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1.054571596e-34 J s: Dirac′s constant, also known as h bar.
1.0973731568549e7m^-1: Rydberg Constant.
1.38062e-23JK^-1: Boltzmanns constant.
1.60217733e-19 J: Electron Volt.
1.602e-19 C: Electron charge.
1.672e-27kg: Proton mass.
1.759e11Ckg^-1: Electron charge to mass ratio.
101325 Pa: Standard atmospheric pressure.
1836.1526675: Proton to electron mass ratio.
2.9979e8 ms^-1: Velocity of light in vacuo.
2D: Having both width and length, but no thickness.
3.289841960368e15 Hz: Rydberg Constant multiplied by the speed of light.
376.73 Ohm: Impedance of free space.
3D: Having length, width, and thickness i.e. space.
4.13566727e-15 eV s: Plancks Constant.
5.67e-8Wm^-2K^-4: Stefan-Boltzmann constant.
6.022e23mol^-1: Avogadro′s number
6.58211889e-16 eV s: Known as h bar or Dirac′s constant.
6.626e-34 Js: Planck′s constant.
6.67e-11 Nm²kg^-2: Gravitational constant.
8.314 JK^-1mol^-1: Molar gas constant.
8.85e-12Fm^-1: Permittivity of free space.
9.109e-31 kg: Electron rest mass.
9.648456e4Cmol^-1: Faraday constant
9.80665 ms^-2: Standard acceleration due to gravity.
A: The abbreviation of Ampere, the SI unit of Electric current.
A: The Ångström is an old unit used for measuring the wavelength of electromagnetic radiation including visible light and X-rays.
aA: Abbreviation of abampere.
ab: A prefix indicating that an electrical unit is part of the CGS absolute electromagnetic system.
Abampere: The CGS electromagnetic unit of current equal to 10 Amperes.
Abbe Number: The ratio of refractivity to dispersion in an optical medium.
Abcoulomb: The CGS unit of electric charge equal to 10 Coulomb.
Abfarad: The CGS unit of capacitance equal to 1.0x10⁹Farad.
Abhenry: The CGS unit of inductance equal to 1.0x10^-9Henry.
Ablate: To carry away.
Ablating Material: A material designed to provide thermal protection to a body in a fluid stream through loss of mass.
Abmho: The CGS unit that is the reciprocal of the ohm equal to 1.0x10⁹Siemens.
Abohm: The CGS unit of electrical resistance equal to 1.0x10^-9Ohms.
Absolute Accuracy: A measure of the uncertainty of an instrument reading compared to that of a primary standard traceable to a National standard.
Absolute Humidity: The total mass of water vapour present in the air per unit volume, generally given in g/m³.
Absolute Pressure: Pressure measured from a starting point of 0 in perfect vacuum.
Absolute Space: Space that is not affected by what occupies it or occurs within it and that provides a standard for distinguishing inertial systems from other frames of reference.
Absolute Temperature: Temperature measured on a scale that sets absolute zero as zero.
Absolute Unit: A unit defined in terms of fundamental quantities.
Absolute Vacuum: A volume which contains no matter.
Absolute Zero: At this temperature atoms have no energy.
Absorb: To transform radiant energy into a different form, with a resultant rise in temperature.
Absorption: Transformation of radiant energy to a different form of energy by the interaction of matter, depending on temperature and wavelength.
Absorption Band: A dark band in the absorption spectrum of a substance, corresponding to a range of wavelengths for which the substance absorbs more strongly than at adjacent wavelengths.
Absorption Lines: Dark lines in a spectrum that are produced when light or other electromagnetic radiation passes through a gas cloud or similar object closer to the observer.
Absorption Spectroscopy: A technique for determining the concentration and structure of a substance by measuring the amount of electromagnetic radiation the sample absorbs at various wavelengths.
Absorption Spectrum: The collection of wavelengths missing from a continuous distribution of wavelengths.
abtesla: The CGS unit of magnetic flux density equal to 10^-4 tesla.
