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Orbit In physics , an ORBIT is the gravitationally curved trajectory of an object around a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating path around a body, although it may occasionally be used for a nonrecurring trajectory around a point in space. To a close approximation, planets and satellites follow elliptic orbits , with the central mass being orbited at a focal point of the ellipse, as described by Kepler\'s laws of planetary motion . Current understanding of the mechanics of orbital motion is based on Albert Einstein Albert Einstein 's general theory of relativity , which accounts for gravity as due to curvature of spacetime , with orbits following geodesics . For ease of calculation, in most situations, orbital motion is adequately approximated by Newtonian mechanics , which explains gravity as a force obeying an inverse square law [...More...]  "Orbit" on: Wikipedia Yahoo 

Physics PHYSICS (from Ancient Greek : φυσική (ἐπιστήμη), translit. physikḗ (epistḗmē), lit. 'knowledge of nature', from φύσις phýsis "nature" ) is the natural science that studies matter and its motion and behavior through space and time and that studies the related entities of energy and force . Physics Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves. Physics Physics is one of the oldest academic disciplines and, through its inclusion of astronomy , perhaps the oldest. Over the last two millennia, physics, chemistry , biology , and certain branches of mathematics were a part of natural philosophy , but during the scientific revolution in the 17th century, these natural sciences emerged as unique research endeavors in their own right [...More...]  "Physics" on: Wikipedia Yahoo 

Physical Body In physics , a PHYSICAL BODY or PHYSICAL OBJECT (sometimes simply called a BODY or OBJECT; also: CONCRETE OBJECT) is an identifiable collection of matter , which may be constrained by an identifiable boundary, and may move as a unit by translation or rotation, in 3dimensional space . In common usage an object is a collection of matter within a defined contiguous boundary in 3dimensional space. The boundary must be defined and identified by the properties of the material. The boundary may change over time. The boundary is usually the visible or tangible surface of the object. The matter in the object is constrained (to a greater or lesser degree) to move as one object. The boundary may move in space relative to other objects that it is not attached to (through translation and rotation). An object's boundary may also deform and change over time in other ways. Also in common usage an object is not constrained to consist of the same collection of matter [...More...]  "Physical Body" on: Wikipedia Yahoo 

Geodesic In differential geometry , a GEODESIC (/ˌdʒiːəˈdɛsɪk, ˌdʒiːoʊ, ˈdiː, zɪk/ ) is a generalization of the notion of a "straight line " to "curved spaces ". The term "geodesic" comes from geodesy , the science of measuring the size and shape of Earth Earth ; in the original sense, a geodesic was the shortest route between two points on the Earth's surface , namely, a segment of a great circle . The term has been generalized to include measurements in much more general mathematical spaces; for example, in graph theory , one might consider a geodesic between two vertices /nodes of a graph . In the presence of an affine connection , a geodesic is defined to be a curve whose tangent vectors remain parallel if they are transported along it. If this connection is the LeviCivita connection induced by a Riemannian metric , then the geodesics are (locally ) the shortest path between points in the space [...More...]  "Geodesic" on: Wikipedia Yahoo 

Albert Einstein ALBERT EINSTEIN (/ˈaɪnstaɪn/ ; German: ( listen ); 14 March 1879 – 18 April 1955) was a Germanborn theoretical physicist . Einstein developed the theory of relativity , one of the two pillars of modern physics (alongside quantum mechanics ). :274 Einstein's work is also known for its influence on the philosophy of science . Einstein is best known by the general public for his mass–energy equivalence formula E = mc2 (which has been dubbed "the world's most famous equation"). He received the 1921 Nobel Prize in Physics Physics "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect ", a pivotal step in the evolution of quantum theory . Near the beginning of his career, Einstein thought that Newtonian mechanics was no longer enough to reconcile the laws of classical mechanics with the laws of the electromagnetic field [...More...]  "Albert Einstein" on: Wikipedia Yahoo 

Spacetime In physics , SPACETIME is any mathematical model that fuses the three dimensions of space and the one dimension of time into a single 4‑dimensional continuum . Spacetime Spacetime diagrams are useful in visualizing and understanding relativistic effects such as how different observers perceive where and when events occur. Until the turn of the 20th century, the assumption had been that the threedimensional geometry of the universe (its description in terms of locations, shapes, distances, and directions) was distinct from time (the measurement of when events occur within the universe). However, Albert Einstein Albert Einstein 's 1905 special theory of relativity postulated that the speed of light through empty space has one definite value—a constant —that is independent of the motion of the light source [...More...]  "Spacetime" on: Wikipedia Yahoo 

Newton's Law Of Universal Gravitation NEWTON\'S LAW OF UNIVERSAL GRAVITATION states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This is a general physical law derived from empirical observations by what Isaac Newton called inductive reasoning . It is a part of classical mechanics and was formulated in Newton's work Philosophiæ Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society , Robert Hooke made a claim that Newton had obtained the inverse square law from him; see the History section below.) In modern language, the law states: Every point mass attracts every single other point mass by a force pointing along the line intersecting both points [...More...]  "Newton's Law Of Universal Gravitation" on: Wikipedia Yahoo 

