nervous system: Dendrites: …provided by specialized structures called dendritic spines, which, by providing discrete regions for the reception of nerve impulses, isolate changes in electrical current from the main dendritic trunk.

Pott disease, disease caused by infection of the spinal column, or vertebral column, by the tuberculosis bacillus, Mycobacterium tuberculosis. Pott disease is characterized by softening and collapse of the vertebrae, often resulting in a hunchback curvature of the spine. The condition is named

swift: …soft-tailed swifts, and Chaeturinae, or spine-tailed swifts. Almost worldwide in distribution, swifts are absent only from polar regions, southern Chile and Argentina, New Zealand, and most of Australia.

John Cena: WWE: …signature moves included the “spinebuster,” in which he would pick up his opponent, spin him around, and drop him. In the “attitude adjustment,” Cena would pick up his opponent and flip him headfirst onto his back.

rabbitfish, any of about 25 species of fishes constituting the family Siganidae (order Perciformes), found in shallow tropical marine waters from the Red Sea to Tahiti. They live in areas near shore or around reefs and graze on algae and other plants. Most rabbitfish are olive or brown in colour

spinel, mineral composed of magnesium aluminum oxide (MgAl2O4) or any member of a group of rock-forming minerals, all of which are metal oxides with the general composition AB2O4, in which A may be magnesium, iron, zinc, manganese, or nickel; B may be aluminum, chromium, or iron; and O is oxygen.

spinel: The spinel group is divided into three immiscible series: the spinel (aluminum-spinel) series, in which B is aluminum; the chromite (chromium-spinel) series, in which B is chromium; and the magnetite (iron-spinel) series, in which B is iron.

spinel: …into three immiscible series: the spinel (aluminum-spinel) series, in which B is aluminum; the chromite (chromium-spinel) series, in which B is chromium; and the magnetite (iron-spinel) series, in which B is iron.

crystal: Ferrimagnetic materials: The crystal structure is called spinel, which is the mineral name for MgAl2O4. Ferrites are electrical insulators with magnetic ordering. Their insulating quality makes them useful as magnetic cores. When metallic ferromagnetic materials are exposed to alternating magnetic fields, significant heating losses occur from eddy currents. Ferrite magnets greatly reduce…

history of Europe: Ever closer union?: …Resistance, led by, among others, Altiero Spinelli. One of the most stubborn of Mussolini’s political prisoners, he was freed in 1943 from confinement on an island off the coast between Rome and Naples. Admiring what he called “the clean, precise thinking of the English federalists,” he echoed it in the…

Spinello Aretino was a late Gothic Italian painter noteworthy for his vigorous narrative sense. His style anticipates the realistic painting of the early Renaissance of the 15th century. Early in his career he came under the influence of Orcagna and Nardo di Cione, whose style shows in his first

Spinello Aretino was a late Gothic Italian painter noteworthy for his vigorous narrative sense. His style anticipates the realistic painting of the early Renaissance of the 15th century. Early in his career he came under the influence of Orcagna and Nardo di Cione, whose style shows in his first

spinet, small form of the harpsichord, generally wing-shaped, with a single set of strings placed at an oblique angle to the keyboard. The wing-shaped spinet may have originated in Italy during the 16th century; later it became known in France and England. Spinets were popular substitutes for the

upright piano: …heights; the shortest are called spinets or consoles, and these are generally considered to have an inferior tone resulting from the shortness of their strings and their relatively small soundboards. The larger upright pianos were quite popular in the later 19th and early 20th centuries. The action (hammer and damper…

Spingarn Medal, gold medal awarded annually by the National Association for the Advancement of Colored People (NAACP) since 1915 to honour “the man or woman of African descent and American citizenship who shall have made the highest achievement during the preceding year or years in any honorable

Spingarn Medal: …29, 1914, is named for Joel Elias Spingarn, a white writer, literary critic, educator, and civil rights activist who served as chairman of the Board of Directors (1913–19), treasurer (1919–30), and president (1930–39) of the NAACP.

branchiopod: Size range and diversity of structure: In the Spinicaudata, however, the number of paired trunk segments varies among its members from 12 up to 32 in some species. A carapace is present in the infraorders Ctenopoda and Anomopoda, but it encloses only the trunk, leaving the head free. In the infraorders Onychopoda and…

