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Meteor Air Burst
A meteor air burst is a type of air burst in which a meteor explodes after entering a planetary body's atmosphere. This fate leads them to be called fireballs or bolides, with the brightest air bursts known as superbolides. Such meteoroids were originally asteroids and comets of a few to several tens of meters in diameter. This separates them from the much smaller and far more common " shooting stars", that usually burn up quickly upon atmospheric entry. The most powerful meteor air burst in the modern era was the 1908 Tunguska event. During this event a stony meteoroid about in size exploded at an altitude of over a sparsely populated forest in Siberia. The resulting shock wave flattened an estimated 80 million trees over a area. Extremely bright fireballs traveling across the sky are often witnessed from a distance, such as the 1947 Sikhote-Alin meteor and the 2013 Chelyabinsk meteor, both over Russia. If the bolide is large enough fragments may survive, as from bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelyabinsk Bolide Plume As Seen By NPP And NASA Models
Chelyabinsk ( rus, Челя́бинск, p=tɕɪˈlʲæbʲɪnsk, a=Ru-Chelyabinsk.ogg; ba, Силәбе, ''Siläbe'') is the administrative center and largest city of Chelyabinsk Oblast, Russia. It is the seventh-largest city in Russia, with a population of over 1.1 million people, and the second-largest city in the Ural Federal District, after Yekaterinburg. Chelyabinsk runs along the Miass River, and is just east of the Ural Mountains. The area of Chelyabinsk contained the ancient settlement of Arkaim, which belonged to the Sintashta culture. In 1736, a fortress by the name of Chelyaba was founded on the site of a Bashkir village. Chelyabinsk was granted town status by 1787. Chelyabinsk began to grow rapidly by the early 20th century as a result of the construction of railway links from the Russian core to Siberia, including the Trans-Siberian Railway. Its population reached 70,000 by 1917. Under the Soviet Union, Chelyabinsk became a major industrial centre during the 1930 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sikhote-Alin Meteorite
An iron meteorite fell on the Sikhote-Alin Mountains, in southeastern Russia, in 1947. Large iron meteorite falls have been witnessed and fragments recovered but never before, in recorded history, a fall of this magnitude. An estimated 23 tonnes of fragments survived the fiery passage through the atmosphere and reached the Earth. Impact At around 10:30 AM on 12 February 1947, eyewitnesses in the Sikhote-Alin Mountains, Primorye, Soviet Union, observed a large bolide brighter than the sun that came out of the north and descended at an angle of about 41 degrees. The bright flash and the deafening sound of the fall were observed for around the point of impact not far from Luchegorsk and approximately northeast of Vladivostok. A smoke trail, estimated at long, remained in the sky for several hours. As the meteor, traveling at a speed of about , entered the atmosphere, it began to break apart, and the fragments fell together, some burying themselves deep. At an altitude of abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a Meteoroid#Fireball, fireball, also known as a shooting star; astronomers call the brightest examples "Bolide#Astronomy, bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and Impact event, impact the Earth are called meteorite falls. All others are known as meteorite finds. Meteorites have traditiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles's Law
Charles's law (also known as the law of volumes) is an experimental gas law that describes how gases tend to expand when heated. A modern statement of Charles's law is: When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion. This relationship of direct proportion can be written as: :V \propto T So this means: :\frac = k, \quad \text \quad V=k T where: * is the volume of the gas, * is the temperature of the gas (measured in kelvins), and * is a non-zero constant. This law describes how a gas expands as the temperature increases; conversely, a decrease in temperature will lead to a decrease in volume. For comparing the same substance under two different sets of conditions, the law can be written as: \frac=\frac The equation shows that, as absolute temperature increases, the volume of the gas also increases in proportion. History The law was named after scientist Jacques Charles, who formulated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. *Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. *Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. *Internal friction is the force resisting motion between the elements making up a so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on various reference points and thermometric substances for definition. The most common scales are the Celsius scale with the unit symbol °C (formerly called ''centigrade''), the Fahrenheit scale (°F), and the Kelvin scale (K), the latter being used predominantly for scientific purposes. The kelvin is one of the seven base units in the International System of Units (SI). Absolute zero, i.e., zero kelvin or −273.15 °C, is the lowest point in the thermodynamic temperature scale. Experimentally, it can be approached very closely but not actually reached, as recognized in the third law of thermodynamics. It would be impossible to extract energy as heat from a body at that temperature. Temperature is important in all fields of natur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ram Pressure
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as :P_\text= \rho u_i u_j, where \rho is the density of the fluid; P_\text is the momentum flux per second in the i direction through a surface with normal in the j direction. u_i,u_j are the components of the fluid velocity in these directions. The total Cauchy stress tensor \sigma_ is the sum of this ram pressure and the isotropic thermal pressure (in the absence of viscosity). In the simple case when the relative velocity is normal to the surface, and momentum is fully transferred to the object, the ram pressure becomes :P_\text = \rho u^2. Derivation The Eulerian form of the Cauchy momentum equation for a fluid is :\rho\frac = -\vec \nabla p - \rho(\vec u \cdot \vec \nabla)\vec u + \rho \vec g for isotropic pressure p, where \v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Earth
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upper Atmosphere
Upper atmosphere is a collective term that refers to various layers of the atmosphere of the Earth above the troposphere and corresponding regions of the atmospheres of other planets, and includes: * The mesosphere, which on Earth lies between the altitudes of about , sometimes considered part of the "middle atmosphere" rather than the upper atmosphere * The thermosphere, which on Earth lies between the altitudes of about * The exosphere, which on Earth lies between the altitudes of about and * The ionosphere, an ionized portion of the upper atmosphere which includes the upper mesosphere, thermosphere, and lower exosphere and on Earth lies between the altitudes of See also *Geospace Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ... * Magnetosphere References {{Reflist Atmos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outer Space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is . The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Observations s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defense Support Program
The Defense Support Program (DSP) is a program of the United States Space Force that operated the reconnaissance satellites which form the principal component of the ''Satellite Early Warning System'' used by the United States. DSP satellites, which are operated by the 460th Space Wing, detect missile or spacecraft launches and nuclear explosions using sensors that detect the infrared emissions from these intense sources of heat. During Desert Storm, for example, DSP was able to detect the launches of Iraqi Scud missiles and provide timely warnings to civilians and military forces in Israel and Saudi Arabia. The satellites are in geosynchronous orbits, and are equipped with infrared sensors operating through a wide-angle Schmidt camera. The entire satellite spins so that the linear sensor array in the focal plane scans over the Earth six times every minute. Typically, DSP satellites were launched on Titan IVB boosters with Inertial Upper Stages. However, one DSP satellite ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