Mass MASS is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion ) when a net force is applied. It also determines the strength of its mutual gravitational attraction to other bodies. The basic SI unit SI unit of mass is the kilogram (kg). In physics , mass is not the same as weight , even though mass is often determined by measuring the object's weight using a spring scale , rather than balance scale comparing it directly with known masses. An object on the Moon Moon would weigh less than it does on Earth Earth because of the lower gravity, but it would still have the same mass. This is because weight is a force, while mass is the property that (along with gravity) determines the strength of this force. In Newtonian physics , mass can be generalized as the amount of matter in an object [...More...]  "Mass" on: Wikipedia Yahoo 

Gravitationally GRAVITY, or GRAVITATION, is a natural phenomenon by which all things with mass are brought toward (or gravitate toward) one another, including planets , stars and galaxies , and other physical objects . Since energy and mass are equivalent , all forms of energy (including light ) cause gravitation and are under the influence of it. On Earth , gravity gives weight to physical objects, and causes the ocean tides . The gravitational attraction of the original gaseous matter present in the Universe Universe caused it to begin coalescing, forming stars – and for the stars to group together into galaxies – so gravity is responsible for many of the large scale structures in the Universe. Gravity has an infinite range, although its effects become increasingly weaker on farther objects [...More...]  "Gravitationally" on: Wikipedia Yahoo 

Automated Cargo Spacecraft CARGO SPACECRAFT are robotic spacecraft that are designed to support space stations operation by transporting food, propellant and other supplies. This is different from space probes , whose missions are to conduct scientific investigations. Automated cargo spacecraft have been used since 1978 and have serviced Salyut 6 , Salyut 7 , Mir Mir , the International Space Station and Tiangong Tiangong space laboratory [...More...]  "Automated Cargo Spacecraft" on: Wikipedia Yahoo 

Launch Pad A LAUNCH PAD is an aboveground platform from which a rocket powered missile or space vehicle is vertically launched. A spaceport (or LAUNCH COMPLEX) is a facility which includes, and provides required support for, one or more launch pads. A launch pad generally contains a fixed or mobile service structure , which provides one or more access platforms to inspect and maintain the vehicle, and an umbilical structure which provides the vehicle with propellants , cryogenic fluids, electrical power, communications, and telemetry prior to launch. The service structure also provides access to the crew cabin for vehicles carrying humans. The pad may contain a flame deflection structure to prevent the intense heat of the rocket exhaust from damaging the vehicle or pad structures, and a sound suppression system spraying large quantities of water may be employed. The pad may also be protected by lightning arrestors [...More...]  "Launch Pad" on: Wikipedia Yahoo 

Spy Satellite A RECONNAISSANCE SATELLITE (commonly, although unofficially, referred to as a SPY SATELLITE) is an Earth observation satellite Earth observation satellite or communications satellite deployed for military or intelligence applications. The first generation type (i.e., Corona and Zenit ) took photographs, then ejected canisters of photographic film which would descend to earth. Corona capsules were retrieved in midair as they floated down on parachutes . Later, spacecraft had digital imaging systems and downloaded the images via encrypted radio links. In the United States, most information available is on programs that existed up to 1972, as this information has been declassified due to its age. Some information about programs prior to that time is still classified , and a small amount of information is available on subsequent missions [...More...]  "Spy Satellite" on: Wikipedia Yahoo 

Newtonian Mechanics CLASSICAL MECHANICS describes the motion of macroscopic objects, from projectiles to parts of machinery , and astronomical objects , such as spacecraft , planets , stars and galaxies . If the present state of an object is known it is possible to predict by the laws of classical mechanics how it will move in the future (determinism) and how it have moved in the past (reversibility) The earliest development of classical mechanics is often referred to as Newtonian mechanics. It consists of the physical concepts employed by and the mathematical methods invented by Isaac Newton Isaac Newton and Gottfried Wilhelm Leibniz and others in the 17th century to describe the motion of bodies under the influence of a system of forces . Later, more abstract methods were developed, leading to the reformulations of classical mechanics known as Lagrangian mechanics and Hamiltonian mechanics [...More...]  "Newtonian Mechanics" on: Wikipedia Yahoo 

Robotic Spacecraft A ROBOTIC SPACECRAFT is an uncrewed spacecraft , usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe . Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn , Uranus , and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Many artificial satellites are robotic spacecraft, as are many landers and rovers [...More...]  "Robotic Spacecraft" on: Wikipedia Yahoo 

Timeline Of Spaceflight This is a TIMELINE OF KNOWN SPACEFLIGHTS , both manned and unmanned, sorted chronologically by launch date. Owing to its large size, the timeline is split into smaller articles, one for each year since 1951. There is a separate list for all flights that occurred before 1951. The 2017 list, and lists for subsequent years, contain planned launches which have not yet occurred. For the purpose of these lists, a spaceflight is defined as any flight that crosses the Kármán line Kármán line , the officially recognised edge of space, which is 100 kilometres (62 miles) above mean sea level (AMSL) . The timeline contains all flights which have crossed the edge of space, were intended to do so but failed, or are planned in the near future. Some lists are further divided into orbital launches (sending a payload into orbit, whether successful or not) and suborbital flights (e.g. ballistic missiles, sounding rockets, experimental spacecraft) [...More...]  "Timeline Of Spaceflight" on: Wikipedia Yahoo 

Space Colonization CORE CONCEPTS * Planetary habitability * Space and survival * Space habitat Space habitat * Terraforming [...More...]  "Space Colonization" on: Wikipedia Yahoo 