YouTube is an American video-sharing website headquartered in San Bruno, California. The service was created by three former PayPal employees—Chad Hurley, Steve Chen, and Jawed Karim—in February 2005, Google bought the site in November 2006 for US$1.65 billion, YouTube now operates as one of Googles subsidiaries. Unregistered users can watch videos on the site, while registered users are permitted to upload an unlimited number of videos. Videos deemed potentially offensive are available only to registered users affirming themselves to be at least 18 years old, YouTube earns advertising revenue from Google AdSense, a program which targets ads according to site content and audience. YouTube was founded by Chad Hurley, Steve Chen, and Jawed Karim, Hurley had studied design at Indiana University of Pennsylvania, and Chen and Karim studied computer science together at the University of Illinois at Urbana-Champaign. Karim could not easily find video clips of either event online and Chen said that the original idea for YouTube was a video version of an online dating service, and had been influenced by the website Hot or Not.
YouTube began as a venture capital-funded technology startup, primarily from an $11.5 million investment by Sequoia Capital between November 2005 and April 2006, YouTubes early headquarters were situated above a pizzeria and Japanese restaurant in San Mateo, California. The domain name www. youtube. com was activated on February 14,2005, the first YouTube video, titled Me at the zoo, shows co-founder Jawed Karim at the San Diego Zoo. The video was uploaded on April 23,2005, and can still be viewed on the site, YouTube offered the public a beta test of the site in May 2005. The first video to reach one million views was a Nike advertisement featuring Ronaldinho in November 2005. Following a $3.5 million investment from Sequoia Capital in November, the site grew rapidly, and in July 2006 the company announced that more than 65,000 new videos were being uploaded every day, and that the site was receiving 100 million video views per day. The site has 800 million unique users a month and it is estimated that in 2007 YouTube consumed as much bandwidth as the entire Internet in 2000.
The choice of the name www. youtube. com led to problems for a similarly named website, the sites owner, Universal Tube & Rollform Equipment, filed a lawsuit against YouTube in November 2006 after being regularly overloaded by people looking for YouTube. Universal Tube has since changed the name of its website to www. utubeonline. com, in October 2006, Google Inc. announced that it had acquired YouTube for $1.65 billion in Google stock, and the deal was finalized on November 13,2006. In March 2010, YouTube began free streaming of certain content, according to YouTube, this was the first worldwide free online broadcast of a major sporting event. On March 31,2010, the YouTube website launched a new design, with the aim of simplifying the interface, Google product manager Shiva Rajaraman commented, We really felt like we needed to step back and remove the clutter. In May 2010, YouTube videos were watched more than two times per day. This increased to three billion in May 2011, and four billion in January 2012, in February 2017, one billion hours of YouTube was watched every day
Turbulence or turbulent flow is a flow regime in fluid dynamics characterized by chaotic changes in pressure and flow velocity. It is in contrast to a flow regime, which occurs when a fluid flows in parallel layers. Turbulence is caused by kinetic energy in parts of a fluid flow. For this reason turbulence is easier to create in low viscosity fluids, in general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. This would increase the energy needed to pump fluid through a pipe, however this effect can be exploited by such as aerodynamic spoilers on aircraft, which deliberately spoil the laminar flow to increase drag and reduce lift. The onset of turbulence can be predicted by a constant called the Reynolds number. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence creates a complex situation. Richard Feynman has described turbulence as the most important unsolved problem of classical physics, smoke rising from a cigarette is mostly turbulent flow.
However, for the first few centimeters the flow is laminar, the smoke plume becomes turbulent as its Reynolds number increases, due to its flow velocity and characteristic length increasing. If the golf ball were smooth, the boundary layer flow over the front of the sphere would be laminar at typical conditions. However, the layer would separate early, as the pressure gradient switched from favorable to unfavorable. To prevent this happening, the surface is dimpled to perturb the boundary layer. This results in higher skin friction, but moves the point of boundary layer separation further along, resulting in form drag. The flow conditions in industrial equipment and machines. The external flow over all kind of such as cars, ships. The motions of matter in stellar atmospheres, a jet exhausting from a nozzle into a quiescent fluid. As the flow emerges into this external fluid, shear layers originating at the lips of the nozzle are created and these layers separate the fast moving jet from the external fluid, and at a certain critical Reynolds number they become unstable and break down to turbulence.
