In 1965, Arno Penzias and Robert Wilson announced the discovery of microwave radiation which uniformly filled the sky and had a blackbody temperature of about 3.5K. The pair had been testing a new radio amplifier that was supposed to be exceptionally quiet. What better way to do such a test than to tune the radio so that it should hear nothing at all? After many attempts to account for all extrane…
Cosmology is the study of the origin, structure and evolution of the universe. The origins of cosmology predate the human written record. The earliest civilizations constructed elaborate myths and folk tales to explain the wanderings of the Sun, Moon, and stars through the heavens. Ancient Egyptians tied their religious beliefs to celestial objects and Ancient Greek and Roman philosophers debated …
While the Upanishads mark the end of the Vedas, the cosmologies introduced there continue to be developed in the subsequent texts (for example, the Manava Dharmashastra or Manusmriti [Laws of Manu], the Vishnu Purana, and sections of the Mahabharata). While these texts differ somewhat in content, they mutually inform what has come to be the prevailing cosmology in the Hindu tradition. This cosmolo…
Cotingas are a highly diverse group of birds that make up the family Cotingidae. Species of cotingas occur widely in tropical forests of South and Central America. Cotingas are fly-catching birds, and are similar in many respects to species of tyrant flycatchers (family Tyrannidae), although these families are not closely related. Species of cotingas are extremely variable in size, shape, color, b…
Cotton is a fiber obtained from various species of plants, genus Gossypium, family Malvaceae (Mallow), and is the most important and widely used natural fiber in the world. Cotton is primarily an agricultural crop, but it can also be found growing wild. Originally cotton species were perennial plants, but in some areas cotton has been selectively bred to develop as an annual plant. There are more …
Every set that can be counted is countable, but this is no surprise. The interesting case for countable sets comes when we abandon finite sets and consider infinite ones. An infinite set of numbers, points, or other elements is said to be "countable" (also called denumerable) if its elements can be paired one-to-one with the natural numbers, 1, 2, 3, etc. The term countable is somewh…
Coursers and the closely related pratincoles are 17 species of birds that comprise the family Glareolidae, in the order Charadriiformes, which also contains the plovers, sandpipers, and other families of waders and shorebirds. The pratincoles occur in southern Europe and Asia, Africa, Southeast Asia, and Australasia, but coursers only occur in Africa, the Middle East, and India. Coursers and prati…
Courtship is a complex set of behaviors in animals that leads to mating. Courtship behavior communicates to each of the potential mates that the other is not a threat. It also reveals information to each animal that the species, gender, and physical condition of the other are suitable for mating. Pre-mating activities are for the most part ritualistic. They consist of a series of fixed action patt…
The coypu or nutria (Myocastor coypu) is a species of semi-aquatic, dog-sized rodent in the family Capromyidae. These animals are native to central and southern South America, but they have become widely established elsewhere, mostly as a result of animals that have escaped from fur farms or that have been deliberately released. Coypus have a stout, 17-25 in (43-64 cm) long body, with a roughly tr…
Crabs are some of the best known arthropods—a terms that means jointed foot (Greek: arthron, joint; pous, foot). They are among the most successful of all living species (about 4,500 species have been described), with members adapted to living on land and in water; some species even succeed in living in both habitats. The majority, however, live in the marine environment. Unlike lobsters (t…
The first true cranes, founded on the principles of levers and counterweights, used a pulley system fixed to a single mast or boom. Lifting power was provided by humans or draft animals operating a treadmill or large wheel. Eventually, a second mast and guy wires were added to increase the strength and stability of this early form of crane. One of the most significant developments in crane design,…
Cranes are tall, wading birds known for their beauty, elaborate courtship dances, and voices that boom across their wetland habitat. Their family Gruidae, is among the oldest on Earth. Today 15 crane species are found throughout the world, except in South America and Antarctica. Two species, the whooping crane (Grus americana) and the sandhill crane (G. canadensis) are found in North America. Cran…
Creationism in a general sense refers to the theory that God made the world on his own, by miraculous means, out of nothing. In a more specific sense, the one encountered in America today, creationism is the theory that the Bible, particularly the early chapters of Genesis, is a literally true guide to the history of the universe and to the history of life, including us humans, down here on earth.…
Because creativity is a complex concept, it has multiple definitions. Of the various conceptions, however, three are currently most common. These are the product, person, and process definitions. According to the first, creativity is manifested in an identifiable outcome, such as a poem, painting, invention, or discovery. Moreover, this product must fulfill two essential conditions. First, it must…
