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Radio Astronomy
RADIO ASTRONOMY is a subfield of astronomy that studies celestial objects at radio frequencies . The first detection of radio waves from an astronomical object was in 1932, when Karl Jansky at Bell Telephone Laboratories observed radiation coming from the Milky Way . Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies , as well as entirely new classes of objects, such as radio galaxies , quasars , pulsars , and masers . The discovery of the cosmic microwave background radiation , regarded as evidence for the Big Bang theory , was made through radio astronomy. Radio astronomy is conducted using large radio antennas referred to as radio telescopes , that are either used singularly, or with multiple linked telescopes utilizing the techniques of radio interferometry and aperture synthesis
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Oliver Lodge
SIR OLIVER JOSEPH LODGE, FRS (12 June 1851 – 22 August 1940) was a British physicist and writer involved in the development of, and holder of key patents for, radio . He identified electromagnetic radiation independent of Hertz ' proof and at his 1894 Royal Institution lectures ("The Work of Hertz and Some of His Successors"), Lodge demonstrated an early radio wave detector he named the "coherer ". In 1898 he was awarded the "syntonic" (or tuning) patent by the United States Patent Office. Lodge was Principal of the University of Birmingham from 1900 to 1920
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Ionosphere
The IONOSPHERE (/aɪˈɒnəˌsfɪər/ ) is a region of Earth's upper atmosphere , from about 60 km (37 mi) to 1,000 km (620 mi) altitude, and includes the thermosphere and parts of the mesosphere and exosphere . It is ionized by solar radiation, plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere . It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth
Earth

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Serendipity
SERENDIPITY means a "fortunate happenstance" or "pleasant surprise". The term was coined by Horace Walpole
Horace Walpole
in 1754. In a letter he wrote to a friend, Walpole explained an unexpected discovery he had made by reference to a Persian fairy tale, The Three Princes of Serendip . The princes, he told his correspondent, were "always making discoveries, by accidents and sagacity, of things which they were not in quest of". The notion of serendipity is a common occurrence throughout the history of scientific innovation. Examples are Alexander Fleming
Alexander Fleming
's accidental discovery of penicillin in 1928, the invention of the microwave oven by Percy Spencer in 1945, and the invention of the Post-it note
Post-it note
by Spencer Silver in 1968. In June 2004, a British translation company voted the word to be one of the ten English words hardest to translate
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Short Wave
SHORTWAVE RADIO is radio transmission using shortwave radio frequencies , generally 1.6–30 MHz
MHz
(187.4–10.0 m), just above the medium wave AM broadcast band. Radio
Radio
waves in this band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere . Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave or skip propagation . Thus shortwave radio can be used for very long distance communication, in contrast to radio waves of higher frequency which travel in straight lines (line-of-sight propagation ) and are limited by the visual horizon, about 40 miles. Shortwave radio
Shortwave radio
is used for broadcasting of voice and music to shortwave listeners over very large areas; sometimes entire continents or beyond
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Julius Scheiner
JULIUS SCHEINER (25 November 1858 – 20 December 1913) was a German astronomer , born in Cologne and educated at Bonn . He became assistant at the astrophysical observatory in Potsdam in 1887 and its observer in chief in 1898, three years after his appointment to the chair of astrophysics in the University of Berlin . Scheiner paid special attention to celestial photography and wrote Die Spektralanalyse der Gestirne (1890); Lehrbuch der Photographie der Gestirne (1897); Strahlung und Temperatur der Sonne (1899); Der Bau des Weltalls (1901); third edition, 1909). In 1899 he began the publication of the Photographische Himmelskarte; Zone +31° bis +40° Deklination. He is also credited with developing the first system for measuring the sensitivity of photographic emulsions in 1894, Scheinergrade , which also inspired the later DIN 4512 standard to measure film speeds . FURTHER READING * Frost, Edwin B. (1915). "Julius Scheiner". The Astrophysical Journal. 41: 1–9
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Johannes Wilsing
JOHANNES WILSING (September 8, 1856 – December 23, 1943) was a German astronomer . He was born in Berlin , where he was educated in addition to Göttingen . In 1880 he was awarded his Ph.D. from Humboldt-Universität of Berlin with a dissertation titled, Über den Einfluss von Luftdruck und Wärme auf die Pendelbewegung (On the influence of air pressure and heat on the movement of a pendulum). In 1881 he joined the Astrophysical Observatory Potsdam (AOP) as an assistant, and would remain there until he retired. His early career was spent on solar studies, including observations of sunspots and derivations of the rotation period. In 1897 he measured the parallax of 61 Cygni , a relatively nearby star. He became an observer at the AOP in 1898, and the following year he collaborated with Julius Scheiner in an unsuccessful attempt to measure the radio emission from the Sun. The same year he attempted to interpret the spectrum of novae
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Maxwell's Equations
MAXWELL\'S EQUATIONS are a set of partial differential equations that, together with the Lorentz force
Lorentz force
law, form the foundation of classical electromagnetism , classical optics , and electric circuits . They underpin all electric, optical and radio technologies, including power generation, electric motors, wireless communication, cameras, televisions, computers etc. Maxwell's equations
Maxwell's equations
describe how electric and magnetic fields are generated by charges , currents , and changes of each other. One important consequence of the equations is that they demonstrate how fluctuating electric and magnetic fields propagate at the speed of light. Known as electromagnetic radiation , these waves may occur at various wavelengths to produce a spectrum from radio waves to γ-rays
