Quantum Physics
Alpha rays: Rays made up of the nuclei of helium, containing two neutrons and two protons, which are produced in the radioactive decays of various heavy nuclei.
Angular momentum: A twisting force imparts angular momentum to objects, causing them to spin. Angular momentum is calculated as the product of the mass of an object  x  its rotational speed.
Anomaly: Due to quantum mechanical effects, a symmetry of nature that appears in a classical theory (such as electromagnetism) can be violated at the quantum level. When this happens the symmetry is said to be anomalous, and the quantum mechanical contribution that violates the symmetry is said to be an anomaly. Several “anomalous symmetries” are known to exist in nature. However, it is very important that quantum mechanical effects do not spoil the gauge and general covariance symmetries that are at the heart of the four known forces in nature. Making sure this does not happen has played a key role in efforts to develop string theories as candidate theories for the natural world.
Antiparticles: The laws of quantum mechanics and special relativity together imply that every elementary particle in nature must have an antiparticle, with equal mass and opposite electric charge. Many antiparticles have been created in the laboratory, and are used regularly in high-energy particle accelerators that explore the nature of matter and energy at fundamental scales. When particles and antiparticles collide, they can annihilate, producing pure radiation. Some neutral particles can be their own antiparticles.
Asymptotic freedom: The remarkable property of the strong interaction, discovered in 1974, that the force between quarks becomes stronger as you pull the quarks apart. This is the opposite behavior from electromagnetism, which gets weaker as elementary charges are moved far apart from each other. Asymptotic freedom is presumably related to the fact that no observable isolated quarks exist in nature (a phenomenon called confinement).
Beta rays:  Rays made up of electrons, which are produced in the radioactive decays of various elementary particles and nuclei.

Black body radiation: When a perfectly black solid, like the heating element on a stove, is heated up, it emits a continuous set of colors of radiation, changing from red hot to blue hot to white hot, for example. This distribution of radiation uniquely determines the temperature of the object, and was explained using the laws of quantum mechanics early in the twentieth century.

