Glossary of the book
The Future Happens Twice


Matt Browne

This book explores the scientific progress
expected to be made in the next 50 years.

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Alphabetical list of subjects

Source: Wikipedia - Click on term to read full article

Abrupt climate change Abrupt climate change refers to an event where large and widespread climate change occurs within about five years. At least two modes of climate are now recognized: a warm-and-wet climate like today's and a climate that is cooler, drier, windy and dusty.
Accelerating universe The Accelerating universe is the idea that our universe is undergoing accelerated expansion: distant objects are receding from our galaxy with speeds that increase over time. If the acceleration continues indefinitely, the ultimate result of this trend will be that galaxies outside the local supercluster will move beyond the cosmic horizon and will no longer be visible.
Albedo measurement Albedo is the ratio of reflected to incident electromagnetic radiation power. It is a unitless measure indicative of a surface's or body's reflectivity. Albedos of typical materials in visible light range from up to 90% for fresh snow, to about 4% for charcoal, one of the darkest substances.
Alpha Magnetic Spectrometer The Alpha Magnetic Spectrometer is a particle physics experiment to be mounted on the International Space Station designed to search for a various types of unusual matter.
Antigravity models Spacetime geometries corresponding to true anti-gravity in general relativity require negative mass. Most physicists believe that at extremely high energies, gravity and the other fundamental forces unify, which would allow gravity to be manipulated in ways that are not readily apparent now. Candidate models for this regime are theories of everything, which attempt to model all four forces (example: string theory), and theories of quantum gravity, which attempt to produce a model of gravity that is consistent with quantum mechanics, though not necessarily unified with the other forces.
Antiproton decelerator The Antiproton Decelerator (AD) is a particle accelerator at the CERN laboratory in Geneva. The decelerated antiprotons are ejected to one of the connected experiments.
Aperture synthesis Aperture synthesis is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and orientation, the lobe-pattern of the interferometer produces an output which is one component of the Fourier transform of the spatial distribution of the brightness of the observed object.
Arcology Arcology is a set of architectural design principles as described by the architect Paolo Soleri. The word combines architecture and ecology. The principles are aimed toward the design of enormous habitats (hyperstructures) of extremely high human population density.
Arecibo radio telescope The Arecibo Observatory is located approximately 9 miles south-southwest from Arecibo, Puerto Rico (near the extreme southwestern corner of Arecibo pueblo). It is operated by Cornell University under cooperative agreement with the National Science Foundation. The observatory works as the National Astronomy and Ionosphere Center (NAIC) although both names are officially used to refer to it.
Artificial gravity Artificial gravity is a simulation of gravity in outer space or free-fall. Artificial gravity is desirable for long-term space travel for ease of mobility and to avoid the adverse health effects of weightlessness.
Artificial insemination Artificial insemination is when sperm is placed into a female's uterus (intrauterine), or cervix (intracervical) using artificial means rather than by natural copulation. Modern techniques for artificial insemination were first developed for the dairy cattle industry to allow many cows to be impregnated with the sperm of a bull with traits for improved milk production.
Artificial intelligence Artificial intelligence (AI) is a subject of study in computer science, psychology and engineering that deals with intelligent behavior, learning, and adaptation in machines. Research in AI is concerned with producing machines to automate tasks requiring intelligent behavior.
Artificial uterus In the field of ectogenesis, an artificial uterus (or artificial womb) is a mechanism that is used to grow an embryo outside of the body of a female organism that would normally internally carry the embryo to term. An artificial uterus, as a replacement organ, could also be used to assist women with damaged or diseased uteri to be able to conceive to term. A particular form of artificial uterus is one in which tanks are filled with amniotic fluid which is maintained at body temperature, and the embryonic umbilical cords are attached to external pumps which regulate nutrient intake and waste outflow. A potential advantage of such a system is that it would allow the fetus to develop in an environment that is not influenced by the presence of disease, environmental pollutants, alcohol, or drugs which the mother may have in her circulatory system.
Asteroseismology Asteroseismology is the study of the internal structure of pulsating stars by the interpretation of their frequency spectra. Different oscillation modes penetrate to different depths inside the star. These oscillations provide information about the otherwise unobservable interiors of stars in a manner similar to how seismologists study the interior of Earth and other solid planets through the use of earthquake oscillations.
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?
Astrochemistry Astrochemistry is the study of the chemical elements found in outer space, generally on larger scales than the Solar System, particularly in molecular gas clouds, and the study of their formation, interaction and destruction. As such, it represents an overlap of the disciplines of astronomy and chemistry. On the Solar System scale, the study of chemical elements is usually called cosmochemistry.
Astrogation The word astrogation denotes navigation of spacecraft, either in interplanetary travel or in interstellar travel. The mathematical principles governing interplanetary astrogation were derived by mathematical physicists in the 19th and 20th centuries.
Astronautics Astronautics is the branch of engineering that deals with machines designed to work outside of Earth's atmosphere, whether manned or unmanned. In other words, it is the science and technology of space flight. Astronautics was coined by analogy with aeronautics. As with aeronautics, the restrictions of weight, heat and external forces require that applications in space survive extreme conditions, whether the heat of reentry, the radiation bombardment of interplanetary space, or the magnetic belts of orbit, space vessels must be designed to withstand forces almost unknown on Earth.
Astronomical inferometer An astronomical interferometer or hypertelescope is an array of telescopes or mirror segments acting together to probe structures with higher resolution.
Astroparticle physics Astroparticle physics is a term used to indicate that branch of particle physics that studies elementary particles of astronomical origin, and their relation to astrophysics and cosmology. The most active topics in astroparticle physics are: Gamma-ray astronomy, Neutrinos and Neutrino astronomy, Magnetic monopoles, and Axions.
Astrophysics Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. The study of cosmology is theoretical astrophysics at the largest scales where Einstein's general theory of relativity plays a major role.
Astrosociobiology Astrosociobiology (also referred to as exosociobiology, extraterrestrial intelligence (eti), and xenosociology) is the speculative scientific study of extraterrestrial civilizations and their possible social characteristics and developmental tendencies. The field involves the convergence of astrobiology, sociobiology and evolutionary biology. Hypothesized comparisons between human civilizations and those of extraterrestrials are frequently posited, placing the human situation in the same context as other extraterrestrial intelligences.
Baryogenesis In physical cosmology, baryogenesis (also referred to as Baryon genesis) is the generic term for hypothetical physical processes that produced an asymmetry between baryons and anti-baryons in the very early universe, resulting in the substantial amounts of residual matter that comprise the universe today. The unsolved problems in physics is: Why does the observable universe have more matter than antimatter? Baryogenesis theories (the most important being electroweak baryogenesis and GUT baryogenesis) employ sub-disciplines of physics such as quantum field theory, and statistical physics, to describe such possible mechanisms.
Baryon In particle physics, the baryons are the family of subatomic particles which are made of three quarks. The family notably includes the proton and neutron, which make up the atomic nucleus, but many other unstable baryons exist as well. Baryons are strongly interacting fermions - that is, they experience the strong nuclear force. Baryons, along with mesons, belong to the family of particles known as hadrons, meaning they are composed of quarks. Baryons are fermions composed of three quarks, while mesons are bosons composed of a quark and an antiquark.
Behavioral genetics Behavioural genetics (behavioral genetics) is the field of biology that studies the role of genetics in animal behaviour. The field is an overlap of genetics, ethology and psychology (particularly evolutionary psychology). Classically, behavioural geneticists have studied the heritability of behavioural traits.
Bio-engineering See Bioengineering
Bio-technology See Biotechnology
Biodiversity Biodiversity or biological diversity is the variation of taxonomic life forms within a given ecosystem, biome or for the entire Earth. Biodiversity is often a measure of the health of biological systems to indicate the degree to which the aggregate of historical species are viable versus extinct.
Bioengineering Bioengineering or biological engineering deals with engineering biological processes in general. It is a broad-based engineering discipline that also may involve product design, sustainability and analysis of biological systems.
Biogeochemical cycle In ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a chemical element or molecule moves through both biotic and abiotic compartments of an ecosystem. In effect, the element is recycled, although in some such cycles there may be places (called "sinks") where the element is accumulated or held for a long period of time. All chemical elements occurring in organisms are part of biogeochemical cycles. In addition to being a part of living organisms, these chemical elements also cycle through abiotic factors of ecosystems such as water (hydrosphere), land (lithosphere), and the air (atmosphere).
Biomedical engineering Biomedical engineering (BME) is the application of engineering principles and techniques to the medical field. It combines the design and problem solving expertise of engineering with the medical expertise of physicians to help improve patient health care and the quality of life of healthy individuals. As a relatively new discipline, much of the work in biomedical engineering consists of research and development, covering an array of fields: bioinformatics, medical imaging, image processing, physiological signal processing, biomechanics, biomaterials and bioengineering, and systems analysis.
Biophilic universe Cosmological natural selection was created by physicist Lee Smolin as a testable alternative to string theory predictions of an enormous landscape of possible universes. CNS holds that the creation of a black hole often or always entails the creation of baby universes, and that through a process of selection that in some ways mimics evolutionary natural selection, universes are created that are optimized for creating black holes. By extension, these same universes are optimized for creating stable atoms, long lived stars, and lots of stable carbon atoms. This last point also happens to explain why our universe seems to be biophilic.
Biosphere The biosphere is the outermost part of the planet's shell, including air, land, surface rocks and water, within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships.
Biotechnological uterus See Artificial uterus
Biotechnology Biotechnology is technology based on biology, especially when used in agriculture, food science, and medicine. Biotechnology means any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use.
Black dwarf A black dwarf is a hypothetical astronomical object: a white dwarf so old that it has cooled down so that it no longer emits significant heat or light. None are expected to exist yet, since the time required for a white dwarf to cool down is calculated to be longer than the current age of the universe. Both black dwarfs and white dwarfs are degenerate dwarfs.
Black hole radiation In physics, Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation thought to be emitted by black holes due to quantum effects. It is named after British physicist Stephen Hawking who worked out the theoretical argument for its existence in 1974.
Bosonic perturbations Bosonic string theory is the original version of string theory, developed in the late 1960s. Although it has many attractive features it has a pair of features that render it unattractive as a physical model. Firstly it predicts only the existence of bosons whereas we know many physical particles are fermions. Secondly, it predicts the existence of a particle whose energy is negative implying that it travels faster than light. The existence of such a particle, commonly known as a tachyon, would conflict with much of what we know about physics, and such particles have never been observed.
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.
Bussard ramjet The Bussard ramjet method of spacecraft propulsion was proposed in 1960 by the physicist Robert W. Bussard as a variant of a fusion rocket capable of fast interstellar spaceflight. It would use a large scoop (on the order of kilometers in diameter) to compress hydrogen from the interstellar medium and fuse it. This mass would then form the exhaust of a rocket to accelerate the ramjet. An ideal ramjet design could in principle accelerate indefinitely until its mechanism failed. Such a ramjet could theoretically accelerate arbitrarily close to the velocity of light, and would be a very effective interstellar spacecraft.
Cambrian explosion The Cambrian explosion is the geologically sudden appearance in the fossil record of the ancestors of familiar animals, starting about 542 million years ago (Mya). In addition, a similar pattern of diversification is seen in other organisms such as phytoplankton and the various colonial calcareous microfossils grouped together as calcimicrobes.
Carbon cycle he carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth (other astronomical objects may have similar carbon cycles, but nothing is yet known about them). The cycle is usually thought of as four major reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere, the terrestrial biosphere (which usually includes freshwater systems and non-living organic material, such as soil carbon), the oceans (which includes dissolved inorganic carbon and living and non-living marine biota), and the sediments (which includes fossil fuels).