Western Australia: Plant and animal life: Spinifex grass is ubiquitous, as is generally the case throughout the portion of the state that lies north of the Tropic of Capricorn. The deserts of the state’s central and eastern regions are partly vegetated by spinifex and various eucalypts; some mulga trees grow in…

baseball: Baseball and the arts: Both Alfred H. Spink’s The National Game (1910) and A.G. Spalding’s America’s National Game (1911), generally regarded as the first attempts at writing a standard history of baseball, cite “Casey at the Bat” as the best baseball poem ever written. Spalding goes so far as to…

Leon Spinks was an American boxer who won an Olympic gold medal in 1976 and was the world heavyweight champion in 1978. He and Michael Spinks became the first brothers to win gold medals in the same sport at the same Olympics and, as professional champions, the first brothers in boxing history to

Michael Spinks is an American former boxer who was both the light heavyweight (1981–85) and heavyweight (1985–88) world champion and an Olympic gold medalist (1976). He and Leon Spinks became the first brothers to win gold medals in the same sport at the same Olympics and the first brothers to win

reproduction: Life cycles of animals: …and an adult stage (imago). One remarkable aspect of this development is that, during the transition from caterpillar to adult, most of the caterpillar tissue disintegrates and is used as food, thereby providing energy for the next stage of development, which begins when certain small structures (imaginal disks) in…

teetotum, form of top having usually 4, 6, 8, or 12 sides marked with distinctive symbols. A teetotum is used for playing games, mostly of the gambling variety, and serves in place of dice. The hexagonal (six-sided) teetotum was known to the ancient Greeks and Romans. A common gambling game with a

carcharhinid: …somewhat larger large blacktip, or spinner shark (C. brevipinna). One small species, C. melanopterus, is found in shallow Indo-Pacific waters. The International Union for Conservation of Nature and Natural Resources (IUCN) lists each of these as vulnerable species.

sericulture: …the insect emerge from the spinneret, a single exit tube in the head, hardening upon exposure to air and forming twin filaments composed of fibroin, a protein material. A second pair of glands secretes sericin, a gummy substance that cements the two filaments together. Because an emerging moth would break…

spinneret, in the spinning of man-made fibre, small, thimble-shaped, metal nozzle having fine holes through which a spinning solution is forced to form a filament. The viscous or syrupy solution, prepared by melting or chemically dissolving raw material, emerges from the spinneret as long fibres

spinneret, in the spinning of man-made fibre, small, thimble-shaped, metal nozzle having fine holes through which a spinning solution is forced to form a filament. The viscous or syrupy solution, prepared by melting or chemically dissolving raw material, emerges from the spinneret as long fibres

The Spinners are an American rhythm and blues (R&B) vocal group that became one of the greatest soul groups of the 1970s with a string of hit songs, including “It’s a Shame,” “I’ll Be Around,” “Could It Be I’m Falling in Love,” and “Games People Play.” Formed in the suburbs of Detroit, the Spinners

Diego Velázquez: Last years of Diego Velázquez: The Spinners; or, The Fable of Arachne (1655–60), a genre scene in a tapestry factory, is at the same time an illustration of the ancient Greek fable of the spinning contest between Pallas Athena and Arachne. Here the mythological subject—like the religious scene in some…

Diego Velázquez: Last years of Diego Velázquez: The Spinners; or, The Fable of Arachne (1655–60), a genre scene in a tapestry factory, is at the same time an illustration of the ancient Greek fable of the spinning contest between Pallas Athena and Arachne. Here the mythological subject—like the religious scene in some…

Big Bird: …created by actor and puppeteer Caroll Spinney, who at the program’s inception and until his retirement in 2018 was the sole performer in the Big Bird role.