Biologically generated turbulence resulting from swimming animals affects ocean mixing, snow fences work by inducing turbulence in the wind, forcing it to drop much of its snow load near the fence
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, with a 2. 4-meter mirror, Hubbles four main instruments observe in the near ultraviolet and near infrared spectra. Hubbles orbit outside the distortion of Earths atmosphere allows it to take extremely high-resolution images, Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe. The HST was built by the United States space agency NASA, the Space Telescope Science Institute selects Hubbles targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923, Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster.
When finally launched in 1990, Hubbles main mirror was found to have been ground incorrectly, the optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the telescope designed to be serviced in space by astronauts. After launch by Space Shuttle Discovery in 1990, five subsequent Space Shuttle missions repaired, the fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved the fifth servicing mission, the telescope is operating as of 2017, and could last until 2030–2040. Its scientific successor, the James Webb Space Telescope, is scheduled for launch in 2018, the history of the Hubble Space Telescope can be traced back as far as 1946, to the astronomer Lyman Spitzers paper Astronomical advantages of an extraterrestrial observatory. In it, he discussed the two advantages that a space-based observatory would have over ground-based telescopes. First, the resolution would be limited only by diffraction, rather than by the turbulence in the atmosphere.
Second, a telescope could observe infrared and ultraviolet light. Spitzer devoted much of his career to pushing for the development of a space telescope, space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, oAO-1s battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out observations of stars and galaxies from its launch in 1968 until 1972. The continuing success of the OAO program encouraged increasingly strong consensus within the community that the LST should be a major goal
Jet Propulsion Laboratory
The Jet Propulsion Laboratory is a federally funded research and development center and NASA field center in La Cañada Flintridge and Pasadena, United States. The JPL is managed by the nearby California Institute of Technology for NASA, the laboratorys primary function is the construction and operation of planetary robotic spacecraft, though it conducts Earth-orbit and astronomy missions. It is responsible for operating NASAs Deep Space Network and they are responsible for managing the JPL Small-Body Database, and provides physical data and lists of publications for all known small Solar System bodies. The JPLs Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks, JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology when the first set of rocket experiments were carried out in the Arroyo Seco. Malinas thesis advisor was engineer/aerodynamicist Theodore von Kármán, who arranged for U. S.
Army financial support for this GALCIT Rocket Project in 1939. In 1941, Parsons, Martin Summerfield, in 1943, von Kármán, Malina and Forman established the Aerojet Corporation to manufacture JATO motors. The project took on the name Jet Propulsion Laboratory in November 1943, during JPLs Army years, the laboratory developed two deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate range ballistic missiles. These missiles were the first US ballistic missiles developed at JPL and it developed a number of other weapons system prototypes, such as the Loki anti-aircraft missile system, and the forerunner of the Aerobee sounding rocket. At various times, it carried out testing at the White Sands Proving Ground, Edwards Air Force Base. A lunar lander was developed in 1938-39 which influenced design of the Apollo Lunar Module in the 1960s. The team lost that proposal to Project Vanguard, and instead embarked on a project to demonstrate ablative re-entry technology using a Jupiter-C rocket.
