harvey in 1628. | Blood | Wikipedia | 347 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Cell production and degradation
In vertebrates, the various cells of blood are made in the bone marrow in a process called hematopoiesis, which includes erythropoiesis, the production of red blood cells; and myelopoiesis, the production of white blood cells and platelets. During childhood, almost every human bone produces red blood cells; as adults, red blood cell production is limited to the larger bones: the bodies of the vertebrae, the breastbone (sternum), the ribcage, the pelvic bones, and the bones of the upper arms and legs. In addition, during childhood, the thymus gland, found in the mediastinum, is an important source of T lymphocytes.
The proteinaceous component of blood (including clotting proteins) is produced predominantly by the liver, while hormones are produced by the endocrine glands and the watery fraction is regulated by the hypothalamus and maintained by the kidney.
Healthy erythrocytes have a plasma life of about 120 days before they are degraded by the spleen, and the Kupffer cells in the liver. The liver also clears some proteins, lipids, and amino acids. The kidney actively secretes waste products into the urine.
Oxygen transport
About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at sea-level pressure is chemically combined with the hemoglobin. About 1.5% is physically dissolved in the other blood liquids and not connected to hemoglobin. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species. Hemoglobin has an oxygen binding capacity between 1.36 and 1.40 ml O2 per gram hemoglobin, which increases the total blood oxygen capacity seventyfold, compared to if oxygen solely were carried by its solubility of 0.03 ml O2 per liter blood per mm Hg partial pressure of oxygen (about 100 mm Hg in arteries).
With the exception of pulmonary and umbilical arteries and their corresponding veins, arteries carry oxygenated blood away from the heart and deliver it to the body via arterioles and capillaries, where the oxygen is consumed; afterwards, venules and veins carry deoxygenated blood back to the heart. | Blood | Wikipedia | 480 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Under normal conditions in adult humans at rest, hemoglobin in blood leaving the lungs is about 98–99% saturated with oxygen, achieving an oxygen delivery between 950 and 1150 ml/min to the body. In a healthy adult at rest, oxygen consumption is approximately 200–250 ml/min, and deoxygenated blood returning to the lungs is still roughly 75% (70 to 78%) saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia). Sustained hypoxia (oxygenation less than 90%), is dangerous to health, and severe hypoxia (saturations less than 30%) may be rapidly fatal.
A fetus, receiving oxygen via the placenta, is exposed to much lower oxygen pressures (about 21% of the level found in an adult's lungs), so fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F) to function under these conditions.
Carbon dioxide transport
CO2 is carried in blood in three different ways. (The exact percentages vary depending whether it is arterial or venous blood). Most of it (about 70%) is converted to bicarbonate ions by the enzyme carbonic anhydrase in the red blood cells by the reaction ; about 7% is dissolved in the plasma; and about 23% is bound to hemoglobin as carbamino compounds. | Blood | Wikipedia | 361 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO2 decreases the amount of oxygen that is bound for a given partial pressure of oxygen. The decreased binding to carbon dioxide in the blood due to increased oxygen levels is known as the Haldane effect, and is important in the transport of carbon dioxide from the tissues to the lungs. A rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.
Transport of hydrogen ions
Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin. Deoxyhemoglobin binds most of the hydrogen ions as it has a much greater affinity for more hydrogen than does oxyhemoglobin.
Lymphatic system
In mammals, blood is in equilibrium with lymph, which is continuously formed in tissues from blood by capillary ultrafiltration. Lymph is collected by a system of small lymphatic vessels and directed to the thoracic duct, which drains into the left subclavian vein, where lymph rejoins the systemic blood circulation.
Thermoregulation
Blood circulation transports heat throughout the body, and adjustments to this flow are an important part of thermoregulation. Increasing blood flow to the surface (e.g., during warm weather or strenuous exercise) causes warmer skin, resulting in faster heat loss. In contrast, when the external temperature is low, blood flow to the extremities and surface of the skin is reduced and to prevent heat loss and is circulated to the important organs of the body, preferentially.
Rate of flow
Rate of blood flow varies greatly between different organs. Liver has the most abundant blood supply with an approximate flow of 1350 ml/min. Kidney and brain are the second and the third most supplied organs, with 1100 ml/min and ~700 ml/min, respectively.
Relative rates of blood flow per 100 g of tissue are different, with kidney, adrenal gland and thyroid being the first, second and third most supplied tissues, respectively. | Blood | Wikipedia | 502 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Hydraulic functions
The restriction of blood flow can also be used in specialized tissues to cause engorgement, resulting in an erection of that tissue; examples are the erectile tissue in the penis and clitoris.
Another example of a hydraulic function is the jumping spider, in which blood forced into the legs under pressure causes them to straighten for a powerful jump, without the need for bulky muscular legs.
Color
Hemoglobin is the principal determinant of the color of blood (hemochrome). Each molecule has four heme groups, and their interaction with various molecules alters the exact color. Arterial blood and capillary blood are bright red, as oxygen imparts a strong red color to the heme group. Deoxygenated blood is a darker shade of red; this is present in veins, and can be seen during blood donation and when venous blood samples are taken. This is because the spectrum of light absorbed by hemoglobin differs between the oxygenated and deoxygenated states.
Blood in carbon monoxide poisoning is bright red, because carbon monoxide causes the formation of carboxyhemoglobin. In cyanide poisoning, the body cannot use oxygen, so the venous blood remains oxygenated, increasing the redness. There are some conditions affecting the heme groups present in hemoglobin that can make the skin appear blue – a symptom called cyanosis. If the heme is oxidized, methemoglobin, which is more brownish and cannot transport oxygen, is formed. In the rare condition sulfhemoglobinemia, arterial hemoglobin is partially oxygenated, and appears dark red with a bluish hue.
Veins close to the surface of the skin appear blue for a variety of reasons. However, the factors that contribute to this alteration of color perception are related to the light-scattering properties of the skin and the processing of visual input by the visual cortex, rather than the actual color of the venous blood.
Skinks in the genus Prasinohaema have green blood due to a buildup of the waste product biliverdin.
Disorders | Blood | Wikipedia | 439 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
General medical
Disorders of volume
Injury can cause blood loss through bleeding. A healthy adult can lose almost 20% of blood volume (1 L) before the first symptom, restlessness, begins, and 40% of volume (2 L) before shock sets in. Thrombocytes are important for blood coagulation and the formation of blood clots, which can stop bleeding. Trauma to the internal organs or bones can cause internal bleeding, which can sometimes be severe.
Dehydration can reduce the blood volume by reducing the water content of the blood. This would rarely result in shock (apart from the very severe cases) but may result in orthostatic hypotension and fainting.
Disorders of circulation
Shock is the ineffective perfusion of tissues, and can be caused by a variety of conditions including blood loss, infection, poor cardiac output.
Atherosclerosis reduces the flow of blood through arteries, because atheroma lines arteries and narrows them. Atheroma tends to increase with age, and its progression can be compounded by many causes including smoking, high blood pressure, excess circulating lipids (hyperlipidemia), and diabetes mellitus.
Coagulation can form a thrombosis, which can obstruct vessels.
Problems with blood composition, the pumping action of the heart, or narrowing of blood vessels can have many consequences including hypoxia (lack of oxygen) of the tissues supplied. The term ischemia refers to tissue that is inadequately perfused with blood, and infarction refers to tissue death (necrosis), which can occur when the blood supply has been blocked (or is very inadequate).
Hematological | Blood | Wikipedia | 348 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Anemia
Insufficient red cell mass (anemia) can be the result of bleeding, blood disorders like thalassemia, or nutritional deficiencies, and may require one or more blood transfusions. Anemia can also be due to a genetic disorder in which the red blood cells do not function effectively. Anemia can be confirmed by a blood test if the hemoglobin value is less than 13.5 gm/dl in men or less than 12.0 gm/dl in women. Several countries have blood banks to fill the demand for transfusable blood. A person receiving a blood transfusion must have a blood type compatible with that of the donor.
Sickle-cell anemia
Disorders of cell proliferation
Leukemia is a group of cancers of the blood-forming tissues and cells.
Non-cancerous overproduction of red cells (polycythemia vera) or platelets (essential thrombocytosis) may be premalignant.
Myelodysplastic syndromes involve ineffective production of one or more cell lines.
Disorders of coagulation
Hemophilia is a genetic illness that causes dysfunction in one of the blood's clotting mechanisms. This can allow otherwise inconsequential wounds to be life-threatening, but more commonly results in hemarthrosis, or bleeding into joint spaces, which can be crippling.
Ineffective or insufficient platelets can also result in coagulopathy (bleeding disorders).
Hypercoagulable state (thrombophilia) results from defects in regulation of platelet or clotting factor function, and can cause thrombosis.
Infectious disorders of blood
Blood is an important vector of infection. HIV, the virus that causes AIDS, is transmitted through contact with blood, semen or other body secretions of an infected person. Hepatitis B and C are transmitted primarily through blood contact. Owing to blood-borne infections, bloodstained objects are treated as a biohazard.
Bacterial infection of the blood is bacteremia or sepsis. Viral Infection is viremia. Malaria and trypanosomiasis are blood-borne parasitic infections.
Carbon monoxide poisoning | Blood | Wikipedia | 437 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Substances other than oxygen can bind to hemoglobin; in some cases, this can cause irreversible damage to the body. Carbon monoxide, for example, is extremely dangerous when carried to the blood via the lungs by inhalation, because carbon monoxide irreversibly binds to hemoglobin to form carboxyhemoglobin, so that less hemoglobin is free to bind oxygen, and fewer oxygen molecules can be transported throughout the blood. This can cause suffocation insidiously. A fire burning in an enclosed room with poor ventilation presents a very dangerous hazard, since it can create a build-up of carbon monoxide in the air. Some carbon monoxide binds to hemoglobin when smoking tobacco.
Treatments
Transfusion
Blood for transfusion is obtained from human donors by blood donation and stored in a blood bank. There are many different blood types in humans, the ABO blood group system, and the Rhesus blood group system being the most important. Transfusion of blood of an incompatible blood group may cause severe, often fatal, complications, so crossmatching is done to ensure that a compatible blood product is transfused.
Other blood products administered intravenously are platelets, blood plasma, cryoprecipitate, and specific coagulation factor concentrates.
Intravenous administration
Many forms of medication (from antibiotics to chemotherapy) are administered intravenously, as they are not readily or adequately absorbed by the digestive tract.
After severe acute blood loss, liquid preparations, generically known as plasma expanders, can be given intravenously, either solutions of salts (NaCl, KCl, CaCl2 etc.) at physiological concentrations, or colloidal solutions, such as dextrans, human serum albumin, or fresh frozen plasma. In these emergency situations, a plasma expander is a more effective life-saving procedure than a blood transfusion, because the metabolism of transfused red blood cells does not restart immediately after a transfusion.
Letting
In modern evidence-based medicine, bloodletting is used in management of a few rare diseases, including hemochromatosis and polycythemia. However, bloodletting and leeching were common unvalidated interventions used until the 19th century, as many diseases were incorrectly thought to be due to an excess of blood, according to Hippocratic medicine.
Etymology | Blood | Wikipedia | 492 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
English blood (Old English blod) derives from Germanic and has cognates with a similar range of meanings in all other Germanic languages (e.g. German Blut, Swedish blod, Gothic blōþ). There is no accepted Indo-European etymology.
History
Classical Greek medicine
Robin Fåhræus (a Swedish physician who devised the erythrocyte sedimentation rate) suggested that the Ancient Greek system of humorism, wherein the body was thought to contain four distinct bodily fluids (associated with different temperaments), were based upon the observation of blood clotting in a transparent container. When blood is drawn in a glass container and left undisturbed for about an hour, four different layers can be seen. A dark clot forms at the bottom (the "black bile"). Above the clot is a layer of red blood cells (the "blood"). Above this is a whitish layer of white blood cells (the "phlegm"). The top layer is clear yellow serum (the "yellow bile").
In general, Greek thinkers believed that blood was made from food. Plato and Aristotle are two important sources of evidence for this view, but it dates back to Homer's Iliad. Plato thinks that fire in our bellies transform food into blood. Plato believes that the movements of air in the body as we exhale and inhale carry the fire as it transforms our food into blood. Aristotle believed that food is concocted into blood in the heart and transformed into our body's matter.
Types
The ABO blood group system was discovered in the year 1900 by Karl Landsteiner. Jan Janský is credited with the first classification of blood into the four types (A, B, AB, and O) in 1907, which remains in use today. In 1907 the first blood transfusion was performed that used the ABO system to predict compatibility. The first non-direct transfusion was performed on 27 March 1914. The Rhesus factor was discovered in 1937.
Culture and religion
Due to its importance to life, blood is associated with a large number of beliefs. One of the most basic is the use of blood as a symbol for family relationships through birth/parentage; to be "related by blood" is to be related by ancestry or descendence, rather than marriage. This bears closely to bloodlines, and sayings such as "blood is thicker than water" and "bad blood", as well as "Blood brother". | Blood | Wikipedia | 511 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Blood is given particular emphasis in the Islamic, Jewish, and Christian religions, because Leviticus 17:11 says "the life of a creature is in the blood." This phrase is part of the Levitical law forbidding the drinking of blood or eating meat with the blood still intact instead of being poured off.
Mythic references to blood can sometimes be connected to the life-giving nature of blood, seen in such events as childbirth, as contrasted with the blood of injury or death.
Indigenous Australians
In many indigenous Australian Aboriginal peoples' traditions, ochre (particularly red) and blood, both high in iron content and considered Maban, are applied to the bodies of dancers for ritual. As Lawlor states: Lawlor comments that blood employed in this fashion is held by these peoples to attune the dancers to the invisible energetic realm of the Dreamtime. Lawlor then connects these invisible energetic realms and magnetic fields, because iron is magnetic.
European paganism
Among the Germanic tribes, blood was used during their sacrifices; the Blóts. The blood was considered to have the power of its originator, and, after the butchering, the blood was sprinkled on the walls, on the statues of the gods, and on the participants themselves. This act of sprinkling blood was called blóedsian in Old English, and the terminology was borrowed by the Roman Catholic Church becoming to bless and blessing. The Hittite word for blood, ishar was a cognate to words for "oath" and "bond", see Ishara.
The Ancient Greeks believed that the blood of the gods, ichor, was a substance that was poisonous to mortals.
As a relic of Germanic Law, the cruentation, an ordeal where the corpse of the victim was supposed to start bleeding in the presence of the murderer, was used until the early 17th century.
Christianity
In Genesis 9:4, God prohibited Noah and his sons from eating blood (see Noahide Law). This command continued to be observed by the Eastern Orthodox Church.
It is also found in the Bible that when the Angel of Death came around to the Hebrew house that the first-born child would not die if the angel saw lamb's blood wiped across the doorway. | Blood | Wikipedia | 454 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
At the Council of Jerusalem, the apostles prohibited certain Christians from consuming blood – this is documented in Acts 15:20 and 29. This chapter specifies a reason (especially in verses 19–21): It was to avoid offending Jews who had become Christians, because the Mosaic Law Code prohibited the practice.
Christ's blood is the means for the atonement of sins. Also, "... the blood of Jesus Christ his [God] Son cleanseth us from all sin." (1 John 1:7), "... Unto him [God] that loved us, and washed us from our sins in his own blood." (Revelation 1:5), and "And they overcame him (Satan) by the blood of the Lamb [Jesus the Christ], and by the word of their testimony ..." (Revelation 12:11).
Some Christian churches, including Roman Catholicism, Eastern Orthodoxy, Oriental Orthodoxy, and the Assyrian Church of the East teach that, when consecrated, the Eucharistic wine actually becomes the blood of Jesus for worshippers to drink. Thus in the consecrated wine, Jesus becomes spiritually and physically present. This teaching is rooted in the Last Supper, as written in the four gospels of the Bible, in which Jesus stated to his disciples that the bread that they ate was his body, and the wine was his blood. "This cup is the new testament in my blood, which is shed for you." ().
Most forms of Protestantism, especially those of a Methodist or Presbyterian lineage, teach that the wine is no more than a symbol of the blood of Christ, who is spiritually but not physically present. Lutheran theology teaches that the body and blood is present together "in, with, and under" the bread and wine of the Eucharistic feast.
Judaism
In Judaism, animal blood may not be consumed even in the smallest quantity (Leviticus 3:17 and elsewhere); this is reflected in Jewish dietary laws (Kashrut). Blood is purged from meat by rinsing and soaking in water (to loosen clots), salting and then rinsing with water again several times. Eggs must also be checked and any blood spots removed before consumption. Although blood from fish is biblically kosher, it is rabbinically forbidden to consume fish blood to avoid the appearance of breaking the Biblical prohibition. | Blood | Wikipedia | 489 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Another ritual involving blood involves the covering of the blood of fowl and game after slaughtering (Leviticus 17:13); the reason given by the Torah is: "Because the life of the animal is [in] its blood" (ibid 17:14). In relation to human beings, Kabbalah expounds on this verse that the animal soul of a person is in the blood, and that physical desires stem from it.
Likewise, the mystical reason for salting temple sacrifices and slaughtered meat is to remove the blood of animal-like passions from the person. By removing the animal's blood, the animal energies and life-force contained in the blood are removed, making the meat fit for human consumption.
Islam
Consumption of food containing blood is forbidden by Islamic dietary laws. This is derived from the statement in the Qur'an, sura Al-Ma'ida (5:3): "Forbidden to you (for food) are: dead meat, blood, the flesh of swine, and that on which has been invoked the name of other than Allah."
Blood is considered unclean, hence there are specific methods to obtain physical and ritual status of cleanliness once bleeding has occurred. Specific rules and prohibitions apply to menstruation, postnatal bleeding and irregular vaginal bleeding. When an animal has been slaughtered, the animal's neck is cut in a way to ensure that the spine is not severed, hence the brain may send commands to the heart to pump blood to it for oxygen. In this way, blood is removed from the body, and the meat is generally now safe to cook and eat. In modern times, blood transfusions are generally not considered against the rules.
Jehovah's Witnesses
Based on their interpretation of scriptures such as Acts 15:28, 29 ("Keep abstaining...from blood."), many Jehovah's Witnesses neither consume blood nor accept transfusions of whole blood or its major components: red blood cells, white blood cells, platelets (thrombocytes), and plasma. Members may personally decide whether they will accept medical procedures that involve their own blood or substances that are further fractionated from the four major components.
Vampirism | Blood | Wikipedia | 460 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
Vampires are mythical creatures that drink blood directly for sustenance, usually with a preference for human blood. Cultures all over the world have myths of this kind; for example the 'Nosferatu' legend, a human who achieves damnation and immortality by drinking the blood of others, originates from Eastern European folklore. Ticks, leeches, female mosquitoes, vampire bats, and an assortment of other natural creatures do consume the blood of other animals, but only bats are associated with vampires. This has no relation to vampire bats, which are New World creatures discovered well after the origins of the European myths.
Invertebrates
In invertebrates, a body fluid analogous to blood called hemolymph is found, the main difference being that hemolymph is not contained in a closed circulatory system. Hemolymph may function to carry oxygen, although hemoglobin is not necessarily used. Crustaceans and mollusks use hemocyanin instead of hemoglobin. In most insects, their hemolymph does not contain oxygen-carrying molecules because their bodies are small enough for their tracheal system to suffice for supplying oxygen.
Other uses
Forensic and archaeological
Blood residue can help forensic investigators identify weapons, reconstruct a criminal action, and link suspects to the crime. Through bloodstain pattern analysis, forensic information can also be gained from the spatial distribution of bloodstains.
Blood residue analysis is also a technique used in archeology.