Carbon nanotubes 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.
Chaos theory In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. In biology chaos theory can explain how small random events may affect large ecosystems in an unpredictable way. Among the characteristics of chaotic systems, described below, is the sensitivity to initial conditions (popularly referred to as the butterfly effect).
Cloning and stem cells Cloning is the process of creating an identical copy of something. In Biology, it collectively refers to processes used to create copies of DNA fragments (Molecular Cloning), Cells (Genetic Cloning), or organisms. Stem cells are primal cells common to all multi-cellular organisms that retain the ability to renew themselves through cell division and can differentiate into a wide range of specialized cell types. The three broad categories of mammalian stem cells exist: embryonic stem cells, derived from blastocysts, adult stem cells, which are found in adult tissues, and cord blood stem cells, which are found in the umbilical cord. In a developing embryo, stem cells are able to differentiate into all of the specialized embryonic tissues.
Cognitive psychology Cognitive Psychology is the school of psychology that examines internal mental processes such as problem solving, memory, and language. It had its foundations in the Gestalt psychology of Max Wertheimer, Wolfgang Köhler, and Kurt Koffka, and in the work of Jean Piaget, who studied intellectual development in children. Cognitive psychologists are interested in how people understand, diagnose, and solve problems, concerning themselves with the mental processes which mediate between stimulus and response.
Cognitive robotics Cognitive robotics is concerned with endowing robots with high-level cognitive capabilities to enable the achievement of complex goals in complex environments using limited computational resources. Robotic cognitive capabilities include perception processing, attention allocation, anticipation, planning, reasoning about other agents, and reasoning about their own mental states. Robotic cognition embodies the behaviour of intelligent agents in the physical world. Cognitive robotics involves the application and integration of various artificial intelligence disciplines, such as knowledge representation, automated reasoning and planning. It also involves the use of agent programming languages for defining transitions between mental states.
Cognitive science Cognitive science is usually defined as the scientific study either of mind or of intelligence (e.g. Luger 1994). Practically every formal introduction to cognitive science stresses that it is a highly interdisciplinary research area in which psychology, education, neuroscience, linguistics, philosophy, computer science, anthropology, and biology are its principal specialized or applied branches.
Colonization of the outer solar system Some of the moons of the outer planets of the solar system are large enough to be suitable places for colonization. Many of the larger moons contain water ice, liquid water, and organic compounds that might be useful for rocket fuel production among other things. Colonies in the outer solar system could also serve as centres for long term investigation of the planet and the other moons.
Comparative genomics Comparative genomics is the study of relationships between the genomes of different species or strains. Comparative genomics is an attempt to take advantage of the information provided by the signatures of selection to understand the function and evolutionary processes that act on genomes. While it is still a young field, it holds great promise to yield insights into many aspects of the evolution of modern species. The sheer amount of information contained in modern genomes (several gigabytes in the case of humans) necessitates that the methods of comparative genomics are mostly computational in nature. Gene finding is an important application of comparative genomics, as is discovery of new, non-coding functional elements of the genome. Comparative genomics exploits both similarities and differences in the proteins, RNA, and regulatory regions of different organisms to infer how selection has acted upon these elements.
Computational linguistics Computational linguistics is an interdisciplinary field dealing with the statistical and logical modeling of natural language from a computational perspective. This modeling is not limited to any particular field of linguistics.
Computational neuroscience Computational Neuroscience is an interdisciplinary science that links the diverse fields of neuroscience, computer science, physics and applied mathematics together. It serves as the primary theoretical method for investigating the function and mechanism of the nervous system. Computational neuroscience is distinct from psychological connectionism and theories of learning from disciplines such as machine learning, neural networks and statistical learning theory in that it emphasizes descriptions of functional and biologically realistic neurons and their physiology and dynamics.
Computer architecture In computer engineering, computer architecture is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements (especially speeds and interconnections) and design implementations for the various parts of a computer — focusing largely on the way by which the central processing unit performs internally and accesses addresses in memory.
Corot mission CoRoT (Convection Rotation and planetary Transits) is a space mission led by the French Space Agency (CNES) in conjunction with the European Space Agency and other international partners. The primary objective of CoRoT will be to search for extrasolar planets, particularly those of large terrestrial size.
Cosmic dust Cosmic dust is composed of particles in space which are a few molecules to 0.1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, circumplanetary dust, dust clouds around other stars, and the major interplanetary dust components to our own zodiacal dust complex.
Cosmochemistry Cosmochemistry is concerned with the origin and development of the elements and their isotopes, primarily within the Solar System. The term was coined by Harold Urey. In contrast with astrochemistry, which is concerned with chemical elements in other parts of our Galaxy and in other galaxies which precludes bringing samples of chemical elements to laboratories on the Earth on a short (less than a few millennia) time scales, cosmochemistry can and frequently does involve direct contact (other than via photons) with celestial samples of chemical elements.
Cryobot A cryobot or Philberth-probe is a robot designed to operate in or around water ice. The cryobot is a surface-controlled, nonrecoverable instrumented vehicle that can penetrate polar ice sheets down to 3600 m by melting. It can be used to measure temperature, stress, ice movement, and seismic, acoustic and dielectric properties. Cryobots are being tested in Antarctica as prototypes for a space probe that may someday penetrate the icy surface of Europa, a moon of Jupiter, and explore the liquid water ocean thought to be present below the ice, which may harbour extraterrestrial life.
Cryonics The emerging medical technology of cryopreserving humans and animals with the intention of future revival. As a technology, cryonics seeks to apply the results of many sciences, including cryobiology, cryogenics, rheology, and emergency medicine. The process is not currently reversible. Cryonics can only be legally performed on humans after clinical death, and a legal determination that further medical care is not appropriate (legal death). The rationale for cryonics is that the process may be reversible in the future if performed soon enough, and that cryopreserved people may not really be dead by standards of future medicine.
Cryopreservation Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures, such as (typically) 77 K or -196 °C (the boiling point of liquid nitrogen). At these low temperatures, any biological activity, including the biochemical reactions that would lead to cell death, is effectively stopped.
Cryonic suspension See Cryonics
Cryopreservation Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures, such as (typically) -80 or -196 degrees Celsius (the boiling point of liquid nitrogen). At these low temperatures, any biological activity, including the biochemical reactions that would lead to cell death, is effectively stopped.
Cryopreserved embryos Employment of cryopreservation techniques for deep-freezing embryos.
Cryotravel Long distance space travel by means of cryopreserved humans or human embryos.
Cryotube Apparatus that contains cryopreserved humans on a spaceship.
Cryptobiosis Cryptobiosis is an ametabolic state of life entered by some lower organisms in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair. An organism in a cryptobiotic state can essentially live indefinitely until environmental conditions return to being hospitable.
Cyborg A cyborg is a cybernetic organism which adds to or enhances its abilities by using technology. Fictional cyborgs are frequently portrayed with a fine granularity mixture of organic and mechanical (synthetic) parts.
Daedalus crater Daedalus is a prominent crater located near the center of the far side of the Moon. The inner wall is terraced, and there is a cluster of central peaks on the relatively flat floor. Because of its location (shielded from radio emissions from the Earth), it has been proposed as the site of a future giant radio telescope, which would be scooped out of the crater itself, much like the Arecibo radio telescope, but on a vastly larger scale.
Daedalus project Project Daedalus was a study conducted by the British Interplanetary Society to design a plausible interstellar unmanned spacecraft. A dozen scientists and engineers led by Alan Bond worked on the project, and settled on proposing a fusion rocket as its drive. The design criteria had specified that the spacecraft had to use current or near-future technology and had to be able to reach its destination within a human lifetime (a flight time of 50 years was allocated). Daedalus would be constructed in Earth orbit and have an initial mass of 54,000 tons, including 50,000 tons of fuel and 500 tons of scientific payload. Daedalus was to be a two-stage spacecraft. The first stage would operate for two years, taking the spacecraft to 7.1% of light speed (0.071 c), and then after it was jettisoned the second stage would fire for 1.8 years, bringing the spacecraft up to about 12% of light speed (0.12 c) before being shut down for a 46-year cruise period. This velocity was well beyond the capabilities of chemical rockets, or even the type of nuclear pulse propulsion studied during Project Orion. Instead, Daedalus would be propelled by a fusion rocket using pellets of deuterium/helium-3 mix that would be ignited in the reaction chamber:
Dark energy In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and has strong negative pressure. According to the Theory of Relativity, the effect of such a negative pressure is qualitatively similar to a force acting in opposition to gravity at large scales. Invoking such an effect is currently the most popular method for explaining recent observations that the universe appears to be expanding at an accelerating rate, as well as accounting for a significant portion of the missing mass in the universe. Repulsive force is the temporary name given to the force that seems to tear away the universe.
Dark matter halo Most of the mass of any galaxy is dominated by a component concentrated at the centre of the galaxy but dominating its dynamics throughout, known as the dark matter halo. The presence of dark matter in the halo is demonstrated by its gravitational effect on a spiral galaxy's rotation curve. Without large amounts of mass in the extended halo, the rotational velocity of the galaxy should decrease at large distance from the galactic core. However, observations of spiral galaxies, particularly radio observations of line emission from neutral atomic hydrogen (known, in astronomical parlance, as HI), show that the rotation curve of most spiral galaxies remains flat far beyond the visible matter. The absence of any visible matter to account for these observations implies the presence of unobserved (i.e. dark) matter.
Darwin mission Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. The launch date will be at or after 2015.
Deep Blue Deep Blue was a chess-playing computer developed by IBM. In 1997, the machine defeated world champion Garry Kasparov. The computer system dubbed "Deep Blue" was the first machine to win a chess game against a reigning world champion (Garry Kasparov) under regular time controls. This first win occurred on February 10, 1996. Deep Blue - Kasparov, 1996, Game 1 is a famous chess game.
Digital microfluidics Digital microfluidics is an alternative technology for lab-on-a-chip systems based upon micromanipulation of discrete droplets. Microfluidic processing is performed on unit-sized packets of fluid which are transported, stored, mixed, reacted, or analyzed in a discrete manner using a standard set of basic instructions. In analogy to digital microelectronics, these basic instructions can be combined and reused within hierarchical design structures so that complex procedures (e.g. chemical synthesis or biological assays) can be built up step-by-step. And in contrast to continuous-flow microfluidics, digital microfluidics works much the same way as traditional bench-top protocols, only with much smaller volumes and much higher automation.
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.
Dyson sphere A Dyson sphere (or shell as it appeared in the original paper) is a hypothetical megastructure that was originally described by Freeman Dyson as a system of orbiting solar power satellites meant to completely encompass a star and capture its entire energy output. Dyson speculated that such structures would be the logical consequence of the long-term survival of technological civilizations, and proposed that searching for evidence of the existence of such structures might lead to the detection of advanced intelligent extraterrestrial life.
Dystopia A dystopia (alternatively, cacotopia, kakotopia or anti-utopia) is a fictional society that is the antithesis of utopia. Some academic circles distinguish between anti-utopia and dystopia. A dystopia does not pretend to be good, while an anti-utopia appears to be utopian or was intended to be so, but a fatal flaw or malefactor has perverted it.
Earth-like planets in the Milky Way A terrestrial planet, telluric planet or rocky planet is a planet that is primarily composed of silicate rocks.
