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Strata (novel)
''Strata'' is a 1981 science fiction comedy novel by Terry Pratchett. It is one of Pratchett's first novels and one of the few purely science fiction novels he wrote, along with ''The Dark Side of the Sun'' and ''The Nome Trilogy''. Although it takes place in a different fictional universe and is more science fiction than fantasy, it could be said to be a kind of precursor to the ''Discworld'' novels, as it also features a flat Earth similar to the Discworld. It has been called a "preconsideration" of Discworld, though the plot and characters are modelled on (or parodies of) the novel ''Ringworld'' by Larry Niven. Plot summary Kin Arad is a human planetary engineer working for “the Company”, a human organisation that manufactures habitable planets using techniques and equipment salvaged from an extinct alien race, the “Spindle Kings”, who excelled at terraforming. The express purpose of the Company’s planet-manufacturing business is to create dispersed branches of hu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terry Pratchett
Sir Terence David John Pratchett (28 April 1948 – 12 March 2015) was an English humourist, satirist, and author of fantasy novels, especially comical works. He is best known for his ''Discworld'' series of 41 novels. Pratchett's first novel, ''The Carpet People'', was published in 1971. The first ''Discworld'' novel, ''The Colour of Magic'', was published in 1983, after which Pratchett wrote an average of two books a year. The final ''Discworld'' novel, ''The Shepherd's Crown'', was published in August 2015, five months after his death. With more than 85 million books sold worldwide in 37 languages, Pratchett was the UK's best-selling author of the 1990s. He was appointed Officer of the Order of the British Empire (OBE) in 1998 and was knighted for services to literature in the 2009 New Year Honours. In 2001 he won the annual Carnegie Medal for ''The Amazing Maurice and his Educated Rodents'', the first ''Discworld'' book marketed for children. He received the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogeneity And Heterogeneity
Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, size, weight, height, distribution, texture, language, income, disease, temperature, radioactivity, architectural design, etc.); one that is heterogeneous is distinctly nonuniform in at least one of these qualities. Heterogeneous Mixtures, in chemistry, is where certain elements are unwillingly combined and, when given the option, will separate. Etymology and spelling The words ''homogeneous'' and ''heterogeneous'' come from Medieval Latin ''homogeneus'' and ''heterogeneus'', from Ancient Greek ὁμογενής (''homogenēs'') and ἑτερογενής (''heterogenēs''), from ὁμός (''homos'', “same”) and ἕτερος (''heteros'', “other, another, different”) respectively, followed by γένος (''genos'', “kind”); - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Suit
A space suit or spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, vacuum and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extravehicular activity (EVA), work done outside spacecraft. Space suits have been worn for such work in Earth orbit, on the surface of the Moon, and en route back to Earth from the Moon. Modern space suits augment the basic pressure garment with a complex system of equipment and environmental systems designed to keep the wearer comfortable, and to minimize the effort required to bend the limbs, resisting a soft pressure garment's natural tendency to stiffen against the vacuum. A self-contained oxygen supply and environmental control system is frequently employed to allow complete freedom of movement, independent of the spacecraft. Three types of space suits exist for different purposes: IVA (intravehicular activity) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geocentric Model
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, and planets all orbit Earth. The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt. Two observations supported the idea that Earth was the center of the Universe: * First, from anywhere on Earth, the Sun appears to revolve around Earth once per day. While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through the geographic poles of Earth. * Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Old World
The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by their inhabitants as comprising the entire world, with the "New World", a term for the newly encountered lands of the Western Hemisphere, particularly the Americas. Etymology In the context of archaeology and world history, the term "Old World" includes those parts of the world which were in (indirect) cultural contact from the Bronze Age onwards, resulting in the parallel development of the early civilizations, mostly in the temperate zone between roughly the 45th and 25th parallels north, in the area of the Mediterranean, including North Africa. It also included Mesopotamia, the Persian plateau, the Indian subcontinent, China, and parts of Sub-Saharan Africa. These regions were connected via the Silk Road trade route, and they have a p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle (carrier rocket). On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface without having gained sufficient energy or velocity to make a full Earth orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myocardial Infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat or feeling tired. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause heart failure, an irregular heartbeat, cardiogenic shock or cardiac arrest. Most MIs occur due to coronary artery disease. Risk factors include high blood pressure, smoking, diabetes, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relativistic Rocket
Relativistic rocket means any spacecraft that travels close enough to light speed for relativistic effects to become significant. The meaning of "significant" is a matter of context, but often a threshold velocity of 30% to 50% of the speed of light (0.3''c'' to 0.5''c'') is used. At 30% c, the difference between relativistic mass and rest mass is only about 5%, while at 50% it is 15%, (at 0.75''c'' the difference is over 50%); so above such speeds special relativity is needed to accurately describe motion, while below this range Newtonian physics and the Tsiolkovsky rocket equation usually give sufficient accuracy. In this context, a rocket is defined as an object carrying all of its reaction mass, energy, and engines with it. No known technology can bring a rocket to relativistic speed. Relativistic rockets require huge advances in spacecraft propulsion, energy storage, and engine efficiency which may or may not ever be possible. Nuclear pulse propulsion could theoretically reach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