Artistic
Blood is one of the body fluids that has been used in art. In particular, the performances of Viennese Actionist Hermann Nitsch, Istvan Kantor, Franko B, Lennie Lee, Ron Athey, Yang Zhichao, Lucas Abela and Kira O'Reilly, along with the photography of Andres Serrano, have incorporated blood as a prominent visual element. Marc Quinn has made sculptures using frozen blood, including a cast of his own head made using his own blood.
Genealogical
The term blood is used in genealogical circles to refer to one's ancestry, origins, and ethnic background as in the word bloodline. Other terms where blood is used in a family history sense are blue-blood, royal blood, mixed-blood and blood relative. | Blood | Wikipedia | 457 | 3997 | https://en.wikipedia.org/wiki/Blood | Biology and health sciences | Biology | null |
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College in 1963. They wanted to enable students in non-scientific fields to use computers. At the time, nearly all computers required writing custom software, which only scientists and mathematicians tended to learn.
In addition to the programming language, Kemeny and Kurtz developed the Dartmouth Time-Sharing System (DTSS), which allowed multiple users to edit and run BASIC programs simultaneously on remote terminals. This general model became popular on minicomputer systems like the PDP-11 and Data General Nova in the late 1960s and early 1970s. Hewlett-Packard produced an entire computer line for this method of operation, introducing the HP2000 series in the late 1960s and continuing sales into the 1980s. Many early video games trace their history to one of these versions of BASIC.
The emergence of microcomputers in the mid-1970s led to the development of multiple BASIC dialects, including Microsoft BASIC in 1975. Due to the tiny main memory available on these machines, often 4 KB, a variety of Tiny BASIC dialects were also created. BASIC was available for almost any system of the era, and became the de facto programming language for home computer systems that emerged in the late 1970s. These PCs almost always had a BASIC interpreter installed by default, often in the machine's firmware or sometimes on a ROM cartridge.
BASIC declined in popularity in the 1990s, as more powerful microcomputers came to market and programming languages with advanced features (such as Pascal and C) became tenable on such computers. By then, most nontechnical personal computer users relied on pre-written applications rather than writing their own programs. In 1991, Microsoft released Visual Basic, combining an updated version of BASIC with a visual forms builder. This reignited use of the language and "VB" remains a major programming language in the form of VB.NET, while a hobbyist scene for BASIC more broadly continues to exist. | BASIC | Wikipedia | 435 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Origin
John G. Kemeny was the chairman of the Dartmouth College Mathematics Department. Based largely on his reputation as an innovator in math teaching, in 1959 the college won an Alfred P. Sloan Foundation award for $500,000 to build a new department building. Thomas E. Kurtz had joined the department in 1956, and from the 1960s Kemeny and Kurtz agreed on the need for programming literacy among students outside the traditional STEM fields. Kemeny later noted that "Our vision was that every student on campus should have access to a computer, and any faculty member should be able to use a computer in the classroom whenever appropriate. It was as simple as that."
Kemeny and Kurtz had made two previous experiments with simplified languages, DARSIMCO (Dartmouth Simplified Code) and DOPE (Dartmouth Oversimplified Programming Experiment). These did not progress past a single freshman class. New experiments using Fortran and ALGOL followed, but Kurtz concluded these languages were too tricky for what they desired. As Kurtz noted, Fortran had numerous oddly formed commands, notably an "almost impossible-to-memorize convention for specifying a loop: . Is it '1, 10, 2' or '1, 2, 10', and is the comma after the line number required or not?"
Moreover, the lack of any sort of immediate feedback was a key problem; the machines of the era used batch processing and took a long time to complete a run of a program. While Kurtz was visiting MIT, John McCarthy suggested that time-sharing offered a solution; a single machine could divide up its processing time among many users, giving them the illusion of having a (slow) computer to themselves. Small programs would return results in a few seconds. This led to increasing interest in a system using time-sharing and a new language specifically for use by non-STEM students. | BASIC | Wikipedia | 389 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Kemeny wrote the first version of BASIC. The acronym BASIC comes from the name of an unpublished paper by Thomas Kurtz. The new language was heavily patterned on FORTRAN II; statements were one-to-a-line, numbers were used to indicate the target of loops and branches, and many of the commands were similar or identical to Fortran. However, the syntax was changed wherever it could be improved. For instance, the difficult to remember DO loop was replaced by the much easier to remember , and the line number used in the DO was instead indicated by the NEXT I. Likewise, the cryptic IF statement of Fortran, whose syntax matched a particular instruction of the machine on which it was originally written, became the simpler . These changes made the language much less idiosyncratic while still having an overall structure and feel similar to the original FORTRAN.
The project received a $300,000 grant from the National Science Foundation, which was used to purchase a GE-225 computer for processing, and a Datanet-30 realtime processor to handle the Teletype Model 33 teleprinters used for input and output. A team of a dozen undergraduates worked on the project for about a year, writing both the DTSS system and the BASIC compiler. The first version BASIC language was released on 1 May 1964.
Initially, BASIC concentrated on supporting straightforward mathematical work, with matrix arithmetic support from its initial implementation as a batch language, and character string functionality being added by 1965. Usage in the university rapidly expanded, requiring the main CPU to be replaced by a GE-235, and still later by a GE-635. By the early 1970s there were hundreds of terminals connected to the machines at Dartmouth, some of them remotely.
Wanting use of the language to become widespread, its designers made the compiler available free of charge. In the 1960s, software became a chargeable commodity; until then, it was provided without charge as a service with expensive computers, usually available only to lease. They also made it available to high schools in the Hanover, New Hampshire, area and regionally throughout New England on Teletype Model 33 and Model 35 teleprinter terminals connected to Dartmouth via dial-up phone lines, and they put considerable effort into promoting the language. In the following years, as other dialects of BASIC appeared, Kemeny and Kurtz's original BASIC dialect became known as Dartmouth BASIC. | BASIC | Wikipedia | 487 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
New Hampshire recognized the accomplishment in 2019 when it erected a highway historical marker in Hanover describing the creation of "the first user-friendly programming language".
Spread on time-sharing services
The emergence of BASIC took place as part of a wider movement toward time-sharing systems. First conceptualized during the late 1950s, the idea became so dominant in the computer industry by the early 1960s that its proponents were speaking of a future in which users would "buy time on the computer much the same way that the average household buys power and water from utility companies".
General Electric, having worked on the Dartmouth project, wrote their own underlying operating system and launched an online time-sharing system known as Mark I. It featured BASIC as one of its primary selling points. Other companies in the emerging field quickly followed suit; Tymshare introduced SUPER BASIC in 1968, CompuServe had a version on the DEC-10 at their launch in 1969, and by the early 1970s BASIC was largely universal on general-purpose mainframe computers. Even IBM eventually joined the club with the introduction of VS-BASIC in 1973.
Although time-sharing services with BASIC were successful for a time, the widespread success predicted earlier was not to be. The emergence of minicomputers during the same period, and especially low-cost microcomputers in the mid-1970s, allowed anyone to purchase and run their own systems rather than buy online time which was typically billed at dollars per minute.
Spread on minicomputers
BASIC, by its very nature of being small, was naturally suited to porting to the minicomputer market, which was emerging at the same time as the time-sharing services. These machines had small main memory, perhaps as little as 4 KB in modern terminology, and lacked high-performance storage like hard drives that make compilers practical. On these systems, BASIC was normally implemented as an interpreter rather than a compiler due to its lower requirement for working memory. | BASIC | Wikipedia | 394 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
A particularly important example was HP Time-Shared BASIC, which, like the original Dartmouth system, used two computers working together to implement a time-sharing system. The first, a low-end machine in the HP 2100 series, was used to control user input and save and load their programs to tape or disk. The other, a high-end version of the same underlying machine, ran the programs and generated output. For a cost of about $100,000, one could own a machine capable of running between 16 and 32 users at the same time. The system, bundled as the HP 2000, was the first mini platform to offer time-sharing and was an immediate runaway success, catapulting HP to become the third-largest vendor in the minicomputer space, behind DEC and Data General (DG).
DEC, the leader in the minicomputer space since the mid-1960s, had initially ignored BASIC. This was due to their work with RAND Corporation, who had purchased a PDP-6 to run their JOSS language, which was conceptually very similar to BASIC. This led DEC to introduce a smaller, cleaned up version of JOSS known as FOCAL, which they heavily promoted in the late 1960s. However, with timesharing systems widely offering BASIC, and all of their competition in the minicomputer space doing the same, DEC's customers were clamoring for BASIC. After management repeatedly ignored their pleas, David H. Ahl took it upon himself to buy a BASIC for the PDP-8, which was a major success in the education market. By the early 1970s, FOCAL and JOSS had been forgotten and BASIC had become almost universal in the minicomputer market. DEC would go on to introduce their updated version, BASIC-PLUS, for use on the RSTS/E time-sharing operating system.
During this period a number of simple text-based games were written in BASIC, most notably Mike Mayfield's Star Trek. David Ahl collected these, some ported from FOCAL, and published them in an educational newsletter he compiled. He later collected a number of these into book form, 101 BASIC Computer Games, published in 1973. During the same period, Ahl was involved in the creation of a small computer for education use, an early personal computer. When management refused to support the concept, Ahl left DEC in 1974 to found the seminal computer magazine, Creative Computing. The book remained popular, and was re-published on several occasions. | BASIC | Wikipedia | 506 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Explosive growth: the home computer era
The introduction of the first microcomputers in the mid-1970s was the start of explosive growth for BASIC. It had the advantage that it was fairly well known to the young designers and computer hobbyists who took an interest in microcomputers, many of whom had seen BASIC on minis or mainframes. Despite Dijkstra's famous judgement in 1975, "It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration", BASIC was one of the few languages that was both high-level enough to be usable by those without training and small enough to fit into the microcomputers of the day, making it the de facto standard programming language on early microcomputers.
The first microcomputer version of BASIC was co-written by Bill Gates, Paul Allen and Monte Davidoff for their newly formed company, Micro-Soft. This was released by MITS in punch tape format for the Altair 8800 shortly after the machine itself, immediately cementing BASIC as the primary language of early microcomputers. Members of the Homebrew Computer Club began circulating copies of the program, causing Gates to write his Open Letter to Hobbyists, complaining about this early example of software piracy.
Partially in response to Gates's letter, and partially to make an even smaller BASIC that would run usefully on 4 KB machines, Bob Albrecht urged Dennis Allison to write their own variation of the language. How to design and implement a stripped-down version of an interpreter for the BASIC language was covered in articles by Allison in the first three quarterly issues of the People's Computer Company newsletter published in 1975 and implementations with source code published in Dr. Dobb's Journal of Tiny BASIC Calisthenics & Orthodontia: Running Light Without Overbyte. This led to a wide variety of Tiny BASICs with added features or other improvements, with versions from Tom Pittman and Li-Chen Wang becoming particularly well known. | BASIC | Wikipedia | 421 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Micro-Soft, by this time Microsoft, ported their interpreter for the MOS 6502, which quickly become one of the most popular microprocessors of the 8-bit era. When new microcomputers began to appear, notably the "1977 trinity" of the TRS-80, Commodore PET and Apple II, they either included a version of the MS code, or quickly introduced new models with it. Ohio Scientific's personal computers also joined this trend at that time. By 1978, MS BASIC was a de facto standard and practically every home computer of the 1980s included it in ROM. Upon boot, a BASIC interpreter in direct mode was presented.
Commodore Business Machines includes Commodore BASIC, based on Microsoft BASIC. The Apple II and TRS-80 each have two versions of BASIC: a smaller introductory version with the initial releases of the machines and a Microsoft-based version introduced as interest in the platforms increased. As new companies entered the field, additional versions were added that subtly changed the BASIC family. The Atari 8-bit computers use the 8 KB Atari BASIC which is not derived from Microsoft BASIC. Sinclair BASIC was introduced in 1980 with the Sinclair ZX80, and was later extended for the Sinclair ZX81 and the Sinclair ZX Spectrum. The BBC published BBC BASIC, developed by Acorn Computers, incorporates extra structured programming keywords and floating-point features. | BASIC | Wikipedia | 280 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
As the popularity of BASIC grew in this period, computer magazines published complete source code in BASIC for video games, utilities, and other programs. Given BASIC's straightforward nature, it was a simple matter to type in the code from the magazine and execute the program. Different magazines were published featuring programs for specific computers, though some BASIC programs were considered universal and could be used in machines running any variant of BASIC (sometimes with minor adaptations). Many books of type-in programs were also available, and in particular, Ahl published versions of the original 101 BASIC games converted into the Microsoft dialect and published it from Creative Computing as BASIC Computer Games. This book, and its sequels, provided hundreds of ready-to-go programs that could be easily converted to practically any BASIC-running platform. The book reached the stores in 1978, just as the home computer market was starting off, and it became the first million-selling computer book. Later packages, such as Learn to Program BASIC would also have gaming as an introductory focus. On the business-focused CP/M computers which soon became widespread in small business environments, Microsoft BASIC (MBASIC) was one of the leading applications.
In 1978, David Lien published the first edition of The BASIC Handbook: An Encyclopedia of the BASIC Computer Language, documenting keywords across over 78 different computers. By 1981, the second edition documented keywords from over 250 different computers, showcasing the explosive growth of the microcomputer era.
IBM PC and compatibles
When IBM was designing the IBM PC, they followed the paradigm of existing home computers in having a built-in BASIC interpreter. They sourced this from Microsoft – IBM Cassette BASIC – but Microsoft also produced several other versions of BASIC for MS-DOS/PC DOS including IBM Disk BASIC (BASIC D), IBM BASICA (BASIC A), GW-BASIC (a BASICA-compatible version that did not need IBM's ROM) and QBasic, all typically bundled with the machine. In addition they produced the Microsoft QuickBASIC Compiler (1985) for power users and hobbyists, and the Microsoft BASIC Professional Development System (PDS) for professional programmers. Turbo Pascal-publisher Borland published Turbo Basic 1.0 in 1985 (successor versions were marketed under the name PowerBASIC). | BASIC | Wikipedia | 461 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
On Unix-like systems, specialized implementations were created such as XBasic and X11-Basic. XBasic was ported to Microsoft Windows as XBLite, and cross-platform variants such as SmallBasic, yabasic, Bywater BASIC, nuBasic, MyBasic, Logic Basic, Liberty BASIC, and wxBasic emerged. FutureBASIC and Chipmunk Basic meanwhile targeted the Apple Macintosh, while yab is a version of yaBasic optimized for BeOS, ZETA and Haiku.
These later variations introduced many extensions, such as improved string manipulation and graphics support, access to the file system and additional data types. More important were the facilities for structured programming, including additional control structures and proper subroutines supporting local variables. The addition of an integrated development environment (IDE) and electronic Help files made the products easier to work with and supported learning tools and school curriculum.
In 1989, Microsoft Press published Learn BASIC Now, a book-and-software system designed to teach BASIC programming to self-taught learners who were using IBM-PC compatible systems and the Apple Macintosh. Learn BASIC Now included software disks containing the Microsoft QuickBASIC Interpreter and a programming tutorial written by Michael Halvorson and David Rygmyr. Learning systems like Learn BASIC Now popularized structured BASIC and helped QuickBASIC reach an installed base of four million active users.
By the late 1980s, many users were using pre-made applications written by others rather than learning programming themselves, and professional developers had a wide range of advanced languages available on small computers. C and later C++ became the languages of choice for professional "shrink wrap" application development.
A niche that BASIC continued to fill was for hobbyist video game development, as game creation systems and readily available game engines were still in their infancy. The Atari ST had STOS BASIC while the Amiga had AMOS BASIC for this purpose. Microsoft first exhibited BASIC for game development with DONKEY.BAS for GW-BASIC, and later GORILLA.BAS and NIBBLES.BAS for QuickBASIC. QBasic maintained an active game development community, which helped later spawn the QB64 and FreeBASIC implementations. An early example of this market is the QBasic software package Microsoft Game Shop (1990), a hobbyist-inspired release that included six "arcade-style" games that were easily customizable in QBasic. | BASIC | Wikipedia | 489 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
In 2013, a game written in QBasic and compiled with QB64 for modern computers entitled Black Annex was released on Steam. Blitz Basic, Dark Basic, SdlBasic, Super Game System Basic, PlayBASIC, CoolBasic, AllegroBASIC, ethosBASIC, GLBasic and Basic4GL further filled this demand, right up to the modern RCBasic, NaaLaa, AppGameKit, Monkey 2, and Cerberus-X.
Visual Basic
In 1991, Microsoft introduced Visual Basic, an evolutionary development of QuickBASIC. It included constructs from that language such as block-structured control statements, parameterized subroutines and optional static typing as well as object-oriented constructs from other languages such as "With" and "For Each". The language retained some compatibility with its predecessors, such as the Dim keyword for declarations, "Gosub"/Return statements and optional line numbers which could be used to locate errors. An important driver for the development of Visual Basic was as the new macro language for Microsoft Excel, a spreadsheet program. To the surprise of many at Microsoft who still initially marketed it as a language for hobbyists, the language came into widespread use for small custom business applications shortly after the release of VB version 3.0, which is widely considered the first relatively stable version. Microsoft also spun it off as Visual Basic for Applications and Embedded Visual Basic.
While many advanced programmers still scoffed at its use, VB met the needs of small businesses efficiently as by that time, computers running Windows 3.1 had become fast enough that many business-related processes could be completed "in the blink of an eye" even using a "slow" language, as long as large amounts of data were not involved. Many small business owners found they could create their own small, yet useful applications in a few evenings to meet their own specialized needs. Eventually, during the lengthy lifetime of VB3, knowledge of Visual Basic had become a marketable job skill. Microsoft also produced VBScript in 1996 and Visual Basic .NET in 2001. The latter has essentially the same power as C# and Java but with syntax that reflects the original Basic language, and also features some cross-platform capability through implementations such as Mono-Basic. The IDE, with its event-driven GUI builder, was also influential on other rapid application development tools, most notably Borland Software's Delphi for Object Pascal and its own descendants such as Lazarus. | BASIC | Wikipedia | 510 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Mainstream support for the final version 6.0 of the original Visual Basic ended on March 31, 2005, followed by extended support in March 2008. Owing to its persistent remaining popularity, third-party attempts to further support it exist. On February 2, 2017, Microsoft announced that development on VB.NET would no longer be in parallel with that of C#, and on March 11, 2020, it was announced that evolution of the VB.NET language had also concluded. Even so, the language was still supported.
Post-1990 versions and dialects
Many other BASIC dialects have also sprung up since 1990, including the open source QB64 and FreeBASIC, inspired by QBasic, and the Visual Basic-styled RapidQ, HBasic, Basic For Qt and Gambas. Modern commercial incarnations include PureBasic, PowerBASIC, Xojo, Monkey X and True BASIC (the direct successor to Dartmouth BASIC from a company controlled by Kurtz).
Several web-based simple BASIC interpreters also now exist, including Microsoft's Small Basic and Google's wwwBASIC. A number of compilers also exist that convert BASIC into JavaScript. such as NS Basic.
Building from earlier efforts such as Mobile Basic, many dialects are now available for smartphones and tablets.
On game consoles, an application for the Nintendo 3DS and Nintendo DSi called Petit Computer allows for programming in a slightly modified version of BASIC with DS button support. A version has also been released for Nintendo Switch, which has also been supplied a version of the Fuze Code System, a BASIC variant first implemented as a custom Raspberry Pi machine. Previously BASIC was made available on consoles as Family BASIC (for the Nintendo Famicom) and PSX Chipmunk Basic (for the original PlayStation), while yabasic was ported to the PlayStation 2 and FreeBASIC to the original Xbox.