Earthquake prediction An earthquake prediction is a prediction that an earthquake in a specific magnitude range will occur in a specific region and time window. Seismologists are not currently able to predict earthquakes with such accuracy, though the early results of the Demeter satellite suggest that this could become possible; instead they focus on calculating the seismic hazards of a region by estimating the probabilities that a given earthquake or suite of earthquakes will occur. With regard to earthquake prediction, people have tried to associate an impending earthquake with such potential precursors as seismicity patterns, electromagnetic fields, weather conditions and unusual clouds, radon or hydrogen gas content of soil or ground water, water level in wells, and animal behavior.
Ectogenesis Ectogenesis is the creation of mammalian life outside the womb. Ectogenesis nominally refers to the complete artificial creation of life, as described in Aldous Huxley's novel Brave New World. However, the term has been applied to all technological developments that would result in a shortening of the time required for the fetus to attain viability following implantation in the womb. Ectogenesis involves the application of extracorporeal membrane oxygenation (ECMO) to previable infants whose lungs are incapable of gas exchange.
Ectosymbiosis Ectosymbiosis is symbiosis in which the symbiont lives on the body surface of the host, including internal surfaces such as the lining of the digestive tube and the ducts of glands.
ELE An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic classes present at the time - birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms.
Electron-positron annihilation Electron-positron annihilation occurs when an electron and a positron (the electron's anti-particle) collide. The result of the collision is the conversion of the electron and positron and the creation of gamma ray photons or, less often, other particles. The process must satisfy a number of conservation laws.
Embryo space colonization Embryo space colonization is a theoretical interstellar space colonization concept that involves sending a robotic mission to a habitable terrestrial planet transporting frozen early-stage human embryos or the technological or biological means to create human embryos. The proposal circumvents the most severe technological problems of other mainstream interstellar colonization concepts. In contrast to the sleeper ship proposal, it does not require the freezing of fully developed humans, which is not technologically feasible today and is regarded by many scientists as never feasible. Embryo space colonization concepts involve various concepts of delivering the embryos from Earth to another extrasolar planet around another star system. The most straightforward concept is to make use of frozen embryos. Modern medicine has made it possible to store frozen embryos in various low-development stages (up to several weeks in the development of the embryo). The technological more challenging but more flexible scenario calls for just carrying the biological means to create embryos, that is various samples of donated sperm and egg cells). Going a step further, the spacecraft "cargo" could be limited just to the DNA-Information of humans stored in digital form. In this case, sperm and egg cells would need to be recreated by a biosequencer at the target planet (this proposal is currently not technologically feasible).
Embryo splitting The forced creation of identical twins.
Embryo transfer Embryo transfer refers to a step in the life and times of in vitro fertilization (IVF) whereby one or several embryos are placed into the uterus of the female with the intent to establish a pregnancy. Embryos can be either fresh from fertilized egg cells of the same menstrual cycle, or frozen, that is they have been generated in a preceding cyle, cryopreserved, and are thawn just prior to the transfer. A colloquial term for babies conceived as the result of IVF, test tube babies, refers to the tube-shaped containers of glass or plastic resin, called test tubes, that are commonly used in chemistry labs and biology labs.
Embryonic interstellar travel See Embryo space colonization
Endosymbiosis An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis. Examples are nitrogen-fixing bacteria (called rhizobia) which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts provide essential nutrients to about 10% - 15% of insects.
Equivalence principle In the physics of relativity, the equivalence principle is applied to several related concepts dealing with gravitation and the uniformity of physical measurements in different frames of reference. They are related to the Copernican idea that the laws of physics should be the same everywhere in the universe, to the equivalence of gravitational and inertial mass, and also to Albert Einstein's assertion that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is actually the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.
Eris 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.
ESA The European Space Agency (ESA), established in 1975, is an inter-governmental organization dedicated to the exploration of space, currently with 17 member states. Its headquarters are in Paris, France. ESA's spaceport is the Centre Spatial Guyanais (Guyana Space Centre) in Kourou, French Guiana, a site chosen because it is close to the equator from which commercially important orbits are easier to access. During the 1990s ESA gained the position of market leader in commercial space launches and in recent years ESA has established itself as a major player in space exploration.
Exo-planet See Exoplanet
Exobiology See Astrobiology
Exogenesis See Panspermia
Exoplanet An extrasolar planet, or exoplanet, is a planet beyond the Solar System. Known exoplanets are members of planetary systems that orbit a star. There have also been unconfirmed reports of free-floating planetary-mass objects ("rogue planets": that is, ones that do not orbit any star). Since such objects do not satisfy the working definition of "planet" adopted by the International Astronomical Union, and since their existence remains unconfirmed, they will not be discussed in this article. For more information, see interstellar planet. Extrasolar planets became a subject of scientific investigation in the mid-nineteenth century. Astronomers generally supposed that some existed, but it was a mystery how common they were and how similar they were to the planets of the Solar System.
Exotic matter Exotic matter is a hypothetical concept of particle physics. It covers any material which violates one or more classical conditions or is not made of known baryonic particles. Such materials would possess qualities like negative mass or being repelled rather than attracted by gravity. It is used in certain speculative theories, such as on the construction of wormholes. The closest known real representative of exotic matter is a region of pseudo-negative pressure density produced by the Casimir effect. The term is also casually attached to any material which is difficult to produce (such as metallic hydrogen or a Bose-Einstein condensate) or which exhibits unusual properties (such as fullerenes or nanotubes), even though these materials have been created and are relatively well understood. It can also refer to material composed of some form of exotic atom.
Exploratory engineering Exploratory engineering is a term coined by K. Eric Drexler to describe the process of designing and analyzing detailed hypothetical models of systems that are not feasible with current technologies or methods, but do seem to be clearly within the bounds of what science considers to be possible within the narrowly defined scope of operation of the hypothetical system model. It usually results in paper prototypes or video prototypes or computer models that are as convincing as possible, to those that know the science, given the lack of experimental confirmation. By analogy with protoscience, it might be considered a form of protoengineering. Due to the difficulty and necessity of anticipating results in such areas as genetic modification, climate change, molecular engineering, and megascale engineering, parallel fields such as bioethics, climate engineering and hypothetical molecular nanotechnology sometimes emerge to develop and examine hypotheses, define limits, and express potential solutions to the anticipated technological problems.
Explosivity of eruptions See Volcanic Explosivity Index
Extinction, Armageddon, Apocalypse In biology and ecology, extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "re-appears" (typically in the fossil record) after a period of apparent absence.
Extinction level event An extinction-level event or Extinction event, also known as mass extinction, occurs when there is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic classes present at the time birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms.
Extinction of species In biology and ecology, extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last individual of that species.
Extra-solar planet See Extrasolar planet
Extrasolar planet An extrasolar planet, or exoplanet, is a planet beyond the Solar System. Known exoplanets are members of planetary systems that orbit a star.
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.
Extremophile species 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.
Fault tolerant design Fault-tolerant design refers to a method for designing a system so it will continue to operate, possibly at a reduced level (also known as "graceful degradation"), rather than failing completely, when some part of the system fails. The term is most commonly used to describe computer-based systems designed to continue more or less fully operational with, perhaps, a reduction in throughput or an increase in response time in the event of some partial failure. That is, the system as a whole is not stopped due to problems either in the hardware or the software.
Feral child A feral child is a human child who, from a very young age, has lived in isolation from human contact and has remained unaware of human social behavior, and unexposed to language. Feral children are extremely rare. Throughout the world, just over a hundred incidences of the phenomenon have been reported. They are thus considered very interesting case studies from a sociological perspective.
Fermi paradox The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence of contact with such civilizations. The extreme age of the universe and its vast number of stars suggest that extraterrestrial life should be common. Considering this with colleagues over lunch in 1950, the physicist Enrico Fermi is said to have asked: "Where are they?" Fermi questioned why, if a multitude of advanced extraterrestrial civilizations exist in the Milky Way galaxy, evidence such as probes, spacecraft or radio transmissions has not been found. The simple question "Where are they?" or "Where is everybody?" is possibly apocryphal, but Fermi is widely credited with simplifying and clarifying the problem of the probability of extraterrestrial life.
Fermionic condensate A fermionic condensate is a superfluid phase formed by fermionic particles at low temperatures. It is closely related to the Bose-Einstein condensate, a superfluid phase formed by bosonic atoms under similar conditions. Unlike the Bose-Einstein condensates, fermionic condensates are formed using fermions instead of bosons. The earliest recognized fermionic condensate described the state of electrons in a superconductor.
Fertility clinic Fertility clinics are staffed medical clinics that assist couples, and sometimes individuals, who want to become parents but for medical reasons have been unable to achieve this goal via the natural course. Clinics apply a number of tests and sometimes very advanced medical procedures to obtain the desired conceptions and pregnancies. For the male, semen collection is a standard diagnostic test to ascertain problems with the semen quality. In vitro fertilisation is one common assisted reproductive technology procedure performed at a fertility clinic.
Fetus development A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth. The plural is fetuses or, very rarely, foeti. In humans, a fetus develops from the end of the eighth week after fertilisation, when the major structures and organ systems have formed, until birth.
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.
First contact First contact is a term used to describe a first meeting of two previously unknown cultures. It is clear from the historical record here on Earth between societies of the same species that the disruptive nature of first contact generally favors the more technologically advanced side, often with dire consequences for the less advanced side. It is nearly impossible to predict what the first interactions between two different intelligent species might be. Beyond the language barrier, physical differences might make a common basis for shared experience impossible
Flood basalt event A flood basalt is a giant volcanic eruption that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges. The Deccan Traps of central India, the Siberian Traps and the Columbia River Plateau of the western United States are three regions covered by prehistoric flood basalts. The two largest flood basalt events in historic time have been at Eldgjá and Lakagigar, both in Iceland. The maria on the Moon are another, even more extensive, example of a flood basalt. Flood basalts on the ocean floor produce the oceanic plateaus. One explanation for flood basalts is that they are caused by the combination of continental rifting and its associated decompression melting in conjunction with a mantle plume also undergoing decompression melting producing vast quantities of a basaltic magma. These lavas have a very low viscosity, which is why they 'flood' rather than forming taller volcanoes.
Foster care Foster care is a system by which adults care for minor children who are not able to live with their parents. Voluntary foster care may be in circumstances where a parent is unable or unwilling to care for a child. For instance, a child may have behavioral problems requiring specialized treatment or the parent might have a problem which results in a temporary or permanent inability to care for the child(ren). Involuntary foster care may be implemented when a child is removed from the normal caregiver for his/her own safety.
Fullerene chemistry Fullerene chemistry is a field of organic chemistry devoted to the chemical properties of fullerenes. Research in this field is driven by the need to functionalize fullerenes and tune their properties. For example fullerene is notoriously insoluble and adding a suitable group can enhance solubility. By adding a polymerizable group, a fullerene polymer can be obtained. Functionalized fullerenes are divided into two classes: exohedral with substituents outside the cage and endohedral fullerenes with trapped molecules inside the cage.
Functional genomics Functional genomics is a field of molecular biology that attempts to make use of the vast wealth of data produced by genomic projects (such as genome sequencing projects) to describe gene (and protein!) functions and interactions. Unlike genomics and proteomics, functional genomics focus on the dynamic aspects such as gene transcription, translation, and protein-protein interactions, as opposed to the static aspects of the genomic information such as DNA sequence or structures.
Functional polymers Functional polymers are polymers with advanced optic and/or electronic properties. Advantages of functional polymers are low cost, ease of processing and a range of attractive mechanical characteristics for functional organic molecules. One can adjust properties while keeping material usage low. This opens interesting environmental perspectives. Polymer bound substances can spread their activity without endangering people or the environment.
