It is possible that ever since people first came to be, stone was used in constructing something: a fence, an oven in a hole or trench, or a shelf in a cave. And it is possible that sometime during this era, someone coined the statement: "Leave no stone unturned." The many cairns and stone hedges erected for religious or astronomical uses were the initial attempts at masonry. However…
Stoneflies or salmonflies are a group of insects with aquatic nymphal stages in the order Plecoptera. Stoneflies have a simple metamorphosis, with three life-history stages: egg, nymph or naiad, and adult. Adult stoneflies have two pairs of membranous wings that are folded back over the abdomen when not in use. Stoneflies are rather weak fliers, and are not usually found very far from the aquatic …
Storks are large wading birds of the tropics and subtropics. They belong to the order Ciconiiformes, which A white stork and its nest in Turkey. JLM Visuals. Reproduced by permission. also includes the ibises and spoonbills. Storks are in the family Ciconiidae. Unlike most tall wading birds, storks will perch in trees. They also nest in high places, and often return to the same nesting sit…
A storm is any disturbance in the atmosphere that has noticeable effects on the earth's surface. The term suggests disagreeable weather conditions that may bring discomfort, inconvenience, economic disaster and loss of human lives. In spite of that fact, storms have a generally positive effect on the environment and on human societies because they are the source of most of the rain and snow…
Storm surge, caused by very low atmospheric pressure, is a volume of oceanic water driven by the wind toward the shore where it "builds up" along the coast producing a localized increase in sea level. Such low atmospheric pressure occurs during cyclonic storms, called typhoons in the Pacific region and hurricanes along the Atlantic seaboard. During these storms, a dome of water forms…
Strata (singular: stratum) are the horizontal layers, or beds, present in most sedimentary rocks. During or immediately after the accumulation of sediments, physical, biological, and chemical processes produce sedimentary structures. Strata are probably the most common sedimentary structures, as almost all sedimentary rocks display some type of bedding. A rock that contains beds is stratified or d…
Stratigraphy is the science of interpreting and describing layers and strata of sediments. Commonly these layers are levels of sedimentary rock, but stratigraphy can also include the study of non-ossified sediments, like those in stream beds and lake bottoms, of inclusions such as volcanic ash and lava, and even the study of different layers of human occupation. Sediment usually forms distinct str…
Stratigraphy is the study of layered materials (strata) that were deposited over time—their lateral and vertical relations, as well as their composition. The basic law of stratigraphy, the law of superposition, states that lower layers are older than upper layers, unless the sequence has been disturbed. Stratified deposits may include soils, sediments, and rocks, as well as man-made structu…
Streams channel water downhill under the influence of gravity. Stream capacity is a measure of the total sediment (material other than water) a stream can carry. Stream competence reflects the ability of a stream to transport a particular size of particle (e.g., boulder, pebble, etc). With regard to calculation of stream capacity and competence, streams broadly include all channelized movement of …
Stream valleys, channels, and floodplains form complicated systems that evolve through time in response to changes in sediment supply, precipitation, land use, and rates of tectonic uplift affecting a drainage basin. Stream channels serve to convey flow during normal periods, whereas floodplains accommodate flow above the bankfull stage (floods) that occurs with frequencies inversely proportional …
Also known as twisted-winged parasites, strepsipterans are small insects which are internal parasites of other insects. Measuring between 0.02-0.16 in (0.5 and 4 mm) long, the males and females lead totally different lives. Males are free, winged insects—resembling some forms of beetles—and females are wingless, shapeless insects living as parasites. Strepsipterans live all over the …
Stress is mental or physical tension brought about by internal or external pressures. Researchers have found significant biochemical changes that take place in the body during stress. Exaggerated, prolonged, or genetic tendencies to stress cause destructive changes which lower the body's immune system response and can lead to a variety of diseases and disorders. These include depression, ca…
Environmental stress refers to physical, chemical, and biological constraints on the productivity of species and on the development of ecosystems. When the exposure to environmental stressors increases or decreases in intensity, ecological responses result. Stressors can be natural environmental factors, or they may result from the activities of humans. Some environmental stressors exert a relativ…
String theory (also termed "superstring" theory) is a mathematical attempt to describe all fundamental forces and particles as manifestations of a single, underlying entity, the "string." String theory's predictions are consistent with all known experimental data, and it is felt by some physicists to be a candidate for the long-sought "theory of every thin…