Calculators
Variants of BASIC are available on graphing and otherwise programmable calculators made by Texas Instruments (TI-BASIC), HP (HP BASIC), Casio (Casio BASIC), and others. | BASIC | Wikipedia | 431 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Windows command-line
QBasic, a version of Microsoft QuickBASIC without the linker to make EXE files, is present in the Windows NT and DOS-Windows 95 streams of operating systems and can be obtained for more recent releases like Windows 7 which do not have them. Prior to DOS 5, the Basic interpreter was GW-Basic. QuickBasic is part of a series of three languages issued by Microsoft for the home and office power user and small-scale professional development; QuickC and QuickPascal are the other two. For Windows 95 and 98, which do not have QBasic installed by default, they can be copied from the installation disc, which will have a set of directories for old and optional software; other missing commands like Exe2Bin and others are in these same directories.
Other
The various Microsoft, Lotus, and Corel office suites and related products are programmable with Visual Basic in one form or another, including LotusScript, which is very similar to VBA 6. The Host Explorer terminal emulator uses WWB as a macro language; or more recently the programme and the suite in which it is contained is programmable in an in-house Basic variant known as Hummingbird Basic. The VBScript variant is used for programming web content, Outlook 97, Internet Explorer, and the Windows Script Host. WSH also has a Visual Basic for Applications (VBA) engine installed as the third of the default engines along with VBScript, JScript, and the numerous proprietary or open source engines which can be installed like PerlScript, a couple of Rexx-based engines, Python, Ruby, Tcl, Delphi, XLNT, PHP, and others; meaning that the two versions of Basic can be used along with the other mentioned languages, as well as LotusScript, in a WSF file, through the component object model, and other WSH and VBA constructions. VBScript is one of the languages that can be accessed by the 4Dos, 4NT, and Take Command enhanced shells. SaxBasic and WWB are also very similar to the Visual Basic line of Basic implementations. The pre-Office 97 macro language for Microsoft Word is known as WordBASIC. Excel 4 and 5 use Visual Basic itself as a macro language. Chipmunk Basic, an old-school interpreter similar to BASICs of the 1970s, is available for Linux, Microsoft Windows and macOS. | BASIC | Wikipedia | 498 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Legacy
The ubiquity of BASIC interpreters on personal computers was such that textbooks once included simple "Try It In BASIC" exercises that encouraged students to experiment with mathematical and computational concepts on classroom or home computers. Popular computer magazines of the day typically included type-in programs.
Futurist and sci-fi writer David Brin mourned the loss of ubiquitous BASIC in a 2006 Salon article as have others who first used computers during this era. In turn, the article prompted Microsoft to develop and release Small Basic; it also inspired similar projects like Basic-256 and the web based Quite Basic. Dartmouth held a 50th anniversary celebration for BASIC on 1 May 2014. The pedagogical use of BASIC has been followed by other languages, such as Pascal, Java and particularly Python.
Dartmouth College celebrated the 50th anniversary of the BASIC language with a day of events on April 30, 2014. A short documentary film was produced for the event.
Syntax
Typical BASIC keywords
Data manipulation
LET assigns a value (which may be the result of an expression) to a variable. In most dialects of BASIC, LET is optional, and a line with no other identifiable keyword will assume the keyword to be LET.
DATA holds a list of values which are assigned sequentially using the READ command.
READ reads a value from a DATA statement and assigns it to a variable. An internal pointer keeps track of the last DATA element that was read and moves it one position forward with each READ. Most dialects allow multiple variables as parameters, reading several values in a single operation.
RESTORE resets the internal pointer to the first DATA statement, allowing the program to begin READing from the first value. Many dialects allow an optional line number or ordinal value to allow the pointer to be reset to a selected location.
DIM Sets up an array. | BASIC | Wikipedia | 365 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Program flow control
IF ... THEN ... {ELSE} used to perform comparisons or make decisions. Early dialects only allowed a line number after the THEN, but later versions allowed any valid statement to follow. ELSE was not widely supported, especially in earlier versions.
FOR ... TO ... {STEP} ... NEXT repeat a section of code a given number of times. A variable that acts as a counter, the "index", is available within the loop.
WHILE ... WEND and REPEAT ... UNTIL repeat a section of code while the specified condition is true. The condition may be evaluated before each iteration of the loop, or after. Both of these commands are found mostly in later dialects.
DO ... LOOP {WHILE} or {UNTIL} repeat a section of code indefinitely or while/until the specified condition is true. The condition may be evaluated before each iteration of the loop, or after. Similar to WHILE, these keywords are mostly found in later dialects.
GOTO jumps to a numbered or labelled line in the program. Most dialects also allowed the form .
GOSUB ... RETURN jumps to a numbered or labelled line, executes the code it finds there until it reaches a RETURN command, on which it jumps back to the statement following the GOSUB, either after a colon, or on the next line. This is used to implement subroutines.
ON ... GOTO/GOSUB chooses where to jump based on the specified conditions. See Switch statement for other forms.
DEF FN a pair of keywords introduced in the early 1960s to define functions. The original BASIC functions were modelled on FORTRAN single-line functions. BASIC functions were one expression with variable arguments, rather than subroutines, with a syntax on the model of DEF FND(x) = x*x at the beginning of a program. Function names were originally restricted to FN, plus one letter, i.e., FNA, FNB ... | BASIC | Wikipedia | 414 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Input and output
LIST displays the full source code of the current program.
PRINT displays a message on the screen or other output device.
INPUT asks the user to enter the value of a variable. The statement may include a prompt message.
TAB used with PRINT to set the position where the next character will be shown on the screen or printed on paper. AT is an alternative form.
SPC prints out a number of space characters. Similar in concept to TAB but moves by a number of additional spaces from the current column rather than moving to a specified column.
Mathematical functions
ABS Absolute value
ATN Arctangent (result in radians)
COS Cosine (argument in radians)
EXP Exponential function
INT Integer part (typically floor function)
LOG Natural logarithm
RND Random number generation
SIN Sine (argument in radians)
SQR Square root
TAN Tangent (argument in radians)
Miscellaneous
REM holds a programmer's comment or REMark; often used to give a title to the program and to help identify the purpose of a given section of code.
USR ("User Serviceable Routine") transfers program control to a machine language subroutine, usually entered as an alphanumeric string or in a list of DATA statements.
CALL alternative form of USR found in some dialects. Does not require an artificial parameter to complete the function-like syntax of USR, and has a clearly defined method of calling different routines in memory.
TRON / TROFF turns on display of each line number as it is run ("TRace ON"). This was useful for debugging or correcting of problems in a program. TROFF turns it back off again.
ASM some compilers such as Freebasic, Purebasic, and Powerbasic also support inline assembly language, allowing the programmer to intermix high-level and low-level code, typically prefixed with "ASM" or "!" statements. | BASIC | Wikipedia | 399 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Data types and variables
Minimal versions of BASIC had only integer variables and one- or two-letter variable names, which minimized requirements of limited and expensive memory (RAM). More powerful versions had floating-point arithmetic, and variables could be labelled with names six or more characters long. There were some problems and restrictions in early implementations; for example, Applesoft BASIC allowed variable names to be several characters long, but only the first two were significant, thus it was possible to inadvertently write a program with variables "LOSS" and "LOAN", which would be treated as being the same; assigning a value to "LOAN" would silently overwrite the value intended as "LOSS". Keywords could not be used in variables in many early BASICs; "SCORE" would be interpreted as "SC" OR "E", where OR was a keyword. String variables are usually distinguished in many microcomputer dialects by having $ suffixed to their name as a sigil, and values are often identified as strings by being delimited by "double quotation marks". Arrays in BASIC could contain integers, floating point or string variables.
Some dialects of BASIC supported matrices and matrix operations, which can be used to solve sets of simultaneous linear algebraic equations. These dialects would directly support matrix operations such as assignment, addition, multiplication (of compatible matrix types), and evaluation of a determinant. Many microcomputer BASICs did not support this data type; matrix operations were still possible, but had to be programmed explicitly on array elements.
Examples
Unstructured BASIC
New BASIC programmers on a home computer might start with a simple program, perhaps using the language's PRINT statement to display a message on the screen; a well-known and often-replicated example is Kernighan and Ritchie's "Hello, World!" program:
10 PRINT "Hello, World!"
20 END
An infinite loop could be used to fill the display with the message:
10 PRINT "Hello, World!"
20 GOTO 10
Note that the END statement is optional and has no action in most dialects of BASIC. It was not always included, as is the case in this example. This same program can be modified to print a fixed number of messages using the common FOR...NEXT statement:
10 LET N=10
20 FOR I=1 TO N
30 PRINT "Hello, World!"
40 NEXT I | BASIC | Wikipedia | 486 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Most home computers BASIC versions, such as MSX BASIC and GW-BASIC, supported simple data types, loop cycles, and arrays. The following example is written for GW-BASIC, but will work in most versions of BASIC with minimal changes:
10 INPUT "What is your name: "; U$
20 PRINT "Hello "; U$
30 INPUT "How many stars do you want: "; N
40 S$ = ""
50 FOR I = 1 TO N
60 S$ = S$ + "*"
70 NEXT I
80 PRINT S$
90 INPUT "Do you want more stars? "; A$
100 IF LEN(A$) = 0 THEN GOTO 90
110 A$ = LEFT$(A$, 1)
120 IF A$ = "Y" OR A$ = "y" THEN GOTO 30
130 PRINT "Goodbye "; U$
140 END
The resulting dialog might resemble:
What is your name: Mike
Hello Mike
How many stars do you want: 7
*******
Do you want more stars? yes
How many stars do you want: 3
***
Do you want more stars? no
Goodbye Mike
The original Dartmouth Basic was unusual in having a matrix keyword, MAT. Although not implemented by most later microprocessor derivatives, it is used in this example from the 1968 manual which averages the numbers that are input:
5 LET S = 0
10 MAT INPUT V
20 LET N = NUM
30 IF N = 0 THEN 99
40 FOR I = 1 TO N
45 LET S = S + V(I)
50 NEXT I
60 PRINT S/N
70 GO TO 5
99 END
Structured BASIC
Second-generation BASICs (for example, VAX Basic, SuperBASIC, True BASIC, QuickBASIC, BBC BASIC, Pick BASIC, PowerBASIC, Liberty BASIC, QB64 and (arguably) COMAL) introduced a number of features into the language, primarily related to structured and procedure-oriented programming. Usually, line numbering is omitted from the language and replaced with labels (for GOTO) and procedures to encourage easier and more flexible design. In addition keywords and structures to support repetition, selection and procedures with local variables were introduced.
The following example is in Microsoft QuickBASIC:
REM QuickBASIC example
REM Forward declaration - allows the main code to call a
REM subroutine that is defined later in the source code
DECLARE SUB PrintSomeStars (StarCount!) | BASIC | Wikipedia | 502 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
REM Main program follows
INPUT "What is your name: ", UserName$
PRINT "Hello "; UserName$
DO
INPUT "How many stars do you want: ", NumStars
CALL PrintSomeStars(NumStars)
DO
INPUT "Do you want more stars? ", Answer$
LOOP UNTIL Answer$ <> ""
Answer$ = LEFT$(Answer$, 1)
LOOP WHILE UCASE$(Answer$) = "Y"
PRINT "Goodbye "; UserName$
END
REM subroutine definition
SUB PrintSomeStars (StarCount)
REM This procedure uses a local variable called Stars$
Stars$ = STRING$(StarCount, "*")
PRINT Stars$
END SUB
Object-oriented BASIC
Third-generation BASIC dialects such as Visual Basic, Xojo, Gambas, StarOffice Basic, BlitzMax and PureBasic introduced features to support object-oriented and event-driven programming paradigm. Most built-in procedures and functions are now represented as methods of standard objects rather than operators. Also, the operating system became increasingly accessible to the BASIC language.
The following example is in Visual Basic .NET:
Public Module StarsProgram
Private Function Ask(prompt As String) As String
Console.Write(prompt)
Return Console.ReadLine()
End Function
Public Sub Main()
Dim userName = Ask("What is your name: ")
Console.WriteLine("Hello {0}", userName)
Dim answer As String
Do
Dim numStars = CInt(Ask("How many stars do you want: "))
Dim stars As New String("*"c, numStars)
Console.WriteLine(stars)
Do
answer = Ask("Do you want more stars? ")
Loop Until answer <> ""
Loop While answer.StartsWith("Y", StringComparison.OrdinalIgnoreCase)
Console.WriteLine("Goodbye {0}", userName)
End Sub
End Module | BASIC | Wikipedia | 418 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
Standards
ANSI/ISO/IEC/ECMA Standard for Minimal BASIC:
ANSI X3.60-1978 "For minimal BASIC"
ISO/IEC 6373:1984 "Data Processing—Programming Languages—Minimal BASIC"
ECMA-55 Minimal BASIC (withdrawn, similar to ANSI X3.60-1978)
ANSI/ISO/IEC/ECMA Standard for Full BASIC:
ANSI X3.113-1987 "Programming Languages Full BASIC"
INCITS/ISO/IEC 10279-1991 (R2005) "Information Technology – Programming Languages – Full BASIC"
ECMA-116 BASIC (withdrawn, similar to ANSI X3.113-1987)
ANSI/ISO/IEC Addendum Defining Modules:
ANSI X3.113 Interpretations-1992 "BASIC Technical Information Bulletin # 1 Interpretations of ANSI 03.113-1987"
ISO/IEC 10279:1991/ Amd 1:1994 "Modules and Single Character Input Enhancement"
Compilers and interpreters | BASIC | Wikipedia | 204 | 4015 | https://en.wikipedia.org/wiki/BASIC | Technology | "Historical" languages | null |
In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state.
The term is closely associated with the work of the mathematician and meteorologist Edward Norton Lorenz. He noted that the butterfly effect is derived from the example of the details of a tornado (the exact time of formation, the exact path taken) being influenced by minor perturbations such as a distant butterfly flapping its wings several weeks earlier. Lorenz originally used a seagull causing a storm but was persuaded to make it more poetic with the use of a butterfly and tornado by 1972. He discovered the effect when he observed runs of his weather model with initial condition data that were rounded in a seemingly inconsequential manner. He noted that the weather model would fail to reproduce the results of runs with the unrounded initial condition data. A very small change in initial conditions had created a significantly different outcome.
The idea that small causes may have large effects in weather was earlier acknowledged by the French mathematician and physicist Henri Poincaré. The American mathematician and philosopher Norbert Wiener also contributed to this theory. Lorenz's work placed the concept of instability of the Earth's atmosphere onto a quantitative base and linked the concept of instability to the properties of large classes of dynamic systems which are undergoing nonlinear dynamics and deterministic chaos.
The concept of the butterfly effect has since been used outside the context of weather science as a broad term for any situation where a small change is supposed to be the cause of larger consequences.
History
In The Vocation of Man (1800), Johann Gottlieb Fichte says "you could not remove a single grain of sand from its place without thereby ... changing something throughout all parts of the immeasurable whole".
Chaos theory and the sensitive dependence on initial conditions were described in numerous forms of literature. This is evidenced by the case of the three-body problem by Poincaré in 1890. He later proposed that such phenomena could be common, for example, in meteorology.
In 1898, Jacques Hadamard noted general divergence of trajectories in spaces of negative curvature. Pierre Duhem discussed the possible general significance of this in 1908.
In 1950, Alan Turing noted: "The displacement of a single electron by a billionth of a centimetre at one moment might make the difference between a man being killed by an avalanche a year later, or escaping." | Butterfly effect | Wikipedia | 511 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
The idea that the death of one butterfly could eventually have a far-reaching ripple effect on subsequent historical events made its earliest known appearance in "A Sound of Thunder", a 1952 short story by Ray Bradbury. "A Sound of Thunder" features time travel.
More precisely, though, almost the exact idea and the exact phrasing —of a tiny insect's wing affecting the entire atmosphere's winds— was published in a children's book which became extremely successful and well-known globally in 1962, the year before Lorenz published:
In 1961, Lorenz was running a numerical computer model to redo a weather prediction from the middle of the previous run as a shortcut. He entered the initial condition 0.506 from the printout instead of entering the full precision 0.506127 value. The result was a completely different weather scenario.
Lorenz wrote:
In 1963, Lorenz published a theoretical study of this effect in a highly cited, seminal paper called Deterministic Nonperiodic Flow (the calculations were performed on a Royal McBee LGP-30 computer). Elsewhere he stated:
Following proposals from colleagues, in later speeches and papers, Lorenz used the more poetic butterfly. According to Lorenz, when he failed to provide a title for a talk he was to present at the 139th meeting of the American Association for the Advancement of Science in 1972, Philip Merilees concocted Does the flap of a butterfly's wings in Brazil set off a tornado in Texas? as a title. Although a butterfly flapping its wings has remained constant in the expression of this concept, the location of the butterfly, the consequences, and the location of the consequences have varied widely. | Butterfly effect | Wikipedia | 349 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
The phrase refers to the effect of a butterfly's wings creating tiny changes in the atmosphere that may ultimately alter the path of a tornado or delay, accelerate, or even prevent the occurrence of a tornado in another location. The butterfly does not power or directly create the tornado, but the term is intended to imply that the flap of the butterfly's wings can cause the tornado: in the sense that the flap of the wings is a part of the initial conditions of an interconnected complex web; one set of conditions leads to a tornado, while the other set of conditions doesn't. The flapping wing creates a small change in the initial condition of the system, which cascades to large-scale alterations of events (compare: domino effect). Had the butterfly not flapped its wings, the trajectory of the system might have been vastly different—but it's also equally possible that the set of conditions without the butterfly flapping its wings is the set that leads to a tornado.
The butterfly effect presents an obvious challenge to prediction, since initial conditions for a system such as the weather can never be known to complete accuracy. This problem motivated the development of ensemble forecasting, in which a number of forecasts are made from perturbed initial conditions.
Some scientists have since argued that the weather system is not as sensitive to initial conditions as previously believed. David Orrell argues that the major contributor to weather forecast error is model error, with sensitivity to initial conditions playing a relatively small role. Stephen Wolfram also notes that the Lorenz equations are highly simplified and do not contain terms that represent viscous effects; he believes that these terms would tend to damp out small perturbations. Recent studies using generalized Lorenz models that included additional dissipative terms and nonlinearity suggested that a larger heating parameter is required for the onset of chaos. | Butterfly effect | Wikipedia | 372 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
While the "butterfly effect" is often explained as being synonymous with sensitive dependence on initial conditions of the kind described by Lorenz in his 1963 paper (and previously observed by Poincaré), the butterfly metaphor was originally applied to work he published in 1969 which took the idea a step further. Lorenz proposed a mathematical model for how tiny motions in the atmosphere scale up to affect larger systems. He found that the systems in that model could only be predicted up to a specific point in the future, and beyond that, reducing the error in the initial conditions would not increase the predictability (as long as the error is not zero). This demonstrated that a deterministic system could be "observationally indistinguishable" from a non-deterministic one in terms of predictability. Recent re-examinations of this paper suggest that it offered a significant challenge to the idea that our universe is deterministic, comparable to the challenges offered by quantum physics.