Fusion rocket and antimatter engine A fusion rocket is a rocket that is driven by fusion power. The process of nuclear fusion is well understood and recent developments indicate this technology will be able to provide terrestial based power within 30 years. However, the proposed reactor vessels are prohibitively large and heavy making them unsuitable to use on spacecraft until at least next century. A smaller and lighter fusion reactor might be possible in the future when better methods have been devised to control magnetic confinement and prevent plasma instabilities. For space flight, the main advantage of fusion would be the very high specific impulse, the main disadvantage the (probable) large mass of the reactor. In addition, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. In antimatter-matter collisions resulting in photon emission, the entire rest mass of the particles is converted to kinetic energy. The energy per unit mass is about 10 orders of magnitude greater than chemical energy, and about 2 orders of magnitude greater (i.e. factor 100) than nuclear energy that can be liberated today using nuclear fission or fusion.
G-type star See Yellow dwarf
Galactic halo The term galactic halo denotes a component of spiral galaxies, including our galaxy, the Milky Way, which extends farther out than the disk, which is the most visible part of a spiral galaxy.
Gamma-ray bursts Gamma-ray bursts (GRBs) are the most luminous events known in the universe since the Big Bang. They are flashes of gamma rays, coming from seemingly random places on the sky and at random times, that last from milliseconds to many minutes, and are often followed by "afterglow" emission at longer wavelengths. The majority of observed GRBs appear to be due to collimated emission (that is, emission in narrow jets) from the core-collapse of a rapidly rotating Wolf-Rayet star into a black hole, but a specific subclass of GRBs appears to be due to another process, possibly the collision of two neutron stars orbiting in a binary.
Gene splicing Genetic engineering, genetic modification (GM) and gene splicing are terms for the process of manipulating genes, generally implying that the process is outside the organism's natural reproductive process. It involves the isolation, manipulation and reintroduction of DNA into cells or model organisms, usually to express a protein. The aim is to introduce new characteristics or attributes physiologically or physically, such as making a crop resistant to a herbicide, introducing a novel trait, or producing a new protein or enzyme, along with altering the organism to produce more of certain traits. Examples can include the production of human insulin through the use of modified bacteria
Gene-environment interaction Gene-environment interaction is a term used to describe any phenotypic effects that are due to interactions between the environment and genes. Naive nature versus nurture debates assume that variation in a given trait is primarily due to either genes, or the individual's experiences. The current scientific view is that neither genetics nor environment are solely responsible for producing individual variation, and that virtually all traits show gene-environment interaction. The specific pattern that relates the average expression of trait across a range of environments is known as a genotype's norm of reaction.
General relativity General relativity is the geometrical theory of gravitation published by Albert Einstein in 1915/16. It unifies special relativity and Sir Isaac Newton's law of universal gravitation with the insight that gravitation is not due to a force but rather is a manifestation of curved space and time, with this curvature being produced by the mass-energy and momentum content of the space-time.
Generation starship A generation ship is a hypothetical starship that travels across great distances between stars at a speed much slower than that of light (see interstellar travel). Since such a ship might take hundreds to tens of thousands of years to reach even nearby stars, the original occupants might die during the journey and leave their descendants to continue traveling, depending on the life span of its inhabitants and relativistic effects. It is estimated that, in order to assure genetic diversity during a centuries-long trip, a generation starship would require at least 500 inhabitants. Sperm banks or egg banks can drastically reduce the requisite number.
Genetic diversity Genetic diversity is a characteristic of ecosystems and gene pools that describes an attribute which is commonly held to be advantageous for survival - that there are many different versions of otherwise similar organisms. For example, the Irish potato famine can be attributed in part to the fact that the genetic distance of all potatoes in the country was very low, making it easier for one virus to infect and kill much of the crop.
Genetic engineering See Gene splicing
Genetic predisposition A genetic predisposition is a genetic effect which influences the phenotype of an organism but which can be modified by the environmental conditions. Genetic testing is able to identify individuals who are genetically predisposed to certain health problems. Predisposition is the capacity we are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) we have to do some things.
Genetic screening Genetic screening or testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a person's ancestry. Every person carries two copies of every gene, one inherited from their mother, one inherited from their father. The human genome is believed to contain about 25,000 genes. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the presence or absence of key proteins that signal aberrant versions of certain genes. Genetic testing identifies changes in chromosomes, genes, or proteins.
GLAST The Gamma-ray Large Area Space Telescope, or GLAST, is a future space-based gamma-ray telescope, designed to explore the high-energy Universe. It will study astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources, and dark matter. GLAST is a joint venture of NASA and the United States Department of Energy, which also includes strong international support.
Global warming Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades. The current scientific consensus is that 'most of the observed warming over the last 50 years is likely to have been attributable to human activities'.
Globular cluster A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. Globular clusters, which are found in the halo of a galaxy, contain considerably more stars and are much older than the less dense galactic, or open clusters, which are found in the disk. Globular clusters are fairly common; there are about 150 currently known globular clusters in the Milky Way, with perhaps 10 or 20 more undiscovered. Large galaxies can have more: Andromeda, for instance, may have as many as 500.
Grand unification theory Grand unification, grand unified theory, or GUT is one of several very similar theories or models in physics that unify what are considered three "fundamental" gauge symmetries: hypercharge, the weak force, and quantum chromodynamics. Grand unification is based on the idea that at extremely high energies, all symmetries have the same gauge coupling strength, which is consistent with the speculation that they are really different manifestations of a single overarching gauge symmetry. Thus far, physicists have been able to merge electromagnetism and the weak nuclear force into the electroweak force, and work is being done to merge electroweak and quantum chromodynamics into a QCD-electroweak interaction. Beyond grand unification, there is also speculation that it may be possible to merge gravity with the other three gauge symmetries into a theory of everything.
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.
Gravitational waves In physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from a moving object or system of objects. Gravitational radiation is the energy transported by these waves. Important examples of systems which emit gravitational waves are binary star systems, where the two stars in the binary are white dwarfs, neutron stars, or black holes. Although gravitational radiation has not yet been directly detected, it has been indirectly shown to exist.
Graviton particle In physics, the graviton is a hypothetical elementary particle that mediates the force of gravity in the framework of quantum field theory. If it exists, the graviton must be massless (because the gravitational force has unlimited range) and must have a spin of 2 (because gravity is a second-rank tensor field). Gravitons are postulated because of the great success of the quantum field theory (in particular, the Standard Model) at modeling the behavior of all other forces of nature with similar particles: electromagnetism with the photon, the strong interaction with the gluons, and the weak interaction with the W and Z bosons.
Great attractor The Great Attractor is a gravity anomaly in intergalactic space within the range of the Centaurus Supercluster which reveals the existence of a localised concentration of mass equivalent to tens of thousands of galaxies, observable by its effect on the motion of galaxies over a region hundreds of millions of light years across. These galaxies are all redshifted, in accordance with the Hubble Flow, indicating that they are receding relative to us and to each other, but the variations in their redshift are sufficient to reveal the existence of the anomaly. The phenomenon was first discovered in 1986 and lies at a distance of somewhere between 150 million and 250 million light years (the latter being the most recent estimate) from the Milky Way, in the direction of the Hydra and Centaurus constellations.
Gynoid Gynoid is a term used to describe a robot designed to look like a human female, as compared to an android modeled after a male. The term is not common, however, with android often being used to refer to both "genders" of robot. The portmanteaus fembot (female robot) and feminoid (female android) have also been used; the latter sparingly.
Habitable planet Planetary habitability is the measure of an astronomical body's (planets and natural satellites of planets) potential to develop and sustain life. The only absolute requirement for life is an energy source, but the notion of planetary habitability implies that many other geophysical, geochemical, and astrophysical criteria must be met before an astronomical body can support life. As the existence of life beyond Earth is currently uncertain, planetary habitability is largely an extrapolation of conditions on Earth and the characteristics of the Sun and solar system which appear favorable to life's flourishing; of particular interest are factors that have sustained complex, multicellular organisms rather than simpler unicellular creatures. Research and theory in this regard is a component of planetary science and the emerging discipline of astrobiology.
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.
Hard science fiction Hard science fiction, or "hard SF," is a category of science fiction characterized by an emphasis on scientific detail and/or accuracy. The complementary term, soft science fiction contrasts the "hardness" of the sciences used in the story: the "hard" sciences are quantitative or material-based disciplines (physics, chemistry, astronomy) versus the "soft" social sciences (sociology, anthropology, psychology). One requirement for hard SF is procedural or intentional: a story should be trying to be accurate and rigorous in its use of the scientific knowledge of its time, and later discoveries do not necessarily invalidate the label.
Hawking radiation In physics, Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation thought to be emitted by black holes due to quantum effects. It is named after British physicist Stephen Hawking who worked out the theoretical argument for its existence in 1974, and sometimes also after the Israeli physicist Jacob Bekenstein who predicted that black holes should have thermal properties. Because Hawking radiation allows black holes to lose mass, black holes which lose more matter than they gain through other means, are expected to evaporate, and shrink, and ultimately vanish.
Head-mounted display A head-mounted display (HMD) is a display device that a person wears on the head to have video information directly displayed in front of the eyes. With two displays, the technology can be used to show stereoscopic images by displaying an offset image to each eye. Lenses are used to give the perception that the images are coming from a greater distance, to prevent eye strain.
Helioseismology Helioseismology is the study of the propagation of pressure waves in the Sun.Unlike seismic waves on earth, solar waves have practically no shear component (s-waves). Solar pressure waves are generated by the turbulence in the convection zone, near the surface of the sun, and certain frequencies are amplified by constructive interference. In other words, the turbulence "rings" the sun like a bell.
Heritability In genetics, heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals. Variation among individuals may be due to genetic and/or environmental factors. Heritability analyses estimate the relative contributions of differences in genetic and non-genetic factors to the total phenotypic variance in a population.
Higgs boson The Higgs boson is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. It is the only Standard Model particle not yet observed, but plays a key role in explaining the origins of the mass of other elementary particles, in particular the difference between the massless photon and the very heavy W and Z bosons.
High-temperature superconductors High-temperature superconductors are generally considered to be those that demonstrate superconductivity at or above the temperature of liquid nitrogen, or -196 C (77 K), since this is the most easily attainable cryogenic temperature.
Horsehead nebula The Horsehead Nebula is a dark nebula in the Orion constellation. The nebula is located just below Alnitak, the easternmost star of Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. It is approximately 1,500 light years from Earth, and is approximately 3.5 light years wide. One of the most identifiable nebulae in the sky, it is part of a swirling cloud of dark dust and gases, shaped like a horse's head (hence its name).
Human cloning Human cloning is the creation of a genetically identical copy of an existing, or previously existing, human being or clone tissue from that individual. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction. Although genes are recognized as influencing behavior and cognition, "genetically identical" does not mean altogether identical; almost no one would deny that identical twins, despite being natural human clones with identical DNA, are separate people, with separate experiences and not altogether overlapping personalities. However undramatic it may sound, the relationship between an "original" and a clone is rather like that between identical twins raised apart; they share all the same DNA, but little of the same environment.
Human experimentation Human experimentation involves medical experiments performed on human beings. It is an important part of medical research, and many people volunteer for clinical trials of medical treatments. People also volunteer to be subjects for experiments in basic medical science and biology. Some experiments can involve the testing of cosmetic products or ingredients on humans instead of animals. In some notable cases, doctors have performed experiments on themselves, when they have been unwilling to risk the lives of others. This is known as self-experimentation.