A stroke, also called a cerebral vascular accident or CVA, is a sudden, often crippling disturbance in blood circulation in the brain. Interruption in blood circulation may be the result of a burst artery or of an artery that has become closed off because a blood clot has lodged in it. Blood circulation to the area of the brain served by that artery stops at the point of disturbance, and the brain…
A stromatolite is a preserved structure in sedimentary rock that is a series of thin layers of sediment. These layers formed when a colony of algae trapped loose sediment particles. Stromatolites occur in rocks that range in age from very recent to more than 3.5 billion years old. Ancient stromatolites are the oldest evidence of life that is visible without a microscope. They are also the most com…
Structuralism was both an intellectual movement with wide ramifications in the twentieth century and an attempt to provide scientific status to the knowledge of language, culture, and society. Structuralism originated in the work of Ferdinand de Saussure (1857–1913), a Swiss linguist whose lectures, when published by his students in 1916 (Course in General Linguistics), launched the new sch…
Structuralism in anthropology is inextricably linked with its founder, Claude Lévi-Strauss. His principal contributions have been in the field of kinship and in the analysis of symbolism, particularly of myths. The characteristic approach of structuralist analysis is to categorize systems, not in terms of the composition or content of their component elements, but in terms of the structure of…
Sturgeons are large shark-like fish, with a heterocercal tail like that of a shark and a small ventral mouth behind an extended snout. The mouth has long barbells used for feeding on small animals on the bottom. Sturgeons feed on aquatic insects, snails, crayfish, small clams, and small fish. Sturgeons have a cartilaginous skeleton with bony plates instead of scales in their skin which cover the s…
Subatomic particles are particles that are smaller than an atom. Early in the twentieth century, electrons, protons, and neutrons were thought to be the only subatomic particles; these were also thought to be elementary (i.e., incapable An electronic display of the decay of an upsilon, a particle made of a bottom quark and an antiquark, in the CLEO detector at the CESR collider at Cornell Uni…
Subjectivism's natural antonym is objectivism, and various species of subjectivism have been developed as alternatives to objectivism of various sorts. One can be a subjectivist about a variety of things—ethics, aesthetics, even science. Many of these topics are covered in related entries, however, and the emphasis here will be on subjectivism with respect to ethics in modern and con…
The first known treatise on submarines was written in 1578. Published by William Bourne in his Inventions or Devices, the document describes a ship with two hulls, the outer made of wood. While no record exists concerning its manufacture, the ship, according to Bourne, could be submerged or raised by taking in or expelling water from between the double hulls. The first known submarine was built by…
Making inferences about the nature and structure of buried rock bodies, without access to them, is called subsurface detection. Using geophysical techniques, we obtain data at the surface that characterize the feature buried below. Then we construct models of the feature, trying to invent combinations of reasonable rock bodies which are consistent with all of the observations. Finally, using intui…
Suckers are cylindrical fish with a downward-pointing suckering mouth in the family Catostomidae, which is in the large suborder Cyprinoidea, which also includes minnows, carps, and loaches. Most species in the sucker family occur in the Americas, over a range that extends from the boreal forest of North America through much of Central America. A few other species occur in eastern Siberia, and the…
Sufism is the English rendering of the Arabic word tasawwuf, which derives from suf, meaning "wool." Tasawwuf in early Islamic history refers to the attitude of people who used to wear a white woolen garment as a sign of renunciation of worldly possessions. To be properly understood, the emergence of Sufism must be situated in the context of Islamic expansion. During the first and se…
The possibility of beet sugar was first discovered in 1605 when a French scientist found that the boiled root of garden beet (Beta vulgaris) yielded a syrup similar to that obtained from sugarcane (Saccharum officinarum). It was not until the mid-1700s, however, that the commercial potential of sugar beets was recognized. Once realized, sugar beets quickly became a major crop in Europe and elsewhe…
The sugarcane (Saccharum officinale) is a 12-26 ft tall (4-8 m), perennial, tropical grass (family Poaceae). The tough, semi-woody stems of sugarcane are up to 2 in (5 cm) in diameter, with leafy nodes and a moist internal Harvesting sugarcane. Photo Researchers, Inc. Reproduced by permission. pith containing 15-20% sucrose-sugar. The sugar concentration is highest just before the plant flo…
Sulfur is the non-metallic chemical element of atomic number 16. It has a symbol of S, an atomic weight of 32.07, and a specific gravity of 2.07 (rhombic form) or 1.96 (monoclimic form). Sulfur boils at 832.5°F (444.7°C) and consists of four stable isotopes of mass numbers 32 (95.0%), 33 (0.75%), 34 (4.2%) and 36 (0.015%). Sulfur atoms found in different locations have slightly diffe…
Sulfur is an important nutrient for organisms, being an key constituent of certain amino acids, proteins, and other biochemicals. Plants satisfy their nutritional needs for sulfur by assimilating simple mineral compounds from the environment. This mostly occurs as sulfate dissolved in soil water that is taken up by roots, or as gaseous sulfur dioxide that is absorbed by foliage in environments whe…