In the book entitled The Essence of Chaos published in 1993, Lorenz defined butterfly effect as: "The phenomenon that a small alteration in the state of a dynamical system will cause subsequent states to differ greatly from the states that would have followed without the alteration." This feature is the same as sensitive dependence of solutions on initial conditions (SDIC) in . In the same book, Lorenz applied the activity of skiing and developed an idealized skiing model for revealing the sensitivity of time-varying paths to initial positions. A predictability horizon is determined before the onset of SDIC. | Butterfly effect | Wikipedia | 313 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
Illustrations
{|class="wikitable" width=100%
|-
! colspan=3|The butterfly effect in the Lorenz attractor
|-
| colspan="2" style="text-align:center;" | time 0 ≤ t ≤ 30 (larger)
| style="text-align:center;" | z coordinate (larger)
|-
| colspan="2" style="text-align:center;"|
| style="text-align:center;"|
|-
|colspan=3 | These figures show two segments of the three-dimensional evolution of two trajectories (one in blue, and the other in yellow) for the same period of time in the Lorenz attractor starting at two initial points that differ by only 10−5 in the x-coordinate. Initially, the two trajectories seem coincident, as indicated by the small difference between the z coordinate of the blue and yellow trajectories, but for t > 23 the difference is as large as the value of the trajectory. The final position of the cones indicates that the two trajectories are no longer coincident at t = 30.
|-
| style="text-align:center;" colspan="3" | An animation of the Lorenz attractor shows the continuous evolution.
|}
Theory and mathematical definition
Recurrence, the approximate return of a system toward its initial conditions, together with sensitive dependence on initial conditions, are the two main ingredients for chaotic motion. They have the practical consequence of making complex systems, such as the weather, difficult to predict past a certain time range (approximately a week in the case of weather) since it is impossible to measure the starting atmospheric conditions completely accurately.
A dynamical system displays sensitive dependence on initial conditions if points arbitrarily close together separate over time at an exponential rate. The definition is not topological, but essentially metrical. Lorenz defined sensitive dependence as follows:
The property characterizing an orbit (i.e., a solution) if most other orbits that pass close to it at some point do not remain close to it as time advances.
If M is the state space for the map , then displays sensitive dependence to initial conditions if for any x in M and any δ > 0, there are y in M, with distance such that and such that | Butterfly effect | Wikipedia | 494 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
for some positive parameter a. The definition does not require that all points from a neighborhood separate from the base point x, but it requires one positive Lyapunov exponent. In addition to a positive Lyapunov exponent, boundedness is another major feature within chaotic systems.
The simplest mathematical framework exhibiting sensitive dependence on initial conditions is provided by a particular parametrization of the logistic map:
which, unlike most chaotic maps, has a closed-form solution:
where the initial condition parameter is given by . For rational , after a finite number of iterations maps into a periodic sequence. But almost all are irrational, and, for irrational , never repeats itself – it is non-periodic. This solution equation clearly demonstrates the two key features of chaos – stretching and folding: the factor 2n shows the exponential growth of stretching, which results in sensitive dependence on initial conditions (the butterfly effect), while the squared sine function keeps folded within the range [0, 1].
In physical systems
In weather
Overview
The butterfly effect is most familiar in terms of weather; it can easily be demonstrated in standard weather prediction models, for example. The climate scientists James Annan and William Connolley explain that chaos is important in the development of weather prediction methods; models are sensitive to initial conditions. They add the caveat: "Of course the existence of an unknown butterfly flapping its wings has no direct bearing on weather forecasts, since it will take far too long for such a small perturbation to grow to a significant size, and we have many more immediate uncertainties to worry about. So the direct impact of this phenomenon on weather prediction is often somewhat wrong."
Differentiating types of butterfly effects
The concept of the butterfly effect encompasses several phenomena. The two kinds of butterfly effects, including the sensitive dependence on initial conditions, and the ability of a tiny perturbation to create an organized circulation at large distances, are not exactly the same. In Palmer et al., a new type of butterfly effect is introduced, highlighting the potential impact of small-scale processes on finite predictability within the Lorenz 1969 model. Additionally, the identification of ill-conditioned aspects of the Lorenz 1969 model points to a practical form of finite predictability. These two distinct mechanisms suggesting finite predictability in the Lorenz 1969 model are collectively referred to as the third kind of butterfly effect. The authors in have considered Palmer et al.'s suggestions and have aimed to present their perspective without raising specific contentions. | Butterfly effect | Wikipedia | 505 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
The third kind of butterfly effect with finite predictability, as discussed in, was primarily proposed based on a convergent geometric series, known as Lorenz's and Lilly's formulas. Ongoing discussions are addressing the validity of these two formulas for estimating predictability limits in.
A comparison of the two kinds of butterfly effects and the third kind of butterfly effect has been documented. In recent studies, it was reported that both meteorological and non-meteorological linear models have shown that instability plays a role in producing a butterfly effect, which is characterized by brief but significant exponential growth resulting from a small disturbance.
Recent debates on butterfly effects
The first kind of butterfly effect (BE1), known as SDIC (Sensitive Dependence on Initial Conditions), is widely recognized and demonstrated through idealized chaotic models. However, opinions differ regarding the second kind of butterfly effect, specifically the impact of a butterfly flapping its wings on tornado formation, as indicated in two 2024 articles. In more recent discussions published by Physics Today, it is acknowledged that the second kind of butterfly effect (BE2) has never been rigorously verified using a realistic weather model. While the studies suggest that BE2 is unlikely in the real atmosphere, its invalidity in this context does not negate the applicability of BE1 in other areas, such as pandemics or historical events.
For the third kind of butterfly effect, the limited predictability within the Lorenz 1969 model is explained by scale interactions in one article and by system ill-conditioning in another more recent study.
Finite predictability in chaotic systems
According to Lighthill (1986), the presence of SDIC (commonly known as the butterfly effect) implies that chaotic systems have a finite predictability limit. In a literature review, it was found that Lorenz's perspective on the predictability limit can be condensed into the following statement:
(A). The Lorenz 1963 model qualitatively revealed the essence of a finite predictability within a chaotic system such as the atmosphere. However, it did not determine a precise limit for the predictability of the atmosphere.
(B). In the 1960s, the two-week predictability limit was originally estimated based on a doubling time of five days in real-world models. Since then, this finding has been documented in Charney et al. (1966) and has become a consensus.
Recently, a short video has been created to present Lorenz's perspective on predictability limit. | Butterfly effect | Wikipedia | 497 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
A recent study refers to the two-week predictability limit, initially calculated in the 1960s with the Mintz-Arakawa model's five-day doubling time, as the "Predictability Limit Hypothesis." Inspired by Moore's Law, this term acknowledges the collaborative contributions of Lorenz, Mintz, and Arakawa under Charney's leadership. The hypothesis supports the investigation into extended-range predictions using both partial differential equation (PDE)-based physics methods and Artificial Intelligence (AI) techniques.
Revised perspectives on chaotic and non-chaotic systems
By revealing coexisting chaotic and non-chaotic attractors within Lorenz models, Shen and his colleagues proposed a revised view that "weather possesses chaos and order", in contrast to the conventional view of "weather is chaotic". As a result, sensitive dependence on initial conditions (SDIC) does not always appear. Namely, SDIC appears when two orbits (i.e., solutions) become the chaotic attractor; it does not appear when two orbits move toward the same point attractor. The above animation for double pendulum motion provides an analogy. For large angles of swing the motion of the pendulum is often chaotic. By comparison, for small angles of swing, motions are non-chaotic.
Multistability is defined when a system (e.g., the double pendulum system) contains more than one bounded attractor that depends only on initial conditions. The multistability was illustrated using kayaking in Figure on the right side (i.e., Figure 1 of ) where the appearance of strong currents and a stagnant area suggests instability and local stability, respectively. As a result, when two kayaks move along strong currents, their paths display SDIC. On the other hand, when two kayaks move into a stagnant area, they become trapped, showing no typical SDIC (although a chaotic transient may occur). Such features of SDIC or no SDIC suggest two types of solutions and illustrate the nature of multistability.
By taking into consideration time-varying multistability that is associated with the modulation of large-scale processes (e.g., seasonal forcing) and aggregated feedback of small-scale processes (e.g., convection), the above revised view is refined as follows:
"The atmosphere possesses chaos and order; it includes, as examples, emerging organized systems (such as tornadoes) and time varying forcing from recurrent seasons." | Butterfly effect | Wikipedia | 500 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
In quantum mechanics
The potential for sensitive dependence on initial conditions (the butterfly effect) has been studied in a number of cases in semiclassical and quantum physics, including atoms in strong fields and the anisotropic Kepler problem. Some authors have argued that extreme (exponential) dependence on initial conditions is not expected in pure quantum treatments; however, the sensitive dependence on initial conditions demonstrated in classical motion is included in the semiclassical treatments developed by Martin Gutzwiller and John B. Delos and co-workers. The random matrix theory and simulations with quantum computers prove that some versions of the butterfly effect in quantum mechanics do not exist.
Other authors suggest that the butterfly effect can be observed in quantum systems. Zbyszek P. Karkuszewski et al. consider the time evolution of quantum systems which have slightly different Hamiltonians. They investigate the level of sensitivity of quantum systems to small changes in their given Hamiltonians. David Poulin et al. presented a quantum algorithm to measure fidelity decay, which "measures the rate at which identical initial states diverge when subjected to slightly different dynamics". They consider fidelity decay to be "the closest quantum analog to the (purely classical) butterfly effect". Whereas the classical butterfly effect considers the effect of a small change in the position and/or velocity of an object in a given Hamiltonian system, the quantum butterfly effect considers the effect of a small change in the Hamiltonian system with a given initial position and velocity. This quantum butterfly effect has been demonstrated experimentally. Quantum and semiclassical treatments of system sensitivity to initial conditions are known as quantum chaos.
In popular culture
The butterfly effect has appeared across mediums such as literature (for instance, A Sound of Thunder), films and television (such as The Simpsons), video games (such as Life Is Strange), webcomics (such as Homestuck), AI-driven expansive language models, and more. | Butterfly effect | Wikipedia | 391 | 4024 | https://en.wikipedia.org/wiki/Butterfly%20effect | Mathematics | Dynamical systems | null |
Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have often been used to describe opposites such as good and evil, the Dark Ages versus the Age of Enlightenment, and night versus day. Since the Middle Ages, black has been the symbolic color of solemnity and authority, and for this reason it is still commonly worn by judges and magistrates.
Black was one of the first colors used by artists in Neolithic cave paintings. It was used in ancient Egypt and Greece as the color of the underworld. In the Roman Empire, it became the color of mourning, and over the centuries it was frequently associated with death, evil, witches, and magic. In the 14th century, it was worn by royalty, clergy, judges, and government officials in much of Europe. It became the color worn by English romantic poets, businessmen and statesmen in the 19th century, and a high fashion color in the 20th century. According to surveys in Europe and North America, it is the color most commonly associated with mourning, the end, secrets, magic, force, violence, fear, evil, and elegance.
Black is the most common ink color used for printing books, newspapers and documents, as it provides the highest contrast with white paper and thus is the easiest color to read. Similarly, black text on a white screen is the most common format used on computer screens. the darkest material is made by MIT engineers from vertically aligned carbon nanotubes. | Black | Wikipedia | 325 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Etymology
The word black comes from Old English blæc ("black, dark", also, "ink"), from Proto-Germanic *blakkaz ("burned"), from Proto-Indo-European *bhleg- ("to burn, gleam, shine, flash"), from base *bhel- ("to shine"), related to Old Saxon blak ("ink"), Old High German blach ("black"), Old Norse blakkr ("dark"), Dutch blaken ("to burn"), and Swedish bläck ("ink"). More distant cognates include Latin flagrare ("to blaze, glow, burn"), and Ancient Greek phlegein ("to burn, scorch"). The Ancient Greeks sometimes used the same word to name different colors, if they had the same intensity. Kuanos could mean both dark blue and black. The Ancient Romans had two words for black: ater was a flat, dull black, while niger was a brilliant, saturated black. Ater has vanished from the vocabulary, but niger was the source of the country name Nigeria, the English word Negro, and the word for "black" in most modern Romance languages (French: noir; Spanish and Portuguese: negro; Italian: nero; Romanian: negru).
Old High German also had two words for black: swartz for dull black and blach for a luminous black. These are parallelled in Middle English by the terms swart for dull black and blaek for luminous black. Swart still survives as the word swarthy, while blaek became the modern English black. The former is cognate with the words used for black in most modern Germanic languages aside from English (German: schwarz, Dutch: zwart, Swedish: svart, Danish: sort, Icelandic: svartr). In heraldry, the word used for the black color is sable, named for the black fur of the sable, an animal.
Art
Prehistoric
Black was one of the first colors used in art. The Lascaux Cave in France contains drawings of bulls and other animals drawn by paleolithic artists between 18,000 and 17,000 years ago. They began by using charcoal, and later achieved darker pigments by burning bones or grinding a powder of manganese oxide.
Ancient | Black | Wikipedia | 496 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
For the ancient Egyptians, black had positive associations; being the color of fertility and the rich black soil flooded by the Nile. It was the color of Anubis, the god of the underworld, who took the form of a black jackal, and offered protection against evil to the dead. To ancient Greeks, black represented the underworld, separated from the living by the river Acheron, whose water ran black. Those who had committed the worst sins were sent to Tartarus, the deepest and darkest level. In the center was the palace of Hades, the king of the underworld, where he was seated upon a black ebony throne. Black was one of the most important colors used by ancient Greek artists. In the 6th century BC, they began making black-figure pottery and later red figure pottery, using a highly original technique. In black-figure pottery, the artist would paint figures with a glossy clay slip on a red clay pot. When the pot was fired, the figures painted with the slip would turn black, against a red background. Later they reversed the process, painting the spaces between the figures with slip. This created magnificent red figures against a glossy black background.
In the social hierarchy of ancient Rome, purple was reserved for the emperor; red was the color worn by soldiers (red cloaks for the officers, red tunics for the soldiers); white the color worn by the priests, and black was worn by craftsmen and artisans. The black they wore was not deep and rich; the vegetable dyes used to make black were not solid or lasting, so the blacks often faded to gray or brown.
In Latin, the word for black, ater and to darken, atere, were associated with cruelty, brutality and evil. They were the root of the English words "atrocious" and "atrocity". For the Romans, black symbolized death and mourning. In the 2nd century BC Roman magistrates wore a dark toga, called a toga pulla, to funeral ceremonies. Later, under the Empire, the family of the deceased also wore dark colors for a long period; then, after a banquet to mark the end of mourning, exchanged the black for a white toga. In Roman poetry, death was called the hora nigra, the black hour. | Black | Wikipedia | 463 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
The German and Scandinavian peoples worshipped their own goddess of the night, Nótt, who crossed the sky in a chariot drawn by a black horse. They also feared Hel, the goddess of the kingdom of the dead, whose skin was black on one side and red on the other. They also held sacred the raven. They believed that Odin, the king of the Nordic pantheon, had two black ravens, Huginn and Muninn, who served as his agents, traveling the world for him, watching and listening.
Postclassical
In the early Middle Ages, black was commonly associated with darkness and evil. In Medieval paintings, the devil was usually depicted as having human form, but with wings and black skin or hair.
12th and 13th centuries
In fashion, black did not have the prestige of red, the color of the nobility. It was worn by Benedictine monks as a sign of humility and penitence. In the 12th century a famous theological dispute broke out between the Cistercian monks, who wore white, and the Benedictines, who wore black. A Benedictine abbot, Pierre the Venerable, accused the Cistercians of excessive pride in wearing white instead of black. Saint Bernard of Clairvaux, the founder of the Cistercians responded that black was the color of the devil, hell, "of death and sin", while white represented "purity, innocence and all the virtues".
Black symbolized both power and secrecy in the medieval world. The emblem of the Holy Roman Empire of Germany was a black eagle. The black knight in the poetry of the Middle Ages was an enigmatic figure, hiding his identity, usually wrapped in secrecy.
Black ink, invented in China, was traditionally used in the Middle Ages for writing, for the simple reason that black was the darkest color and therefore provided the greatest contrast with white paper or parchment, making it the easiest color to read. It became even more important in the 15th century, with the invention of printing. A new kind of ink, printer's ink, was created out of soot, turpentine and walnut oil. The new ink made it possible to spread ideas to a mass audience through printed books, and to popularize art through black and white prints. Because of its contrast and clarity, black ink on white paper continued to be the standard for printing books, newspapers and documents; and for the same reason black text on a white background is the most common format used on computer screens. | Black | Wikipedia | 499 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
14th and 15th centuries
In the early Middle Ages, princes, nobles and the wealthy usually wore bright colors, particularly scarlet cloaks from Italy. Black was rarely part of the wardrobe of a noble family. The one exception was the fur of the sable. This glossy black fur, from an animal of the marten family, was the finest and most expensive fur in Europe. It was imported from Russia and Poland and used to trim the robes and gowns of royalty.
In the 14th century, the status of black began to change. First, high-quality black dyes began to arrive on the market, allowing garments of a deep, rich black. Magistrates and government officials began to wear black robes, as a sign of the importance and seriousness of their positions. A third reason was the passage of sumptuary laws in some parts of Europe which prohibited the wearing of costly clothes and certain colors by anyone except members of the nobility. The famous bright scarlet cloaks from Venice and the peacock blue fabrics from Florence were restricted to the nobility. The wealthy bankers and merchants of northern Italy responded by changing to black robes and gowns, made with the most expensive fabrics.
The change to the more austere but elegant black was quickly picked up by the kings and nobility. It began in northern Italy, where the Duke of Milan and the Count of Savoy and the rulers of Mantua, Ferrara, Rimini and Urbino began to dress in black. It then spread to France, led by Louis I, Duke of Orleans, younger brother of King Charles VI of France. It moved to England at the end of the reign of King Richard II (1377–1399), where all the court began to wear black. In 1419–20, black became the color of the powerful Duke of Burgundy, Philip the Good. It moved to Spain, where it became the color of the Spanish Habsburgs, of Charles V and of his son, Philip II of Spain (1527–1598). European rulers saw it as the color of power, dignity, humility and temperance. By the end of the 16th century, it was the color worn by almost all the monarchs of Europe and their courts.
Modern
16th and 17th centuries | Black | Wikipedia | 447 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
While black was the color worn by the Catholic rulers of Europe, it was also the emblematic color of the Protestant Reformation in Europe and the Puritans in England and America. John Calvin, Philip Melanchthon and other Protestant theologians denounced the richly colored and decorated interiors of Roman Catholic churches. They saw the color red, worn by the pope and his cardinals, as the color of luxury, sin, and human folly. In some northern European cities, mobs attacked churches and cathedrals, smashed the stained glass windows and defaced the statues and decoration. In Protestant doctrine, clothing was required to be sober, simple and discreet. Bright colors were banished and replaced by blacks, browns and grays; women and children were recommended to wear white.
In the Protestant Netherlands, Rembrandt used this sober new palette of blacks and browns to create portraits whose faces emerged from the shadows expressing the deepest human emotions. The Catholic painters of the Counter-Reformation, like Rubens, went in the opposite direction; they filled their paintings with bright and rich colors. The new Baroque churches of the Counter-Reformation were usually shining white inside and filled with statues, frescoes, marble, gold and colorful paintings, to appeal to the public. But European Catholics of all classes, like Protestants, eventually adopted a sober wardrobe that was mostly black, brown and gray.
In the second part of the 17th century, Europe and America experienced an epidemic of fear of witchcraft. People widely believed that the devil appeared at midnight in a ceremony called a Black Mass or black sabbath, usually in the form of a black animal, often a goat, a dog, a wolf, a bear, a deer or a rooster, accompanied by their familiar spirits, black cats, serpents and other black creatures. This was the origin of the widespread superstition about black cats and other black animals. In medieval Flanders, in a ceremony called Kattenstoet, black cats were thrown from the belfry of the Cloth Hall of Ypres to ward off witchcraft.