Human extinction Risks to civilization, humans and planet Earth are existential risks that would imperil humankind as a whole and/or have major adverse consequences for the course of human civilization, human extinction or even the end of planet Earth. There are many scenarios that have been suggested that could happen in the future. Some are certain to happen and will almost certainly end humanity, but will only happen on a very long timescale.
Human genome decoding The Human Genome Project (HGP) is a project to code 3 billion nucleotides contained in the human genome and to identify all the genes present in it. There are currently two human genome projects: the first is the international HGP which is being produced by a group of international government bodies and organizations, and the second by a private company Celera Genomics.
Human survival 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, stockpiling food and water, or building structures that will help them to survive, e.g. an underground shelter.
Humanoid robot A humanoid robot is a robot with its overall appearance based on that of the human body. In general humanoid robots have a torso with a head, two arms and two legs, although some forms of humanoid robots may model only part of the body, for example, from the waist up.
Hydrothermal vent A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found in places that are also volcanically active, where hot magma is relatively near the planet's surface. Hydrothermal vents are abundant on Earth because it is both geologically active and has large amounts of water on its surface. Common land types include hot springs, fumaroles and geysers.
Hyperdrive Hyperdrive is a name given to certain methods of traveling faster than light (FTL) in science fiction. Related concepts are jump drive and warp drive. The idea of hyperdrive in most science fiction relies on the existence of a separate and adjacent dimension. Explanations of why ships can travel faster than light in hyperspace vary; hyperspace may be smaller than real space or provide a shortcut between two points in real space, thus effectively increasing the ship's speed by reducing distance travelled rather than speed, or the speed of light in hyperspace is not a barrier as it is in real space. While in hyperspace, starships are typically isolated from the normal universe; they cannot communicate with nor perceive things in real space until they emerge. Often there can be no interaction between two ships even when both are in hyperspace. To people traveling in hyperspace, time typically moves at its normal pace, with little or no time dilation.
Hypernova A hypernova is many times more violent than a supernova and refers to an exceptionally large star that collapses at the end of its lifespan - for example, a collapsar, or a large supernova. The core of the hypernova collapses directly into a black hole and two extremely energetic jets of plasma are emitted from its rotational poles at nearly the speed of light. These jets emit intense gamma rays, and are a candidate explanation for gamma ray bursts.
Hypertelescope See Astronomical interferometer
ICSI Intracytoplasmic sperm injection (ICSI) is an in vitro fertilization procedure in which a single sperm is injected directly into an egg; this procedure is most commonly used to overcome male infertility problems. The procedure is done under a microscope using micromanipulation devices (micromanipulators, microinjectors and micropipettes).
Immortality Immortality (or eternal life) is the concept of living for a potentially infinite, or indeterminate, length of time. In the many worlds interpretation of quantum mechanics, the wavefunction never collapses, and thus all possible outcomes of a quantum event exist simultaneously, with each event apparently spawning an entirely new universe in which a single possible outcome exists. In this physical theory, one could hypothetically live forever as there might exist a string of possible quantum outcomes in which one never dies. Technological immortality is the prospect for much longer life spans made possible by scientific advances in a variety of fields: nanotechnology, emergency room procedures, genetics, biological engineering, regenerative medicine, microbiology, and others. Contemporary life spans in the advanced industrial societies are already markedly longer than those of the past because of better nutrition, availability of health care, standard of living and bio-medical scientific advances. An important aspect of current scientific thinking about immortality is that some combination of human cloning, cryonics or nanotechnology will play an essential role in extreme life extension. Cryonics is the practice of preserving organisms (either intact specimens or only their brains) for possible future revival by storing them at cryogenic temperatures where metabolism and decay are almost completely stopped.
Impact event mpact events are caused by the collision of large meteoroids, asteroids or comets (generically: bolides) with Earth and may sometimes be followed by mass extinctions of life. In the past 600 million years there have been five major mass extinctions that on average extinguished half of all species. The largest mass extinction to have affected life on Earth was in the Permian-Triassic, which ended the Permian period 250 million years ago and killed off 90% of all species.
Incompleteness theorem In mathematical logic, Goedel's incompleteness theorems, are two celebrated theorems stating inherent limitations of all but the most trivial formal systems for arithmetic of mathematical interest. Thus the theorems are of considerable importance to the philosophy of mathematics. Some claim implications in wider areas of philosophy and even cognitive science, but these claims are less generally accepted.
Intergalactic travel Intergalactic travel is travel between galaxies, and it is even more difficult than interstellar travel. At the speed of light, travelling from Earth in the Milky Way galaxy to the Andromeda Galaxy (the nearest major galaxy) would take roughly two and a half million years from the perspective of observers on Earth, but would take an arbitrarily short amount of time for the traveller (due to the effects of time dilation), depending on exactly how close to the speed of light their vessel is traveling.
Interstellar cloud Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium.
Interstellar travel Interstellar space travel is unmanned or manned travel between stars, though the term usually denotes the latter. There is a tremendous difference between interstellar travel and interplanetary travel, mainly due to the much larger distances involved. Many scientific papers have been published about related concepts. Given sufficient travel time and engineering work, unmanned and generational interstellar travel seems possible, though representing a very considerable technological and economic challenge unlikely to be met for some time.
Ion thruster An ion thruster (or ion drive), one of several types of spacecraft propulsion, uses beams of ions (electrically charged atoms or molecules) for propulsion. The precise method for accelerating the ions may vary, but all designs take advantage of the charge-to-mass ratio of ions to accelerate them to very high velocities using a high electric field.
ITER ITER is an international tokamak (magnetic confinement fusion) research project designed to demonstrate the scientific and technological feasibility of a full-scale fusion power reactor. ITER is intended to be an experimental step between today's studies of plasma physics and future electricity-producing fusion power plants.
IVF See In vitro fertilisation
James webb space telescope The James Webb Space Telescope (JWST) is a planned space infrared observatory, intended to be a significant improvement on the aging Hubble Space Telescope. It will be constructed and operated by NASA with help from ESA and CSA.

K-type star See Orange dwarf
Kardashev scale The Kardashev scale is a general method of classifying how technologically advanced a civilization is, first proposed in 1964 by the Russian astronomer Nikolai Kardashev. It has three categories, based on the amount of usable energy a civilization has at its disposal and increasing logarithmically. Type 1: A civilization that is able to harness all of the power available on a single planet. Type 2: A civilization that is able to harness all of the power available from a single star. Type 3: A civilization that is able to harness all of the power available from a single galaxy.
Keck interferometer The Keck Interferometer is a two-telescope astronomical interferometer. It forms part of NASA's overall effort to find planets and ultimately life beyond our solar system. It combines the light from the twin Keck telescopes to measure the emission from dust orbiting nearby stars, directly detect the hottest gas giant planets, image disks around young stars and other objects of astrophysical interest, and survey hundreds of stars for the presence of planets the size of Uranus or larger.
Kepler mission The Kepler Mission is a space observatory being developed by NASA. It will search for extrasolar planets and will only be the second space-based telescope particularly constructed for that task (the first one being COROT). For this purpose, it will observe the brightness of about 100,000 stars over four years to detect periodical transits of a star by its planets. Kepler will not be in an Earth orbit but in an Earth-trailing solar orbit so that Earth will not occult the stars which are to be observed continuously and the photometer will not be influenced by stray light from Earth.
Knowledge representation Knowledge representation is a research and application domain in artificial intelligence, cognitive science, as well as in the knowledge management and knowledge engineering.
L2 Lagrange point The Lagrangian points are the five positions in interplanetary space where a small object affected only by gravity can theoretically be stationary relative to two larger objects. The L2 point lies on the line defined by the two large masses, beyond the smaller of the two.
Laplace Computer A Laplace Computer, or Laplace Demon Computer, is a notional computer capable of predicting the future state of the universe based on knowledge of its current state. The possibility of performing this computation was postulated by Laplace, a firm believer in determinism.
Large hadron collider The Large Hadron Collider (LHC) is a particle accelerator and collider located at CERN, near Geneva, Switzerland. LHC is expected to become the world's largest and highest energy particle accelerator in 2008, when commissioning at 7 TeV is completed.
Laser interferometer space antenna The LISA is the Laser Interferometer Space Antenna experiment, a joint venture of NASA and the European Space Agency (ESA). It is currently in a design phase and is expected to begin observations in or around 2015. LISA is intended to measure gravitational waves by using laser interferometry over astronomical distances.
Lateral gene transfer Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. By contrast, vertical transfer occurs when an organism receives genetic material from its ancestor, e.g. its parent or a species from which it evolved. Most thinking in genetics has focussed on the more prevalent vertical transfer, but there is a recent awareness that horizontal gene transfer is a significant phenomenon. Artificial horizontal gene transfer is a form of genetic engineering.
Launch window Launch window is a term used in aerospace to describe a time period in which a particular rocket must be launched. If the rocket does not launch within the "window", it has to wait for the next one before it can be launched. For trips into largely arbitrary Earth orbits almost any time will do, but if the spacecraft intends to rendezvous with a space station or another vehicle that is already in an orbit the launch must be carefully timed to occur around the times that the target vehicle's orbital planes intersects the launch site. To go to another planet without using any kind of gravitational slingshot, if eccentricity of orbits is not a factor, launch windows are periodic according to the synodic period.
Leadership models n the functional leadership model, one conceives of leadership not as a person but rather as a set of behaviors that help a group perform their task or reach their goal. The model says that the leadership function meets needs in areas: task, team, and individuals.
Lepton In physics, a lepton is a particle with spin-1/2 (a fermion) that does not experience the strong nuclear force. The leptons form a family of elementary particles that are distinct from the other known family of fermions, the quarks. There are three known flavors of lepton: the electron, the muon and the tau. Each flavor is represented by a pair of particles called a weak doublet.
Life-critical system A life-critical system or safety-critical system is a system whose failure or malfunction may result in: death or serious injury to people, or loss or severe damage to equipment or environmental harm. Risks of this sort are usually managed with the methods and tools of safety engineering. A life-critical system is designed to lose less than one life per billion (109) hours of operation. Fail-operational systems continue to operate when they fail. Fail-safe systems become safe when they cannot operate. Fail-secure systems maintain maximum security when they can not operate. Fault-tolerant systems continue to operate correctly when subsystems operate incorrectly. Some examples include autopilots on commercial aircraft, and control systems for ordinary nuclear reactors. Software engineering for life-critical systems is particularly difficult, but the avionics industry has succeeded in producing standard methods for producing life-critical avionics software.
Life extension Life extension refers to an increase in maximum or average lifespan, especially in humans, by slowing down or reversing the processes of aging. Average lifespan is determined by vulnerability to accidents and age-related afflictions such as cancer or cardiovascular disease. Extension of average lifespan can be achieved by good diet, exercise and avoidance of hazards such as smoking and excessive eating of sugar-containing foods. Maximum lifespan is determined by the rate of aging for a species inherent in its genetic code. Currently, the only widely recognized method of extending maximum lifespan is by calorie restriction with adequate nutrient supplementation. Theoretically, extension of maximum lifespan can be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues.
Light helium Helium-3 is a light, non-radioactive isotope of helium. The helion, the nucleus of a helium-3 atom, consists of two protons but only one neutron, in contrast to two neutrons in ordinary helium. Helium-3 is rare on Earth and sought-after for use in nuclear fusion research. More abundant helium-3 is thought to exist on the Moon. The appeal of helium-3 fusion stems from the nature of its reaction products. Most proposed fusion processes for power generation produce energetic neutrons which render reactor components radioactive with their bombardment, and power generation must occur through thermal means.
