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Optical telescope:
An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum, for directly viewing a magnified image, making a photograph, etc. The term is used especially for a monocular with static mounting for observing the sky. Handheld binoculars are common for other purposes. Professional telescopes often focus the light onto electronic image sensors. There are three primary types of optical telescope: Refractors (Dioptrics) which use lenses, Reflectors (Catoptrics) which use mirrors, and Combined Lens-Mirror Systems (Catadioptrics) which use lenses and mirrors in combination (for example the Maksutov telescope and the Schmidt camera).
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Space observatory:
A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects. A large number of observatories have been launched into orbit, and most of them have greatly enhanced our knowledge of the cosmos. Performing astronomy from the Earth's surface is limited by the filtering and distortion of electromagnetic radiation due to the Earth's atmosphere. This makes it desirable to place astrononomical observation devices into space. As a telescope orbits the Earth outside the atmosphere it is subject neither to twinkling (distortion due to thermal turbulences of the air) nor to light pollution from artificial light sources on the Earth. Some terrestrial telescopes (such as the Very Large Telescope) can counter turbulences with the help of their novel adaptive optics. But space-based astronomy is even more important for frequency ranges which are outside of the optic window and the radio window, the only two wavelength ranges of the electromagnetic spectrum that are not severely attenuated by the atmosphere.
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Gravitational lensing:
A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is "bent" around a massive object (such as a massive galaxy) between the source object and the observer. The process is known as gravitational lensing, and is one of the predictions of Albert Einstein's general relativity theory. Gravitational microlensing can provide information on comparatively small astronomical objects, such as MACHOs within our own galaxy, or extrasolar planets (planets beyond the solar system). Three extrasolar planets have been found in this way, and this technique has the promise of finding Earth-mass planets around sunlike stars within the 21st century. Gravitational lensing can be used to calculate an estimate of the amount of dark matter contained in the lensing body.
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Astronomical interferometer:
An astronomical interferometer or hypertelescope is an array of telescopes or mirror segments acting together to probe structures with higher resolution. Astronomical interferometers are widely used for optical astronomy, infraredastronomy, submillimetre astronomy and radio astronomy. Aperture synthesis can be used to perform high-resolution imaging using astronomical interferometers. Projects are now beginning that will use interferometers to search for extrasolar planets, either by astrometric measurements of the reciprocal motion of the star (as used by the Palomar Testbed Interferometer and the VLTI), through the use of nulling (as will be used by the Keck Interferometer and Darwin) or through direct imaging (as proposed for Labeyrie's Hypertelescope).
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Nulling interferometry:
Nulling interferometry is a type of interferometry in which two or more signals are mixed to produce observational regions in which the incoming signals cancel themselves out. This creates a set of virtual 'blind spots' which prevent unwanted signals from those areas from interfering with other, possibly much weaker signals that are nearby. This technique is used by SIM, and is being considered for use by the Terrestrial Planet Finder, both NASA missions. Also the ESA Darwin mission is considering the use of it. It is being used on the Keck Interferometer.
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Extraterrestrial life:
Extraterrestrial life is life that may exist and originate outside the planet Earth, the only place in the universe currently known to support life. Its existence is currently purely hypothetical as there is yet no evidence of any other planets that can support life, or actual extraterrestrial life that has been widely accepted by the scientific community. Most scientists believe that if extraterrestrial life exists, its evolution occurred independently, in different places. An alternative hypothesis, held by a minority, is panspermia. This suggests that life could have been created elsewhere and spread across the universe, between habitable planets. The putative study and theorisation of extraterrestrial life is known as astrobiology or exobiology or xenobiology. Speculative forms of extraterrestrial life range from sapient beings, to life at the scale of bacteria.
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Astrobiology:
Astrobiology is the study of life in space, combining aspects of astronomy, biology and geology. It is focused primarily on the study of the origin, distribution and evolution of life. Some major astrobiological research topics include addressing the following questions. What is life? How did life arise on Earth? What kind of environments can life tolerate? How can we determine if life exists on other planets? How often can we expect to find complex life? What will life consist of? Is it always DNA-based? Carbon based? What is the physiology of life on other planets?