Abvolt: The CGS unit of electromotive force equal to 1.0x10^-9Volt.
abwatt: The CGS unit of power equal to 10^-7 watt.
abweber: The CGS unit of magnetic flux equal to 10^-8 weber. Also known as the maxwell.
AC Line: The set of conductors that route ac voltage from one point to another.
AC Line Filter: A circuit filter placed in the ac line to condition or smooth out variations that are higher in frequency than the line frequency.
AC: An electric current whose direction changes direction with a frequency independent of circuit components.
Acausal: If a system is acausal it means the output begins before the input.
Accelerate: To increase the speed of an object.
Acceleration: The change in velocity divided by the time it takes to make the change.
Accelerator: A machine used to accelerate particles to high speeds.
Acceptor: An atom which is likely to take on one or more electrons when placed in a crystal.
Accretion: The process by which the terrestrial planets grew.
Accretion Disc: An accretion disc is a disc-shaped rotating mass formed by gravitational attraction.
Accuracy: Accuracy is the correctness of a single measurement.
Achromatic Lens: Lens for which all light colours have the same focal length.
Acoustic Agglomeration: High intensity sound waves are used in a fluid to group suspended particles into larger aggregates.
Acoustic Ducts: Ducts with an acoustic treatment or shaped to reduce or control acoustic wave propagation.
Acoustic Emission: A measure of integrity of a material determined by sound emission when a material is stressed.
Acoustic Excitation: The process of inducing vibration in a structure by exposure to sound waves.
Acoustic Filter Elements: There are a number of different types of acoustic filter elements that are used in many different applications.
Acoustic Impedance: The total reaction of a medium to the transmission of sound through it.
Acoustic Ohm: The unit of acoustic impedance.
Acoustic Streaming: Unidirectional flow currents in a fluid that are due to the presence of sound waves.
Acoustics: From the Greek akouein ( "to hear") a term sometimes used for the science of sound in general.
Acre: A British unit of area, traditionally used in agriculture.
Actinic: Pertaining to electromagnetic radiation capable of initiating photochemical reactions.
Actinic Ray: A ray of light of short wavelengths, as ultraviolet or violet, that produces photochemical effects.
Actinometer: An actinometer is an instrument for measuring heat radiation.
Actinometry: The science of measurement of radiant energy.
Active Sun: The Sun during its 11-year cycle of activity when spots, flares, prominences, and variations in radio frequency radiation are at a maximum.
Activity: The rate at which a collection of radioactive nuclei decay.
Additive Colour System: An additive colour system is a colour reproduction system in which an image is displayed by mixing appropriate amounts of red, green and blue light, as for example in a cathode-ray tube.
Additive Primaries: Red, green, and blue are the primary colours of light from which all other colours can be made.
Adhesive Force: The attractive force exerted on a liquid molecule by the molecules in the surface of the solid.
Adiabatic Process: A process in which the system does not exchange heat with the surroundings.
Advection: The transfer of matter such as water vapour or heat through the atmosphere as a result of horizontal movement of an air mass.
Aeolipile: A round vessel caused to rotate by the force of tangentially escaping steam: an early example of jet propulsion.
Aeolotropy: Aeolotropy is the antithesis of isotropy.
Aeon: In astronomical terms, 1,000 million years.
Aerodynamic Diameter: The diameter of a sphere with unit density that has aerodynamic behavior identical to that of the particle in question; an expression of aerodynamic behavior of an irregularly shaped particle in terms of the diameter of an idealized particle. Particles having the same aerodynamic diameter may have different dimensions and shapes.
Aerofoil: An aerofoil is shaped so that air flows faster over the top than under the bottom. There is, therefore, a greater pressure below the aerofoil than above it. This difference in pressure produces the lift.
Aerolite: A stony meteorite, composed primarily of silicates.
Aerosol: A colloid in which solid particles or liquid droplets are suspended in a gas.
Aerothermodynamic: A branch of thermodynamics relating to the heating effects associated with the dynamics of a gas.
Aether: An invisible medium that was thought to suffuse all space.
After Image: An image seen after the eye′s retina has been exposed for a time to an intense or stationary light source.