Bootstrap model: An idea that achieved prominence in the 1960s in response to the growing number of strongly interacting elementary particles, which suggested that no elementary particles were truly fundamental, but rather that all particles could be made up of other elementary particles. It proposed instead that what was fundamental was the mathematical relationship between particles that governed their interactions with each other. Bootstrap models eventually led to the development of string theories that attempted to describe the interactions of strongly interacting elementary particles.
Bosons:  Elementary particles in which the spin angular momentum is quantized, having a value equal to an integer multiple of some fundamental quantum of angular momentum.
Chirality: Certain objects, like our two hands, or the spiral structures that make up DNA can be said to be left handed or right handed, i.e., mirror images of each other. This property is called chirality. Elementary particles with spin angular momentum can be chiral, in that they can appear to be spinning in either a clockwise or a counterclockwise direction about their spin axis. One type of particle is called left handed, and the other right handed. Theories that distinguish between left- and right-handed particles are called chiral theories. The weak interaction is one such example as, for example, only left-handed neutrinos appear to sense the weak interaction. (As a result we do not even know if right-handed neutrinos exist in nature.)
Cloud chamber: A device developed in the early part of the twentieth century that produces observable tracks when charged elementary particles, such as the particles in cosmic rays, traverse the chamber. When these particles more through the chamber the gas vapor surrounding the particles with which they collide condens“condenses, producing a visible vapor trail. Different particles produce qualitatively different tracks.
Compactification: In theories with extra dimensions beyond the three space and one time dimension of our experience, one has to explain why the other dimensions are not observed. One solution involves compactification, in which the extra dimensions are curled up into “balls” that are so small that no experiment yet performed could detect their existence. The process by which one goes from a higher-dimensional theory to an effective four-dimensional theory is called compactification, and trying to understand how this might occur is one of the major challenges of string theory, and other higher-dimensional theories.
Conformal invariance: A mathematical symmetry that encompasses not only the general covariance that is at the basis of general relativity but extends it to include so-called scale transformations. If the world were conformally invariant, then the world would appear unchanged if I doubled the size of all objects, their masses, etc. This is clearly not the case, so conformal invariance is not a property of the real world as we measure it. However, it is an underlying property of string theories, and clearly one of the challenges of having string theory touch base with the world that we observe is to find mechanisms by which this symmetry is broken in our world.
Connection tensor: A mathematical quantity that encodes the geometric nature of space. The connection tensor in particular explains how the length and orientation of a standard ruler might be measured to change as it moved between nearby points in a curved space. The connection tensor therefore encodes information about the curvature of space.
Cosmic microwave background: The afterglow of the big bang, this radiation is a remnant from the earliest era of the expansion, when the temperature was so high that matter and radiation were in thermal equilibrium. Once the temperature had cooled sufficiently (to about three thousand degrees above absolute zero), protons and electrons began to be able to combine to form neutral atoms, which decoupled from the radiation so that the universe became transparent. The remnant radiation cooled as the universe expanded, and is now at a temperature of about three degrees above absolute zero.
Cosmic rays:  Energetic elementary particles of many different types that bombard the earth regularly from space. They originate from locations as close as our own sun, and as far away as the centers of distant galaxies.
Dark Energy: When we add up the total amount of mass in the visible universe, and compare it to the total energy needed to result in the flat universe (see Flat universe) that we appear to live in, there is a factor of three too little mass to account for the flatness of space on large scales. At the same time, the observed expansion of the universe appears to be accelerating, which could only be the case if empty space possessed energy (see Vacuum energy). The amount of energy needed to result in the observed acceleration turns out to be precisely that required to also account for a flat universe. We currently understand very little about this “dark energy,” which resides in empty space, and do not know if it is vacuum energy, or some other kind of yet more exotic form of energy.
D-branes: Multidimensional surfaces (generalizations of two-dimensional membranes—hence the name) on which “open strings” that is, “strings that are not closed loops, and that propagate in higher dimensions, can end. The “D” in D-branes does not refer to the dimensionality of the brane, but rather to the specific boundary conditions that are imposed at the end of the string as it merges with the brane. D-branes are now understood to be very important objects within string theory, though they were not known in the earliest formulations of the theory.
Density fluctuations:  Observed stars, galaxies, planets (and ultimately people) initially arose as very small inhomogeneities in the distribution of matter and radiation in the early universe, which collapsed due to their internal gravitational attraction. Regions where there was a very small excess of matter, for example, compared to the background value, would expand slightly more slowly than the background, eventually becoming so much more dense than the background that they decoupled from the expansion of the universe, and started to collapse. We believe this is how all large-scale structures now observable in the universe first formed. The question then becomes, what caused these initial density fluctuations in the early universe? We currently have reason to believe that they formed due to the quantum mechanical effects at very early times, as a result of inflation.
Electron: An elementary particle with negative electric charge that comprises the outer parts of all atoms. Neutral atoms contain an equal number of electrons and protons, with the latter existing within a dense nucleus at the center of the atoms. As far as we know, the electron is absolutely stable.
Equivalence principle: The principle that all objects fall at the same rate in a gravitational field. Einstein argued that this is equivalent to the notion that in a local free-falling frame, the effects of gravity will be unobservable. This principle formed a fundamental pillar of his general theory of relativity, because it allowed him to present a completely geometric description of gravity in which its effects could be ascribed to the curvature of space.
Ether (also Aether): The hypothetical substance that was believed for centuries to fill space and in which it was believed that light waves propagated. In 1887 the physicist Albert A. Michelson and his colleague, chemist Edward Morley, demonstrated experimentally that the ether, as a medium in which light traveled, did not exist. Later, in 1905, Einstein demonstrated that the existence of such an ether was in fact inconsistent with the laws of physics.