Extremophiles (organisms able to survive in extreme environments) are a core research element for astrobiologists. Such organisms include biota able to survive kilometers below the ocean's surface near hydrothermal vents and microbes that thrive in highly acidic environments. Characterization of these organisms—their environments and their evolutionary pathways—is considered a crucial component to understanding how life might evolve elsewhere in the universe. Recently, a number of astrobiologists have teamed up with marine biologists and geologists to search for extremophiles and other organisms living around hydrothermal vents on the floors of our own oceans. Scientists hope to use their findings to help them create hypotheses on whether life could potentially exist on certain moons in our own solar system.
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Extremophiles:
An extremophile is an organism, usually unicellular, which thrives in or requires 'extreme' conditions that would exceed optimal conditions for growth and reproduction in the majority of mesophilic terrestrial organisms. Most extremophiles are microbes. The domain Archaea is known for widespread extremophily, but extremophiles are present in numerous and diverse genetic lineages of both the bacteria and archaea. Although the terms archaea and extremophile are occasionally used interchangeably, there are many mesophile archaeans and many extremophile bacteria. Additionally, not all extremophiles are unicellular. Examples of extremophilic metazoa are the Pompeii worm, the psychrophilic Grylloblattodea (insects), antarctic krill (crustaceans) and the Tardigrade. Extremophiles and astrobiology: Astrobiologists are particularly interested in studying extremophiles, as many organisms of this type are capable of surviving in environments similar to those known to exist on other planets. For example, Mars may have regions in its deep subsurface permafrost that could harbor endolith communities. The subsurface water ocean of Jupiter's moon Europa may harbor life, especially at hypothesized hydrothermal vents at the ocean floor.
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Panspermia:
Panspermia is the hypothesis that the seeds of life are in the Universe, that they may have delivered life to Earth, and that they may deliver or have delivered life to other habitable bodies; also the process of such delivery. Exogenesis is a related, but less radical, hypothesis that simply proposes that life did not originate on Earth, but was transferred to Earth from elsewhere in the Universe, with no prediction about how widespread life is. The term 'panspermia' is more well-known, however, and tends to be used in reference to what would properly be called exogenesis, too. Space is a damaging environment for life, as it would be exposed to radiation, cosmic rays and stellar winds. However, some bacteria may be able to survive these conditions. Also, environments may exist within meteorites or comets that are somewhat shielded from these hazards.
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SETI:
SETI is the acronym for Search for Extra-Terrestrial Intelligence; organized efforts to detect intelligent aliens. A number of efforts with 'SETI' in the project name have been organized, including projects funded by the United States Government. The generic approach of SETI projects is to survey the sky to detect the existence of transmissions from a civilization on a distant planet - an approach widely endorsed by the scientific community as hard science. There are great challenges in searching across the sky to detect a first transmission that can be characterised as intelligent, since its direction, spectrum and method of communication are all unknown beforehand.
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Zoo hypothesis:
The zoo hypothesis is one of a number of suggestions that have been advanced in response to the Fermi paradox, regarding the apparent absence of evidence in support of the existence of advanced extraterrestrial life. According to this hypothesis, aliens would generally avoid making their presence known to humanity, or avoid exerting an influence on human development, somewhat akin to zookeepers observing animals in a zoo. Adherents of the hypothesis consider that Earth and humans are being secretly sureveyed using equipment located on Earth or elsewhere in the solar system which relays information back to the observers. It is also suggested that overt contact will eventually be made with humanity once they reach a certain level of development.
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Drake equation:
The Drake equation (also known as the Green Bank equation or the Sagan equation) is a famous result in the speculative fields of xenobiology, astrosociobiology and the search for extraterrestrial intelligence. This equation was devised by Dr Frank Drake (now Emeritus Professor of Astronomy and Astrophysics at the University of California, Santa Cruz) in the 1960s in an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. The main purpose of the equation is to allow scientists to quantify the uncertainty of the factors which determine the number of extraterrestrial civilizations. In recent years, the Rare Earth hypothesis, which posits that conditions for intelligent life are quite rare in the universe, has been seen as a possible refutation of the equation.
The Drake equation is closely related to the Fermi paradox.
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Rare Earth Hypothesis:
In planetary astronomy and astrobiology, the Rare Earth hypothesis asserts that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. The Rare Earth hypothesis is explained in detail in the book Rare Earth: Why Complex Life Is Uncommon in the Universe, by Peter Ward, a geologist and paleontologist, and Donald Brownlee, an astronomer and astrobiologist. The Rare Earth hypothesis is the contrary of the principle of mediocrity (also called the Copernican principle), whose best known recent advocates include Carl Sagan and Frank Drake. The principle of mediocrity maintains that the Earth is a typical rocky planet in a typical planetary system, located in an unexceptional region of a large but conventional barred-spiral galaxy. Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the solar system, and our region of the Milky Way are probably extremely rare.