Agravic: Or pertaining to a condition of no gravitation.
Ah: Abbreviation of ampere-hour.
Air Spring: A simple mass on an air spring.
Airflow: A flow or stream of air.
Airflow Resistance: The quotient of the air pressure difference across a specimen divided by the volume velocity of airflow through the specimen. The pressure difference and the volume velocity may be either steady or alternating.
Airfoil: A structure designed to obtain a useful reaction on itself in its motion through the air.
Airy Disc: A pattern of illumination caused by diffraction at the edge of a circular aperture.
Albedo: The ratio of the amount of radiation reflected from an object's surface compared to the amount that strikes it.
Albedometer: An instrument used for the measurement of the reflecting power, the albedo, of a surface.
Alfven Waves: Waves moving perpendicularly through a magnetic field.
Aliasing: The erroneous interpretation of high-frequency signals as lower-frequency signals.
Alidade: That part of an optical measuring instrument comprising the optical system, indicator, vernier, etc.
Allobar: A form of an element that has isotopic abundances that are different from the naturally occuring form.
Allomer: Substances with different chemical composition but the same crystalline form.
Allotropy: The reversible phenomenon by which certain metals may exist in more than one crystal structure.
Alloy: A metal produced by mixing other metals.
Alpha: The first letter of the Greek alphabet.
Alpha Particle: The nucleus of helium consisting of two protons and two neutrons.
Alternating Current: An electric current whose direction changes direction with a frequency independent of circuit components.
Altitude: Height in space of an object or point relative to sea level or ground level.
Alvarez, Luis Walter: American physicist who produced free protons with a particle accelerator.
Ambient Environment: The conditions characterizing the air or other medium that surrounds materiel.
Ambient Temperature: The average temperature of the surroundings.
Ammeter: Instrument for measuring the current in amps, milliamps or microamps.
Amor Asteroids: Have orbits that cross the orbit of Mars and approach Earth′s orbit.
Amorphography: The branch of science concerned with the determination of amorphous solid structures and their systemmatic classification.
Amorphous: Non-crystalline, without long-range order.
amp: The informal name for Ampere.
Ampere: The SI unit of Electric current.
Ampere-Hour: An alternative unit of electrical charge.
Amplitude: The maximum distance from the equilibrium position that occurs in periodic motion.
AMU: Defined as one twelfth of the mass of the most abundant isotope of carbon (¹²C)
Analogue: Any representation of a physical quantity in terms of a continuous variation of a second physical quantity.
Analyser: An Analyser is another name for a secondary polariser in an optical system.
Anelasticity: The property of a solid in which deformation depends on the time rate of change of stress as well as on the stress itself.
Anemometer: A sensor that measures wind speed.
Aneroid Barometer: An instrument used to measure atmospheric pressure consisting of an evacuated container with a flexible wall.
Angle of Incidence: Angle between direction of motion of waves and a line perpendicular to the surface the waves are striking.
Angle of Reflection: Angle between direction of motion of waves and a line perpendicular to surface the waves are reflected from.
Angstrom: It is an old unit used for measuring the wavelength of electromagnetic radiation including visible light and X-rays.
Angular Frequency: The frequency of a steady recurring phenomenum in radians per second.
Angular Momentum: A vector quantity giving the rotational momentum.
Angular Velocity: The rate of change of angle turned in radians.
Anisotropic: Unequal physical properties along different axes.
Annihilation: A process in which a particle meets its corresponding antiparticle and both disappear.
Annual Aberration: The component of stellar aberration resulting from the motion of the Earth about the Sun.
Anode: The electrode where electrons are lost (oxidized) in redox reactions.
Anomalous Dispersion: A sudden change in the refractive index of a material for wavelengths in the vicinity of absorption bands in the spectrum of the material.
Antenna: A length of wire or similar that radiates (such as a transmitting antenna) or absorbs (such as a radio antenna) radio waves.
Anthropic Principle: Principles describing what conditions are necessary for the development of intelligent life.
Anti-Aliasing Filter: A device that attenuates signal content outside the desired bandwidth.