Linguistics Linguistics is the scientific study of language. Someone who engages in this study is called a linguist. Linguistics can be theoretical or applied. Theoretical (or general) linguistics encompasses a number of sub-fields, such as the study of language structure (grammar), and meaning (semantics). The study of grammar encompasses morphology (formation and alteration of words) and syntax (the rules that determine the way words combine into phrases and sentences). Phonology, the study of sound systems and abstract sound units, and phonetics, which is concerned with the actual properties of speech sounds.
Machine learning As a broad subfield of artificial intelligence, machine learning is concerned with the development of algorithms and techniques that allow computers to "learn". At a general level, there are two types of learning: inductive, and deductive. Inductive machine learning methods create computer programs by extracting rules and patterns out of massive data sets. Some parts of machine learning are closely related to data mining. Machine learning has a wide spectrum of applications including natural language processing, search engines, medical diagnosis, bioinformatics and cheminformatics, detecting credit card fraud, stock market analysis, classifying DNA sequences, speech and handwriting recognition, object recognition in computer vision, game playing and robot locomotion.
Macho Massive compact halo object, or MACHO, is a general name for any kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a small chunk of normal baryonic matter, which emits little or no radiation and drifts through interstellar space unassociated with any solar system. Since MACHOs would not emit any light of their own, they would be very hard to detect. MACHOs may sometimes be black holes or neutron stars as well as brown dwarfs or unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs.
Magnetar A magnetar is a neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious amounts of high-energy electromagnetic radiation, particularly X-rays and gamma-rays.
Magnetic storms A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere. Associated with solar coronal mass ejections (CME), coronal holes, or solar flares, a geomagnetic storm is caused by a solar wind shock wave which typically strikes the Earth's magnetic field 24 to 36 hours after the event.
Mantle plume A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. As the heads of mantle plumes can partly melt when they reach shallow depths, they are thought to be the cause of volcanic centers known as hotspots and probably also to have caused flood basalts. It is a secondary way that Earth loses heat, much less important in this regard than is heat loss at plate margins.
Megaproject A megaproject is an extremely large scale investment project.
Megastructure In science fiction and speculative (or exploratory) engineering, a megastructure is an enormous self-supporting artificial construct. The definition is often informal and varies from source to source, but generally requires at least one dimension to be in the hundreds of kilometers. Other criteria such as rigidity or contiguousness are sometimes also applied, so large clusters of associated smaller structures may or may not qualify. The products of megascale engineering or astroengineering are megastructures. Examples: Alderson disk, Dyson sphere, Niven ring, Matrioshka brain, Stellar engine, Shkadov thruster, Topopolis, Globus Cassus, Bernal sphere, Stanford torus, O'Neill cylinder, Space fountain, Skyhook, Rotovator, Space elevator
Megatsunami Megatsunami is an informal term used mostly by popular media and popular scientific societies to describe a very large tsunami wave beyond the size reached by typical tsunamis. A megatsunami is associated with waves beyond the norm for tsunamis, ranging from over 40 meters (131 feet) to giants over 100 meters (328 feet) tall.
Metaverse The Metaverse contains the Multiverses and all universes past and present. The popular online virtual world Second Life has now become the leading contender in the emerging field of 3D multiplayer metaverses. It has pushed the envelope both in its independance, flexibility and the building & scripting aspects.
Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earth's surface without being destroyed. While in space it is called a meteoroid. When it enters the atmosphere, air resistance causes the body to heat up and emit light, thus forming a fireball, also known as a meteor or shooting star. The term bolide refers to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.
Mind transfer In transhumanism and science fiction, mind transfer (also referred to as mind uploading or mind downloading, depending on one's point of reference), whole body emulation, or electronic transcendence refers to the hypothetical transfer of a human mind to an artificial substrate.
Molecular nanotechnology Molecular nanotechnology (MNT) is the engineering of functional systems at the molecular scale. An equivalent definition would be "machines at the molecular scale designed and built atom-by-atom". This is distinct from nanoscale materials.
Multiple births A multiple birth occurs where more than one fetus exits the womb in a single pregnancy. Different names for multiple birth are used, depending on the actual multiple. Common multiples are two and three, known as twins and triplets respectively.
Multiverse A multiverse (or meta-universe) is the hypothetical set of multiple possible universes (including our universe) that together comprise all of physical reality. The different universes within a multiverse are called parallel universes. According to Max Tegmark, the existence of other universes is a direct implication of cosmological observations. Tegmark describes the set of related concepts which share the notion that there are universes beyond the familiar observable one, and goes on to provide a taxonomy of parallel universes organized by levels.
Nanomedicine Nanomedicine is the medical application of nanotechnology and related research. It covers areas such as nanoparticle drug delivery and possible future applications of molecular nanotechnology (MNT) and nanovaccinology. Current problems for nanomedicine involve understanding the issues related to toxicity and environmental impact of nanoscale materials.
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.
Nature or nurture Nature vs. Nurture is a shorthand expression for debates about the relative importance of an individual's innate qualities ('nature') versus personal experiences ('nurture') in determining or causing individual differences in physical and behavioral traits.
Near-Earth asteroid Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earth's orbit. Some NEAs' orbits intersect Earth's so they pose a collision danger. On the other hand, NEAs are most easily accessible for spacecraft from Earth.
Neutrino astronomy Neutrino astronomy is the science of observing astronomical phenomena by detecting neutrinos, a product of weak thermonuclear reactions going on inside every star. Neutrinos interact only very rarely with matter. The enormous flux of solar neutrinos racing through our earth is sufficient to produce only 1 interaction for 1036 target atoms, and each interaction produces only a few photons or one transmuted element. To observe neutrino interactions a large detector mass is required, along with a sensitive amplification system.
Nulling interferometer 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.
Omega particle In particle physics, the omega minus is a type of baryon (more specifically, a hyperon). Its discovery was a great triumph in the study of quark processes, since it was found only after its existence, mass, and decay products had already been predicted. Besides the ordinary omega particle there is also a charmed omega particle, in which a strange quark is replaced by a charm quark. The omega particle decays only via the weak interaction and has therefore a relatively long lifetime.
Oort cloud The Oort cloud is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the Sun.
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.
Orbital decay Orbital decay is the process of prolonged reduction in the height of a satellite’s orbit due to drag produced by an atmosphere. The drag intensifies during periods of high solar activity and sunspots, due to frequent collisions between the satellite and surrounding air molecules.
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.
Pluripotency Pluripotency in the broad sense refers to "having more than one potential outcome". In biological systems, this can refer either to cells or to biological compounds. In cell biology, the definition of pluripotency has come to refer to a stem cell that has the potential to differentiate into any of the three germ layers: endoderm (interior stomach lining, gastrointestinal tract, the lungs), mesoderm (muscle, bone, blood, urogenital), or ectoderm (epidermal tissues and nervous system).
Primordial black hole A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a star but by the extreme density of matter present during the universe's early expansion. According to the Hot Big Bang Model, during the first few moments after the big bang, pressure and temperature were extremely great. Under these conditions, simple fluctuations in the density of matter may have resulted in local regions dense enough to create black holes. One way to detect primordial black holes is by their Hawking radiation. All black holes are believed to emit Hawking radiation at a rate inversely proportional to their mass.
Progressor Progressors in science fiction are people of an advanced space-faring civilization who facilitate progress of less advanced civilizations.
Project management Project management is the discipline of organizing and managing resources in such a way that these resources deliver all the work required to complete a project within defined scope, time, and cost constraints. A project is a temporary and one-time endeavor undertaken to create a unique product or service, that brings about beneficial change or added value. This property of being a temporary and a one-time undertaking contrasts with processes, or operations, which are permanent or semi-permanent ongoing functional work to create the same product or service over and over again. The management of these two systems is often very different and requires varying technical skills and philosophy, hence requiring the development of project management.
Protein engineering Protein engineering is the application of science, mathematics, and economics to the process of developing useful or valuable proteins. It is a young discipline, with much research currently taking place into the understanding of protein folding and protein recognition for protein design principles.
Proteomics Proteomics is the large-scale study of protein, particularly their structures and functions. This term was coined to make an analogy with genomics, and while it is often viewed as the "next step", proteomics is much more complicated than genomics. Most importantly, while the genome is a rather constant entity, the proteome differs from cell to cell and is constantly changing through its biochemical interactions with the genome and the environment. One organism has radically different protein expression in different parts of its body, in different stages of its life cycle and in different environmental conditions.
Proton decay In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, usually a neutral pion and a positron. Proton decay has not been observed. In the Standard Model, protons, a type of baryon, are theoretically stable because baryon number is approximately conserved.
Protoplanetary disk A protoplanetary disk (or proplyd) is a rotating disk of dense gas surrounding a young newly formed star. The protoplanetary disk may be considered an accretion disk because gaseous material may be falling from the inner edge of the disk onto the surface of the star, but this process should not be confused with the accretion process thought to build up the planets themselves.
Quantum chromodynamics Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (colour force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion).
Quantum computer A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, the data is measured by qubits. The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that quantum mechanisms can be devised and built to perform operations with these data.
Quantum electrodynamics Quantum electrodynamics (QED) is a relativistic quantum field theory of electromagnetism. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons, whether the interaction is between light and matter or between two charged particles.
Quantum entanglement Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated. This leads to correlations between observable physical properties of the systems. But quantum entanglement does not enable the transmission of classical information faster than the speed of light. Quantum entanglement has applications in the emerging technologies of quantum computing and quantum cryptography, and has been used to experimentally realize quantum teleportation.
Quantum gravity Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. The ultimate goal of some is a unified framework for all fundamental forces: The Theory Of Everything (TOE).
Quantum teleportation In quantum information, quantum teleportation, or entanglement-assisted teleportation, is a technique that transfers a quantum state to an arbitrarily distant location using a distributed entangled state and the transmission of some classical information. Quantum teleportation does not transport energy or matter, nor does it allow communication of information at superluminal speed, but is useful to quantum communication and computation.
Quaoar Quaoar is a Trans-Neptunian object orbiting the Sun in the Kuiper belt. It was discovered on June 4, 2002
Quarkonium In particle physics, quarkonium (pl. quarkonia) designates a flavorless meson whose constituents are a quark and its own antiquark.
Quark-gluon plasma A quark-gluon plasma (QGP) is a phase of quantum chromodynamics (QCD) which exists at extremely high temperature and density. It is believed to have existed during the first 20 or 30 microseconds after the universe came into existence in the Big Bang.
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.
Rational-emotive behavior therapy Rational Emotive Behavior Therapy (REBT) is an active-directive, solution-oriented therapy which focuses on resolving emotional, cognitive and behavioral problems in clients. REBT is the first forms of Cognitive Behavior Therapy and was first expounded by Albert Ellis in 1953. Fundamental to REBT is the concept that emotional suffering results primarily, though not completely, from our evaluations of a negative event, not solely by the events per se. In other words, human beings on the basis of their belief system actively, though not always consciously, disturb themselves, and even disturb themselves about their disturbances.
Recombinant DNA Recombinant DNA (rDNA) is an artificial DNA sequence resulting from the combining of two other DNA sequences in a plasmid. A recombinant protein is a protein produced by an organism after the relevant DNA is inserted into its genome (that is, by a genetically modified organism). This recombines the DNA of two different organisms.
Red dwarf According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type. They constitute the vast majority of stars and have a diameter and mass of less than one-third that of the Sun (down to 0.08 solar masses, which are brown dwarfs) and a surface temperature of less than 3,500 K. Red dwarfs fuse hydrogen to helium via the proton-proton (PP) chain. Red dwarfs never initiate helium fusion via the triple alpha process and so cannot evolve beyond the red giant phase. In any event, there has not been sufficient time since the Big Bang for red dwarfs to evolve off the main sequence.