fishing: Methods: spin casting differ essentially in the type of reel, the rod length, and the strength of the line used. Bait casting usually employs a reel with heavier line, often in the 10- to 20-pound (4,500- to 9,000-gram) test range. Most spinning reels are usually spooled…

spinning, In metalwork, a technique for making hollow metal utensils and artifacts. Developed in the 19th century, the method can be used for most metals. A metal disk is set on a lathe behind an appropriately shaped metal or wooden chuck; while the lathe is rotating, the metal is pressed onto the

spinning, in textiles, process of drawing out fibres from a mass and twisting them together to form a continuous thread or yarn. In man-made fibre production the name is applied to the extrusion of a solution to form a fibre, a process similar to the method by which silkworms and similar insect

drawing frame, Machine for drawing, twisting, and winding yarn. Invented in the 1730s by Lewis Paul and John Wyatt, the spinning machine operated by drawing cotton or wool through pairs of successively faster rollers. It was eventually superseded by R. Arkwright’s water

spinning jenny, early multiple-spindle machine for spinning wool or cotton. The hand-powered spinning jenny was patented by James Hargreaves in 1770. The development of the spinning wheel into the spinning jenny was a significant factor in the industrialization of the textile industry, though its

spinning mule, Multiple-spindle spinning machine invented by Samuel Crompton (1779), which permitted large-scale manufacture of high-quality thread for the textile industry. Crompton’s machine made it possible for a single operator to work more than 1,000 spindles simultaneously, and was capable of

fishing: Early history: …patent on the fixed-spool, or spinning, reel. In this kind of reel, the spool permanently faces toward the tip of the rod, and the line peels off during the cast. The increased casting distance afforded by the spinning reel—and facilitated by new lines with smaller diameters—revolutionized freshwater fishing.

top, a toy having a body of conical, circular, or oval shape, often hollow, with a point or peg on which it turns or is made to whirl. If given a knock, a spinning top will go around in a circle at a slant; if spun with a slant at the start, it will quickly stand upright until halted by friction.

man-made fibre: Solution spinning: …a heated column called the spinning tower, where the solvent evaporates, leaving a fibre. The emerging fibre may contain solvent that may have to be removed by further heating or by washing. This operation is followed by stretching, application of finish, and either take-up on a spindle or cutting to…

Blood, Sweat & Tears: David Clayton-Thomas, BS&T’s chart-topping success, and beyond: Three hit singles—“Spinning Wheel,” “And When I Die,” and “You’ve Made Me So Very Happy”—all of which reached number two on the Billboard Hot 100 chart, helped the group achieve worldwide recognition, and the U.S. State Department asked the band to do a goodwill tour abroad.

spinning wheel, early machine for turning fibre into thread or yarn, which was then woven into cloth on a loom. The spinning wheel was probably invented in India, though its origins are obscure. It reached Europe via the Middle East in the European Middle Ages. It replaced the earlier method of

nervous system disease: Spinocerebellar degenerations: Spinocerebellar degenerations are genetically determined conditions characterized by dysfunction of the dorsal columns or of the corticospinal and spinocerebellar tracts of the spinal cord. These conditions usually appear in the first 20 years of life and cause position sensation, gait, limb power, balance, and coordination…

human nervous system: Spinocerebellar tracts: Impulses from stretch receptors are carried by fibers that synapse upon cells in deep laminae of the dorsal horn or in lamina VII. The posterior spinocerebellar tract arises from the dorsal nucleus of Clarke and ascends peripherally in the dorsal part of the…

coloration: Naphthoquinones: These are the echinochromes and spinochromes, so named because they are conspicuous in tissues and in the calcareous tests (shells) of echinoids, or sea urchins.

industrial glass: Phase separation: …the nucleated droplet and the spinodal; the microstructures produced by these two mechanisms, as revealed by electron microscopy, are shown in Figure 4. In Figure 4A the interface between the droplets and the matrix is sharp, owing to a sharp change in composition. With time the droplets increase in size…

Spinola Family, one of the noble families that dominated the history of Genoa, Italy, during the city-state’s great period, from the 12th to the 14th century. They were descended from a younger son of Ido, the viscount who ruled Genoa in the 10th century as the representative of its feudal lord,

Ambrogio di Filippo Spinola, marquis de los Balbases served Spain as a military commander and was considered one of the ablest soldiers of his time. Though he won fame in the wars against the Dutch Republic in the early 17th century, he was ultimately unable to break Dutch military power. Spinola

Doria Family: …Oberto Doria (died 1295) and Oberto Spinola, member of another great Genoese family, inaugurated a series of two-man governments headed by their families, with dictatorial powers as captains of the people. Ruling for 15 years during what has been termed the golden age of the Genoese medieval commune, Oberto Doria…

Élie-Joseph Cartan: …year later he discovered the spinors, complex vectors that are used to transform three-dimensional rotations into two-dimensional representations.

pain: Physiology of pain: …sensation of pain, and the spinoreticular tract is thought to effect the arousal and emotional aspects of pain.