Antibaryon: The antiparticle of a baryon.
Antielectron: The anti particle of an electron.
Antimatter: Material made from antifermions. We define the fermions that are common in our universe as matter and their antiparticles as antimatter.
Antiparticle: A subatomic particle with the same-size properties as those of the particle although some may have the opposite sign.
Antiquark: The antiparticle of a quark.
Antistatic: Of or pertaining to the ability to either prevent the accumulation of or to enable the dissipation of static charge.
Anyon: An elementary particle or particle-like excitation having properties intermediate between those of bosons and fermions.
Aphelion: The point in a planet's orbit furthest from the Sun.
Apocentre: The point on a spacecraft′s orbit at which it is furthest away from the body it is orbiting.
Apollo Asteroids: Have orbits that cross the Earth′s orbit.
Apostilb: A unit of surface luminance used when defining diffusing surfaces equal to 1 lumenm^-2
Apparent Horizon: Where the shy appears to meet the Earth.
Arago Spot: A bright spot that appears in the shadow of a uniform disc being backlit by monochromatic light emanating from a point source.
Archimedes: Forever to be known for the Archimedean principle: "a body plunged in a fluid loses as much weight as …"
Archimedes′ Principle: The buoyant force is equal to the weight of the displaced fluid.
Are: A derived SI Unit of area. 1 Are = 100m²
Area: The derived SI unit of area is the m².
Aristotle: A Greek philosopher who stressed the importance of direct observations in securing facts and data.
Arjuna Asteroids: Asteroids that orbit the Sun in a near circular path and are no more than 100m in diameter.
Astable: A circuit that has no stable state and thus oscillates at a frequency dependent on component values.
Asterism: A group of stars which are traditionally imagined to represent a pattern.
Asteroids: These are rocky bodies, the vast majority of which orbit the Sun between Mars and Jupiter.
Astigmatism: An aberration, or defect, in a mirror or lens that causes the image of a point to spread out into a line.
Astrolabe: An instrument that was used to determine the altitude of objects in the sky.
Astronomical Unit: Defined as the mean distance of the Earth from the Sun.
Astronomy: The generic name for the study of the universe around us.
Astrophysics: The physics of astronomical objects such as stars and galaxies.
Aten Asteroids: Have orbits that lie inside the Earth′s orbit.
atm: An abbreviation of atmosphere.
Atmometer: An instrument for measuring the rate at which water evaporates, also called an evaporimeter.
Atmometry: The science of measuring the rate at which water evaporates.
Atmosphere: The gases around a planet or star.
Atmospheric Pressure: Atmospheric pressure is the force exerted by the weight of the atmosphere of the Earth at ground level.
Atom: The smallest particle of an element that can exist and still retain the ordinary chemical properties of that element.
Atom Percent: Concentration specification on the basis of the number of moles or atoms of a particular element relative to the total number of moles or atoms of all elements within an alloy.
Atomic Mass Unit: Defined as one twelfth of the mass of the most abundant isotope of carbon (¹²C)
Atomic Number: The atomic number (Z) of an element is the number of protons each atom of that element has in its nucleus.
Atomic Orbital: A wavefunction that describes the behavior of an electron in an atom.
Atomic Packing Factor: The fraction of the volume of a unit cell that is occupied by ′hard sphere′ atoms or ions.
Atomic weight: The weighted average mass of the atoms in a naturally occurring element.
Attenuation: The reduction of a physical quantity.
Attenuation of Sound in Air: The attenuation of sound in air at 20°C due to viscous, thermal and rotational loss mechanisms is 1.6E-10f²dB/m.
Atto: Prefix representing a multiplication of 10^-18
Atwood′s Machine: A weight-and-pulley system devised to measure the acceleration due to gravity at the Earth′s surface
AU: Defined as the mean distance of the Earth from the Sun.
Aufbau Principle: An approximate procedure for writing the ground state electronic configuration of atoms.
Aurora: A faint visual phenomenon associated with geomagnetic activity, which occurs mainly in the high-latitude night sky.
Aurora Borealis: Latin for Northern Dawn, an old name for the Aurora.