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Electricity
ELECTRICITY is the set of physical phenomena associated with the presence of electric charge . Although initially considered a phenomenon separate from magnetism , since the development of Maxwell's Equations, both are recognized as part of a single phenomenon: electromagnetism . Various common phenomena are related to electricity, including lightning , static electricity , electric heating , electric discharges and many others. In addition, electricity is at the heart of many modern technologies. The presence of an electric charge, which can be either positive or negative, produces an electric field . On the other hand, the movement of electric charges, which is known as electric current , produces a magnetic field . When a charge is placed in a location with non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb\'s Law . Thus, if that charge were to move, the electric field would be doing work on the electric charge
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Magnetism
MAGNETISM is a class of physical phenomena that are mediated by magnetic fields . Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets , producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron , nickel and cobalt and their alloys. The prefix ferro- refers to iron , because permanent magnetism was first observed in lodestone , a form of natural iron ore called magnetite , Fe3O4. Although ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, all other materials are influenced to some extent by a magnetic field, by several other types of magnetism
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Wavelength
In physics , the WAVELENGTH of a sinusoidal wave is the SPATIAL PERIOD of the wave—the distance over which the wave's shape repeats, and thus the inverse of the spatial frequency . It is usually determined by considering the distance between consecutive corresponding points of the same phase , such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves , as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids
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Directional Antenna
A DIRECTIONAL ANTENNA or BEAM ANTENNA is an antenna which radiates or receives greater power in specific directions allowing for increased performance and reduced interference from unwanted sources. Directional antennas provide increased performance over dipole antennas – or omnidirectional antennas in general – when greater concentration of radiation in a certain direction is desired. A HIGH-GAIN ANTENNA (HGA) is a directional antenna with a focused, narrow radiowave beam width. This narrow beam width allows more precise targeting of the radio signals. Most commonly referred to during space missions , these antennas are also in use all over Earth , most successfully in flat, open areas where no mountains lie to disrupt radiowaves. By contrast, a LOW-GAIN ANTENNA (LGA) is an omnidirectional antenna with a broad radiowave beam width, that allows for the signal to propagate reasonably well even in mountainous regions and is thus more reliable regardless of terrain
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Analog Signal
An ANALOG SIGNAL is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. For example, in an analog audio signal , the instantaneous voltage of the signal varies continuously with the pressure of the sound waves. It differs from a digital signal , in which the continuous quantity is a representation of a sequence of discrete values which can only take on one of a finite number of values. The term analog signal usually refers to electrical signals ; however, mechanical , pneumatic , hydraulic , human speech, and other systems may also convey or be considered analog signals. An analog signal uses some property of the medium to convey the signal's information. For example, an aneroid barometer uses rotary position as the signal to convey pressure information
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Black Hole
A BLACK HOLE is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light —can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon . Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like an ideal black body , as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation , with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass , making it essentially impossible to observe
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Flux Density
FLUX is either of two separate simple and ubiquitous concepts throughout physics and applied mathematics . Within a discipline, the term is generally used consistently, but care must be taken when comparing phenomena from different disciplines. Both concepts have mathematical rigor, enabling comparison of the underlying math when the terminology is unclear. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In electromagnetism , flux is a scalar quantity, defined as the surface integral of the component of a vector field perpendicular to the surface at each point. As will be made clear, the easiest way to relate the two concepts is that the surface integral of a flux according to the first definition is a flux according to the second definition
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James Stanley Hey
JAMES STANLEY HEY FRS (3 May 1909 – 27 February 2000) was an English physicist and radio astronomer . With the targeted application of radar technology for astronomical research, he laid the basis for the development of radio astronomy . He discovered that the Sun radiates radio waves and localized for the first time an extragalactic radio source in the constellation Cygnus . CONTENTS * 1 Biography * 2 Awards * 3 Publications by Hey * 3.1 Popular science books * 4 References BIOGRAPHYHe was born in 1909 in Nelson, Lancashire , the third son of a cotton manufacturer, which was the main industry in Lancashire. Hey studied physics at the University of Manchester , graduating in 1930, and obtained his master's degree in X-ray crystallography the next year. His wife, Edna Heywood, was a fellow student there. He was then a teacher of physics in a northern grammar school for some years
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