Event horizon:  A region surrounding a black hole, from which classically nothing, even light, can escape. As a result, once objects cross the event horizon observers outside of the black hole lose all information as to their future behavior.
False vacuum: If we describe the vacuum state as the lowest energy state in which a system can exist (such as a region of empty space devoid of matter or energy), a false vacuum occurs when the lowest energy state in certain circumstances turns out not to remain the lowest energy state as those circumstance change. Possible examples include when the value of some external field, or the temperature of the system, changes. The system may exist in this false vacuum state for a long time, but it will eventually decay, by the rules of quantum mechanics, into the new lower energy state, releasing energy in the process.
Fermions: Elementary particles in which the spin angular momentum is quantized, having a value equal to a half-integer multiple of some fundamental quantum of angular momentum.
Flat universe: General relativity implies that space can curve in the presence of mass and energy. On the largest scales, if light travels in straight lines, this implies that the universe is spatially flat. A spatially flat universe is infinite in extent, and, if dominated by matter, will continue to expand forever, with the expansion rate slowing asymptotically, but never quite falling to zero. We appear to live in a flat universe, as far as we can tell, although not one dominated by matter.
Gamma rays: The most energetic electromagnetic rays. The photons making up gamma rays can have energies as great as or greater than the energy associated with the rest mass of elementary particles such as electrons and protons.
General covariance: A mathematical notion at the heart of Einstein’s general relativity theory that implies that the laws of physics are independent of any specific coordinate frame in which we choose to measure them. One of the implications of this is that for an observer in free fall in a gravitational field, the effects of gravity will appear to disappear. Another is that an observer accelerating upward in an elevator in empty space will experience a force pushing him toward the floor that will be completely indistinguishable from the force of gravity that he would experience if he was at rest in a gravitational field.
Grand unification: The theoretical notion that the three nongravitational forces in nature—the weak, electromagnetic, and strong forces—can actually be unified in a single framework, and moreover, that at a very small scale, perhaps fifteen orders of magnitude smaller than we can measure today, all of these forces will appear to have the same strength.
Grassmann variable: A mathematical quantity that has some properties of a normal number, but nevertheless has some vastly different properties. For example, when a Grassman number is multiplied by itself, it produces zero. Two different Grassman variables, A and B, when multiplied together in one order, say AB, equal the negative value when multiplied in the other order, so that AB=-BA. It turns out that these properties mimic the quantum mechanical properties that govern the behavior of fermions.
Graviton: When one combines quantum mechanics and relativity, all forces are conveyed by the exchange of elementary particles, like the photon, the fundamental quantum of electromagnetism. We call the hypothetical particle that conveys gravitation the graviton. Individual gravitons have not yet been measured because of the weakness of gravity, although we have no reason not to believe they exist.
GSO construction: A particular construction in string theory in ten dimensions, associated with the names Gliozzi, Scherk, and Olive, which removed the unwanted tachyon modes by introducing supersymmetry on the strings.
Hadrons: Elementary particles that have strong interactions with other particles.
Heterotic string: A string theory involving closed string loops in ten dimensions in which the different excitations of the string, moving in different directions along the string, behave quite differently. In fact, the left movers appear to live in a different number of dimensions than the right movers. In this way, it turns out that one can have consistent string theories in ten dimensions instead of twenty-six dimensions. Moreover the gauge symmetries that one hopes might be associated with the observed gauge symmetries in our world arise naturally as a part of this construction.
Hierarchy problem: Gravity is much weaker than all of the other forces in nature. This extreme hierarchy of forces is currently not understood, and is one form of what is often called the hierarchy problem. Another example is that the length scale at which the strength of all the nongravitational forces appears to become the same—the length scale at which grand unification is thought to occur—appears to be very much smaller than the scale associated with the size of particles such as protons and neutrons, and nuclei. It turns out to be very difficult mathematically to devise theories in which this is the case, and trying to resolve this difficulty is the hierarchy problem.
Hubble constant: In a uniformly expanding universe the recession velocity of distant objects away from us is proportional to their distance from us. The quantity determining the precise numerical relationship between velocity and distance is named the Hubble constant, in honor of Edwin Hubble, who first discovered this relation. Note that this quantity is not in fact a constant over cosmological times for most cosmological models.
Hypercube: Another name for a four-dimensional cube (tesseract).
Inflation: The idea, based on notions coming from the physics of elementary particles, that at very early times the universe underwent a brief period of extremely rapid expansion, during which distances increased by a factor greater than a billion, billion, billion, billion, in a fraction of a second. Such an expansion can naturally occur as the universe expanded and cooled at early times if there was a phase transition associated with a grand unified theory (see Grand unification), and can moreover explain all of the observed features of the universe today on the largest scales we can measure.
Large hadron collider (LHC): The new large proton-proton collider being built at the European Center for Nuclear Research (CERN) in Geneva. Planned to come online by 2007-2008, it will achieve energies large enough to explore for the mechanism underlying the origin of mass of elementary particles, and may reveal other new phenomena such as supersymmetry and possible large extra dimensions.
Local supersymmetry: This involves the mathematical formalism in which gravity and supersymmetry are combined together in one framework.  One consequence of this is that the graviton, the fundamental quantum thought to convey the gravitational force, must have a fermionic partner, called the gravitino.
Matrices: Mathematical objects which take the form of tables of numbers with separate entries in the different rows and columns. Matrices can be multiplied together, added together, etc. and thus have their own kind of algebra that is more complex than the algebra of simple real numbers. One of the eleven-dimensional limits of string theories that form a part of M-theory involves a description of nature in which matrices form the fundamental quantities akin to the numbers that describe positions in our four-dimensional space.