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Habitable zone:
In astronomy a habitable zone (HZ) is a region of space where conditions are favorable for the creation of life. There are two regions that must be favorable, one within a solar system and the other within the galaxy. Planets and moons in these regions are the likeliest candidates to be habitable and thus capable of bearing extraterrestrial life. Astronomers believe that life is most likely to form within the circumstellar habitable zone (CHZ) within a solar system, and the galactic habitable zone (GHZ) of the larger galaxy (though research on the latter point remains nascent). The HZ may also be referred to as the 'life zone', 'Green Belt' or the 'Goldilocks Zone'. Within a solar system, it is believed a planet must lie within the habitable zone in order to sustain life. The circumstellar habitable zone (or ecosphere) is a notional spherical shell of space surrounding stars where the surface temperatures of any planets present might maintain liquid water. Many believe liquid water is vital because of its role as the solvent needed for biochemical reactions. The location of a solar system within the galaxy must also be favorable to the development of life, and this leads to the concept of a galactic habitable zone. To harbor life, a solar system must be close enough to the galactic center that a sufficiently high level of heavy elements exist to favor the formation of rocky planets, and heavier elements are also necessary to form complex molecules of life. On the other hand, the solar system must be far enough from the galaxy center to avoid hazards such as impacts from comets and asteroids, close encounters with passing stars, and outbursts of radiation from supernovae and from the black hole at the center of the galaxy.
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Fine-tuned universe:
The term fine-tuned universe refers to the idea that conditions that allow life in the universe are the result of the exact values of the universal physical constants, and that small changes in these constants would correspond to a very different universe, not conducive to the establishment and development of matter, astronomical structures, or life as we know them. The arguments relating to the fine-tuned universe concept are related to the weak anthropic principle, which states that any valid theory of the universe must be consistent with our existence as human beings at this particular time and place in the universe. The premise of the fine-tuned universe assertion is that any small change in the approximately 26 dimensionless fundamental physical constants would make the universe radically different: if, for example, the strong nuclear force were 2% stronger than it is (i.e. if the constant representing its strength were 2% larger), diprotons would be stable and hydrogen would fuse into them instead of deuterium and helium. This would drastically alter the physics of stars, and presumably prevent the universe from developing life as we know it.
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Trans-Neptunian objects:
A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. The Kuiper belt, Scattered disk, and Oort cloud are names for three divisions of this volume of space. The orbit of each of the planets is affected by the gravitational influences of all the other planets. Discrepancies in the early 1900s between the observed and expected orbits of the known planets suggested that there were one or more additional planets beyond Neptune. The search for these led to the discovery of Pluto. It took more than 60 years to discover another TNO. Since 1992 however, more than 1000 objects have been discovered, differing in sizes, orbits and surface composition. Notable trans-Neptunian objects: Pluto (dwarf planet), Charon (largest moon of Pluto), Eris (dwarf planet, currently the largest known TNO with one known satellite, Dysnomia), Varuna and Quaoar, Orcus and Ixion, Sedna, 2005 FY9 (third largest known TNO) and 2003 EL61.
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Eris:
Eris, also designated 136199 Eris, is the largest known dwarf planet in the solar system. It is a trans-Neptunian object (TNO), orbiting the Sun in a region of space known as the scattered disc, just beyond the Kuiper belt, and accompanied by at least one moon, Dysnomia. Mike Brown, who led the Mount Palomar-based discovery team, announced in April 2006 that the Hubble Telescope has measured Eris's diameter to be 2400 km, slightly larger than that of Pluto. Eris' size resulted in its discoverers and NASA labelling it the solar system's tenth planet. This, along with the prospect of other similarly sized objects being discovered in the future, stimulated the International Astronomical Union (IAU) to define the term 'planet' more precisely. Under a new definition approved on August 24, 2006, Eris was designated a 'dwarf planet' along with Pluto and Ceres.
