Earths artificial

Singer has received numerous awards for his research, including a Special Commendation from the White House for achievements in artificial earth satellites, a U.S. Department of Commerce Gold Medal Award, and the first Science Medal from the British Interplanetary Society. He has served on state and federal advisory panels, including five years as vice chairman of the National Advisory Committee on Oceans and Atmospheres. He frequently testifies before Congress. 

Explorer series of artificial earth satellites 6 E359... 

The most interesting feature of the decomposition flames is their analogy to flames of the solid monopropellants. In fact, many of these substances, which are ordinarily liquids, may support a flame directly from the liquid phase without auxiliary vaporization of the liquid. In this case, the flame supplies the necessary heat of vaporization or decomposition in exact analogy to the solid propellant flame.8 The principal usefulness of a decomposition flame is found in the simplicity of design and control of a rocket powered by such a flame, even though more powerful fuels are readily available. A recent example, which has been featured in the news, is the hydrogen peroxide attitude-control rocket used in the artificial earth satellites of the U.S.A. 

The average height of the first artificial earth satellites is still well within the frame of the drawing. 

The first silicon solar battery was developed in 1954 at the American company Bell. Due to its high production costs, which could not compete with production costs for electric energy produced in conventional thermal power plants, this new device at first drew little attention from the scientific community. In 1954 began the era of artificial earth satelites. The first satelites were equipped with electrochemical batteries, which allowed only for a limited operational time. Soon it was realized that semiconductor solar batteries are the only alternative for the power supply of satelites (and later spaceships) with an extended operational lifetime, and extended research and development (R D) work was started in this field. In 1958 the first sattelite with a silicon solar battery Vanguard 1 was launched. The conversion efficiency of its solar battery was 10%. The battery remained operable for about 8 years. 

Most of NASA s anticorrosion efforts are concentrated on the launch site, where the high temperamres of the launch and the humid coastal atmosphere encourage corrosion. However, corrosion is a concern in other aspects of the space program, as well. Batteries used in the International Space Station (ISS) must be prevented from corroding in the ISS s artificial, earth-like atmosphere NASA s mission of planetary exploration requires that scientists know the corrosivity of a planet s atmosphere before a craft can land safely. Venus, for example, has a highly corrosive atmosphere that makes lander design very difficult. 

As we have already pointed out, comets may have been very important for the Earth and terrestrial planets because they deposited during collisions considerable amounts of water on the surfaces of these planets. On March 18, 1988 dark features on nine consecutive photographs were observed on Venus. Since film defects and other interferences (e.g. from an artificial Earth satellite or interplanetary object) can be ruled out, it is highly probable that this event was an impact of a small cometary like object that took place on the upper haze layer of the dense Venusian atmosphere. Because such an object consists mainly of water, evaporation of H2SO4 particles occurred which decreased the albedo at the point of entrance and therefore a dark feature appeared (Kolovos, Varvoglis and Pylarinou, 1991 [189]). 

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

Silicon [7440-21-3] Si, from the Latin silex, silicis for flint, is the fourteenth element of the Periodic Table, has atomic wt 28.083, and a room temperature density of 2.3 gm /cm. SiUcon is britde, has a gray, metallic luster, and melts at 1412°C. In 1787 Lavoisier suggested that siUca (qv), of which flint is one form, was the oxide of an unknown element. Gay-Lussac and Thenard apparently produced elemental siUcon in 1811 by reducing siUcon tetrafluoride with potassium but did not recognize it as an element. In 1817 BerzeHus reported evidence of siUcon occurring as a precipitate in cast iron. Elemental siUcon does not occur in nature. As a constituent of various minerals, eg, siUca and siUcates such as the feldspars and kaolins, however, siUcon comprises about 28% of the earth s cmst. There are three stable isotopes that occur naturally and several that can be prepared artificially and are radioactive (Table 1) (1). 