They carried out three successful flights in 1956 and 1957. Using a spare Juno I, the two organizations launched the United States first satellite, Explorer 1, on February 1,1958, JPL was transferred to NASA in December 1958, becoming the agencys primary planetary spacecraft center. JPL engineers designed and operated Ranger and Surveyor missions to the Moon that prepared the way for Apollo, JPL led the way in interplanetary exploration with the Mariner missions to Venus and Mercury. In 1998, JPL opened the Near-Earth Object Program Office for NASA, as of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earths orbit. JPL was early to employ women mathematicians, in the 1940s and 1950s, using mechanical calculators, women in an all-female computations group performed trajectory calculations. In 1961, JPL hired Dana Ulery as their first woman engineer to work alongside male engineers as part of the Ranger and Mariner mission tracking teams, when founded, JPLs site was a rocky flood-plain just outside the city limits of Pasadena.
Almost all of the 177 acres of the U. S, the city of La Cañada Flintridge, California was incorporated in 1976, well after JPL attained international recognition with a Pasadena address
In mathematics, the gradient is a multi-variable generalization of the derivative. While a derivative can be defined on functions of a variable, for functions of several variables. The gradient is a function, as opposed to a derivative. If f is a differentiable, real-valued function of several variables, like the derivative, the gradient represents the slope of the tangent of the graph of the function. More precisely, the gradient points in the direction of the greatest rate of increase of the function, the components of the gradient in coordinates are the coefficients of the variables in the equation of the tangent space to the graph. The Jacobian is the generalization of the gradient for vector-valued functions of several variables, a further generalization for a function between Banach spaces is the Fréchet derivative. Consider a room in which the temperature is given by a field, T. At each point in the room, the gradient of T at that point will show the direction in which the temperature rises most quickly, the magnitude of the gradient will determine how fast the temperature rises in that direction.
Consider a surface whose height above sea level at point is H, the gradient of H at a point is a vector pointing in the direction of the steepest slope or grade at that point. The steepness of the slope at point is given by the magnitude of the gradient vector. The gradient can be used to measure how a scalar field changes in other directions, rather than just the direction of greatest change, suppose that the steepest slope on a hill is 40%. If a road goes directly up the hill, the steepest slope on the road will be 40%, if, the road goes around the hill at an angle, it will have a shallower slope. This observation can be stated as follows. If the hill height function H is differentiable, the gradient of H dotted with a unit vector gives the slope of the hill in the direction of the vector. More precisely, when H is differentiable, the dot product of the gradient of H with a unit vector is equal to the directional derivative of H in the direction of that unit vector. The gradient of a function f is denoted ∇f or ∇→f where ∇ denotes the vector differential operator.
The notation grad f is commonly used for the gradient. The gradient of f is defined as the vector field whose dot product with any vector v at each point x is the directional derivative of f along v. That is
In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earths surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles, lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the location of features on the surface of the Earth. Without qualification the term latitude should be taken to be the latitude as defined in the following sections. Also defined are six auxiliary latitudes which are used in special applications, there is a separate article on the History of latitude measurements. Two levels of abstraction are employed in the definition of latitude and longitude, in the first step the physical surface is modelled by the geoid, a surface which approximates the mean sea level over the oceans and its continuation under the land masses. The second step is to approximate the geoid by a mathematically simpler reference surface, the simplest choice for the reference surface is a sphere, but the geoid is more accurately modelled by an ellipsoid.
The definitions of latitude and longitude on such surfaces are detailed in the following sections. Lines of constant latitude and longitude together constitute a graticule on the reference surface and longitude together with some specification of height constitute a geographic coordinate system as defined in the specification of the ISO19111 standard. This is of importance in accurate applications, such as a Global Positioning System, but in common usage, where high accuracy is not required. In English texts the latitude angle, defined below, is denoted by the Greek lower-case letter phi. It is measured in degrees and seconds or decimal degrees, the precise measurement of latitude requires an understanding of the gravitational field of the Earth, either to set up theodolites or to determine GPS satellite orbits. The study of the figure of the Earth together with its field is the science of geodesy. These topics are not discussed in this article and this article relates to coordinate systems for the Earth, it may be extended to cover the Moon and other celestial objects by a simple change of nomenclature.