Auroral Kilometric Radiation: Intense radio waves whose wavelength is of the order of a kilometre, emitted from regions above the ionosphere where the aurora is accelerated.
Avalanche: A cumulative ionization process.
Average Speed: The distance traveled divided by the time taken.
Averaging: In any process it is often necessary to average a number of measurements to gain any confidence in the measured value.
Avogadro′s Law: Equal volumes of an ideal gas contain equal numbers of molecules, if both volumes are at the same temperature and pressure.
Avogadros Number: N = 6.022045x10²³ mol^-1
Axial Load: A load applied along or parallel to and concentric with the primary axis.
Axis: The line, real or imaginary, passing through the centre of an object about which it could rotate; a point of reference.
Back Electromotive Force: The emf that opposes the normal flow of current in a circuit.
Backscattering: Primary radiation deflected or secondary radiation emitted in the general direction of the incident radiation beam.
Balmer Series: A series of lines in the emission spectrum of hydrogen that involve transitions to the n=2 state from states with n>2.
Band Gap Energy: For semiconductors and insulators, the energies that lie between the valence and conduction bands.
Bandgap: The range of energies between existing energy bands where no energy levels exist.
Bandwidth: The bandwidth of a filter is the separation between the lower and upper frequencies at which the amplitude of a sinusoidal signal is attenuated by a factor of 2.
bar: A derived unit of pressure used in meteorology. 1 bar = 1x10⁵ Pa.
Barn: A unit of nuclear cross section, 1 Barn = 10^-28m².
Barometer: A device for measuring atmospheric pressure.
Barometric Pressure: The total pressure exerted by the atmosphere.
Baromil: The unit of length used in graduating a mercury barometer in the centimetre-gram-second system.
Bartels Rotation Number: The serial number assigned to 27-day recurrence periods of solar and geophysical parameters.
Barycentre: This is the centre of gravity of 2 or more masses.
Barye: The CGS unit of pressure, equal to 1 dyne per square centimetre.
Baryon: A particle with spin 1/2 (or 3/2) which consists of three elementary particles known as quarks.
Base Terminal: That electrode of a transistor which compares generally to the grid of a vacuum tube.
Base Unit: Base units are units that are fundamental building blocks in a system of measurement.
Battery: A group of voltaic cells connected in series.
bcc: Abbreviation of body centred cubic. About 15% of all the elements crystallize into this structure.
Beam Steering: The method of steering the main lobe of a transducer to a certain direction.
Beam Width: The width of the main beam lobe, in degrees, of the transducer. It is usually defined as the width between the "half power point" or "-3dB" point.
Beats: Periodic fluctuations that are heard when sounds of slightly different frequencies are superimposed.
Becquerel: The Becquerel is a unit used to measure a radioactivity. One Becquerel is that quantity of a radioactive material that will have 1 transformations in one second.
Bells′ Inequality: A quantum mechanical theorem which demonstrates that quantum mechanics must have nonlocal properties.
Bernoulli′s Principle: The pressure in a fluid decreases as its velocity increases.
Beta Particle: An electron emitted by a radioactive nucleus.
Bhabda Scattering: Scattering of positrons by electrons.
Big Bang Theory: A theory that suggests that the universe started with a giant explosion.
Bimetallic Strip: Two metals with different thermal expansion coefficients are bonded together and wound into a spiral.
Binding Energy: The amount of energy required to take a nucleus apart.
Biot-Savart Law: A law describing the magnetic flux density at a distance r away from an electrical conductor.
Black Box: A unit whose output is a specified function of the input, but for which the method of converting input to output is not necessarily specified.
Black Hole: A massive star that has collapsed to such a small size that its gravitational force is so strong that not even light can escape from its 'surface'.
Blackbody: A hypothetical body that absorbs without reflection all of the electromagnetic radiation incident on its surface.
Blackbody Radiation: The electromagnetic radiation emitted by an ideal black body.
Blackett, Patrick Maynard Stuart: English chemist who developed the cloud chamber.
Blackman Window: A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
Blanking Distance: Minimum sensing range in an ultrasonic proximity sensor.