Spinosaurus, genus of theropod dinosaurs belonging to the family Spinosauridae, known from incomplete North African fossils that date to Cenomanian times (roughly 100 to 94 million years ago). Spinosaurus, or “spined reptile,” was named for its “sail back” feature, created by tall vertebral spines.

human nervous system: Spinothalamic tracts: Fibers concerned with pain, thermal sense, and light touch enter the lateral-root entry zone and then ascend or descend near the periphery of the spinal cord before entering superficial laminae of the dorsal horn—largely parts of laminae I, IV, and V. Cells in…

Norman Taurog: Elvis movies: …Presley musicals completed Taurog’s career: Spinout (1966), Double Trouble (1967), Speedway (1968), and Live a Little, Love a Little (1968).

The Spinoza of Market Street, title story of a short-story collection by Isaac Bashevis Singer, published in Yiddish in 1944 as “Der Spinozist.” The collection was published in English in 1961. The story is set in Warsaw on the brink of World War I. There Dr. Nahum Fischelson lives a meagre,

Benedict de Spinoza was a Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

Benedict de Spinoza was a Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

Benedict de Spinoza was a Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

The Spinoza of Market Street, title story of a short-story collection by Isaac Bashevis Singer, published in Yiddish in 1944 as “Der Spinozist.” The collection was published in English in 1961. The story is set in Warsaw on the brink of World War I. There Dr. Nahum Fischelson lives a meagre,

annelid: Annotated classification: …on sponges; small; single genus, Spinther. Order Phyllodocida Free-moving; a large group characterized by a protrusible proboscis that may or may not be armed with chitinous jaws, teeth, or papillae; prostomium with 1 to 5 antennae, with palpi, and with 0 to 3 pairs of eyes; parapodia well developed into…

annelid: Annotated classification: Order Spintherida Body oval; median antenna on prostomium; pharynx retractable; dorsal surface with membranous ridges; ventral setae strongly curved; found on sponges; small; single genus, Spinther. Order Phyllodocida Free-moving; a large group characterized by a protrusible proboscis that may or may not be armed with

nanotechnology: Spintronics: Spintronics refers to electronic devices that perform logic operations based on not just the electrical charge of carriers but also their spin. For example, information could be transported or stored through the spin-up or spin-down states of electrons. This is a new area of…

sea star: Spiny sea stars, order Spinulosa, typically have clusters of spines; they have suction-tube feet but rarely pedicellariae. A common example in stony-bottomed European waters is the gibbous starlet (Asterina gibbosa). The sea bat (Patiria miniata) usually has webbed arms; it is common from Alaska to…

goldfinch: The 10-cm (4-inch) dark-backed goldfinch (C. psaltria) ranges from the western U.S. (where it is called lesser goldfinch) to Peru.

American goldfinch, (Spinus tristis), small acrobatic songbird native to North America. Males are known for their distinctive, bright yellow plumage that contrasts with their black tail, cap, and wings. They are also known for their call, a vocalization that sounds like “po-ta-to-chip” or

pigweed: …stems rising at the tips; spiny pigweed, or spiny amaranth (A. spinosus), has spines at the base of the leafstalks; and rough pigweed, or redroot (A. retroflexus), is a stout plant up to 3 metres (about 10 feet) tall.

echidna, (family Tachyglossidae), any of four species of peculiar egg-laying mammals from Australia, Tasmania, and New Guinea that eat and breathe through a bald tubular beak protruding from a dome-shaped body covered in spines. Echidnas have beady eyes and mere slits for ears, and at the end of

dogfish: The spiny dogfishes of the family Squalidae possess a sharp spine in front of each of their two dorsal fins. The most widely known species is Squalus acanthias, called the spiny dogfish, spurdog, or skittle dog. It is abundant along northern Atlantic and Pacific coasts; a…