Metric: The mathematical quantity, called a tensor, that determines how physical lengths are measured in terms of the coordinates one uses to label the points in some space. For example, on a sphere, the physical distance between neighboring lines of longitude decreases as one moves to the poles. The metric tensor contains this information of how the distance between lines of longitude changes as you move around the surface of the sphere.
Moduli fields: In extra-dimensional theories such as string theory there are usually dynamical “fields” observable in our three-dimensional world that are associated with the actual radius of the presumably compactified and unobservable extra dimensions. These fields are called moduli fields, and their dynamics can either cause interesting new effects that might be measurable in our space, or cause severe empirical problems for model builders.
Momentum: A force acting on an object over some time imparts momentum to that object. For objects moving slowly compared to the speed of light, the momentum of the object is given by multiplying the mass of the object by its speed”
M-theory: The eleven-dimensional theory that is thought to underlie all known ten-dimensional string theories. Its existence was suggested once it was recognized that D-branes must be included in string descriptions, and these clarified the relationship between formerly disparate string models, suggesting some evidence of a yet higher dimensional theory. To date, no one has a clear understanding of the precise nature of this theory, or even what its fundamental variables are.
Muon: An unstable elementary particle, with a lifetime of one millionth of a second, that appears to be identical to the electron, except that its mass is about two hundred times greater. When it was first observed, the physicist I. I. Rabi uttered, “Who ordered that?”
Naturalness: In physics formulas one often finds numbers comparable to unity, such as 2 or pi. However, physicists call it “unnatural” when one finds in a formula a very large or very small dimensionless number, like 0.00000000000000000000000001 or 35,000,000,000,000,000,000,000,000,000. The ratio between the strength of gravity and electromagnetism is one such very small number, for example, which is why the hierarchy problem is one form of a naturalness problem.
Neutrino:  A light neutral particle produced in the radioactive decay of a neutron (and various other particles). The neutrino has no electromagnetic or strong interactions, and thus interacts so weakly with matter that neutrinos produced in the decay of a neutron can, on average, travel right through the Earth without a single collision or interaction.
Neutron: A neutral elementary particle with a mass comparable to that of the proton, and comprising, along with the proton, all atomic nuclei. Free neutrons are unstable, decaying into protons, electrons, and neutrinos with an average lifetime of about ten minutes.
Nonabelian gauge theory: A different name for Yang-Mills theories that reflects the mathematical symmetry, called gauge invariance, that underlies them.
Non-Euclidean geometry: The specific application of Riemannian geometry to spaces that are not flat.
Parallax: The amount by which nearby objects, when viewed from different vantage points, will shift in comparison to distant background objects. The magnitude of this shift can be used to determine the distance of the nearby objects.
Parity: A parity transformation interchanges left and right. Certain interactions, like the electromagnetic interaction, do not distinguish between left and right. However, the weak interaction remarkably does distinguish between left and right, so that neutrons rotating around a certain axis will produce electrons that preferentially head off in one hemisphere, as opposed to the other hemisphere.
Photon: The elementary “quantum” of the electromagnetic field, a.k.a. light. Because of quantum mechanics, light has both wavelike and particlelike properties. In particular light of a given frequency is transmitted via many individual photons, so that for light of a low enough intensity, a detector will be able to detect the individual packets of energy carried by these particles, and never any smaller amounts.
Pions: Elementary particles produced in the collisions of energetic protons with matter. These particles, about ten times lighter than the proton, are made up of a quark and an antiquark, and are unstable with a lifetime of less than a millionth of a billionth of a second.
Planck scale: This is the length scale (or equivalently the energy scale) at which quantum mechanical effects relevant to gravity cannot be ignored. Because gravity is so weak at normal scales, it turns out that one must go to incredibly small scales before quantum effects become important. The Planck scale is about 10-33cm.
Precession: If a rotating or orbiting object returns to its initial position, and repeats precisely the same motion again, there is no precession. However, if upon returning to the same position, the next orbit, or rotation, is shifted compared to the first, so that the motion does not exactly repeat after one such cycle, one says that the orbit or rotation is precessing.
Proton: An elementary particle with positive electric charge equal and opposite to that found on the electron. The proton, which weighs almost two thousand times as much as the electron, is located, along with neutral particles called neutrons, within the dense nucleus at the center of atoms. As far as we can measure, the proton is absolutely stable, but most grand unified theories predict the proton can decay with a lifetime too long to have yet been measured.
Quantum electrodynamics (QED): The theory that successfully combines quantum mechanics, relativity, and electromagnetism to correctly predict all phenomena that have been observed associated with the interactions of matter and electromagnetic radiation.
Quark confinement: The property that is associated with the fact that isolated quarks are not observed in nature. While this property of the strong interaction has not been mathematically proved yet, it appears to arise naturally as a corollary to the fact that the force between quarks gets weaker as they get closer together, and stronger as you pull them apart. If this behavior continues indefinitely as you try and pull them apart, it would take an infinite amount of energy to produce a single quark, isolated from all its neighbors.
Riemannian geometry: A generalization of the flat two-dimensional geometric relations of Euclid, applied instead to spaces that can also be curved and that can also involve more than two dimensions.
Scattering: When two elementary particles collide together many different things can happen, from a simple grazing collision in which the particles are each deflected, to collisions in which the particles change their identities, and in which new elementary particles are created. All of these processes are called scattering processes.
Singularity: Generally describes the mathematical characteristic of any quantity that can grow infinitely large. When referred to points in space, a singularity refers to a region of space where the density of matter and energy grows infinitely large, and where the classical laws of general relativity appear to break down.
Spacetime supersymmetry: A mathematical symmetry that incorporates supersymmetry with the other known symmetries of space and time, including the fact that the laws of physics are unchanged from place to place, and from time to time.