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Oort cloud:
The Oort cloud is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the Sun. This is approximately 2000 times the distance from the Sun to Pluto or roughly one light year, almost a quarter of the distance from the Sun to Proxima Centauri, the star nearest the Sun. The Oort cloud would have its inner disk at the ecliptic from the Kuiper belt. Although not confirmed direct observations have been made of such a cloud, astronomers believe it to be the source of most or all comets entering the inner solar system (some short-period comets may come from the Kuiper belt), based on direct observations of the orbits of comets.
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Brown dwarf:
Brown dwarfs are sub-stellar objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores, as do stars on the main sequence, but which have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas-giant planets and the lowest mass stars (anywhere between 75 and 80 Jupiter masses). Currently there is a large ambiguity as to what separates a brown dwarf from a giant planet at very low brown dwarf masses (approx. 13 Jupiter masses). For most stars, gas and radiation pressure generated by the thermonuclear fusion reactions within the core of the star will support it against any further gravitational contraction. Hydrostatic equilibrium is reached and the star will spend most of its lifetime burning hydrogen to helium as a main-sequence star. If, however, the mass of the protostar is less than about 0.08 solar mass, normal hydrogen thermonuclear fusion reactions will not ignite in the core. Gravitational contraction does not heat the small protostar very effectively, and before the temperature in the core can increase enough to trigger fusion, the density reaches the point where electrons become closely packed enough to create quantum electron degeneracy pressure.
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Yellow dwarf:
A yellow dwarf or G-type star is a small (about 0.9 to 1.4 solar masses), yellow main sequence star that is in the process of converting hydrogen to helium in its core by means of nuclear fusion. Our Sun is the most well-known example of a yellow dwarf. A yellow dwarf's lifespan is about 10 billion years, until its supply of hydrogen runs out. When this happens, the star expands to many times its previous size and becomes a red giant. The star Aldebaran is an example of a red giant. Eventually the red giant sheds its outer layers of gas, which become a planetary nebula, while the core collapses into a small, dense white dwarf.
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Orange dwarf:
Orange dwarfs are main sequence stars of spectral type K. These stars are intermediate in size between M class red dwarf stars and yellow G class stars such as the Earth's Sun. Orange dwarfs vary from 0.5 to 0.9 times the mass of the Sun and have a surface temperature between 4000 and 5200 degrees Celsius. Examples include Alpha Centauri B and Epsilon Indi. These stars are of particular interest in the search for extraterrestrial life because they are stable on the main sequence for a very long time (15 to 30 billion years, compared to 10 billion for the Earth's Sun). This may create an opportunity for life to evolve on terrestrial planets orbiting such stars.
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Supernova:
A supernova (pl. supernovae) is a stellar explosion which produces an extremely bright object made of plasma that declines to invisibility over weeks or months. A supernova briefly outshines its entire host galaxy. It would take 10 billion years for the Sun to produce the energy output of an ordinary Type II supernova. Stars beneath the Chandrasekhar limit, such as the Sun, are too light to ever become supernovae and will evolve into white dwarfs. There are several different types of supernovae and two possible routes to their formation. A massive star may cease to generate fusion energy from fusing the nuclei of atoms in its core, and collapse under the force of its own gravity to form a neutron star or black hole. A widely-observed supernova in the year 1054 produced the Crab Nebula.
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Survivalism:
A survivalist is a person who anticipates and prepares for a future disruption in local, regional or worldwide social or political order. Survivalists often prepare for this anticipated disruption by learning skills (e.g., emergency medical training), stockpiling food and water, or building structures that will help them to survive (e.g., an underground shelter). The specific preparations made by survivalists depend on the nature of the anticipated disruption, some of the most commonly anticipated being
- Natural disasters, such as tornadoes, hurricanes, earthquakes, blizzards, and severe thunderstorms
- A disaster brought about by the activities of humankind: chemical spills, release of radioactive materials, or war.
- General collapse of society, resulting from the unavailability of electricity, fuel, food, and water.
- Widespread chaos, or some other apocalyptic event.
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Space and survival:
Space and survival is the relationship between space and the long-term survival of the human species and civilization. It is based on the observation that space colonization and space science would prevent many human extinction scenarios. A related observation is the limited time and resources available for the colonization of space. Extinction can be prevented by improving the physical barrier or increasing the distance between people and the potential extinction event. For example, people survive imminent explosions by being in a bunker or evacuating. Pandemics are controlled by putting exposed people in quarantine and moving healthy people away. Life support systems that enable people to live in space may also allow them to survive hazardous events. For example, an infectious disease or biological weapon that transmits through the air could not infect a person in a life support system. There is an internal supply of air and a physical barrier between the person and the environment. Increasing the number of places where humans live also prevents extinction. For example, if a massive impact event occurred on Earth without warning, the human species would probably become extinct, and its art, culture and technology would be lost. However, if humans had previously colonized locations outside Earth, the species would survive and possibly recover. do not currently exist. There is a concern that the human species may lose its technological knowledge, use up required resources or become extinct before it colonizes space.