ostariophysan: Annotated classification: Family Scoloplacidae (spiny dwarf catfishes) Body with 2 bilateral series of teethlike-bearing plates, 1 midventral series of plates. Maximum length about 20 mm (less than 1 inch). South America. 1 genus, 4 species. Family Astroblepidae (climbing catfishes) Mouth and fins modified for adhesion to rocks in mountain…

spiny eel, any of two groups of fishes, those of the freshwater family Mastacembelidae (order Perciformes) and of the deep-sea family Notacanthidae (order Notacanthiformes). Members of both groups are elongated and eel-like but are not related to true eels. The freshwater spiny eels comprise about

brush-footed butterfly: The larvae, often known as spiny elm caterpillars, are gregarious in habit and feed principally on elm, willow, and poplar foliage.

scorpaeniform: Annotated classification: Family Hoplichthyidae (ghost flatheads or spiny flatheads) Small fishes with very depressed bodies. Scaleless; body with bony plates. Head with heavy spiny ridges. Vertebrae 26. Size to 43 cm (17 inches). Found in moderately deep water in Indo-Pacific region. 1 genus, Hoplichthys, with about 11 species. Family…

lobster: Unlike true lobsters, spiny lobsters (Palinuridae), so called because of their very spiny bodies, do not have large claws. People eat the abdomen, which is marketed as lobster tail. The antennae are long. Most species live in tropical waters; Palinurus elephas, however, is found from Great Britain to…

pigweed: …stems rising at the tips; spiny pigweed, or spiny amaranth (A. spinosus), has spines at the base of the leafstalks; and rough pigweed, or redroot (A. retroflexus), is a stout plant up to 3 metres (about 10 feet) tall.

pocket mouse: Natural history: The five species of spiny pocket mice (genus Liomys) are found in extreme southern Texas, but they live mostly in Mexico southward to Panama in semiarid brushy and rocky habitats. These pocket mice weigh 34 to 50 grams and have a body length of 10 to 14 cm and…

saltbush: canescens), and spiny saltbush (A. confertifolia).

sea star: Spiny sea stars, order Spinulosa, typically have clusters of spines; they have suction-tube feet but rarely pedicellariae. A common example in stony-bottomed European waters is the gibbous starlet (Asterina gibbosa). The sea bat (Patiria miniata) usually has webbed arms; it is common from Alaska to…

spiny shark, any of a group of more than 150 species of small extinct fishes traditionally classified in the class Acanthodii and considered by many paleontologists as the earliest known jawed vertebrates (or gnathostomes). Historically, spiny sharks were thought to make up a transitional group

human nervous system: Basal ganglia: Spiny striatal neurons are medium-size cells with radiating dendrites that are studded with spines. Axons of these cells project beyond the boundaries of the caudate nucleus and putamen. All nerves providing input to the caudate nucleus and the putamen terminate upon the dendritic spines of…

sea star: …cm across; the very common spiny sun star (Crossaster papposus) has as many as 15 arms. Cushion stars, of the circumboreal genus Pteraster, are plump five-rayed forms with raised tufts of spines and webbed, short, blunt arms.

Asian tree mouse: The Malabar spiny tree mouse (Platacanthomys lasiurus) lives only in the old-growth rainforests of southwestern India. Nocturnal and arboreal, it builds nests in tree cavities and eats fruits and nuts. The animal is named for its flat, grooved spines and bristles, which are tipped with white and…

Great Lakes: Plant and animal life: …the 1980s two nonindigenous creatures—the spiny water flea (a crustacean) and the zebra mussel (a mollusk)—gained access to the lakes and established large populations. Both have threatened the food web of native species, and the zebra mussel has become a nuisance by clogging water-intake pipes, covering spawning reefs, and fouling…

spiny-finned fish, any member of the superorder Acanthopterygii, including four orders of marine and freshwater fishes having fins with some spiny (as opposed to soft) rays—Atheriniformes, Beryciformes, Zeiformes, and Lampridiformes. The atheriniform is the best known of the spiny-finned group,

mouse: General features: At one extreme are the spiny-furred species in the subgenus Pyromys, whose upperparts and undersides are covered with flat, channeled spines nestled in soft underfur (juveniles are not spiny). At the other extreme are the shrew-mice from Sumatra (M. crociduroides) and Java (M. vulcani), whose soft, short, and dense coat…