Spacetime: The four-dimensional universe made up of three dimensions of space and one dimension of time, unified together by Einstein in his special theory of relativity, and first described by Hermann Minkowski.
Spectra: The set of colors of electromagnetic radiation emitted by different gases when you heat them up. Each element has a unique set of such colors that identifies it. The laws of quantum mechanics allow us to calculate the spectrum of light emitted by atoms, in agreement with observations.
Spontaneous symmetry breaking: This occurs when some symmetry of nature, such as left-right symmetry, is violated by the particular circumstances in which we find ourselves, but not by the underlying laws of physics that govern that situation. So, for example, while electromagnetism does not distinguish left from right, and electromagnetic interactions are those that are chiefly responsible for the makeup of material objects, I can nevertheless find myself standing next to a mountain on one side of me and an ocean on another side of me. In this case, I can clearly distinguish my left side from my right side. Such an accident of my particular circumstances represents an example of spontaneous symmetry breaking. Here is another one: Say you are having dinner at a large round table. After everyone sits down, every place-setting looks identical, and glasses are located both to the left and right of each person. Nothing distinguishes which glass is associated with which person until the first person picks up a glass. After that, the original symmetry is broken, and every glass is associated with a unique person.
Supergravity: Another name for local supersymmetry.
Supersymmetry: A mathematical symmetry that relates elementary particles having different spin angular momentum. Specifically, supersymmetry implies that for all particles having integer spin (bosons) there should exist particles of equal mass having half-integer spin (fermions).
Tachyon: A hypothetical elementary particle which travels faster than the speed of light, and which can never be slowed down to below the speed of light. Such a particle could appear to an outside observer to be traveling backward in time. Generally, if a theory appears to predict tachyonic states, it is a sign that there is something unstable in the theory. Often such a prediction is associated with a violation of unitarity in the theory.
Tensor algebra: Mathematical relations that involve objects with multiple separate components, each of which can have a different dependence on both space and time.
Tesseract: A four-dimensional version of a three-dimensional cube. The “faces” of this hypercube comprise eight different three-dimensional cubes.
Torus: A donut-shaped object, with a hole in the center. One can produce such an object by taking a flat piece of paper and pasting together two opposite edges, and then the other two opposite edges. Alternatively, one can simply lay the paper flat and merely “identify” the two edges, so that for example, whenever an object heads off the right edge of the paper it would appear coming in from the left edge. In the language of topology, a torus therefore is topologically distinct from a flat piece of paper, in that it has a hole, but geometrically it can still be considered flat.
Uncertainty principle: One of the fundamental principles of quantum mechanics that implies there are certain combinations of quantities associated with any object that can never be measured exactly. For example, both the position and the momentum (see momentum) of an object cannot be known together with absolute accuracy. As one measures the position of an object more and more accurately, the uncertainty in knowledge about its momentum will increase. Since this minimum combined uncertainty in position and momentum is, however, very small, the effect of the uncertainty principle is not usually directly observed on scales much larger than the size of atoms.
Unitarity: A fundamental mathematical property of nature that essentially says that probabilities do not change over time. Simply put, it implies that when one considers all of the different possibilities that may arise when one particle interacts with another, and sums up the different probabilities, they will add up to unity.
Vacuum energy: The energy associated with empty space, containing no matter or radiation. While common sense says that this energy should be zero, the laws of quantum mechanics and relativity together imply that empty space is full of a swarm of “virtual particles” that pop in and out of existence on a timescale so short we cannot observe them directly. When we try to calculate what the contribution of these particles might be to the energy of empty space, we come up with a very large number—indeed, far larger than anything we measure today. We currently do not understand why this prediction is incorrect. At the “same time, any such energy, if it exists, is gravitationally repulsive, and could cause the observed expansion of the universe to accelerate. This is what we observe today in the universe on large scales.
Virtual particles: The laws of quantum mechanics and special relativity together imply that elementary particles and their antiparticles can spontaneously appear together out of empty space, exist for a short time, and then annihilate again, leaving nothing but empty space. As long as they do so for periods so short that we cannot measure them directly, their existence is ensured by the uncertainty principle. While virtual particles cannot be directly observed, their indirect effects can be observed, and predictions agree well with observations.
Vortex rings: A ring, like a smoke ring, that is stable and can move about, maintaining its form even as it moves through some background medium like air.
Warped space: This has, alas, nothing to do with Star Trek. Rather, it is a term that has been used to describe certain extra-dimensional theories with possibly large extra dimensions. In these theories the geometry (and hence the strength of gravity) in the three spatial dimensions we experience is not separated from the existence of the higher dimension(s), but is rather a function of where you are located in the higher dimension(s). In this case, it is possible not only for all familiar particles and non-gravitational forces to be confined on our three-dimensional space, but also for gravity to be effectively restricted to lie in our space, leaving the higher dimensions thus far undetected, but in fact allowing the possibility of their detection in new high energy accelerators such as the large hadron collider, and also allowing a possible new approach to the hierarchy problem.
Wavelength: For any periodic wave, with peaks and crests, the distance between successive peaks is called the wavelength of the wave.
Weak scale: This is the energy (or length) scale at which the weak interaction, responsible for the nuclear reactions inside the sun, for example, becomes of roughly comparable order in strength as the electromagnetic interaction, and which the mathematical symmetry between these two forces of nature, which is spontaneously broken at large scales, becomes manifest.
Yang-Mills theory: This represents a wide class of physical theories that are generalizations of electromagnetism, in which the particles that play the role of photons in electromagnetism, which are neutral, are instead charged, and also can have a mass, and therefore have more complicated interactions with one another and with other particles than photons do. Both the weak force and the strong force are described by Yang-Mills theories.