Witch trials were common in both Europe and America during this period. During the notorious Salem witch trials in New England in 1692–93, one of those on trial was accused of being able turn into a "black thing with a blue cap," and others of having familiars in the form of a black dog, a black cat and a black bird. Nineteen women and men were hanged as witches. | Black | Wikipedia | 488 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
18th and 19th centuries
In the 18th century, during the European Age of Enlightenment, black receded as a fashion color. Paris became the fashion capital, and pastels, blues, greens, yellow and white became the colors of the nobility and upper classes. But after the French Revolution, black again became the dominant color. Black was the color of the industrial revolution, largely fueled by coal, and later by oil. Thanks to coal smoke, the buildings of the large cities of Europe and America gradually turned black. By 1846 the industrial area of the West Midlands of England was "commonly called 'the Black Country'". Charles Dickens and other writers described the dark streets and smoky skies of London, and they were vividly illustrated in the wood-engravings of French artist Gustave Doré.
A different kind of black was an important part of the romantic movement in literature. Black was the color of melancholy, the dominant theme of romanticism. The novels of the period were filled with castles, ruins, dungeons, storms, and meetings at midnight. The leading poets of the movement were usually portrayed dressed in black, usually with a white shirt and open collar, and a scarf carelessly over their shoulder, Percy Bysshe Shelley and Lord Byron helped create the enduring stereotype of the romantic poet.
The invention of inexpensive synthetic black dyes and the industrialization of the textile industry meant that high-quality black clothes were available for the first time to the general population. In the 19th century black gradually became the most popular color of business dress of the upper and middle classes in England, the Continent, and America. Black dominated literature and fashion in the 19th century, and played a large role in painting. James McNeill Whistler made the color the subject of his most famous painting, Arrangement in grey and black number one (1871), better known as Whistler's Mother. | Black | Wikipedia | 376 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Some 19th-century French painters had a low opinion of black: "Reject black," Paul Gauguin said, "and that mix of black and white they call gray. Nothing is black, nothing is gray." But Édouard Manet used blacks for their strength and dramatic effect. Manet's portrait of painter Berthe Morisot was a study in black which perfectly captured her spirit of independence. The black gave the painting power and immediacy; he even changed her eyes, which were green, to black to strengthen the effect. Henri Matisse quoted the French impressionist Pissarro telling him, "Manet is stronger than us all – he made light with black."
Pierre-Auguste Renoir used luminous blacks, especially in his portraits. When someone told him that black was not a color, Renoir replied: "What makes you think that? Black is the queen of colors. I always detested Prussian blue. I tried to replace black with a mixture of red and blue, I tried using cobalt blue or ultramarine, but I always came back to ivory black."
Vincent van Gogh used black lines to outline many of the objects in his paintings, such as the bed in the famous painting of his bedroom. making them stand apart. His painting of black crows over a cornfield, painted shortly before he died, was particularly agitated and haunting. In the late 19th century, black also became the color of anarchism. (See the section political movements.)
20th and 21st centuries
In the 20th century, black was utilised by Italian and German fascism. (See the section political movements). In art, the colour regained some of the territory that it had lost during the 19th century. The Russian painter Kasimir Malevich, a member of the Suprematist movement, created the Black Square in 1915, is widely considered the first purely abstract painting. He wrote, "The painted work is no longer simply the imitation of reality, but is this very reality ... It is not a demonstration of ability, but the materialization of an idea."
Black was appreciated by Henri Matisse. "When I didn't know what color to put down, I put down black," he said in 1945. "Black is a force: I used black as ballast to simplify the construction ... Since the impressionists it seems to have made continuous progress, taking a more and more important part in color orchestration, comparable to that of the double bass as a solo instrument." | Black | Wikipedia | 512 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
In the 1950s, black came to be a symbol of individuality and intellectual and social rebellion, the color of those who did not accept established norms and values. In Paris, it was worn by Left-Bank intellectuals and performers such as Juliette Gréco, and by some members of the Beat Movement in New York and San Francisco. Black leather jackets were worn by motorcycle gangs such as the Hells Angels and street gangs on the fringes of society in the United States. Black as a color of rebellion was celebrated in such films as The Wild One, with Marlon Brando. By the end of the 20th century, black was the emblematic color of the punk subculture punk fashion, and the goth subculture. Goth fashion, which emerged in England in the 1980s, was inspired by Victorian era mourning dress.
In men's fashion, black gradually ceded its dominance to navy blue, particularly in business suits. Black evening dress and formal dress in general were worn less and less. In 1960, John F. Kennedy was the last American President to be inaugurated wearing formal dress; Lyndon Johnson and his successors were inaugurated wearing business suits.
Women's fashion was revolutionized and simplified in 1926 by the French designer Coco Chanel, who published a drawing of a simple black dress in Vogue magazine. She famously said, "A woman needs just three things; a black dress, a black sweater, and, on her arm, a man she loves." French designer Jean Patou also followed suit by creating a black collection in 1929. Other designers contributed to the trend of the little black dress. The Italian designer Gianni Versace said, "Black is the quintessence of simplicity and elegance," and French designer Yves Saint Laurent said, "black is the liaison which connects art and fashion. One of the most famous black dresses of the century was designed by Hubert de Givenchy and was worn by Audrey Hepburn in the 1961 film Breakfast at Tiffany's.
The American civil rights movement in the 1950s was a struggle for the political equality of African Americans. It developed into the Black Power movement in the early 1960s until the late 1980s, and the Black Lives Matter movement in the 2010s and 2020s. It also popularized the slogan "Black is Beautiful".
Science
Physics | Black | Wikipedia | 453 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
In the visible spectrum, black is the result of the absorption of all light wavelengths. Black can be defined as the visual impression (or color) experienced when no visible light reaches the eye. Pigments or dyes that absorb light rather than reflect it back to the eye look black. A black pigment can, however, result from a combination of several pigments that collectively absorb all wavelengths of visible light. If appropriate proportions of three primary pigments are mixed, the result reflects so little light as to be called black. This provides two superficially opposite but actually complementary descriptions of black. Black is the color produced by the absorption of all wavelengths of visible light, or an exhaustive combination of multiple colors of pigment.
In physics, a black body is a perfect absorber of light, but, by a thermodynamic rule, it is also the best emitter. Thus, the best radiative cooling, out of sunlight, is by using black paint, though it is important that it be black (a nearly perfect absorber) in the infrared as well. In elementary science, far ultraviolet light is called "black light" because, while itself unseen, it causes many minerals and other substances to fluoresce.
Absorption of light is contrasted by transmission, reflection and diffusion, where the light is only redirected, causing objects to appear transparent, reflective or white respectively. A material is said to be black if most incoming light is absorbed equally in the material. Light (electromagnetic radiation in the visible spectrum) interacts with the atoms and molecules, which causes the energy of the light to be converted into other forms of energy, usually heat. This means that black surfaces can act as thermal collectors, absorbing light and generating heat (see Solar thermal collector).
As of September 2019, the darkest material is made from vertically aligned carbon nanotubes. The material was grown by MIT engineers and was reported to have a 99.995% absorption rate of any incoming light. This surpasses any former darkest materials including Vantablack, which has a peak absorption rate of 99.965% in the visible spectrum.
Chemistry | Black | Wikipedia | 431 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Pigments
The earliest pigments used by Neolithic man were charcoal, red ocher and yellow ocher. The black lines of cave art were drawn with the tips of burnt torches made of a wood with resin. Different charcoal pigments were made by burning different woods and animal products, each of which produced a different tone. The charcoal would be ground and then mixed with animal fat to make the pigment.
Vine black was produced in Roman times by burning the cut branches of grapevines. It could also be produced by burning the remains of the crushed grapes, which were collected and dried in an oven. According to the historian Vitruvius, the deepness and richness of the black produced corresponded to the quality of the wine. The finest wines produced a black with a bluish tinge the color of indigo.
The 15th-century painter Cennino Cennini described how this pigment was made during the Renaissance in his famous handbook for artists: "...there is a black which is made from the tendrils of vines. And these tendrils need to be burned. And when they have been burned, throw some water onto them and put them out and then mull them in the same way as the other black. And this is a lean and black pigment and is one of the perfect pigments that we use."
Cennini also noted that "There is another black which is made from burnt almond shells or peaches and this is a perfect, fine black." Similar fine blacks were made by burning the pits of the peach, cherry or apricot. The powdered charcoal was then mixed with gum arabic or the yellow of an egg to make a paint. | Black | Wikipedia | 342 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Different civilizations burned different plants to produce their charcoal pigments. The Inuit of Alaska used wood charcoal mixed with the blood of seals to paint masks and wooden objects. The Polynesians burned coconuts to produce their pigment.
Lamp black was used as a pigment for painting and frescoes, as a dye for fabrics, and in some societies for making tattoos. The 15th century Florentine painter Cennino Cennini described how it was made during the Renaissance: "... take a lamp full of linseed oil and fill the lamp with the oil and light the lamp. Then place it, lit, under a thoroughly clean pan and make sure that the flame from the lamp is two or three fingers from the bottom of the pan. The smoke that comes off the flame will hit the bottom of the pan and gather, becoming thick. Wait a bit. take the pan and brush this pigment (that is, this smoke) onto paper or into a pot with something. And it is not necessary to mull or grind it because it is a very fine pigment. Re-fill the lamp with the oil and put it under the pan like this several times and, in this way, make as much of it as is necessary." This same pigment was used by Indian artists to paint the Ajanta Caves, and as dye in ancient Japan.
Ivory black, also known as bone char, was originally produced by burning ivory and mixing the resulting charcoal powder with oil. The color is still made today, but ordinary animal bones are substituted for ivory.
Mars black is a black pigment made of synthetic iron oxides. It is commonly used in water-colors and oil painting. It takes its name from Mars, the god of war and patron of iron.
Dyes
Good-quality black dyes were not known until the middle of the 14th century. The most common early dyes were made from bark, roots or fruits of different trees; usually walnuts, chestnuts, or certain oak trees. The blacks produced were often more gray, brown or bluish. The cloth had to be dyed several times to darken the color. One solution used by dyers was add to the dye some iron filings, rich in iron oxide, which gave a deeper black. Another was to first dye the fabric dark blue, and then to dye it black. | Black | Wikipedia | 472 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
A much richer and deeper black dye was eventually found made from the oak apple or "gall-nut". The gall-nut is a small round tumor which grows on oak and other varieties of trees. They range in size from 2–5 cm, and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae. The dye was very expensive; a great quantity of gall-nuts were needed for a very small amount of dye. The gall-nuts which made the best dye came from Poland, eastern Europe, the near east and North Africa. Beginning in about the 14th century, dye from gall-nuts was used for clothes of the kings and princes of Europe.
Another important source of natural black dyes from the 17th century onwards was the logwood tree, or Haematoxylum campechianum, which also produced reddish and bluish dyes. It is a species of flowering tree in the legume family, Fabaceae, that is native to southern Mexico and northern Central America. The modern nation of Belize grew from 17th century English logwood logging camps.
Since the mid-19th century, synthetic black dyes have largely replaced natural dyes. One of the important synthetic blacks is Nigrosin, a mixture of synthetic black dyes (CI 50415, Solvent black 5) made by heating a mixture of nitrobenzene, aniline and aniline hydrochloride in the presence of a copper or iron catalyst. Its main industrial uses are as a colorant for lacquers and varnishes and in marker-pen inks.
Inks
The first known inks were made by the Chinese, and date back to the 23rd century B.C. They used natural plant dyes and minerals such as graphite ground with water and applied with an ink brush. Early Chinese inks similar to the modern inkstick have been found dating to about 256 BC at the end of the Warring States period. They were produced from soot, usually produced by burning pine wood, mixed with animal glue. To make ink from an inkstick, the stick is continuously ground against an inkstone with a small quantity of water to produce a dark liquid which is then applied with an ink brush. Artists and calligraphists could vary the thickness of the resulting ink by reducing or increasing the intensity and time of ink grinding. These inks produced the delicate shading and subtle or dramatic effects of Chinese brush painting. | Black | Wikipedia | 506 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
India ink (or "Indian ink" in British English) is a black ink once widely used for writing and printing and now more commonly used for drawing, especially when inking comic books and comic strips. The technique of making it probably came from China. India ink has been in use in India since at least the 4th century BC, where it was called masi. In India, the black color of the ink came from bone char, tar, pitch and other substances.
The ancient Romans had a black writing ink they called atramentum librarium. Its name came from the Latin word atrare, which meant to make something black. (This was the same root as the English word atrocious.) It was usually made, like India ink, from soot, although one variety, called atramentum elephantinum, was made by burning the ivory of elephants.
Gall-nuts were also used for making fine black writing ink. Iron gall ink (also known as iron gall nut ink or oak gall ink) was a purple-black or brown-black ink made from iron salts and tannic acids from gall nut. It was the standard writing and drawing ink in Europe, from about the 12th century to the 19th century, and remained in use well into the 20th century. | Black | Wikipedia | 263 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Astronomy
A black hole is a region of spacetime where gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined boundary called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies. Although a black hole itself is black, infalling material forms an accretion disk, one of the brightest types of object in the universe.
Black-body radiation refers to the radiation coming from a body at a given temperature where all incoming energy (light) is converted to heat.
Black sky refers to the appearance of space as one emerges from Earth's atmosphere.
Why the night sky and space are black – Olbers' paradox
The fact that outer space is black is sometimes called Olbers' paradox. In theory, because the universe is full of stars, and is believed to be infinitely large, it would be expected that the light of an infinite number of stars would be enough to brilliantly light the whole universe all the time. However, the background color of outer space is black. This contradiction was first noted in 1823 by German astronomer Heinrich Wilhelm Matthias Olbers, who posed the question of why the night sky was black. | Black | Wikipedia | 372 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
The current accepted answer is that, although the universe may be infinitely large, it is not infinitely old. It is thought to be about 13.8 billion years old, so we can only see objects as far away as the distance light can travel in 13.8 billion years. Light from stars farther away has not reached Earth, and cannot contribute to making the sky bright. Furthermore, as the universe is expanding, many stars are moving away from Earth. As they move, the wavelength of their light becomes longer, through the Doppler effect, and shifts toward red, or even becomes invisible. As a result of these two phenomena, there is not enough starlight to make space anything but black.
The daytime sky on Earth is blue because light from the Sun strikes molecules in Earth's atmosphere scattering light in all directions. Blue light is scattered more than other colors, and reaches the eye in greater quantities, making the daytime sky appear blue. This is known as Rayleigh scattering.
The nighttime sky on Earth is black because the part of Earth experiencing night is facing away from the Sun, the light of the Sun is blocked by Earth itself, and there is no other bright nighttime source of light in the vicinity. Thus, there is not enough light to undergo Rayleigh scattering and make the sky blue. On the Moon, on the other hand, because there is virtually no atmosphere to scatter the light, the sky is black both day and night. This also holds true for other locations without an atmosphere, such as Mercury.
Biology
Culture
In China, the color black is associated with water, one of the five fundamental elements believed to compose all things; and with winter, cold, and the direction north, usually symbolized by a black tortoise. It is also associated with disorder, including the positive disorder which leads to change and new life. When the first emperor of China Qin Shi Huang seized power from the Zhou dynasty, he changed the Imperial color from red to black, saying that black extinguished red. Only when the Han dynasty appeared in 206 BC was red restored as the imperial color.
In Japan, black is associated with mystery, the night, the unknown, the supernatural, the invisible and death. Combined with white, it can symbolize intuition. In 10th- and 11th-century Japan, it was believed that wearing black could bring misfortune. It was worn at court by those who wanted to set themselves apart from the established powers or who had renounced material possessions. | Black | Wikipedia | 500 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
In Japan black can also symbolize experience, as opposed to white, which symbolizes naiveté. The black belt in martial arts symbolizes experience, while a white belt is worn by novices. Japanese men traditionally wear a black kimono with some white decoration on their wedding day.
Black is associated with depth in Indonesia, as well as the subterranean world, demons, disaster, and the left hand. When combined with white, however, it symbolizes harmony and equilibrium.
Political movements
Anarchism
Anarchism is a political philosophy, most popular in the late 19th and early 20th centuries, which holds that governments and capitalism are harmful and undesirable. The symbols of anarchism was usually either a black flag or a black letter A. More recently it is usually represented with a bisected red and black flag, to emphasise the movement's socialist roots in the First International. Anarchism was most popular in Spain, France, Italy, Ukraine and Argentina. There were also small but influential movements in the United States, Russia and many other countries all around the world.
Fascism
The Blackshirts () were Fascist paramilitary groups in Italy during the period immediately following World War I and until the end of World War II. The Blackshirts were officially known as the Voluntary Militia for National Security (Milizia Volontaria per la Sicurezza Nazionale, or MVSN).
Inspired by the black uniforms of the Arditi, Italy's elite storm troops of World War I, the Fascist Blackshirts were organized by Benito Mussolini as the military tool of his political movement. They used violence and intimidation against Mussolini's opponents. The emblem of the Italian fascists was a black flag with fasces, an axe in a bundle of sticks, an ancient Roman symbol of authority. Mussolini came to power in 1922 through his March on Rome with the blackshirts. | Black | Wikipedia | 385 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Black was also adopted by Adolf Hitler and the Nazis in Germany. Red, white and black were the colors of the flag of the German Empire from 1870 to 1918. In Mein Kampf, Hitler explained that they were "revered colors expressive of our homage to the glorious past." Hitler also wrote that "the new flag ... should prove effective as a large poster" because "in hundreds of thousands of cases a really striking emblem may be the first cause of awakening interest in a movement." The black swastika was meant to symbolize the Aryan race, which, according to the Nazis, "was always anti-Semitic and will always be anti-Semitic." Several designs by a number of different authors were considered, but the one adopted in the end was Hitler's personal design. Black became the color of the uniform of the SS, the Schutzstaffel or "defense corps", the paramilitary wing of the Nazi Party, and was worn by SS officers from 1932 until the end of World War II.
The Nazis used a black triangle to symbolize anti-social elements. The symbol originates from Nazi concentration camps, where every prisoner had to wear one of the Nazi concentration camp badges on their jacket, the color of which categorized them according to "their kind". Many Black Triangle prisoners were either mentally disabled or mentally ill. The homeless were also included, as were alcoholics, the Romani people, the habitually "work-shy", prostitutes, draft dodgers and pacifists. More recently the black triangle has been adopted as a symbol in lesbian culture and by disabled activists.
Black shirts were also worn by the British Union of Fascists before World War II, and members of fascist movements in the Netherlands. | Black | Wikipedia | 351 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Patriotic resistance
The Lützow Free Corps, composed of volunteer German students and academics fighting against Napoleon in 1813, could not afford to make special uniforms and therefore adopted black, as the only color that could be used to dye their civilian clothing without the original color showing. In 1815 the students began to carry a red, black and gold flag, which they believed (incorrectly) had been the colors of the Holy Roman Empire (the imperial flag had actually been gold and black). In 1848, this banner became the flag of the German confederation. In 1866, Prussia unified Germany under its rule, and imposed the red, white and black of its own flag, which remained the colors of the German flag until the end of the Second World War. In 1949 the Federal Republic of Germany returned to the original flag and colors of the students and professors of 1815, which is the flag of Germany today.
Military
Black has been a traditional color of cavalry and armoured or mechanized troops. German armoured troops (Panzerwaffe) traditionally wore black uniforms, and even in others, a black beret is common. In Finland, black is the symbolic color for both armoured troops and combat engineers, and military units of these specialities have black flags and unit insignia.