The primary reference points are the poles where the axis of rotation of the Earth intersects the reference surface, the plane through the centre of the Earth and perpendicular to the rotation axis intersects the surface at a great circle called the Equator. Planes parallel to the plane intersect the surface in circles of constant latitude. The Equator has a latitude of 0°, the North Pole has a latitude of 90° North, the latitude of an arbitrary point is the angle between the equatorial plane and the radius to that point. The latitude, as defined in this way for the sphere, is termed the spherical latitude
It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses.
Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, night vision and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight.
Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
Atlas is an inner satellite of Saturn. Atlas was discovered by Richard Terrile in 1980 from Voyager photos and was designated S/1980 S28, in 1983 it was officially named after Atlas of Greek mythology, because it holds the rings on its shoulders like the Titan Atlas held the sky up above the Earth. It is designated Saturn XV, Atlas is the closest satellite to the sharp outer edge of the A ring, and was long thought to be a shepherd satellite for this ring. However, now it is known that the edge of the ring is instead maintained by a 7,6 orbital resonance with the larger. In 2004 a faint, thin ring, temporarily designated R/2004 S1, was discovered in the Atlantean orbit, high-resolution images taken in June 2005 by Cassini revealed Atlas to have a roughly spherical centre surrounded by a large, smooth equatorial ridge. In fact, the size of the ridge is comparable with the expected Roche lobe of the moon. This would mean that for any additional particles impacting the equator, the force will nearly overcome Atlass tiny gravity.
Because the orbits of Prometheus and Pandora are chaotic, it is suspected that Atlass may be as well, citations Sources Green, Daniel W. E. S/2004 S3, S/2004 S4, and R/2004 S1. Marsden, Brian G.1980 S28, archived from the original on 2011-12-13. Marsden, Brian G. Satellites of Jupiter and Saturn, spitale, J. N. Jacobson, R. A. Porco, C. C. The orbits of Saturns small satellites derived from combined historic and Cassini imaging observations, sizes and derived properties of the saturnian satellites after the Cassini nominal mission. Atlas Profile by NASAs Solar System Exploration The Planetary Society, Atlas NASA factsheet
Great White Spot
The spots can be several thousands of kilometers wide. Cassini data has revealed a loss of acetylene in the clouds, an increase of phosphine. After the visible aspects of the storm subsized, in 2012 a belch of heat, the phenomenon is somewhat periodic at 28. 5-year intervals, when Saturns northern hemisphere tilts most toward the Sun. The following is a list of recorded sightings,1876 – Observed by Asaph Hall. He used the white spots to determine the period of rotation. 1903 – Observed by Edward Barnard,1933 – Observed by Will Hay, comic actor and amateur astronomer. Until recent times the most celebrated observation,1960 – Observed by JH Botham. 1990 – Observed by Stuart Wilber, from 24 September through November,1994 – Studied by ground-based observers and the Hubble Space Telescope. 2006 – Observed by Erick Bondoux and Jean-Luc Dauvergne,2010 – First observed by Anthony Wesley, photographed by Cassini space probe 2010-2011. It is not known if the record was simply poor, or if the 1876 GWS was truly a first for the telescopic era.