The author Sylvia Engdahl wrote about the 'Critical Stage', a period of time when a civilization has both the technology to expand into space and the technology to destroy itself. Engdahl states that the human civilization is at a Critical Stage, but that the funding for space exploration and colonization is minuscule compared to the funding for weapons of mass destruction and military forces. NBC News space analyst James Oberg commented that "It's just a matter of waiting until we get some kind of cosmic 9/11 that will make everyone say 'why didn't we see this before,' and then we'll have enough money to afford these programs."
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Terraforming:
Terraforming (literally, 'Earth-shaping') is the theoretical process of modifying a planet, moon, or other body to a more habitable atmosphere, temperature, or ecology. It is a type of planetary engineering. The term is sometimes used broadly as a synonym for planetary engineering in general. The concepts of terraforming are rooted both in science fiction and actual science. The term was probably coined by Jack Williamson in a science-fiction story published in 1942.
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Nanotechnology:
Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale below 100 nanometers, as well as the fabrication of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry. Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research. Despite the apparent simplicity of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, including colloidal science, chemistry, applied physics, biology. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a 'bottom-up' approach where materials and devices are built from molecular components which assemble themselves chemically using principles of molecular recognition; the other being a "top-down" approach nano-objects are constructed from larger entities without atomic-level control.
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Carbon nanotube:
Carbon nanotubes (CNTs) are an allotrope of carbon. They take the form of cylindrical carbon molecules and have novel properties that make them potentially useful in a wide variety of applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized. Nanotubes are members of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several millimeters in length.
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Redundancy in engineering:
Redundancy in engineering is the duplication of critical components of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe. In many safety-critical systems, such as fly-by-wire aircraft, some parts of the control system may be triplicated. An error in one component may then be out-voted by the other two. In a triply redundant system, the system has three sub components, all three of which must fail before the system fails. Since each one rarely fails, and the sub components are expected to fail independently, the probability of all three failing is calculated to be extremely small.
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Faster-than-light starship:
Faster-than-light (also superluminal or FTL) communications and travel refer to the propagation of information or matter faster than the speed of light. This concept is a staple of the science fiction genre, but is generally considered impossible by the mainstream physics community, due to special relativity. In the context of this article, FTL refers to transmitting information or matter faster than c, a constant equal to the speed of light in a vacuum, 299,792,458 meters per second, or roughly 186,000 miles per second. This is the simplest solution, and is particularly popular in science fiction. However, empirical evidence unanimously support Einstein's theory of special relativity as the correct description of high-speed motion, which reduces in the low-speed case to Galilean relativity, which is an approximation only valid for slow speeds. Similarly, general relativity is unanimously supported as the correct theory of gravitation in the regime of very large masses and long distances. Unfortunately, general relativity breaks down at small distances and is no longer valid in the quantum regime. Special relativity is easily incorporated into nongravitational quantum field theories, however it only applies to a flat Minkowski universe.
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Time dilation:
Time dilation is the phenomenon whereby an observer finds that another's clock which is physically identical to their own is ticking at a slower rate as measured by their own clock. This is often taken to mean that time has "slowed down" for the other clock, but that is only true in the context of the observer's frame of reference. Locally, time is always passing at the same rate. The time dilation phenomenon applies to any process that manifests change over time. Time dilation would make it possible for passengers in a fast moving vehicle to travel into the further future while aging very little, in that their great speed retards the rate of passage of onboard time. That is, the ship's clock (and according to relativity, any human travelling with it) shows less elapsed time than stationary clocks. For sufficiently high speeds the effect is dramatic. For example, one year of travel might correspond to ten years at home. Indeed, a constant 1 g acceleration would permit humans to circumnavigate the known universe (with a radius of some 13.7 billion light years) in one human lifetime. A more likely use of this effect would be to enable humans to travel to nearby stars without spending their entire lives aboard the ship. However, any such application of time dilation would require the use of some new, advanced method of propulsion.
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