One drawback to this approach is that for every ton of sulfur dioxide that reacts, two tons of solid calcium sulfite are produced, and they must be disposed of. Sulfur dioxide is used widely to prevent dried fruits (especially apricots and peaches) from becoming discolored. Sulfur dioxide is a strong reducing agent, and prevents the formation of discolored oxidation products in the fruits. It…
One of the major uses of sulfuric acid is in the production of fertilizers. Phosphate rock is treated with sulfuric acid to produce water soluble phosphates, which are essential for plant growth and survival. It is also the acid used in car batteries. Automobile batteries contain lead, lead oxide, and sulfuric acid. These lead storage batteries are used because they can not only provide the electr…
The Sun is the star at the center of our solar system. It has a diameter of about 420,000 mi (700,000 km) and a surface temperature of 9,981°F (5,527°C). Its visible "surface" is actually a thin gas, as is the rest of its atmosphere and interior. The Sun shines as a result of thermonuclear fusion reactions in its core, and the energy produced by these reactions heats th…
Sunbirds are 105 species of small, lovely birds that make up the family Nectariniidae. Sunbirds occur in Africa, South and Southeast Asia, New Guinea, and Australia. They occupy a wide range of habitats, from forests and savannas to shrubby grasslands, and some agricultural habitats. Sunbirds range in body length from 4-9 in (9-22 cm). The wings are short and rounded, and the tail is quite long in…
Superstition has had different meanings in different cultures and epochs. One thing binding these meanings together is that they are usually negative—superstition is a concept defined principally by its self-declared opponents. A second is that superstition is defined as the opposite of something praiseworthy—usually true religion or true science. The word superstition itself origina…
Surface tension is the result of the cohesive forces that attract water molecules to one another. This surface force keeps objects which are more dense than water (meaning they should not float) from sinking into it. The surface tension of water makes it puddle on the ground and keeps it in a droplet shape when it falls. If you use a table fork to carefully place a paper clip on the surface of som…
Surveying is the apportionment of land by measuring and mapping. It is employed to determine boundaries and property lines, and to plan construction projects. The classic surveyors were the Romans. In order to forge an Empire that stretched from the Scottish border to the Persian Gulf, a large system of roads, bridges, aqueducts, and canals was built, binding the country economically and militaril…
The term "survival of the fittest" was first used by the Victorian naturalist Herbert Spencer as a metaphor to help explain natural selection, the central element of Charles Darwin's revolutionary theory of evolutionary change, first published in 1859 in his famous book, The Origin of Species by Means of Natural Selection. In this extremely influential and important book, Darw…
Sustainable development is the management of renewable resources for the good of the entire human and natural community. Built into this concept is an awareness of the animal and plant life of the surrounding environment, as well as inorganic components such as water and the atmosphere. The goal of sustainable development is to provide resources for the use of present populations without compromis…
Belonging to the order Synbranchiformes, swamp eels are very slim fish with elongated bodies and reduced fins. Their gill system, which is very small, is linked to other organs to help them breathe air. Swamp eels live in tropical and subtropical habitats. They usually are found in stagnant fresh or brackish water; only one species lives in the sea. These fish are found in Central and South Americ…
Swans are large birds in the waterfowl family, Anatidae, which also includes ducks and geese. There are seven species of swans, occurring on all continents except Antarctica. Three species of swan, the mute swan (Cygnus olor), the tundra swan (C. colombianus), and the trumpeter swan (C. buccinator) breed regularly in North America. Swans have a very long neck, and all North American species have a…
The sweet gale or bayberry family (Myricaceae) is made up of about 50 species of shrubs and trees. Minor economic uses of some species involve the extraction of a fragrant wax from their fruits and cultivation as ornamental shrubs. The foliage of plants in the Myricaceae can be deciduous or evergreen, and the leaves are commonly fragrant when crushed. The flowers are small and occur in catkin-like…
The sweet potato (Ipomoea batatas) is a creeping, vine-like plant that is cultivated in tropical climates for its starchy, nutritious tubers. The sweet potato is in the morning glory family (Convolvulaceae). The sweet potato is sometimes referred to as a yam, but it is quite different from the true yam (Dioscorea batatas), which is another species of tropical root-crop. The sweet potato is a peren…
Swifts are the fastest fliers of all of the small birds, reaching speeds of 172-218 mph (275-349 kph), although 35-80 mph (56-128 kph) is more common. They belong to the family Apodidae, a name meaning "without feet" and a reference to the fact that a swift in flight appears to have no legs or feet. Indeed, the legs of swifts are small and weak so that a swift that lands on the groun…