Paranormal Terms

​Agent – A living person who is the focus of poltergeist activity.
Amulet - An object that is thought to bring good luck or have the power to protect from ghosts or spirits and ward off evil. AKA "charm", "talisman".

Anomaly - Irregular or unusual event that does not follow a standard rule or law or that cannot be explained by currently accepted scientific theories.
Apparition - Spectral image of a person or creature that materializes even though a physical body is not present; experienced in a wakeful state.
Apport – Physical object that can materialize and appear at will in the presence of a medium.

Artifact - Term used to describe the slight noises or residual images produced by the internal mechanisms of equipment which could be misinterpreted as paranormal sounds or images.
Asport – Physical object that a spirit teleports to another location or makes disappear. 
Astral Body – The body that a person occupies during an out-of-body experience.
Astral Plane – A world that is believed to exist above our physical world.
Astral Projection – The intentional act of having the spirit leave the body, whereas an out-of-body experience will happen involuntarily. (See Out-of-Body Experience).
Astrology - The theory and practice of interpreting the positions and aspects of celestial bodies in the belief that they have an influence on the course of natural earthly occurrences and human affairs. 
Aura – Invisible emanation of electromagnetic energy that surrounds a person or thing; often thought to reflect a person’s personality, health or emotional state; can be viewed by Kirlian photography in color frequencies as with light. 
Automatic Writing – This method of obtaining information from disembodied spirits is used by mediums in which the spirit takes control over the medium causing them to translate unconscious information on paper without being aware of the contents.
Automatism – An unconscious or involuntary muscular movement caused by spirits. (See Automatic Writing).
Autoscopy – The visual hallucination or image of one's body looking back at themselves from a position outside the body. (See Out-of-Body Experience).
Banshee – A wailing spirit or “death omen” that will appear to be in two different places at the same time. 
Case Study – An in-depth investigation of an individual subject.
Channeling – In this method of spirit communication, a spirit will pass information directly to a medium or channeler who will then relay the information on to the listener(s).

Clairalience - Ability to perceive or experience odor outside the range of normal olfactory sense. (See ESP) (For more information see section on Types of ESP). 
Clairaudience – An auditory form of ESP; paranormal information is received outside the range of normal perception through voices, whispers and auditory impressions. (See ESP) (For more information see section on Types of ESP).

Clairgustance - Ability to perceive or experience taste without putting anything in the mouth. (See ESP) ( For more information see section on Types of ESP).
Clairsentience – Ability to perceive or experience the emotions of others without the use of the normal five physical senses. A general term for clairvoyance and clairaudience. (See ESP) (For more information see section on Types of ESP).
Clairvoyance – An acute insight or perceptiveness that enables one to see objects or events that cannot be perceived by the senses; comes in the form of mental imagery and intuition. (See ESP For more information see section on Types of ESP).

Contact Session - Period of time in which paranormal investigators attempt to establish communication with an entity.
Control – Procedure in paranormal psychology which ensures that the experiment is conducted in a standard fashion so that results will not be influenced by any extraneous factors.
Control Group – Group of outside subjects whose performance or abilities are compared with the experimental subjects. 
Collective Apparition - Rare type of sighting in which more than one person sees the same apparition or phenomena.
Crisis Apparition – An apparition that is seen when a person is seriously ill, seriously injured or at the point of death.
Dematerialization – Term used to describe a spirit or specter losing apparent physical substance.
Déjà vu - An impression or dull familiarity of having seen or experienced something before.
Demon - An inferior deity recognized by all religions but known by differing names and physical descriptions; often spoken of in religious text as pure evil; capable of human possession, possessed of inhuman strength, malevolent and destructive. Documented cases of demons are extremely rare.
Demonic Wind - a auditory “spirit caused” ferocious sounding wind, like a hurricane or tornado that whips around inside a house or building, but in fact does not exist

Direct Voice Phenomenon (DVP) – An auditory “spirit” voice that is spoken directly to the sitters at a séance. 
Doppleganger – An exact spirit double or mirror image of a person which is considered to be very negative.

Dowsing Rod - Simple tool of metal or wood used to locate water, lost objects, energy fields or in spirit communication. Established use has been known for centuries but carries little or no weight within current scientific arenas.
Earthbound – Term referring to a ghost or spirit that was unable to cross over to the other side at the time of death and is therefore stuck in this physical plane. 
Ectoplasm – An immaterial or ethereal substance associated with spirit manifestations. Often photographed as fog-like mist, white masses or vortexes.

Electromagnetic Field (EMF) - Energy field surrounding all things, both natural and man-made.
Electromagnetic Field (EMF) Detector – (See Magnetometer)
Electronic Voice Phenomenon (EVP) – Voices and sounds from beyond that are captured and recorded on magnetic tape or digitally. Controversial in that many believe the sounds are misinterpretations of natural phenomena or equipment artifacts.
Elementals – Term commonly referring to natural spirits. AKA “Earth spirits.”  They can be pesky and bothersome but rarely dangerous

Entity - Any thing that has a separate, distinct existence, though not necessarily material in nature.
Extra Sensory Perception (ESP) - Communication or perception by means other than the normal five physical senses. AKA "sixth sense".
Exorcism - The banishment of an entity or entities (spirits, ghosts, demons) that are thought to possess or haunt a location or human being or animal. The ritual, which can be religious in nature, is conducted by an exorcist who will call upon a Higher Power to cast away any evil forces that may be present.
False Awakening – Event in which a person believes they are awake but are actually dreaming.