This book presents a unified treatment of the chemistry of the elements. At present 112 elements are known, though not all occur in nature of the 92 elements from hydrogen to uranium all except technetium and promethium are found on earth and technetium has been detected in some stars. To these elements a further 20 have been added by artificial nuclear syntheses in the laboratory. Why are there only 90 elements in nature Why do they have their observed abundances and why do their individual isotopes occur with the particular relative abundances observed Indeed, we must also ask to what extent these isotopic abundances commonly vary in nature, thus causing variability in atomic weights and possibly jeopardizing the classical means of determining chemical composition and structure by chemical analysis. 

Nucleosynthesis is the formation of elements. Hydrogen and helium were produced in the Big Bang all other elements are descended from these two, as a result of nuclear reactions taking place either in stars or in space. Some elements—among them technetium and promethium—are found in only trace amounts on Earth. Although these elements were made in stars, their short lifetimes did not allow them to survive long enough to contribute to the formation of our planet. However, nuclides that are too unstable to be found on Earth can be made by artificial techniques, and scientists have added about 2200 different nuclides to the 300 or so that occur naturally. 

All isotopes of technetium (Z = 43) are unstable, so the element is not found an Avhere in the Earth s crust. Its absence left a gap in the periodic table below manganese. The search for this missing element occupied researchers for many years. It was not until 1937 that the first samples of technetium were prepared in a nuclear reactor. In fact, technetium was the first element to be made artificially in the laboratory. To date, 21 radioactive isotopes of technetium have been identified, some of them requiring millions of years to decompose. 

Different minerals contain different metal cations to balance the -4 charge on the orthosilicate ion. Examples Include calcium silicate (Ca2 Si04), an important ingredient in cement, and zircon (ZrSi04), which is often sold as artificial diamond. One of the most prevalent minerals in the Earth s mantle is olivine, Af2(Si04), in which M is one or two of the abundant metal cations, Fe -, Mg -, and Mn +. 

The silver gray metal can be cut with a knife, although it only melts at 1545 °C (for comparison, iron 1538 °C). It is the rarest of the "rare earths", but is nevertheless more abundant than iodine, mercury, and silver. Thulium has few applications, especially because it is relatively expensive. The element occurs naturally as a single isotope, namely 169Tm (compare bismuth). The artificial, radioactive 170Tm is a transportable source of X-rays for testing materials. Occasionally used in laser optics and microwave technology. 

Radioisotopes may occur in the earth naturally as primordial radioisotopes, formed when the planet was created, or be produced by natural or artificial processes. Most fast decaying primordial radioisotopes have long disappeared from the planet since the earth originated about 4.5 billion years ago, such isotopes have decayed and reached a final, stable form. The relatively few primordial radioisotopes still extant in the earth today, therefore, decay very slowly. Among these are potassium-40 and some isotopes of uranium, such as uranium-235 and uranium-238, which are of use for dating archaeologically related minerals and rocks (see Textboxes 15 and 16). 

Some radioisotopes are continuously being produced by the bombardment of atoms on the surface of the earth or in its atmosphere with extraterrestrial particles or radiation. One of these is carbon-14, also known as radiocarbon, which is widely used for dating archaeological materials (see Textbox 55). Many radioisotopes that are not primordial or are not created by natural processes are now produced artificially using specialized equipment many of the "artificial" isotopes are of use for probing and analyzing materials. 

Pottery, one of the earliest human-made ceramic materials, is actually an artificial form of stone, made by combining the four basic elements recognized by the ancient Greeks earth (clay), water, air, and fire. In fact pottery is made from a circumstantial or deliberately prepared mixture of clay, other solid materials known by the generic name of fillers, and water. When a wet mixture of clay and fillers is formed into a desired shape, then dried and finally heated to high temperature (above 600°C), it becomes consolidated... 

Photochemical fixation of carbon dioxide is a function of green plants and some bacteria in nature in the form of photosynthesis. All living organisms on the Earth are indebted directly or indirectly to photosynthesis. Thus, many attempts have been made to simulate the photosynthetic system and make artificial systems, although to date very little success has been achieved. 

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