The black beret and the color black is also a symbol of special forces in many countries. Soviet and Russian OMON special police and Russian naval infantry wear a black beret. A black beret is also worn by military police in the Canadian, Czech, Croatian, Portuguese, Spanish and Serbian armies.
The silver-on-black skull and crossbones symbol or Totenkopf and a black uniform were used by Hussars and Black Brunswickers, the German Panzerwaffe and the Nazi Schutzstaffel, and U.S. 400th Missile Squadron (crossed missiles), and continues in use with the Estonian Kuperjanov Battalion.
Religion
In Christian theology, black was the color of the universe before God created light. In many religious cultures, from Mesoamerica to Oceania to India and Japan, the world was created out of a primordial darkness. In the Bible the light of faith and Christianity is often contrasted with the darkness of ignorance and paganism. | Black | Wikipedia | 450 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
In Christianity, the devil is often called the "prince of darkness". The term was used in John Milton's poem Paradise Lost, published in 1667, referring to Satan, who is viewed as the embodiment of evil. It is an English translation of the Latin phrase princeps tenebrarum, which occurs in the Acts of Pilate, written in the fourth century, in the 11th-century hymn Rhythmus de die mortis by Pietro Damiani, and in a sermon by Bernard of Clairvaux from the 12th century. The phrase also occurs in King Lear by William Shakespeare (), Act III, Scene IV, l. 14:
'The prince of darkness is a gentleman."
Priests and pastors of the Roman Catholic, Eastern Orthodox and Protestant churches commonly wear black, as do monks of the Benedictine Order, who consider it the color of humility and penitence.
In Islam, black, along with green, plays an important symbolic role. It is the color of the Black Standard, the banner that is said to have been carried by the soldiers of Muhammad. It is also used as a symbol in Shi'a Islam (heralding the advent of the Mahdi), and the flag of followers of Islamism and Jihadism.
In Hinduism, the goddess Kali, goddess of time and change, is portrayed with black or dark blue skin. wearing a necklace adorned with severed heads and hands. Her name means "The black one". She destroys anger and passion according to Hindu mythology and her devotees are supposed to abstain from meat or intoxication. Kali does not eat meat, but it is the śāstra's injunction that those who are unable to give up meat-eating, they may sacrifice one goat, not cow, one small animal before the goddess Kali, on amāvāsya (new moon) day, night, not day, and they can eat it.
In Paganism, black represents dignity, force, stability, and protection. The color is often used to banish and release negative energies, or binding. An athame is a ceremonial blade often having a black handle, which is used in some forms of witchcraft. | Black | Wikipedia | 440 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Sports
The national rugby union team of New Zealand is called the All Blacks, in reference to their black outfits, and the color is also shared by other New Zealand national teams such as the Black Caps (cricket) and the Kiwis (rugby league).
Association football (soccer) referees traditionally wear all-black uniforms, however nowadays other uniform colors may also be worn.
In auto racing, a black flag signals a driver to go into the pits.
In baseball, "the black" refers to the batter's eye, a blacked out area around the center-field bleachers, painted black to give hitters a decent background for pitched balls.
A large number of teams have uniforms designed with black colors even when the team does not normally feature that color. Many feel the color sometimes imparts a psychological advantage in its wearers. Black is used by numerous professional and collegiate sports teams
Idioms and expressions | Black | Wikipedia | 184 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
In general, the Negro race of African origin is called "Black", while the Caucasian race of European origin is called "White".
In the United States, "Black Friday" (the day after Thanksgiving Day, the fourth Thursday in November) is traditionally the busiest shopping day of the year. Many Americans are on holiday because of Thanksgiving, and many retailers open earlier and close later than normal, and offer special prices. The day's name originated in Philadelphia sometime before 1961, and originally was used to describe the heavy and disruptive downtown pedestrian and vehicle traffic which would occur on that day. Later an alternative explanation began to be offered: that "Black Friday" indicates the point in the year that retailers begin to turn a profit, or are "in the black", because of the large volume of sales on that day.
"In the black" means profitable. Accountants originally used black ink in ledgers to indicate profit, and red ink to indicate a loss.
Black Friday also refers to any particularly disastrous day on financial markets. The first Black Friday (1869), 24 September 1869, was caused by the efforts of two speculators, Jay Gould and James Fisk, to corner the gold market on the New York Gold Exchange.
A blacklist is a list of undesirable persons or entities (to be placed on the list is to be "blacklisted").
Black comedy is a form of comedy dealing with morbid and serious topics. The expression is similar to black humor or black humour.
A black mark against a person relates to something bad they have done.
A black mood is a bad one (cf Winston Churchill's clinical depression, which he called "my black dog").
Black market is used to denote the trade of illegal goods, or alternatively the illegal trade of otherwise legal items at considerably higher prices, e.g. to evade rationing.
Black propaganda is the use of known falsehoods, partial truths, or masquerades in propaganda to confuse an opponent.
Blackmail is the act of threatening someone to do something that would hurt them in some way, such as by revealing sensitive information about them, in order to force the threatened party to fulfill certain demands. Ordinarily, such a threat is illegal.
If the black eight-ball, in billiards, is sunk before all others are out of play, the player loses.
The black sheep of the family is the ne'er-do-well. | Black | Wikipedia | 499 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
To blackball someone is to block their entry into a club or some such institution. In the traditional English gentlemen's club, members vote on the admission of a candidate by secretly placing a white or black ball in a hat. If upon the completion of voting, there was even one black ball amongst the white, the candidate would be denied membership, and he would never know who had "blackballed" him.
Black tea in the Western culture is known as "crimson tea" in Chinese and culturally influenced languages (, Mandarin Chinese hóngchá; Japanese kōcha; Korean hongcha).
"The black" is a wildfire suppression term referring to a burned area on a wildfire capable of acting as a safety zone.
Black coffee refers to coffee without sugar or cream. | Black | Wikipedia | 156 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Associations and symbolism
In the West, black is commonly associated with mourning and bereavement, and usually worn at funerals and memorial services. In some traditional societies, for example in Greece and Italy, some widows wear black for the rest of their lives. In contrast, across much of Africa and parts of Asia like Vietnam, white is a color of mourning.
A "black day" (or week or month) usually refers to tragic date. The Romans marked fasti days with white stones and nefasti days with black. The term is often used to remember massacres. Black months include the Black September in Jordan, when large numbers of Palestinians were killed, and Black July in Sri Lanka, the killing of members of the Tamil population by the Sinhalese government. In the financial world, the term often refers to a dramatic drop in the stock market. For example, the Wall Street crash of 1929, the stock market crash on 29 October 1929, which marked the start of the Great Depression, is nicknamed Black Tuesday, and was preceded by Black Thursday, a downturn on 24 October the previous week.
In western popular culture, black has long been associated with evil and darkness. It is the traditional color of witchcraft and black magic.
Black is frequently used as a color of power, law and authority. In many countries judges and magistrates wear black robes. That custom began in Europe in the 13th and 14th centuries. Jurists, magistrates and certain other court officials in France began to wear long black robes during the reign of Philip IV of France (1285–1314), and in England from the time of Edward I (1271–1307). The custom spread to the cities of Italy at about the same time, between 1300 and 1320. The robes of judges resembled those worn by the clergy, and represented the law and authority of the King, while those of the clergy represented the law of God and authority of the church. Until the 20th century most police uniforms were black, until they were largely replaced by blue in France, the U.S. and other countries. In the United States, police cars are frequently Black and white. The riot control units of the Basque Autonomous Police in Spain are known as beltzak ("blacks") after their uniform. | Black | Wikipedia | 460 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Black formal attire is still worn at many solemn occasions or ceremonies, from graduations to formal balls. Graduation gowns are copied from the gowns worn by university professors in the Middle Ages, which in turn were copied from the robes worn by judges and priests, who often taught at the early universities. The mortarboard hat worn by graduates is adapted from a square cap called a biretta worn by Medieval professors and clerics.
In the 19th and 20th centuries, many machines and devices, large and small, were painted black, to stress their functionality. These included telephones, sewing machines, steamships, railroad locomotives, and automobiles. The Ford Model T, the first mass-produced car, was available only in black from 1914 to 1926. Of means of transportation, only airplanes were rarely ever painted black.
The term "Black" is often used in the West to describe people whose skin is darker. In the United States, it is particularly used to describe African Americans. Black is also commonly used as a racial description in the United Kingdom, since ethnicity was first measured in the 2001 census. In Canada, census respondents can identify themselves as Black. In Brazil, the Brazilian Institute of Geography and Statistics (IBGE) asks people to identify themselves as branco (white), pardo (brown), preto (black), or amarelo (yellow). | Black | Wikipedia | 276 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Black and white have often been used to describe opposites, particularly light and darkness and good and evil. In Medieval literature, the white knight usually represented virtue, the black knight something mysterious and sinister. In American westerns, the hero often wore a white hat, the villain a black hat.
In philosophy and arguments, the issue is often described as black-and-white, meaning that the issue at hand is dichotomized (having two clear, opposing sides with no middle ground).
Black is commonly associated with secrecy.
The Black Chamber was a term given to an office which secretly opened and read diplomatic mail and broke codes. Queen Elizabeth I had such an office, headed by her Secretary, Sir Francis Walsingham, which successfully broke the Spanish codes and broke up several plots against the Queen. In France a cabinet noir was established inside the French post office by Louis XIII to open diplomatic mail. It was closed during the French Revolution but re-opened under Napoleon I. The Habsburg Empire and Dutch Republic had similar black chambers.
The United States created a secret peacetime Black Chamber, called the Cipher Bureau, in 1919. It was funded by the State Department and Army and disguised as a commercial company in New York. It successfully broke a number of diplomatic codes, including the code of the Japanese government. It was closed down in 1929 after the State Department withdrew funding, when the new Secretary of State, Henry Stimson, stated that "Gentlemen do not read each other's mail." The Cipher Bureau was the ancestor of the U.S. National Security Agency.
A black project is a secret unacknowledged military project, such as Enigma Decryption during World War II, or a secret counter-narcotics or police sting operation.
Black ops are covert operations carried out by a government, government agency or military.
A black budget is a government budget that is allocated for classified or other secret operations of a nation. The black budget is an account expenses and spending related to military research and covert operations. The black budget is mostly classified due to security reasons. | Black | Wikipedia | 418 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
Black is the color most commonly associated with elegance in Europe and the United States. Black first became a fashionable color for men in Europe in the 17th century, in the courts of Italy and Spain. In the 19th century, it was the fashion for men both in business and for evening wear. For women's fashion, the defining moment was the invention of the simple black dress by Coco Chanel in 1926. Thereafter, a long black gown was used for formal occasions, while the simple black dress could be used for everything else. The expression "X is the new black" is a reference to the latest trend or fad that is considered a wardrobe basic for the duration of the trend, on the basis that black is always fashionable. The phrase has taken on a life of its own and has become a cliché. | Black | Wikipedia | 164 | 4035 | https://en.wikipedia.org/wiki/Black | Physical sciences | Color terms | null |
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have complex internal and external structures. They are lightweight yet strong and hard and serve multiple functions.
Bone tissue (osseous tissue), which is also called bone in the uncountable sense of that word, is hard tissue, a type of specialised connective tissue. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Osteoblasts and osteocytes are involved in the formation and mineralisation of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralised matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts. Bone tissue is mineralized tissue of two types, cortical bone and cancellous bone. Other types of tissue found in bones include bone marrow, endosteum, periosteum, nerves, blood vessels and cartilage.
In the human body at birth, approximately 300 bones are present. Many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones. The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.
The Greek word for bone is ὀστέον ("osteon"), hence the many terms that use it as a prefix—such as osteopathy. In anatomical terminology, including the Terminologia Anatomica international standard, the word for a bone is os (for example, os breve, os longum, os sesamoideum).
Structure
Bone is not uniformly solid, but consists of a flexible matrix (about 30%) and bound minerals (about 70%), which are intricately woven and continuously remodeled by a group of specialized bone cells. Their unique composition and design allows bones to be relatively hard and strong, while remaining lightweight. | Bone | Wikipedia | 497 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Bone matrix is 90 to 95% composed of elastic collagen fibers, also known as ossein, and the remainder is ground substance. The elasticity of collagen improves fracture resistance. The matrix is hardened by the binding of inorganic mineral salt, calcium phosphate, in a chemical arrangement known as bone mineral, a form of calcium apatite. It is the mineralization that gives bones rigidity.
Bone is actively constructed and remodeled throughout life by specialized bone cells known as osteoblasts and osteoclasts. Within any single bone, the tissue is woven into two main patterns: cortical and cancellous bone, each with a distinct appearance and characteristics.
Cortex
The hard outer layer of bones is composed of cortical bone, which is also called compact bone as it is much denser than cancellous bone. It forms the hard exterior (cortex) of bones. The cortical bone gives bone its smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult human skeleton. It facilitates bone's main functions—to support the whole body, to protect organs, to provide levers for movement, and to store and release chemical elements, mainly calcium. It consists of multiple microscopic columns, each called an osteon or Haversian system. Each column is multiple layers of osteoblasts and osteocytes around a central canal called the osteonic canal. Volkmann's canals at right angles connect the osteons together. The columns are metabolically active, and as bone is reabsorbed and created the nature and location of the cells within the osteon will change. Cortical bone is covered by a periosteum on its outer surface, and an endosteum on its inner surface. The endosteum is the boundary between the cortical bone and the cancellous bone. The primary anatomical and functional unit of cortical bone is the osteon.
Trabeculae | Bone | Wikipedia | 410 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Cancellous bone or spongy bone, also known as trabecular bone, is the internal tissue of the skeletal bone and is an open cell porous network that follows the material properties of biofoams. Cancellous bone has a higher surface-area-to-volume ratio than cortical bone and it is less dense. This makes it weaker and more flexible. The greater surface area also makes it suitable for metabolic activities such as the exchange of calcium ions. Cancellous bone is typically found at the ends of long bones, near joints, and in the interior of vertebrae. Cancellous bone is highly vascular and often contains red bone marrow where hematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula. The trabeculae are aligned towards the mechanical load distribution that a bone experiences within long bones such as the femur. As far as short bones are concerned, trabecular alignment has been studied in the vertebral pedicle. Thin formations of osteoblasts covered in endosteum create an irregular network of spaces, known as trabeculae. Within these spaces are bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells and white blood cells. Trabecular marrow is composed of a network of rod- and plate-like elements that make the overall organ lighter and allow room for blood vessels and marrow. Trabecular bone accounts for the remaining 20% of total bone mass but has nearly ten times the surface area of compact bone.
The words cancellous and trabecular refer to the tiny lattice-shaped units (trabeculae) that form the tissue. It was first illustrated accurately in the engravings of Crisóstomo Martinez.
Marrow
Bone marrow, also known as myeloid tissue in red bone marrow, can be found in almost any bone that holds cancellous tissue. In newborns, all such bones are filled exclusively with red marrow or hematopoietic marrow, but as the child ages the hematopoietic fraction decreases in quantity and the fatty/ yellow fraction called marrow adipose tissue (MAT) increases in quantity. In adults, red marrow is mostly found in the bone marrow of the femur, the ribs, the vertebrae and pelvic bones. | Bone | Wikipedia | 478 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Vascular supply
Bone receives about 10% of cardiac output. Blood enters the endosteum, flows through the marrow, and exits through small vessels in the cortex. In humans, blood oxygen tension in bone marrow is about 6.6%, compared to about 12% in arterial blood, and 5% in venous and capillary blood.
Cells
Bone is metabolically active tissue composed of several types of cells. These cells include osteoblasts, which are involved in the creation and mineralization of bone tissue, osteocytes, and osteoclasts, which are involved in the reabsorption of bone tissue. Osteoblasts and osteocytes are derived from osteoprogenitor cells, but osteoclasts are derived from the same cells that differentiate to form macrophages and monocytes. Within the marrow of the bone there are also hematopoietic stem cells. These cells give rise to other cells, including white blood cells, red blood cells, and platelets.
Osteoblast
Osteoblasts are mononucleate bone-forming cells. They are located on the surface of osteon seams and make a protein mixture known as osteoid, which mineralizes to become bone. The osteoid seam is a narrow region of a newly formed organic matrix, not yet mineralized, located on the surface of a bone. Osteoid is primarily composed of Type I collagen. Osteoblasts also manufacture hormones, such as prostaglandins, to act on the bone itself. The osteoblast creates and repairs new bone by actually building around itself. First, the osteoblast puts up collagen fibers. These collagen fibers are used as a framework for the osteoblasts' work. The osteoblast then deposits calcium phosphate which is hardened by hydroxide and bicarbonate ions. The brand-new bone created by the osteoblast is called osteoid. Once the osteoblast is finished working it is actually trapped inside the bone once it hardens. When the osteoblast becomes trapped, it becomes known as an osteocyte. Other osteoblasts remain on the top of the new bone and are used to protect the underlying bone, these become known as bone lining cells. | Bone | Wikipedia | 491 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Osteocyte
Osteocytes are cells of mesenchymal origin and originate from osteoblasts that have migrated into and become trapped and surrounded by a bone matrix that they themselves produced. The spaces the cell body of osteocytes occupy within the mineralized collagen type I matrix are known as lacunae, while the osteocyte cell processes occupy channels called canaliculi. The many processes of osteocytes reach out to meet osteoblasts, osteoclasts, bone lining cells, and other osteocytes probably for the purposes of communication. Osteocytes remain in contact with other osteocytes in the bone through gap junctions—coupled cell processes which pass through the canalicular channels.
Osteoclast
Osteoclasts are very large multinucleate cells that are responsible for the breakdown of bones by the process of bone resorption. New bone is then formed by the osteoblasts. Bone is constantly remodeled by the resorption of osteoclasts and created by osteoblasts. Osteoclasts are large cells with multiple nuclei located on bone surfaces in what are called Howship's lacunae (or resorption pits). These lacunae are the result of surrounding bone tissue that has been reabsorbed. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with phagocytic-like mechanisms similar to circulating macrophages. Osteoclasts mature and/or migrate to discrete bone surfaces. Upon arrival, active enzymes, such as tartrate-resistant acid phosphatase, are secreted against the mineral substrate. The reabsorption of bone by osteoclasts also plays a role in calcium homeostasis.
Composition | Bone | Wikipedia | 379 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Bones consist of living cells (osteoblasts and osteocytes) embedded in a mineralized organic matrix. The primary inorganic component of human bone is hydroxyapatite, the dominant bone mineral, having the nominal composition of Ca10(PO4)6(OH)2. The organic components of this matrix consist mainly of type I collagen—"organic" referring to materials produced as a result of the human body—and inorganic components, which alongside the dominant hydroxyapatite phase, include other compounds of calcium and phosphate including salts. Approximately 30% of the acellular component of bone consists of organic matter, while roughly 70% by mass is attributed to the inorganic phase. The collagen fibers give bone its tensile strength, and the interspersed crystals of hydroxyapatite give bone its compressive strength. These effects are synergistic. The exact composition of the matrix may be subject to change over time due to nutrition and biomineralization, with the ratio of calcium to phosphate varying between 1.3 and 2.0 (per weight), and trace minerals such as magnesium, sodium, potassium and carbonate also be found.
Type I collagen composes 90–95% of the organic matrix, with the remainder of the matrix being a homogenous liquid called ground substance consisting of proteoglycans such as hyaluronic acid and chondroitin sulfate, as well as non-collagenous proteins such as osteocalcin, osteopontin or bone sialoprotein. Collagen consists of strands of repeating units, which give bone tensile strength, and are arranged in an overlapping fashion that prevents shear stress. The function of ground substance is not fully known. Two types of bone can be identified microscopically according to the arrangement of collagen: woven and lamellar.