Frank's Box - Controversial invention which some believe allow "real-time" communication with entities; works by continuously scanning AM and FM radio frequencies from which broadcast syllables or words are used by an entity to "speak". AKA "ghost box".
Ghost – Generic term referring to a form of apparition or supernatural entity; typically the visual appearance of a deceased human spirit.
Ghost Hunt – Carefully controlled research project in which various methods and equipment are used to investigate reports of ghosts and hauntings. Differs from an investigation in that no intervention of the research team has been requested.
Ghoul – Demonic or parasitic entity that feeds upon human remains.
Hallucination – Vivid perception of sights and/or sounds that are not physically present. Usually associated with an altered state of consciousness induced by alcohol, drugs, illness or psychological instability.
Haunting – Reoccurring ghostly phenomena that returns to a location where no one is physically present. Ghosts generally haunt places and not people. (See Intelligent and Residual Haunting)
Hellhound – Spectral death omen in the form of a ghostly dog. AKA "black shuck".
Hot Reading – Devious or fraudulent reading in which the reader has been given prior knowledge of the sitter. (See Reading).
Hypnosis – Technique that induces a sleep-like state in which the subject acts only on external suggestion.
Ignis fatuus - Phosphorescent or spectral light that that is alleged to be an indication of death. This phenomenon is thought to be caused by spontaneous combustion of gases emitted by rotting organic matter. Popular in cultural and regional folklore. AKA "coffin light' "corpse candle", "corpse light", "death light".
Illusion – A perception between what is perceived and what is reality.

Infra-red Camera (IR Camera) - Camera with incorporated infra-red technology that allows photography or filming in low light conditions. AKA "night vision camera".

Infra-red non-contact thermometer (IR Thermometer) - Instrument with incorporated infra-red technology that allows the measurement of both ambient and surface temperatures without physically being in contact. Extreme and rapid temperature change is believed to be an indicator of paranormal activity.

Instrumental Trans-Communication (ITC) - Term used to describe the many ways unexpected "spirit" voices can be collected through modern technological          methods. Includes EVP, white noise, video frequency feedback.

Intelligent Haunting - Case in which there is interaction on the physical plane as in communication or object movement.
Intuition – Non-paranormal knowledge that is gained through perceptive insight. AKA "gut feeling".

Investigation - Carefully controlled research project in which various methods and equipment are used to seek confirmation of reports of ghosts or hauntings. Differs from a ghost hunt in that the research team was requested to intervene.

K-II Meter - (See Magnetometer)
Levitation – To lift or raise a physical object in apparent defiance of gravity.
Life Review – Flashback of a person’s life that is typically associated with near-death experiences. Lucid Dreaming - Dream state in which one is conscious enough to recognize that one is in the dream state and is then able to control dream events.

Magnetometer (EMF meter, Gaussmeter) - Instrument for measuring the magnitude and direction of a magnetic field; typically used by paranormal researchers to detect a ghost’s magnetic energy.

Marian Apparition – Event in which the Virgin Mary is seen.

Materialization – The act of forming something solid from the air. One of the most difficult and impressive materializations is when part or all of a ghost or spirit can be seen, especially if the face is recognizable. Medium - Someone who professes to be able communicate with spirits on behalf of another living being, acting as a midway point halfway between the worlds of the living and the dead.

Mesmerism – Hypnotic induction of a sleep or trance state (See Hypnotism).

MIP - Mirror Images Phenomenon - a term we coined for the images that appear in a mirror that have no rational explanation for them.

Mist – Photographed anomaly that appears as a blanket of light. There is no substantial proof that these are related to paranormal phenomenon. YES, We have substantial proof it is a paranormal event.

Motor Automatism – Bodily movement or functions that are accompanied but not controlled by consciousness (See Automatic Writing).

Near Death Experience (NDE) – Event that is reported by people who clinically die, or come close to actual death and are revived. These often include encounters with spirit guides, seeing dead relatives or friends, life review, out-of-body experiences

(OBE), or a moment of decision where they are able to decide or are told to turn back. Old Hag Syndrome – Nocturnal phenomena that involves a feeling of immobilization, suffocation, odd smells and feelings and is sometimes accompanied by immense fear (See Sleep Paralysis).

Orb – Most commonly photographed anomaly that theoretically represents the “spirit” of a deceased person. Often appears as a ball of light on film though in some cases they are not seen at the time of the photo. Differing characteristics include size, color, density, shape, motion and flexibility. Since there are many reasonable causes for their origin (dust, moisture, insects, lens reflection, etc.) orbs remain highly controversial.
Orb Color Theory (OCT) - Experimental concept that allows interpretation of an orb's "emotional" state or meaning by its primary color characteristics.