Some believe that neither scenario is likely, for instance, the 1960 GWS was high-latitude, and the 1990 GWS was equatorial. The high-latitude GWSs recur at a shorter interval than the equatorial GWSs. The high-latitude GWSs tend to be less prominent than their equatorial counterparts. Based on these apparent regularities, in 1992 Kidger forecast that the next GWS will occur in the NTZ in 2016, and will probably be less spectacular than the 1990 GWS. A classic Great White Spot is an event, in which a brilliant white storm enlivens Saturns usually bland atmosphere. They typically begin as discrete, literal spots, but rapidly expand in longitude, as the 1933 and 1990 GWSs did, in fact, low-density upper-layer gases tend to suppress convection, but high-density upper layers are unstable and cause a thunderstorm when they break into lower layers. The theory is that the storms are significantly delayed from the winter due to the time it takes for the very large atmosphere to cool. The team proposes that similar storms are not seen on Jupiter because that planet has less water vapor in its upper atmosphere, volunteers Help NASA Track Return of the Dragon Kidger, Mark
The New York Times
The New York Times is an American daily newspaper and continuously published in New York City since September 18,1851, by The New York Times Company. The New York Times has won 119 Pulitzer Prizes, more than any other newspaper, the papers print version in 2013 had the second-largest circulation, behind The Wall Street Journal, and the largest circulation among the metropolitan newspapers in the US. The New York Times is ranked 18th in the world by circulation, following industry trends, its weekday circulation had fallen in 2009 to fewer than one million. Nicknamed The Gray Lady, The New York Times has long been regarded within the industry as a newspaper of record. The New York Times international version, formerly the International Herald Tribune, is now called the New York Times International Edition, the papers motto, All the News Thats Fit to Print, appears in the upper left-hand corner of the front page. On Sunday, The New York Times is supplemented by the Sunday Review, The New York Times Book Review, The New York Times Magazine and T, some other early investors of the company were Edwin B.
Morgan and Edward B. We do not believe that everything in Society is either right or exactly wrong, —what is good we desire to preserve and improve, —what is evil, to exterminate. In 1852, the started a western division, The Times of California that arrived whenever a mail boat got to California. However, when local California newspapers came into prominence, the effort failed, the newspaper shortened its name to The New-York Times in 1857. It dropped the hyphen in the city name in the 1890s, One of the earliest public controversies it was involved with was the Mortara Affair, the subject of twenty editorials it published alone. At Newspaper Row, across from City Hall, Henry Raymond and editor of The New York Times, averted the rioters with Gatling guns, in 1869, Raymond died, and George Jones took over as publisher. Tweed offered The New York Times five million dollars to not publish the story, in the 1880s, The New York Times transitioned gradually from editorially supporting Republican Party candidates to becoming more politically independent and analytical.
In 1884, the paper supported Democrat Grover Cleveland in his first presidential campaign, while this move cost The New York Times readership among its more progressive and Republican readers, the paper eventually regained most of its lost ground within a few years. However, the newspaper was financially crippled by the Panic of 1893, the paper slowly acquired a reputation for even-handedness and accurate modern reporting, especially by the 1890s under the guidance of Ochs. Under Ochs guidance and expanding upon the Henry Raymond tradition, The New York Times achieved international scope, circulation, in 1910, the first air delivery of The New York Times to Philadelphia began. The New York Times first trans-Atlantic delivery by air to London occurred in 1919 by dirigible, airplane Edition was sent by plane to Chicago so it could be in the hands of Republican convention delegates by evening. In the 1940s, the extended its breadth and reach. The crossword began appearing regularly in 1942, and the section in 1946
Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the movement of air. Winds are commonly classified by their scale, their speed, the types of forces that cause them, the regions in which they occur. The strongest observed winds on a planet in the Solar System occur on Neptune, Winds have various aspects, an important one being its velocity, another the density of the gas involved, another its energy content or wind energy. In meteorology, winds are referred to according to their strength. Short bursts of high speed wind are termed gusts, strong winds of intermediate duration are termed squalls. Long-duration winds have various names associated with their strength, such as breeze, storm. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet, within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds, in areas that have variable terrain, Wind powers the voyages of sailing ships across Earths oceans.
Hot air balloons use the wind to take trips, and powered flight uses it to increase lift. Areas of wind caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong and man-made structures are damaged or destroyed, Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Wind affects the spread of wildfires, Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with temperatures, wind has a negative impact on livestock. Wind affects animals food stores, as well as their hunting, Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the pressure area. On a rotating planet, air will be deflected by the Coriolis effect, the two major driving factors of large-scale wind patterns are the differential heating between the equator and the poles and the rotation of the planet.
Outside the tropics and aloft from frictional effects of the surface, near the Earths surface, friction causes the wind to be slower than it would be otherwise