Woven bone (also known as fibrous bone), which is characterized by a haphazard organization of collagen fibers and is mechanically weak.
Lamellar bone, which has a regular parallel alignment of collagen into sheets ("lamellae") and is mechanically strong. | Bone | Wikipedia | 439 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Woven bone is produced when osteoblasts produce osteoid rapidly, which occurs initially in all fetal bones, but is later replaced by more resilient lamellar bone. In adults, woven bone is created after fractures or in Paget's disease. Woven bone is weaker, with a smaller number of randomly oriented collagen fibers, but forms quickly; it is for this appearance of the fibrous matrix that the bone is termed woven. It is soon replaced by lamellar bone, which is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone, which makes its first appearance in humans in the fetus during the third trimester, is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). In cross-section, the fibers run in opposite directions in alternating layers, much like in plywood, assisting in the bone's ability to resist torsion forces. After a fracture, woven bone forms initially and is gradually replaced by lamellar bone during a process known as "bony substitution". Compared to woven bone, lamellar bone formation takes place more slowly. The orderly deposition of collagen fibers restricts the formation of osteoid to about 1 to 2 μm per day. Lamellar bone also requires a relatively flat surface to lay the collagen fibers in parallel or concentric layers.
Deposition
The extracellular matrix of bone is laid down by osteoblasts, which secrete both collagen and ground substance. These cells synthesise collagen alpha polypetpide chains and then secrete collagen molecules. The collagen molecules associate with their neighbors and crosslink via lysyl oxidase to form collagen fibrils. At this stage, they are not yet mineralized, and this zone of unmineralized collagen fibrils is called "osteoid". Around and inside collagen fibrils calcium and phosphate eventually precipitate within days to weeks becoming then fully mineralized bone with an overall carbonate substituted hydroxyapatite inorganic phase. | Bone | Wikipedia | 446 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
In order to mineralise the bone, the osteoblasts secrete alkaline phosphatase, some of which is carried by vesicles. This cleaves the inhibitory pyrophosphate and simultaneously generates free phosphate ions for mineralization, acting as the foci for calcium and phosphate deposition. Vesicles may initiate some of the early mineralization events by rupturing and acting as a centre for crystals to grow on. Bone mineral may be formed from globular and plate structures, and via initially amorphous phases.
Types | Bone | Wikipedia | 117 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Five types of bones are found in the human body: long, short, flat, irregular, and sesamoid.
Long bones are characterized by a shaft, the diaphysis, that is much longer than its width; and by an epiphysis, a rounded head at each end of the shaft. They are made up mostly of compact bone, with lesser amounts of marrow, located within the medullary cavity, and areas of spongy, cancellous bone at the ends of the bones. Most bones of the limbs, including those of the fingers and toes, are long bones. The exceptions are the eight carpal bones of the wrist, the seven articulating tarsal bones of the ankle and the sesamoid bone of the kneecap. Long bones such as the clavicle, that have a differently shaped shaft or ends are also called modified long bones.
Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. Short bones provide stability and support as well as some limited motion. The bones of the wrist and ankle are short bones.
Flat bones are thin and generally curved, with two parallel layers of compact bone sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum.
Sesamoid bones are bones embedded in tendons. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the leverage of the muscle is increased. Examples of sesamoid bones are the patella and the pisiform.
Irregular bones do not fit into the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. Often this irregular shape is due to their many centers of ossification or because they contain bony sinuses. The bones of the spine, pelvis, and some bones of the skull are irregular bones. Examples include the ethmoid and sphenoid bones.
Terminology | Bone | Wikipedia | 420 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
In the study of anatomy, anatomists use a number of anatomical terms to describe the appearance, shape and function of bones. Other anatomical terms are also used to describe the location of bones. Like other anatomical terms, many of these derive from Latin and Greek. Some anatomists still use Latin to refer to bones. The term "osseous", and the prefix "osteo-", referring to things related to bone, are still used commonly today.
Some examples of terms used to describe bones include the term "foramen" to describe a hole through which something passes, and a "canal" or "meatus" to describe a tunnel-like structure. A protrusion from a bone can be called a number of terms, including a "condyle", "crest", "spine", "eminence", "tubercle" or "tuberosity", depending on the protrusion's shape and location. In general, long bones are said to have a "head", "neck", and "body".
When two bones join, they are said to "articulate". If the two bones have a fibrous connection and are relatively immobile, then the joint is called a "suture".
Development
The formation of bone is called ossification. During the fetal stage of development this occurs by two processes: intramembranous ossification and endochondral ossification. Intramembranous ossification involves the formation of bone from connective tissue whereas endochondral ossification involves the formation of bone from cartilage.
Intramembranous ossification mainly occurs during formation of the flat bones of the skull but also the mandible, maxilla, and clavicles; the bone is formed from connective tissue such as mesenchyme tissue rather than from cartilage. The process includes: the development of the ossification center, calcification, trabeculae formation and the development of the periosteum.
Endochondral ossification occurs in long bones and most other bones in the body; it involves the development of bone from cartilage. This process includes the development of a cartilage model, its growth and development, development of the primary and secondary ossification centers, and the formation of articular cartilage and the epiphyseal plates. | Bone | Wikipedia | 501 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Endochondral ossification begins with points in the cartilage called "primary ossification centers". They mostly appear during fetal development, though a few short bones begin their primary ossification after birth. They are responsible for the formation of the diaphyses of long bones, short bones and certain parts of irregular bones. Secondary ossification occurs after birth and forms the epiphyses of long bones and the extremities of irregular and flat bones. The diaphysis and both epiphyses of a long bone are separated by a growing zone of cartilage (the epiphyseal plate). At skeletal maturity (18 to 25 years of age), all of the cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure). In the upper limbs, only the diaphyses of the long bones and scapula are ossified. The epiphyses, carpal bones, coracoid process, medial border of the scapula, and acromion are still cartilaginous. | Bone | Wikipedia | 234 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
The following steps are followed in the conversion of cartilage to bone:
Zone of reserve cartilage. This region, farthest from the marrow cavity, consists of typical hyaline cartilage that as yet shows no sign of transforming into bone.
Zone of cell proliferation. A little closer to the marrow cavity, chondrocytes multiply and arrange themselves into longitudinal columns of flattened lacunae.
Zone of cell hypertrophy. Next, the chondrocytes cease to divide and begin to hypertrophy (enlarge), much like they do in the primary ossification center of the fetus. The walls of the matrix between lacunae become very thin.
Zone of calcification. Minerals are deposited in the matrix between the columns of lacunae and calcify the cartilage. These are not the permanent mineral deposits of bone, but only a temporary support for the cartilage that would otherwise soon be weakened by the breakdown of the enlarged lacunae.
Zone of bone deposition. Within each column, the walls between the lacunae break down and the chondrocytes die. This converts each column into a longitudinal channel, which is immediately invaded by blood vessels and marrow from the marrow cavity. Osteoblasts line up along the walls of these channels and begin depositing concentric lamellae of matrix, while osteoclasts dissolve the temporarily calcified cartilage. | Bone | Wikipedia | 295 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Bone development in youth is extremely important in preventing future complications of the skeletal system. Regular exercise during childhood and adolescence can help improve bone architecture, making bones more resilient and less prone to fractures in adulthood. Physical activity, specifically resistance training, stimulates growth of bones by increasing both bone density and strength. Studies have shown a positive correlation between the adaptations of resistance training and bone density. While nutritional and pharmacological approaches may also improve bone health, the strength and balance adaptations from resistance training are a substantial added benefit. Weight-bearing exercise may assist in osteoblast (bone-forming cells) formation and help to increase bone mineral content. High-impact sports, which involve quick changes in direction, jumping, and running, are particularly effective with stimulating bone growth in the youth. Sports such as soccer, basketball, and tennis have shown to have positive effects on bone mineral density as well as bone mineral content in teenagers. Engaging in physical activity during childhood years, particularly in these high-impact osteogenic sports, can help to positively influence bone mineral density in adulthood. Children and adolescents who participate in regular physical activity will place the groundwork for bone health later in life, reducing the risk of bone-related conditions such as osteoporosis. | Bone | Wikipedia | 256 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Functions
Bones have a variety of functions:
Mechanical
Bones serve a variety of mechanical functions. Together the bones in the body form the skeleton. They provide a frame to keep the body supported, and an attachment point for skeletal muscles, tendons, ligaments and joints, which function together to generate and transfer forces so that individual body parts or the whole body can be manipulated in three-dimensional space (the interaction between bone and muscle is studied in biomechanics).
Bones protect internal organs, such as the skull protecting the brain or the ribs protecting the heart and lungs. Because of the way that bone is formed, bone has a high compressive strength of about , poor tensile strength of 104–121 MPa, and a very low shear stress strength (51.6 MPa). This means that bone resists pushing (compressional) stress well, resist pulling (tensional) stress less well, but only poorly resists shear stress (such as due to torsional loads). While bone is essentially brittle, bone does have a significant degree of elasticity, contributed chiefly by collagen.
Mechanically, bones also have a special role in hearing. The ossicles are three small bones in the middle ear which are involved in sound transduction.
Synthetic
The cancellous part of bones contain bone marrow. Bone marrow produces blood cells in a process called hematopoiesis. Blood cells that are created in bone marrow include red blood cells, platelets and white blood cells. Progenitor cells such as the hematopoietic stem cell divide in a process called mitosis to produce precursor cells. These include precursors which eventually give rise to white blood cells, and erythroblasts which give rise to red blood cells. Unlike red and white blood cells, created by mitosis, platelets are shed from very large cells called megakaryocytes. This process of progressive differentiation occurs within the bone marrow. After the cells are matured, they enter the circulation. Every day, over 2.5 billion red blood cells and platelets, and 50–100 billion granulocytes are produced in this way.
As well as creating cells, bone marrow is also one of the major sites where defective or aged red blood cells are destroyed.
Metabolic
Mineral storage – bones act as reserves of minerals important for the body, most notably calcium and phosphorus. | Bone | Wikipedia | 480 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Determined by the species, age, and the type of bone, bone cells make up to 15 percent of the bone. Growth factor storage—mineralized bone matrix stores important growth factors such as insulin-like growth factors, transforming growth factor, bone morphogenetic proteins and others.
Fat storage – marrow adipose tissue (MAT) acts as a storage reserve of fatty acids.
Acid-base balance – bone buffers the blood against excessive pH changes by absorbing or releasing alkaline salts.
Detoxification – bone tissues can also store heavy metals and other foreign elements, removing them from the blood and reducing their effects on other tissues. These can later be gradually released for excretion.
Endocrine organ – bone controls phosphate metabolism by releasing fibroblast growth factor 23 (FGF-23), which acts on kidneys to reduce phosphate reabsorption. Bone cells also release a hormone called osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number of insulin-producing cells and reducing stores of fat.
Calcium balance – the process of bone resorption by the osteoclasts releases stored calcium into the systemic circulation and is an important process in regulating calcium balance. As bone formation actively fixes circulating calcium in its mineral form, removing it from the bloodstream, resorption actively unfixes it thereby increasing circulating calcium levels. These processes occur in tandem at site-specific locations.
Calcium
Strong bones during our youth is essential for preventing osteoporosis and bone fragility as we age. The importance of insuring factors that could influence increases in BMD while lowering our risks for further bone degradation is necessary during our childhood as these factors lead to a supportive and healthy lifestyle/bone health. Up till the age of 30, the bone stores that we have will ultimately start to decrease as we surpass this age. Influencing factors that can help us have larger stores and higher amounts of BMD will allow us to see less harmful results as we reach older adulthood. | Bone | Wikipedia | 434 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
The issue of having fragile bones during our childhood leads to an increase in certain disorders and conditions such as juvenile osteoporosis, though it is less common to see, the necessity for a healthy routine especially when it comes to bone development is essential in our youth. Children that naturally have lower bone mineral density have a lower quality of life and therefore lead a life that is less fulfilling and uncomfortable. Factors such as increases in Calcium intake has been shown to increase BMD stores. Studies have shown that increasing calcium stores whether that be through supplementation or intake via foods and beverages such as leafy greens and milk have pushed the notion that prepuberty or even early pubertal children will see increases in BMD with the addition of increase Calcium intake.
Another research study goes on to show that long-term calcium intake has been proven to significantly contribute to overall BMD in children without certain conditions or disorders. This data shows that ensuring adequate calcium intake in children reinforces the structure and rate at which bones will begin to densify. Further detailing how structuring a strong nutritional plan with adequate amounts of Calcium sources can lead to strong bones but also can be a worth-while strategy into preventing further damage or degradation of bone stores as we age.
The connection between Calcium intake & BMD and its effects on youth as a whole is a very world-wide issue and has been shown to affect different ethnicities in a variety of differing ways. In a recent study, there was a strong correlation between calcium intake and BMD across a variety of diverse populations of children and adolescence ultimately coming to the conclusion that fundamentally, achieving optimal bone health is necessary for providing our youth with the ability to undergo hormonal changes as well. They found in a study of over 10,000 children ages 8-19 that in females, African Americans, and the 12-15 adolescent groups that at 2.6-2.8g/kg of body weight, they began to see a decrease in BMD. They elaborate on this by determining that this is strongly influenced by a lower baseline in calcium intake throughout puberty. Genetic factors have also been shown to influence lower acceptance of calcium stores. | Bone | Wikipedia | 437 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Ultimately, the window that youth have for accruing and building resilient bones is very minimal. Being able to consistently meet calcium needs while also engaging in weight-bearing exercise is essential for building a strong initial bone foundation at which to build upon. Being able to reach our daily value of 1300mg for ages 9-18 is becoming more and more necessary and as we progress in health, the chance that osteoporosis and other factors such as bone fragility or potential for stunted growth can be greatly reduced through these resources, ultimately leading to a more fulfilling and healthier lifestyle.
Remodeling
Bone is constantly being created and replaced in a process known as remodeling. This ongoing turnover of bone is a process of resorption followed by replacement of bone with little change in shape. This is accomplished through osteoblasts and osteoclasts. Cells are stimulated by a variety of signals, and together referred to as a remodeling unit. Approximately 10% of the skeletal mass of an adult is remodelled each year. The purpose of remodeling is to regulate calcium homeostasis, repair microdamaged bones from everyday stress, and to shape the skeleton during growth. Repeated stress, such as weight-bearing exercise or bone healing, results in the bone thickening at the points of maximum stress (Wolff's law). It has been hypothesized that this is a result of bone's piezoelectric properties, which cause bone to generate small electrical potentials under stress.
The action of osteoblasts and osteoclasts are controlled by a number of chemical enzymes that either promote or inhibit the activity of the bone remodeling cells, controlling the rate at which bone is made, destroyed, or changed in shape. The cells also use paracrine signalling to control the activity of each other. For example, the rate at which osteoclasts resorb bone is inhibited by calcitonin and osteoprotegerin. Calcitonin is produced by parafollicular cells in the thyroid gland, and can bind to receptors on osteoclasts to directly inhibit osteoclast activity. Osteoprotegerin is secreted by osteoblasts and is able to bind RANK-L, inhibiting osteoclast stimulation. | Bone | Wikipedia | 492 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Osteoblasts can also be stimulated to increase bone mass through increased secretion of osteoid and by inhibiting the ability of osteoclasts to break down osseous tissue. Increased secretion of osteoid is stimulated by the secretion of growth hormone by the pituitary, thyroid hormone and the sex hormones (estrogens and androgens). These hormones also promote increased secretion of osteoprotegerin. Osteoblasts can also be induced to secrete a number of cytokines that promote reabsorption of bone by stimulating osteoclast activity and differentiation from progenitor cells. Vitamin D, parathyroid hormone and stimulation from osteocytes induce osteoblasts to increase secretion of RANK-ligand and interleukin 6, which cytokines then stimulate increased reabsorption of bone by osteoclasts. These same compounds also increase secretion of macrophage colony-stimulating factor by osteoblasts, which promotes the differentiation of progenitor cells into osteoclasts, and decrease secretion of osteoprotegerin.
Volume
Bone volume is determined by the rates of bone formation and bone resorption. Certain growth factors may work to locally alter bone formation by increasing osteoblast activity. Numerous bone-derived growth factors have been isolated and classified via bone cultures. These factors include insulin-like growth factors I and II, transforming growth factor-beta, fibroblast growth factor, platelet-derived growth factor, and bone morphogenetic proteins. Evidence suggests that bone cells produce growth factors for extracellular storage in the bone matrix. The release of these growth factors from the bone matrix could cause the proliferation of osteoblast precursors. Essentially, bone growth factors may act as potential determinants of local bone formation. Cancellous bone volume in postmenopausal osteoporosis may be determined by the relationship between the total bone forming surface and the percent of surface resorption.
Clinical significance | Bone | Wikipedia | 426 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
A number of diseases can affect bone, including arthritis, fractures, infections, osteoporosis and tumors. Conditions relating to bone can be managed by a variety of doctors, including rheumatologists for joints, and orthopedic surgeons, who may conduct surgery to fix broken bones. Other doctors, such as rehabilitation specialists may be involved in recovery, radiologists in interpreting the findings on imaging, and pathologists in investigating the cause of the disease, and family doctors may play a role in preventing complications of bone disease such as osteoporosis.
When a doctor sees a patient, a history and exam will be taken. Bones are then often imaged, called radiography. This might include ultrasound X-ray, CT scan, MRI scan and other imaging such as a Bone scan, which may be used to investigate cancer. Other tests such as a blood test for autoimmune markers may be taken, or a synovial fluid aspirate may be taken.
Fractures
In normal bone, fractures occur when there is significant force applied or repetitive trauma over a long time. Fractures can also occur when a bone is weakened, such as with osteoporosis, or when there is a structural problem, such as when the bone remodels excessively (such as Paget's disease) or is the site of the growth of cancer. Common fractures include wrist fractures and hip fractures, associated with osteoporosis, vertebral fractures associated with high-energy trauma and cancer, and fractures of long-bones. Not all fractures are painful. When serious, depending on the fractures type and location, complications may include flail chest, compartment syndromes or fat embolism.
Compound fractures involve the bone's penetration through the skin. Some complex fractures can be treated by the use of bone grafting procedures that replace missing bone portions.
Fractures and their underlying causes can be investigated by X-rays, CT scans and MRIs. Fractures are described by their location and shape, and several classification systems exist, depending on the location of the fracture. A common long bone fracture in children is a Salter–Harris fracture. When fractures are managed, pain relief is often given, and the fractured area is often immobilised. This is to promote bone healing. In addition, surgical measures such as internal fixation may be used. Because of the immobilisation, people with fractures are often advised to undergo rehabilitation.
Tumors | Bone | Wikipedia | 501 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Tumor that can affect bone in several ways. Examples of benign bone tumors include osteoma, osteoid osteoma, osteochondroma, osteoblastoma, enchondroma, giant-cell tumor of bone, and aneurysmal bone cyst.
Cancer
Cancer can arise in bone tissue, and bones are also a common site for other cancers to spread (metastasise) to. Cancers that arise in bone are called "primary" cancers, although such cancers are rare. Metastases within bone are "secondary" cancers, with the most common being breast cancer, lung cancer, prostate cancer, thyroid cancer, and kidney cancer. Secondary cancers that affect bone can either destroy bone (called a "lytic" cancer) or create bone (a "sclerotic" cancer). Cancers of the bone marrow inside the bone can also affect bone tissue, examples including leukemia and multiple myeloma. Bone may also be affected by cancers in other parts of the body. Cancers in other parts of the body may release parathyroid hormone or parathyroid hormone-related peptide. This increases bone reabsorption, and can lead to bone fractures.