Ouija Board - A pre-printed board with letters, numerals, and words used to receive spirit communications. Typically a planchette, a triangular or heart-shaped pointer, is employed to spell out words or messages and point out numbers or letters. Many believe the controversial board is a gateway allowing negative entities into the physical plane while others believe it no more harmful than any other board game. AKA "spirit board", "talking board".  The board's name is derived from the French and German words for 'yes'.

Out-of-body experience (OBE or OOBE) – Sensation or experience in which one's self or spirit travels to a different location other than their physical body (See Astral Projection and Near Death Experience). Paranormal – Term referring to something that is beyond the range of normal human experience or scientific explanation.

Parapsychology - The study of the evidence for psychological phenomena that are inexplicable by science.
Pareidolia - Psychological phenomena whereby random and vague stimuli are perceived as being significant. Common examples include finding images of animals or faces in clouds, the "man in the moon" or hearing "hidden messages" in reversed audio recordings. (See Simulacra).

Percipient - Person who sees (perceives) an apparition. Phantom - Something that is seen, heard and/or sensed, but has no physical reality (See Ghost).
Poltergeist - Non-human spirit entity which literally means "noisy ghost" but is usually more malicious and destructive than ghosts of deceased humans. Traditional poltergeist activities are thumping and banging, levitation or movement of objects, stone throwing and starting fires. It is thought that poltergeist activity in some instances may be brought on subconsciously by an adolescent agent, females under the age of 25 or by individuals under extreme emotional duress. Documented cases of poltergeists are relatively few. Precognition – Ability to predict or have knowledge of an event in advance of its occurrence, especially by extrasensory perception (See Clairvoyance).

Psi – Twenty-third letter in the Greek alphabet use to denote psychic phenomena.

Psychic - Term used to describe a person who has above average ESP abilities or paranormal powers; term used to describe forces of a paranormal nature.

Psychokinesis (PK) - The power of the mind to affect matter without physical contact, especially in inanimate and remote objects by the exercise of psychic powers.

Psychometry - The ability or art of divining information about people or events associated with an object solely by touching or being near to it.

Pyrokinesis – The ability to unconsciously control and sometimes in rare cases produce fire with their mind only.

Radio Voice Phenomenon (RVP) - Receiving the voice of a deceased human being through a regular radio.
Reading - Session during which a medium or psychic reveals information to a sitter through various means such as astrology, palmistry or tarot cards.

Reciprocal Apparition - Extremely rare type of spirit phenomenon in which both the agent and percipient are able to see and respond to each other.

Remote Viewing – Used by some psychics, a procedure in which the percipient or psychic attempts to become physically aware of the experience of an agent who is at a distant, unknown location through ESP.
Residual Haunting - Case in which an event or scene is re-enacted and is not affected by any external influences.

Retrocognition – Experience in which a person finds themselves in the past and is able to see and experience events of which they had no prior knowledge.

Séance - Meeting or gathering of people, usually lead by a medium, to receive spiritualistic messages, manifestations of and/or communication with the dead.
Sensitive - Term referring to persons who possess extrasensory talents.
Shadow People - Shadow-like entities most often seen in one's peripheral vision. Differs from ghosts in that recognizable characteristics like facial features or clothing are lacking. Very frequently sightings are accompanied by feelings of dread, menace or threat. AKA "shadow beings", "shadow folk", "shadow ghosts".
Shaman – A member of certain tribal societies who acts as a medium between the visible world and an invisible spirit world and who practices magic or sorcery for purposes of healing, divination, and control over natural events.

Simulacra – Term used to describe the faces, figures and images in ordinary, everyday object such as clouds, rocks, foliage, etc. (See Pareidolia).
Sleep Paralysis - Form of paralysis often striking as a person falls asleep, awakens or moves into or out of the rapid-eye movement (REM) stage of sleep. (See Old Hag Syndrome).

Specter – A ghostly apparition; a phantom (See Ghost).

Spiritualism - The belief system that the dead are able to communicate with the living, most often through an intermediary or medium.

Stigmata – Unexplained bodily marks, sores, or sensations of pain corresponding in location to the crucifixion wounds of Christ.

Subjective Apparition – Hallucination of apparitions or other phenomena that are created by our own minds. Supernatural - Of or relating to existence outside the natural world. As opposed to paranormal, the term "supernatural" often connotes divine or demonic intervention.

Telekinesis - The paranormal movement of objects by scientifically inexplicable means.

Telepathy – Communication from one mind to another through means other than the senses.

Teleportation - Method of transportation in which matter or information is dematerialized, usually instantaneously, at one point and recreated at another.

Thought Form – An apparition produced solely by the power of the human mind.

Trance - A hypnotic, cataleptic, or ecstatic state in which one becomes detached from their physical surroundings.

Vortex – An anomaly that appears as a funnel or rope-like image in photographs. Sometimes thought to represent ghosts, collections of orbs or gateways which travel to a wormhole in time-space, there is no substantial scientific evidence to support any of these theories.

White Noise – An acoustical or electrical noise of which the intensity is the same at all frequencies within a given band.

Austin Paranormal Research

Ghost Hunting Terminology 

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