The concept of creolization lies at the very center of discussions of transculturalism, transnationalism, multiculturalism, diversity, and hybridization. This essay begins by examining the term's roots in the ethnic and cultural complexities of the Caribbean experience. It then goes on to look at the transformation of this experience into a theoretical framework for pluralism that conscious…
Crestfish, also called unicornfish, are a small family (Lophotidae) of deepwater, marine bony fish in the order Lampridiformes. These rare fish have unusual boxlike heads with protruding foreheads and ribbon-shaped silvery bodies with crimson fins. The prominent dorsal fin extends from the tip of the head to beyond the tail; the first rays of this fin form a crest above the head, giving these fish…
Creutzfeldt-Jakob disease is a rare encephalopathy, or brain disease, that causes a swift, progressive dementia and neuromuscular changes. It was first described by German psychiatrist Alfons Maria Jakob (1884–1931) in 1921. He gave credit to Hans Gerhard Creutzfeldt (1885–1964), also a German psychiatrist, for describing the syndrome first without realizing he had stumbled onto a re…
Crickets (order Orthoptera, family Grillidae) are found throughout the world except for the polar regions. More than 900 species have been described. Often heard, but more seldom seen, at first glance crickets are quite similar to grasshoppers and bush crickets—also known as long-horned grasshoppers or katydids—but may be distinguished from these insects by their much longer, thread-…
The term crisis comes from the Greek noun krisis (choice, decision, judgment), deriving from the Greek verb krinein (to decide). The word makes an ancient debut in Greek historical writing via the legal, medical, and rhetorical terminology as the turning point in a decision, illness, or argument. Its definitive reappearance with reference to historical events, periods, or processes dates from the …
All species have particular requirements for their ecological habitat. These specific needs are known as critical habitat, and they must be satisfied if the species is to survive. Critical habitat can involve specific types of food, a habitat required for breeding (as is the case of species that nest in tree cavities), or some other crucial environmental requirement. Some critical habitat features…
One of a family of related progressive movements in the law—others include critical legal studies, Latino critical legal studies ("Lat/Crit"), and feminist legal theory—critical race theory sprang up in the late l970s in response to a widespread perception that the powerful civil rights coalition of the 1960s and early 1970s had stalled. Conservative administrations an…
In the humanities, the term critical theory has had many meanings in different historical contexts. From the end of World War II through the 1960s, the term signified the use of critical and theoretical approaches within major disciplines of the humanities such as art history, literary studies, and more broadly, cultural studies. From the 1970s, the term entered into the rapidly evolving area of f…
The crocodile order (Crocodylia) consists of several families of large, unmistakable, amphibious reptiles: the crocodiles (Crocodylidae), gavials (Gavialidae), and the alligators and caimans (Alligatoridae). Although these animals look superficially like lizards, they are different in many important respects, and are believed by biologists to be the most highly evolved of the living reptiles. Croc…
Crops are any organisms that humans utilize as a source of food, materials, or energy. Crops may be utilized for subsistence purposes, to barter for other goods, or to sell for a cash profit. They may be harvested from wild ecosystems, or they may be husbanded and managed, as occurs with domesticated species in agriculture. In general, the purpose of management is to increase the amount of crop pr…
In solid geometry, the cross section of a three-dimensional object is a two-dimensional figure obtained by slicing the object perpendicular to its axis and viewing it end on. Thus, a sausage has a circular cross section, a 4 × 4 fence post has a square cross section, and a football has a circular cross section when sliced one way and an elliptical cross section when sliced another way. More…
The members of the crow family (Corvidae) are among the world's most intelligent birds. The family has recently undergone taxonomic expansion, brought about by evidence gathered through genetic testing, and now includes such diverse species as birds-of-paradise, orioles, and drongos. Crows and jays belong to the subfamily Corvinae. The corvids comprise 113 species in 25 genera, which includ…
The crustacea (subphylum Mandibulata, class Crustacea) are a diverse group of animals. This class includes some of the more familiar arthropods, including barnacles, copepods, crabs, prawns, lobsters, and wood lice. More than 30,000 species have been identified, the majority of which are marine-dwelling. Terrestrial species such as woodlice and pill bugs are believed to have evolved from marine sp…
Cryobiology is the scientific study of the effects of freezing and sub-freezing temperatures on biological fluids, cells, and tissues. It is an extension of cryogenics, which is the study of the properties of matter at very low temperatures. Cryobiological techniques have application in genetic research, livestock breeding, infertility treatment, and organ transplantation. A related field, cryogen…