Bone tissue that is destroyed or altered as a result of cancers is distorted, weakened, and more prone to fracture. This may lead to compression of the spinal cord, destruction of the marrow resulting in bruising, bleeding and immunosuppression, and is one cause of bone pain. If the cancer is metastatic, then there might be other symptoms depending on the site of the original cancer. Some bone cancers can also be felt.
Cancers of the bone are managed according to their type, their stage, prognosis, and what symptoms they cause. Many primary cancers of bone are treated with radiotherapy. Cancers of bone marrow may be treated with chemotherapy, and other forms of targeted therapy such as immunotherapy may be used. Palliative care, which focuses on maximising a person's quality of life, may play a role in management, particularly if the likelihood of survival within five years is poor.
Diabetes
Type 1 diabetes is an autoimmune disease in which the body attacks the insulin-producing pancreas cells causing the body to not make enough insulin. In contrast type 2 diabetes in which the body creates enough Insulin, but becomes resistant to it over time. | Bone | Wikipedia | 486 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Children makeup approximately 85% of Type 1 Diabetes cases and in America there was an average 22% rise in cases over the first 24 months of the Covid-19 Pandemic. With the increase of developing some form of diabetes across all ranges continually growing the health impacts on bone development and bone health in these populations are still being researched. Most evidence suggests that diabetes, either Type 1 and Type 2, inhibits osteoblastic activity and causes both lower BMD and BMC in both adults and children. The weakening of these developmental aspects is thought to lead to an increased risk of developing many diseases such as osteoarthritis, osteoporosis, osteopenia and fractures. Development of any of these diseases is thought to be correlated with a decrease in ability to perform in athletic environments and activities of daily living.
Focusing on therapies that target molecules like osteocalcin or AGEs could provide new ways to improve bone health and help manage the complications of diabetes more effectively.
Other painful conditions
Osteomyelitis is inflammation of the bone or bone marrow due to bacterial infection.
Osteomalacia is a painful softening of adult bone caused by severe vitamin D deficiency.
Osteogenesis imperfecta
Osteochondritis dissecans
Ankylosing spondylitis
Skeletal fluorosis is a bone disease caused by an excessive accumulation of fluoride in the bones. In advanced cases, skeletal fluorosis damages bones and joints and is painful.
Osteoporosis | Bone | Wikipedia | 310 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Osteoporosis is a disease of bone where there is reduced bone mineral density, increasing the likelihood of fractures. Osteoporosis is defined in women by the World Health Organization as a bone mineral density of 2.5 standard deviations below peak bone mass, relative to the age and sex-matched average. This density is measured using dual energy X-ray absorptiometry (DEXA), with the term "established osteoporosis" including the presence of a fragility fracture. Osteoporosis is most common in women after menopause, when it is called "postmenopausal osteoporosis", but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking and medications, specifically glucocorticoids. Osteoporosis usually has no symptoms until a fracture occurs. For this reason, DEXA scans are often done in people with one or more risk factors, who have developed osteoporosis and are at risk of fracture.
One of the most important risk factors for osteoporosis is advanced age. Accumulation of oxidative DNA damage in osteoblastic and osteoclastic cells appears to be a key factor in age-related osteoporosis.
Osteoporosis treatment includes advice to stop smoking, decrease alcohol consumption, exercise regularly, and have a healthy diet. Calcium and trace mineral supplements may also be advised, as may Vitamin D. When medication is used, it may include bisphosphonates, Strontium ranelate, and hormone replacement therapy.
Osteopathic medicine
Osteopathic medicine is a school of medical thought that links the musculoskeletal system to overall health. , over 77,000 physicians in the United States are trained in osteopathic medical schools.
Bone health | Bone | Wikipedia | 398 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Bone health is vastly important all throughout life due to a number of reasons, some of those being, without strong healthy bones we are more at risk for different chronic diseases, and fractures as well as day to day function being more difficult with poor bone health. Developing strong bones as a child is one of the most important steps to having healthy bones all throughout life because this is when a strong foundation is built, which will make it much easier to maintain musculoskeletal health in later years. Adolescence offers a window to really develop bones in either a positive or negative way. It is estimated that diet and exercise during these years can impact peak bone mass as an adult nearly 20-40%. One study done on children with developmental coordination disorder found an increase in bone mass up to 4% and 5% in the cortical areas of the tibia alone from a 13 week training period, which is truly significant when considering how participants only participated in the multimodal workouts twice per week, and it would be reasonable to expect these increases to be greater if workouts were more frequent, especially in youth without developmental coordination disorder. Peak bone mass occurs between the second and third decade of most people's lives, and with this being the case if we can really stockpile as much bone mass and increase our BMD and BMC by living healthy active lives, and having good diets that consume adequate calcium and vitamin D then we will truly have a leg up in our later lives as well as actively decreasing risks of certain chronic diseases such as osteoporosis.
Osteology
The study of bones and teeth is referred to as osteology. It is frequently used in anthropology, archeology and forensic science for a variety of tasks. This can include determining the nutritional, health, age or injury status of the individual the bones were taken from. Preparing fleshed bones for these types of studies can involve the process of maceration.
Typically anthropologists and archeologists study bone tools made by Homo sapiens and Homo neanderthalensis. Bones can serve a number of uses such as projectile points or artistic pigments, and can also be made from external bones such as antlers.
Other animals
Bird skeletons are very lightweight. Their bones are smaller and thinner, to aid flight. Among mammals, bats come closest to birds in terms of bone density, suggesting that small dense bones are a flight adaptation. Many bird bones have little marrow due to them being hollow. | Bone | Wikipedia | 498 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
A bird's beak is primarily made of bone as projections of the mandibles which are covered in keratin.
Some bones, primarily formed separately in subcutaneous tissues, include headgears (such as bony core of horns, antlers, ossicones), osteoderm, and os penis/os clitoris. A deer's antlers are composed of bone which is an unusual example of bone being outside the skin of the animal once the velvet is shed.
The extinct predatory fish Dunkleosteus had sharp edges of hard exposed bone along its jaws.
The proportion of cortical bone that is 80% in the human skeleton may be much lower in other animals, especially in marine mammals and marine turtles, or in various Mesozoic marine reptiles, such as ichthyosaurs, among others. This proportion can vary quickly in evolution; it often increases in early stages of returns to an aquatic lifestyle, as seen in early whales and pinnipeds, among others. It subsequently decreases in pelagic taxa, which typically acquire spongy bone, but aquatic taxa that live in shallow water can retain very thick, pachyostotic, osteosclerotic, or pachyosteosclerotic bones, especially if they move slowly, like sea cows. In some cases, even marine taxa that had acquired spongy bone can revert to thicker, compact bones if they become adapted to live in shallow water, or in hypersaline (denser) water.
Many animals, particularly herbivores, practice osteophagy—the eating of bones. This is presumably carried out in order to replenish lacking phosphate.
Many bone diseases that affect humans also affect other vertebrates—an example of one disorder is skeletal fluorosis.
Society and culture
Bones from slaughtered animals have a number of uses. In prehistoric times, they have been used for making bone tools. They have further been used in bone carving, already important in prehistoric art, and also in modern time as crafting materials for buttons, beads, handles, bobbins, calculation aids, head nuts, dice, poker chips, pick-up sticks, arrows, scrimshaw, ornaments, etc. | Bone | Wikipedia | 455 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Bone glue can be made by prolonged boiling of ground or cracked bones, followed by filtering and evaporation to thicken the resulting fluid. Historically once important, bone glue and other animal glues today have only a few specialized uses, such as in antiques restoration. Essentially the same process, with further refinement, thickening and drying, is used to make gelatin.
Broth is made by simmering several ingredients for a long time, traditionally including bones.
Bone char, a porous, black, granular material primarily used for filtration and also as a black pigment, is produced by charring mammal bones.
Oracle bone script was a writing system used in ancient China based on inscriptions in bones. Its name originates from oracle bones, which were mainly ox clavicle. The Ancient Chinese (mainly in the Shang dynasty), would write their questions on the oracle bone, and burn the bone, and where the bone cracked would be the answer for the questions.
To point the bone at someone is considered bad luck in some cultures, such as Australian aborigines, such as by the Kurdaitcha.
The wishbones of fowl have been used for divination, and are still customarily used in a tradition to determine which one of two people pulling on either prong of the bone may make a wish.
Various cultures throughout history have adopted the custom of shaping an infant's head by the practice of artificial cranial deformation. A widely practised custom in China was that of foot binding to limit the normal growth of the foot.
Additional images | Bone | Wikipedia | 320 | 4099 | https://en.wikipedia.org/wiki/Bone | Biology and health sciences | Biology | null |
Brouwer's fixed-point theorem is a fixed-point theorem in topology, named after L. E. J. (Bertus) Brouwer. It states that for any continuous function mapping a nonempty compact convex set to itself, there is a point such that . The simplest forms of Brouwer's theorem are for continuous functions from a closed interval in the real numbers to itself or from a closed disk to itself. A more general form than the latter is for continuous functions from a nonempty convex compact subset of Euclidean space to itself.
Among hundreds of fixed-point theorems, Brouwer's is particularly well known, due in part to its use across numerous fields of mathematics. In its original field, this result is one of the key theorems characterizing the topology of Euclidean spaces, along with the Jordan curve theorem, the hairy ball theorem, the invariance of dimension and the Borsuk–Ulam theorem. This gives it a place among the fundamental theorems of topology. The theorem is also used for proving deep results about differential equations and is covered in most introductory courses on differential geometry. It appears in unlikely fields such as game theory. In economics, Brouwer's fixed-point theorem and its extension, the Kakutani fixed-point theorem, play a central role in the proof of existence of general equilibrium in market economies as developed in the 1950s by economics Nobel prize winners Kenneth Arrow and Gérard Debreu.
The theorem was first studied in view of work on differential equations by the French mathematicians around Henri Poincaré and Charles Émile Picard. Proving results such as the Poincaré–Bendixson theorem requires the use of topological methods. This work at the end of the 19th century opened into several successive versions of the theorem. The case of differentiable mappings of the -dimensional closed ball was first proved in 1910 by Jacques Hadamard and the general case for continuous mappings by Brouwer in 1911.
Statement
The theorem has several formulations, depending on the context in which it is used and its degree of generalization. The simplest is sometimes given as follows:
In the plane Every continuous function from a closed disk to itself has at least one fixed point.
This can be generalized to an arbitrary finite dimension:
In Euclidean spaceEvery continuous function from a closed ball of a Euclidean space into itself has a fixed point.
A slightly more general version is as follows: | Brouwer fixed-point theorem | Wikipedia | 496 | 4101 | https://en.wikipedia.org/wiki/Brouwer%20fixed-point%20theorem | Mathematics | Topology | null |
Convex compact setEvery continuous function from a nonempty convex compact subset K of a Euclidean space to K itself has a fixed point.
An even more general form is better known under a different name:
Schauder fixed point theoremEvery continuous function from a nonempty convex compact subset K of a Banach space to K itself has a fixed point.
Importance of the pre-conditions
The theorem holds only for functions that are endomorphisms (functions that have the same set as the domain and codomain) and for nonempty sets that are compact (thus, in particular, bounded and closed) and convex (or homeomorphic to convex). The following examples show why the pre-conditions are important.
The function f as an endomorphism
Consider the function
with domain [-1,1]. The range of the function is [0,2]. Thus, f is not an endomorphism.
Boundedness
Consider the function
which is a continuous function from to itself. As it shifts every point to the right, it cannot have a fixed point. The space is convex and closed, but not bounded.
Closedness
Consider the function
which is a continuous function from the open interval (−1,1) to itself. Since x = 1 is not part of the interval, there is not a fixed point of f(x) = x. The space (−1,1) is convex and bounded, but not closed. On the other hand, the function f have a fixed point for the closed interval [−1,1], namely f(1) = 1.
(The domain of f is (-1,1) but the range is (0,1), which are not the same. Earlier, one of the conditions for functions satisfying the theorem is that the domain and range were the same, not that one be a subset of the other. Thus the reason for f failing is not closure.)
Convexity
Convexity is not strictly necessary for Brouwer's fixed-point theorem. Because the properties involved (continuity, being a fixed point) are invariant under homeomorphisms, Brouwer's fixed-point theorem is equivalent to forms in which the domain is required to be a closed unit ball . For the same reason it holds for every set that is homeomorphic to a closed ball (and therefore also closed, bounded, connected, without holes, etc.). | Brouwer fixed-point theorem | Wikipedia | 499 | 4101 | https://en.wikipedia.org/wiki/Brouwer%20fixed-point%20theorem | Mathematics | Topology | null |
The following example shows that Brouwer's fixed-point theorem does not work for domains with holes. Consider the function , which is a continuous function from the unit circle to itself. Since -x≠x holds for any point of the unit circle, f has no fixed point. The analogous example works for the n-dimensional sphere (or any symmetric domain that does not contain the origin). The unit circle is closed and bounded, but it has a hole (and so it is not convex) . The function f have a fixed point for the unit disc, since it takes the origin to itself.
A formal generalization of Brouwer's fixed-point theorem for "hole-free" domains can be derived from the Lefschetz fixed-point theorem. | Brouwer fixed-point theorem | Wikipedia | 158 | 4101 | https://en.wikipedia.org/wiki/Brouwer%20fixed-point%20theorem | Mathematics | Topology | null |
Benzoic acid () is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. The benzoyl group is often abbreviated "Bz" (not to be confused with "Bn," which is used for benzyl), thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula –. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source.
Benzoic acid occurs naturally in many plants and serves as an intermediate in the biosynthesis of many secondary metabolites. Salts of benzoic acid are used as food preservatives. Benzoic acid is an important precursor for the industrial synthesis of many other organic substances. The salts and esters of benzoic acid are known as benzoates ().
History
Benzoic acid was discovered in the sixteenth century. The dry distillation of gum benzoin was first described by Nostradamus (1556), and then by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596).
Justus von Liebig and Friedrich Wöhler determined the composition of benzoic acid. These latter also investigated how hippuric acid is related to benzoic acid.
In 1875 Salkowski discovered the antifungal properties of benzoic acid, which explains the preservation of benzoate-containing cloudberry fruits.
Production
Industrial preparations
Benzoic acid is produced commercially by partial oxidation of toluene with oxygen. The process is catalyzed by cobalt or manganese naphthenates. The process uses abundant materials, and proceeds in high yield.
The first industrial process involved the reaction of benzotrichloride (trichloromethyl benzene) with calcium hydroxide in water, using iron or iron salts as catalyst. The resulting calcium benzoate is converted to benzoic acid with hydrochloric acid. The product contains significant amounts of chlorinated benzoic acid derivatives. For this reason, benzoic acid for human consumption was obtained by dry distillation of gum benzoin. Food-grade benzoic acid is now produced synthetically.
Laboratory synthesis
Benzoic acid is cheap and readily available, so the laboratory synthesis of benzoic acid is mainly practiced for its pedagogical value. It is a common undergraduate preparation. | Benzoic acid | Wikipedia | 510 | 4106 | https://en.wikipedia.org/wiki/Benzoic%20acid | Physical sciences | Specific acids | Chemistry |
Benzoic acid can be purified by recrystallization from water because of its high solubility in hot water and poor solubility in cold water. The avoidance of organic solvents for the recrystallization makes this experiment particularly safe. This process usually gives a yield of around 65%.
By hydrolysis
Like other nitriles and amides, benzonitrile and benzamide can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions.
From Grignard reagent
Bromobenzene can be converted to benzoic acid by "carboxylation" of the intermediate phenylmagnesium bromide. This synthesis offers a convenient exercise for students to carry out a Grignard reaction, an important class of carbon–carbon bond forming reaction in organic chemistry.
Oxidation of benzyl compounds
Benzyl alcohol and benzyl chloride and virtually all benzyl derivatives are readily oxidized to benzoic acid.
Uses
Benzoic acid is mainly consumed in the production of phenol by oxidative decarboxylation at 300−400 °C:
The temperature required can be lowered to 200 °C by the addition of catalytic amounts of copper(II) salts. The phenol can be converted to cyclohexanol, which is a starting material for nylon synthesis.
Precursor to plasticizers
Benzoate plasticizers, such as the glycol-, diethyleneglycol-, and triethyleneglycol esters, are obtained by transesterification of methyl benzoate with the corresponding diol. These plasticizers, which are used similarly to those derived from terephthalic acid ester, represent alternatives to phthalates. | Benzoic acid | Wikipedia | 359 | 4106 | https://en.wikipedia.org/wiki/Benzoic%20acid | Physical sciences | Specific acids | Chemistry |
Precursor to sodium benzoate and related preservatives
Benzoic acid and its salts are used as food preservatives, represented by the E numbers E210, E211, E212, and E213. Benzoic acid inhibits the growth of mold, yeast and some bacteria. It is either added directly or created from reactions with its sodium, potassium, or calcium salt. The mechanism starts with the absorption of benzoic acid into the cell. If the intracellular pH changes to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase is decreased by 95%. The efficacy of benzoic acid and benzoate is thus dependent on the pH of the food. Benzoic acid, benzoates
and their derivatives are used as preservatives for acidic foods and beverages such as citrus fruit juices (citric acid), sparkling drinks (carbon dioxide), soft drinks (phosphoric acid), pickles (vinegar) and other acidified foods.
Typical concentrations of benzoic acid as a preservative in food are between 0.05 and 0.1%. Foods in which benzoic acid may be used and maximum levels for its application are controlled by local food laws.
Concern has been expressed that benzoic acid and its salts may react with ascorbic acid (vitamin C) in some soft drinks, forming small quantities of carcinogenic benzene.
Medicinal
Benzoic acid is a constituent of Whitfield's ointment which is used for the treatment of fungal skin diseases such as ringworm and athlete's foot. As the principal component of gum benzoin, benzoic acid is also a major ingredient in both tincture of benzoin and Friar's balsam. Such products have a long history of use as topical antiseptics and inhalant decongestants.
Benzoic acid was used as an expectorant, analgesic, and antiseptic in the early 20th century.
Niche and laboratory uses
In teaching laboratories, benzoic acid is a common standard for calibrating a bomb calorimeter. | Benzoic acid | Wikipedia | 439 | 4106 | https://en.wikipedia.org/wiki/Benzoic%20acid | Physical sciences | Specific acids | Chemistry |
Biology and health effects
Benzoic acid occurs naturally as do its esters in many plant and animal species. Appreciable amounts are found in most berries (around 0.05%). Ripe fruits of several Vaccinium species (e.g., cranberry, V. vitis macrocarpon; bilberry, V. myrtillus) contain as much as 0.03–0.13% free benzoic acid. Benzoic acid is also formed in apples after infection with the fungus Nectria galligena. Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e.g., in viscera and muscles of the rock ptarmigan (Lagopus muta) as well as in gland secretions of male muskoxen (Ovibos moschatus) or Asian bull elephants (Elephas maximus). Gum benzoin contains up to 20% of benzoic acid and 40% benzoic acid esters.
In terms of its biosynthesis, benzoate is produced in plants from cinnamic acid. A pathway has been identified from phenol via 4-hydroxybenzoate.
Reactions
Reactions of benzoic acid can occur at either the aromatic ring or at the carboxyl group.
Aromatic ring
Electrophilic aromatic substitution reaction will take place mainly in 3-position due to the electron-withdrawing carboxylic group; i.e. benzoic acid is meta directing.
Carboxyl group
Reactions typical for carboxylic acids apply also to benzoic acid. | Benzoic acid | Wikipedia | 329 | 4106 | https://en.wikipedia.org/wiki/Benzoic%20acid | Physical sciences | Specific acids | Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.