Red giant Red giants are stars of 0.4 to 10 times the mass of the Sun which have exhausted the supply of hydrogen in their cores and switched to fusing hydrogen in a shell outside the core. Since the inert helium core has no source of energy of its own, it contracts and heats up, and its gravity compresses the hydrogen in the layer immediately above it, thus causing it to fuse faster. This in turn causes the star to become more luminous (from 1,000 to 10,000 times brighter) and expand. In stars massive enough to ignite helium fusion, an analogous process occurs when central helium is exhausted and the star switches to fusing helium in a shell. Stars with more than about 10 solar masses after burning their hydrogen become red supergiants during their helium-burning phase. These stars have very cool surface temperatures (3500-4500 K), and enormous radii.
Redundancy 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.
Rejuvenation See Life extension
Robot A robot is an electro-mechanical or bio-mechanical device or group of devices that can perform autonomous or preprogrammed tasks. A telerobot may act under the direct control of a human, such as the robotic arm on a space shuttle, or autonomously under the control of a programmed computer.
Selfish DNA Selfish DNA refers to those sequences of DNA which, in their purest form, have two distinct properties: the DNA sequence spreads by forming additional copies of itself within the genome; and it makes no specific contribution to the reproductive success of its host organism. The theory of natural selection, in its more general formulation, deals with the competition between replicating entities. It shows that, in such a competition, the more efficient replicators increase in number at the expense of their less efficient competitors. After a sufficient time, only the most efficient replicators survive.
Semantic network A semantic network is often used as a form of knowledge representation. It is a directed graph consisting of vertices, which represent concepts, and edges, which represent semantic relations between the concepts. Semantic networks are a common type of machine-readable dictionary.
Sentinel hypothesis The Sentinel Hypothesis suggests that if advanced alien civilizations exist they might place intelligent monitoring devices on or near the worlds of other evolving species to track their progress. A robot sentinel might establish contact with a developing race once that race had reached a certain technological threshold, such as large-scale radio communication or interplanetary flight. Already, scientists are beginning to understand the basic conditions necessary for carbon-based life to develop. They can identify those stars in the solar neighborhood most like the Sun, and can delineate approximately the habitable zone around any given star in which complex biochemistry might be expected to flourish. Scientists are also starting to acquire the ability to detect extrasolar planets. More advanced species would presumably be able to stake out with reasonable accuracy those stars and their associated worlds upon which intelligent life had a good chance of eventually developing, particularly if scout ships had revealed the presence of proto-intelligence. Such promising locations might then be expected to come under increasingly intense scrutiny by automatic sentinels.
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.
Silicon-based life Alternative biochemistry is the biochemistry of alien life forms that differ radically from those on Earth. It includes biochemistries that use atoms other than carbon to construct primary cellular structures and/or use solvents besides water. Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the molecular machinery necessary for life. Since we are in fact carbon-based beings, excluding the possibility of all other elements may be considered carbon chauvinism since we have never encountered any life that has evolved outside the earth's environment. The most common proposed basis for an alternative biochemical system is the silicon atom, since silicon has many chemical properties similar to carbon and is in the same periodic table group, the carbon group. But silicon has a number of handicaps as a carbon alternative. Because silicon atoms are much bigger, having a larger mass and atomic radius, they have difficulty forming double or triple covalent bonds, which are important for a biochemical system. Silanes, which are chemical compounds of hydrogen and silicon that are analogous to the alkane hydrocarbons, are highly reactive with water, and long-chain silanes spontaneously decompose.
Simulation A computer simulation is an attempt to model a real-life situation on a computer so that it can be studied to see how the system works. By changing variables, predictions may be made about the behaviour of the system. An interesting application of computer simulation is to simulate computers using computers. The related software is called computer architecture simulators, which can be further divided into instruction set simulators or full system simulators. Computer simulation has become a useful part of modeling many natural systems in physics, chemistry and biology, and human systems in economics and social science (the computational sociology) as well as in engineering to gain insight into the operation of those systems.
Smart materials Smart materials are materials that have one or more properties that can be significantly altered in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields. Piezoelectric materials are materials that produce a voltage when stress is applied. Thermoresponsive materials, either shape memory alloys or shape memory polymers, are materials that can hold different shapes at various temperatures. Chromogenic systems change colour in response to electrical, optical or thermal changes.
Software engineering Software engineering (SE) is the design, development, documentation and maintenance of software by applying technologies and practices from computer science, project management, engineering, application domains, interface design, digital asset management and other fields. Software engineering is concerned with the conception, development and verification of a software system. This discipline deals with identifying, defining, realizing and verifying the required characteristics of the resultant software. These software characteristics may include: functionality, reliability, maintainability, availability, testability, ease-of-use, portability, and other attributes. Software engineering addresses these characteristics by preparing design and technical specifications that, if implemented properly, will result in software that can be verified to meet these requirements. Software engineering is also concerned with the characteristics of the software development process.
Solar proton event A Solar proton event occurs when high-energy protons, ejected from the sun's surface during a solar flare, get caught by the Earth's magnetic field and cause ionization in the ionosphere. The effect is similar to auroral events, the difference being that electrons and not protons are involved. The events typically occur where the Earth's magnetic field is lowest, at the north pole, south pole, and South Atlantic magnetic anomaly. The more severe proton events can cause widespread disruption to electrical grids and the propagation of electromagnetic signals.
Solar variation Solar variations are fluctuations in the amount of energy emitted by the Sun. Small variations have been measured from satellites during recent decades. Of interest to climate scientists is whether these variations have a significant effect on the temperature of Earth's atmosphere.
Solar wind A solar wind is a stream of charged particles (i.e., a plasma) which are ejected from the upper atmosphere of a star. When originating from stars other than the Earth's Sun, it is sometimes called a stellar wind. It consists mostly of high-energy electrons and protons that are able to escape the star's gravity in part because of the high temperature of the corona and the high kinetic energy particles gain through a process that is not well understood at this time. Many phenomena are directly related to the solar wind, including: geomagnetic storms that can knock out power grids on Earth, auroras, why the tail of a comet always points away from the Sun, and the formation of distant stars.
Space advocacy Space advocacy is a political position that favors the exploration, utilization, and colonization of outer space. There are many different organizations dedicated to space advocacy. They are usually active in lobbying governments for increased funding in space-related activities. They also recruit members, fund projects, and provide information for their membership and interested visitors. They are sub-divided into three categories depending on their primary work: practice, advocacy, and theory.
Space colonization Space colonization (also called space settlement, space humanization, or space habitation) is the concept of permanent autonomous (self-sufficient) human habitation of locations outside Earth. The first step is the permanent human presence in space, as with the International Space Station.
Space elevator A space elevator is a proposed structure designed to transport material from a planet's surface into space. Many different types of space elevators have been suggested. They all share the goal of replacing rocket propulsion with the traversal of a fixed structure via a mechanism not unlike an elevator in order to move material into or beyond orbit. Space elevators have also sometimes been referred to as beanstalks, space bridges, space lifts, space ladders or orbital towers. The most common proposal is a tether, usually in the form of a cable or ribbon, spanning from the surface to a point beyond geosynchronous orbit. As the planet rotates, the inertia at the end of the tether counteracts the centripetal force of gravity and keeps the cable taut. Vehicles can then climb the tether and escape the planet's gravity without the use of rocket propulsion. Such a structure could theoretically permit delivery of cargo and people to orbit with transportation costs a fraction of those of more traditional methods of launching a payload into orbit. Recent proposals for a space elevator are notable in their plans to incorporate carbon nanotubes into the tether design, thus providing a link between space exploration and nanotechnology.
Space habitat A space habitat, also called space colony or orbital colony, is a space station intended as a permanent settlement rather than as a simple waystation or other specialized facility. It would be a "city" in space, where people would live, work and raise families. No space habitats have yet been constructed, but many design proposals have been made with varying degrees of realism by both science fiction authors and engineers.
Space-time continuum In physics, spacetime is a mathematical model that combines space and time into a single construct called the space-time continuum. Spacetime is usually interpreted as a four-dimensional object with space being three-dimensional and time playing the role of the 4th dimension. According to Euclidean space perception, our universe has three dimensions of space, and one dimension of time. By combining space and time into a single manifold, physicists have significantly simplified a good deal of physical theory, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels. The term spacetime has taken on a generalized meaning with the advent of higher-dimensional theories. How many dimensions are needed to describe the universe is still an open question. Speculative theories such as string theory predict 10 or 26 dimensions (With M-theory predicting 11 dimensions, 10 spatial and 1 temporal), but the existence of more than four dimensions would only appear to make a difference at the subatomic level.
Sparticle Sparticle is a merging of the words supersymmetric and particle. Supersymmetry, one of the cutting-edge theories in current high-energy physics, predicts the existence of these "shadow" particles. According to the theory, when the more familiar leptons, photons, and quarks were produced in the Big Bang, each one was accompanied by a matching sparticle: sleptons, photinos and squarks.
Star formation Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astrophysics Star Formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of early type stars and planet formation as its immediate products. Star formation theory, as well as accounting the formation of a single star, must also account for the statistics of binary stars and the initial mass function.
Starburst galaxy A starburst galaxy is a galaxy in the process of an exceptionally high rate of star formation, compared to the usual star formation rate seen in most galaxies. Normal galaxies also form stars, but at a much lower rate. Galaxies are often observed to have a burst of star formation after a collision or close encounter between two galaxies.
Starquake A starquake is an astrophysical phenomenon that occurs when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth. This is thought to be the source of the giant gamma ray flares that are produced approximately once per decade from soft gamma repeaters.
Starship A starship is a spaceship designed for interstellar travel, specifically between star systems. Space-going vessels that are not intended for travel between star systems are often referred to as spaceships.
Stellar black hole A stellar black hole is a black hole formed by the gravitational collapse of a massive star (3 or more solar masses) at the end of its lifetime. The process is observed as a supernova explosion or as a gamma ray burst. Such a black hole will have a mass of at least 1.44 solar masses.
Stellar nucleosynthesis Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. The processes involved began to be understood early in the twentieth century, when it was first realised that the energy released from nuclear reactions accounted for the longevity of the Sun as a source of heat and light. The prime energy producer in the sun is the fusion of hydrogen to helium, which occurs at a minimum temperature of 3 million kelvin. The most important reactions in stellar nucleosynthesis are: the proton-proton chain, the carbon-nitrogen-oxygen cycle, the triple-alpha process, the alpha process, the carbon burning process, the neon burning process, the oxygen burning process, and the silicon burning process.
Superclusters Superclusters are large groupings of smaller galaxy groups and clusters, and are among the largest structures of the cosmos. The existence of superclusters indicates that the galaxies in our Universe are not uniformly distributed; most of them are drawn together in groups and clusters, with groups containing up to 50 galaxies and clusters up to several thousand.
Supermassive black hole A supermassive black hole is a black hole with a mass of an order of magnitude between 105 and 1010 of solar masses. It is currently thought that most, if not all galaxies, including the Milky Way, contain supermassive black holes at their galactic centers.
Supernova A supernova 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.
Superstring theory Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modeling them as vibrations of tiny supersymmetric strings. It is considered one of the most promising candidate theories of quantum gravity. Superstring theory is a shorthand for "supersymmetric string theory" because unlike bosonic string theory, it is the version of string theory that incorporates fermions and supersymmetry.
Supervolcano A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is enough to radically alter the landscape and severely impact global climate for years, with a cataclysmic effect on life (see also nuclear winter).