Cryogenics is the science of producing and studying low-temperature environments. The word cryogenics comes from the Greek word "kryos," meaning cold; combined with a shortened form of the English verb "to generate," it has come to mean the generation of temperatures well below those of normal human experience. More specifically, a low-temperature environment is termed …
Cryptography is a division of applied mathematics concerned with developing schemes and formula to enhance the privacy of communications through the use of codes. Cryptography allows its users, whether governments, military, businesses, or individuals, to maintain privacy and confidentiality in their communications. Encryption is any form of coding, ciphering, or secret writing. Encryption of data…
A crystal is a solid in which the particles that make up the solid take up a highly ordered, definite, geometric arrangement that is repeated in all directions within the crystal. In ancient Greece, Archimedes made a study of regular solids, and Plato and Aristotle speculated on the relationship between regular solids and the elements. In the sixteenth century, the German naturalist, Giorgius Agri…
Cuckoos, coucals, anis, malkohas, and roadrunners are approximately 127 species of birds that make up the family Cuculidae. These birds are mostly tropical in distribution, but some species also breed in the temperate zones. Many species are parasitic breeders, laying their eggs in the nests of other species of birds. Species of the cuckoo family occupy a great diversity of habitats, ranging from …
The concept of cultural capital originated in the work of Pierre Bourdieu (1979, pp. 10, 12), who defined it as high cultural knowledge that ultimately redounds to the owner's financial and social advantage. An example would be knowing how to "dress for success." This cultural knowledge can pay off. Although they naturally seek competent personnel, employers also prefer execut…
As a discipline, cultural history is a bit over two centuries old, but it has an extensive prehistory going back to Renaissance scholarship, especially in areas of the history of literature and the history of philosophy. In the Renaissance, cultus or cultura was commonly associated with the cultivation of literature, philosophy, eloquence, law, arts, and sciences, whose fruits were the human virtu…
Literary critics and historians use cultural nationalism to refer to collective practices that form modern political communities within, unsanctioned by, or even undercutting state authority. Such collective practices include the "high" culture disseminated via public media, established in publicly funded institutions such as universities and museums; as well as the "low…
The term cultural revival refers to the formation of group identity around a common culture, where a claim is forwarded that the aspects of culture with which the group identifies have been recovered after losses due to colonization, forced or voluntary relocation, oppression, or modernization. Cultural revival is predominantly associated with minority populations and frequently underwrites demand…
Curare (pronounced cue-rah'-ree) is a general term for certain chemical substances found in different plants throughout the world's rainforests. These plants produce a harmless sap which for centuries the natives of the rainforests have refined into a deadly poison. The way of refining and delivering the poison from certain types of plants is similar for natives occupying equatorial …
Curlews are large, brownish shorebirds (family Scolopacidae) with long legs and lengthy, downward curving bills, adapted for probing into sediment and soil for their food of invertebrates. Although neither species of North American curlew is common, the most abundant ones are the long-billed curlew (Numenius americanus) and the whimbre, or Hudsonian curlew (N. phaeopus). The long-billed curlew bre…
Currents are steady, smooth movements of water following a specific course; they proceed either in a cyclical pattern or as a continuous stream. In the Northern Hemisphere, currents generally move in a clockwise direction, while in the Southern Hemisphere they move counterclockwise. There are three basic types of ocean currents: surface currents; currents produced by long wave movements or tides; …
Informally, one can picture a curve as either a line, a line segment, or a figure obtained from a line or a line segment by having the line or line segment bent, stretched, or contracted in any way. A plane curve, such as a circle, is one that lies in a plane; a curve in three dimensional space, such as one on a sphere or cylinder, is called a skew curve. A closed curve is a curve with no endpoint…
In the early twentieth century, Harvey Cushing, (1869–1939), an American neurosurgeon, described a set of symptoms that he identified as a syndrome later called Cushing syndrome or disease. The cause of the syndrome at the time was unknown, but since then, a better understanding of the underlying causes of Cushing syndrome have been elucidated. Cushing syndrome is a disorder that is caused …
Cuttlefish are squid-like cephalopod mollusks of the family Sepiidae, in the order Sepioidea. Cephalopod literally means "head-footed animal" and is the name given to advanced mollusks (such as cuttlefish, squid and octopus) whose heads are circled with tentacles. Cuttlefish have a relatively well-developed brain, sensitive organs of smell and hearing, highly developed eyes, and a re…