spiny-headed worm, any animal of the invertebrate phylum Acanthocephala. A proboscis, or snout, which bears hooks, gives the group its name. There are about 1,150 recorded species, all of which parasitize vertebrates (usually fish) as adults and arthropods (usually insects or crustaceans) as

spiny-finned fish, any member of the superorder Acanthopterygii, including four orders of marine and freshwater fishes having fins with some spiny (as opposed to soft) rays—Atheriniformes, Beryciformes, Zeiformes, and Lampridiformes. The atheriniform is the best known of the spiny-finned group,

spiny-tailed lizard, (Uromastyx), any of more than a dozen species belonging to the lizard family Agamidae. Spiny-tailed lizards live in arid and semiarid habitats from northern Africa to India. They are limbed lizards with broad heads and stout bodies, and most adults grow up to about 25 to 30 cm

annelid: Annotated classification: …of genera: Chaetopterus (parchment worm), Spiochaetopterus. Order Magelonida Long, slender bodies divided into 2 regions; prostomium flattened with 2 long palpi arising from the ventral surface at the junction of the prostomium and next segment; capillary and hooded hooks; single genus, Magelona. Order

annelid: Annotated classification: Order Spionida Sedentary; at least 2 long feeding tentacles adapted for grasping and arising from prostomium; size, 0.5 to 25 cm; examples of genera: Spio, Polydora. Order Chaetopterida Two to 3 distinct body regions; prostomium with palpi; modified setae on segment 4; tube dweller; examples of

typography: Italy: The brothers Johann and Wendelin von Speyer (sometimes called da Spira and sometimes of Spire) opened the first press in Venice in 1469 and, until Johann died in 1470, had a one-year monopoly on all printing in that city. They used a clear and legible typeface that…

typography: Italy: Wendelin von Speyer (sometimes called da Spira and sometimes of Spire) opened the first press in Venice in 1469 and, until Johann died in 1470, had a one-year monopoly on all printing in that city. They used a clear and legible typeface that represented another…

spiracle, in arthropods, the small external opening of a trachea (respiratory tube) or a book lung (breathing organ with thin folds of membrane resembling book leaves). Spiracles are usually found on certain thoracic and abdominal segments. In elasmobranch and ganoid fishes a pair of spiracles,

spirea, (genus Spiraea), genus of nearly 100 species of flowering shrubs in the rose family (Rosaceae). Native to the north temperate zone, many spirea species are commonly cultivated for their pleasing growth habit and attractive flower clusters. Members of the genus Spiraea are hardy deciduous

Rosales: Evolution: …genus Spiraea, of the subfamily Spiraeoideae, is known from fossil fruits and leaves, and the related genus Physocarpus is represented in fossils dating to the middle of the Cenozoic Era. In the subfamily Maloideae, fruit and seed remains have been recognized from the genera Crataegus and Pyrus. Leaf fossils are…

rocket and missile system: Antitank and guided assault: The AT-6 Spiral, a Soviet version of TOW and Hellfire, became the principal antiarmour munition of Soviet attack helicopters.

Samuel L. Jackson: …following year he appeared in Spiral, an installment in the Saw horror film series.

spiral, plane curve that, in general, winds around a point while moving ever farther from the point. Many kinds of spirals are known, the first dating from the days of ancient Greece. The curves are observed in nature, and human beings have used them in machines and in ornament, notably

Norman Lewis: …was a founding member of Spiral, a group of black artists, including Hale Woodruff, Bearden, and Alston, who committed to the civil rights movement visually, through their art. From 1965 through 1971 he taught art at Harlem Youth in Action, an antipoverty organization. Lewis was active in the protest against…

aloe: Major species and uses: Spiral aloe (Aloe polyphylla) is a popular specimen for its compact geometric spiral of spiny leaves. Arabian aloe (A. rubroviolacea) has long blue-green leaves with red teeth and is planted outdoors in warm climates; the leaves turn red if exposed to full sun. Snake, or…

nebula: …galaxy’s mass, but within a spiral arm its mass fraction increases to about 20 percent. About 1 percent of the mass of the interstellar medium is in the form of “dust”—small solid particles that are efficient in absorbing and scattering radiation. Much of the rest of the mass within a…