Supramolecular chemistry Supramolecular chemistry refers to the area of chemistry which focuses on the noncovalent bonding interactions of molecules. Traditional organic synthesis involves the making and breaking of covalent bonds to construct a desired molecule.
Surrogate mother Surrogacy is an arrangement whereby a woman agrees to become pregnant for the purpose of gestating and giving birth to a child for others to raise. She may be the child's genetic mother or not, depending on the type of arrangement agreed to. A surrogate mother is a woman who carries a child for a couple or single person with the intention of giving that child to that person/people once the child is born (also called surrogate pregnancy). The surrogate mother may be the baby's biological mother (traditional surrogacy) or she may be implanted with someone else's fertilized egg (gestational surrogacy).
Suspended animation Suspended animation is the slowing of life processes by external means without termination. Breathing, heartbeat, and other involuntary functions may still occur, but they can only be detected by artificial means. Extreme cold is used to precipitate the slowing of an individual's functions; use of this process has led to the developing science of cryonics. Outside of science fiction, the technique has never been applied to humans for more than a few hours. Placing astronauts in suspended animation has been proposed as one way for an individual to reach the end of an interplanetary or interstellar journey, avoiding the necessity for a gigantic generation ship; occasionally the two concepts have been combined, with generations of "caretakers" supervising a large population of frozen passengers.
Tachyon A tachyon is any hypothetical particle that travels at superluminal velocity. Tachyons have recurred in a variety of contexts, such as string theory. In the language of special relativity, a tachyon is a particle with space-like four-momentum and imaginary proper time. A tachyon is constrained to the space-like portion of the energy-momentum graph. Therefore, it can never slow to light speed or below. To date, the existence of tachyons has been neither confirmed nor explicitly ruled out.
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.
Terrestrial planet finder The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets.
Theory of everything A theory of everything (TOE) is a hypothetical theory of theoretical physics that fully explains and links together all known physical phenomena. The primary problem in producing a TOE is that the accepted theories of quantum mechanics and general relativity propose radically different descriptions of the universe, and straightforward ways of combining the two lead quickly to the renormalization problem in which the theory does not give finite results for experimentally testable quantities.
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.
Toba catastrophe theory According to the Toba catastrophe theory, 70 to 75 thousand years ago, a super volcanic event at Lake Toba reduced the human population to 1,000 to 10,000 breeding pairs, creating a bottleneck in human evolution.
Tokamak A tokamak is a machine producing a toroidal (doughnut-shaped) magnetic field for confining a plasma. It is one of several types of magnetic confinement devices and the leading candidate for producing fusion energy.
Transgenic plants Transgenic plants are plants that possess a gene or genes that have been transferred from a different species. Such modification may be performed through ordinary hybridization through cross-pollination of plants, but the term today refers to plants produced in a laboratory using recombinant DNA technology in order to create plants with specific characteristics by artificial insertion of genes from other species, and sometimes entirely different kingdoms./td>
Transhumanism Transhumanism is an international intellectual and cultural movement supporting the use of new sciences and technologies to enhance human mental and physical abilities and aptitudes, and ameliorate what it regards as undesirable and unnecessary aspects of the human condition, such as disease, aging, and death. Transhumanist thinkers study the possibilities and consequences of developing and using human enhancement techniques and other emerging technologies for these purposes. More generally, transhumanists support the convergence of emerging technologies such as nanotechnology, biotechnology, information technology, and cognitive science (converging technologies, or NBIC), and hypothetical future technologies such as simulated reality, artificial intelligence, mind transfer, and cryonics. They believe that humans can and should use these technologies to become more than human. They therefore support the recognition and protection of cognitive liberty, morphological freedom, and procreative liberty as civil liberties, so as to guarantee individuals the choice of using human enhancement technologies on themselves and their children, and progressively become transhuman and ultimately posthuman, which is seen as the climax of participant evolution. Some speculate that human enhancement techniques and other emerging technologies may facilitate such a transformation by the midpoint of the 21st century.
Trans-Neptunian object 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. Examples are: Pluto, Eris, Sedna, Quaoar, Ixion, Orcus, and Varuna, which are all classified as dwarf planets.
Triple star system A triple star consists of three stars which appear from the Earth to be close to one another. This closeness may be merely apparent, in which case the triple star is optical, or result from the three stars being physically close and gravitationally bound to each other, in which case it is physical. A physical triple star is also called trinary, ternary, or a triple star system. In a triple star system, each star orbits the center of mass of the system, usually so that two of the stars form a close binary star and the third is further away. This configuration is often called a hierarchical triple star system. Multiple star systems containing more than three stars can usually be decomposed into binary and single stars that are in a hierarchically bound system.
Tunguska event The Tunguska event was an explosion that occurred near the Tunguska River in what is now Krasnoyarsk Krai of Russia, on June 30, 1908. The event is sometimes referred to as the Great Siberian Explosion. In scientific circles, the leading explanation for the explosion is the airburst of a meteoroid 6 to 10 kilometers above the Earth's surface. Meteoroids enter the Earth's atmosphere from outer space every day, usually travelling at a speed of more than 10 kilometers per second. Most are small but occasionally a larger one enters from space.
Turing test The Turing Test is a proposal for a test of a machine's capability to perform human-like conversation. Described by Professor Alan Turing in the 1950 paper "Computing machinery and intelligence," it proceeds as follows: a human judge engages in a natural language conversation with two other parties, one a human and the other a machine.
Twin studies A twin study is a kind of genetic study done to determine heritability. The premise is that since identical twins have identical genotypes, differences between them are solely due to environmental factors. By examining the degree to which twins (especially twins raised apart) are differentiated, a study may determine the extent to which a particular trait is influenced by genes or the environment.
Universe Based on observations of the observable universe, physicists attempt to describe the whole of space-time, including all matter and energy and events which occur, as a single system corresponding to a mathematical model. The currently-accepted theory of the universe's formation is the Big Bang model, which describes the expansion of space-time from a gravitational singularity. The universe underwent a rapid period of cosmic inflation that flattened out nearly all initial irregularities.
Utopian and dystopian fiction The utopian genre and its child-genre, the dystopia, are uses of literature to explore social and political structures. Utopian fiction is the creation of an ideal world, or utopia, as the setting for a novel. Dystopian fiction is the opposite: creation of a nightmare world, where utopian ideals have been subverted. Many novels combine both, often as a metaphor for the different directions humanity can take in its choices, ending up with one of two possible futures. Both utopias and dystopias are commonly found in science fiction writing.
Virtual Reality Virtual reality (VR) is a technology which allows a user to interact with a computer-simulated environment, be it a real or imagined one. Most current virtual reality environments are primarily visual experiences, displayed either on a computer screen or through special stereoscopic displays, but some simulations include additional sensory information, such as sound through speakers or headphones. Some advanced, haptic systems now include tactile information, generally known as force feedback, in medical and gaming applications. Users can interact with a virtual environment or a virtual artifact (VA) either through the use of standard input devices such as a keyboard and mouse, or through multimodal devices such as a wired glove, the Polhemus boom arm, and omnidirectional treadmill.
Volcanic explosivity index The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value.
Volcanic winter A volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun, usually after a volcanic eruption. The causes of the bottleneck phenomenon, i.e., a sharp decrease in a species' population immediately followed by a period of great genetic divergence (differentiation) among survivors might be attributed to volcanic winters. A terrific case of volcanic winter happened around 71,000 - 73,000 years ago following the supereruption of Lake Toba on Sumatra island (Indonesia). In the following 6 years there was the highest amount of volcanic sulphur deposited in the last 110,000 years, possibly causing complete deforestation in Southeast Asia and the drastic cooling of sea temperatures. Remarkably, the eruption almost caused an instant Ice Age on Earth by accelerating the glacial shift that already was going on, therefore causing massive population reduction among animals and human beings on Earth. This, combined with the fact that most human differentiations abruptly occurred at that same period, is a probable case of bottleneck linked to volcanic winters. On average, such supereruptions and subsequent volcanic winters occur on our planet every 50,000 years.
Volcanology Volcanology is the study of volcanoes, lava, magma, and related geological phenomena. A volcanologist is a person who studies in this field. Volcanologists frequently visit volcanoes, especially active ones, to observe volcanic eruptions, collect eruptive products including tephra (such as ash or pumice), rock and lava samples. One major focus of enquiry is the prediction of eruptions; there is currently no accurate way to do this, but predicting eruptions, like predicting earthquakes, could save many lives.
Von Neumann probe A von Neumann probe is a specific example of a hypothetical concept based on the work of Hungarian-born American mathematician and physicist John von Neumann. Von Neumann rigorously studied the concept of self-replicating machines that he called "Universal Assemblers", which are most often referred to as von Neumann machines. While von Neumann never applied his work to the idea of spacecraft, theoreticians since then have done so. The idea of self-replicating spacecraft has been applied in theory to several distinct "tasks", and the particular variant of this idea applied to the idea of space exploration is known as a von Neumann probe. Other variants include the Berserker and an automated seeder ship.
Weak anthropic principle In physics and cosmology, the anthropic principle is an umbrella term for various dissimilar attempts to explain the structure of the universe by way of coincidentally balanced features that are necessary and relevant to the existence on Earth of biochemistry, carbon-based life, and eventually human beings to observe such a universe. The common form, called the weak anthropic principle is a truism or tautology that begins with the observation that the universe appears surprisingly hospitable to the emergence of life, particularly complex multicellular life, that can make such an observation and concludes with that premise that in only such a fine-tuned universe can such living observers exist. Given the extreme simplicity of the universe at the start of the Big Bang, the friendliness of the universe to complex structures such as galaxies, planetary systems, and biology is unexpected by any normal model of turbulence driven structuring that science has been able to derive.
Weightlessness Weightlessness or microgravity is the experience (by people and objects) during free-fall, of having no apparent weight. Weightlessness in common spacecraft is not due to an increased distance from the earth; the acceleration due to gravity at an altitude of 100 km is only 3% less than at the surface of the earth. Weightlessness means a zero g-force or zero apparent weight; acceleration is only due to gravity, as opposed to the cases where other forces are acting.
Wired glove A wired glove is a glove-like input device for virtual reality environments. Various sensor technologies are used to capture physical data such as bending of fingers. Often a motion tracker, such as a magnetic tracking device or inertial tracking device, is attached to capture the global position / rotation data of the glove. These movements are then interpreted by the software that accompanies the glove, so any one movement can mean any number of things. Gestures can then be categorized into useful information, such as to recognize American Sign Language or other symbolic functions. Expensive high-end wired gloves can also provide haptic feedback, which is a simulation of the sense of touch. This allows a wired glove to also be used as an output device.
Wormhole In physics, a wormhole is a hypothetical topological feature of spacetime that is essentially a 'shortcut' through space and time. A wormhole has at least two mouths which are connected to a single throat. If the wormhole is traversable, matter can 'travel' from one mouth to the other by passing through the throat. While there is no observational evidence for wormholes, spacetimes containing wormholes are known to be valid solutions in general relativity. A wormhole could allow time travel. This could be accomplished by accelerating one end of the wormhole to a high velocity relative to the other, and then sometime later bringing it back; relativistic time dilation would result in the accelerated wormhole mouth aging less than the stationary one as seen by an external observer, similar to what is seen in the twin paradox. However, time connects differently through the wormhole than outside it, so that synchronized clocks at each mouth will remain synchronized to someone traveling through the wormhole itself, no matter how the mouths move around. This means that anything which entered the accelerated wormhole mouth would exit the stationary one at a point in time prior to its entry.
Xenobiology See Astrobiology

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.
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.

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