Blue Shift: The apparant (Doppler) shift of the wavelength towards the higher frequency region of radiation emitted by an approaching object.
Blue Supergiant: A supergiant star with spectral type O or B.
Body Centred Cubic: About 15% of elements crystallize with a body centred cubic structure.
Bohman Window: A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
Bohr Magneton: b = 9.27x10^-24 Am²
Bohr, Niels: While at Copenhagen University, Bohr, in 1922, won the Nobel Prize in Physics "for his services in the investigation of the structure of atoms and of the radiation emanating from them."
Bohr Radius: a₀ = 5.291772x10^-11 m
Boiling Point: The temperature at which the vapour pressure of a liquid is equal to the external pressure on the liquid.
Boiling Point Elevation: The boiling point of a solution is higher than the boiling point of the pure solvent.
Bolide: A brilliant meteor, especially one which explodes, a detonating fireball.
Bolometer: A device for measuring minute amounts of radiant energy.
Boltzmann′s Constant: Constant named after Stefan Boltzmann. Used in the determination of energy radiation from bodies.
Bond Order: In Lewis structures, the number of electron pairs shared by two atoms.
Bonding Energy: The energy required to separate two atoms that are chemically bonded to each other.
Born, Max: Won the Nobel Prize in Physics for his fundamental research in quantum mechanics.
Bose-Einstein Statistics: Quantum statistics for particles not obeying the exclusion principle.
Bosons: Particles which do not obey the Pauli exclusion principle, for example, photons.
Bottom: The flavor of the fifth quark.
Bottoming: A transistor in the fully conducting state.
Boundary Layer: The portion of a fluid flowing past a body that is in the immediate vicinity of the body.
Bow Shock: The shock wave caused by the edge our Solar System travelling through deep space.
Boyle, Robert: Known for that scientific law named after him.
Boyles Gas Law: For a fixed mass of gas at constant temperature the product of pressure and volume is constant.
bp: Abbreviation of boiling point, the temperature at which the vapour pressure of a liquid is equal to the external pressure on the liquid.
Brackett Series: The series which describes the emission spectrum of hydrogen when the electron is jumping to the fourth orbital.
Bragg′s Law: A relationship that stipulates the condition for diffraction by a set of crystallographic planes.
Breaking Stress: Also known as the ultimate tensile strength. This is the maximum stress that can be applied to a material.
Bremsstrahlung: X-rays emitted when a charged particle (such as an electron) is decelerated by passing through matter.
Bremsstrahlung Effect: The emission of electromagnetic radiation as a consequence of the acceleration of charged elementary particles.
Brewsters Law: Unpolarised light can be polarised by reflection. When unpolarised light is reflected from the surface of an optical material (glass, say) then preferential reflection occurs for the electric-field vector that is perpendicular to plane of incidence.
British Thermal Unit: The amount of heat required to raise the temperature of 1 pound of water by 1° Fahrenheit.
Brittleness: The tendency of a material to fracture without first undergoing significant plastic deformation.
Broglie, Louis-Victor de: He demonstrated mathematically that electrons and other subatomic particles exhibit wavelike properties.
Brown Dwarf: These straddle the domain between stars and giant planets.
Brown, Robert: Discovered the brownian movement of minute particles.
Brownian Motion: Small particles suspended in liquid move spontaneously in a random fashion.
Btu h^-1: An abbreviation of British thermal units per hour, the unit of heat flow rate in the British system of units.
Bubble Chamber: A chamber filled with liquid at low pressure chosen so that small bubbles form along the path of any charged particle.
Bulk Modulus: The bulk modulus of a gas is a measure of its compressibility (elastic property).
Buoyant Force: The upward force exerted by a fluid on a submerged or floating object.
Burgess Vector: A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
Bushel: A dry or liquid measure equal to eight gallons.
C: An abbreviation of coulomb, the quantity of charge which passes any section of a conductor in one second when a current of one ampere is flowing.
c: Prefix representing a multiplication of 10^-2
Cable Length: Originally the length of a ship′s anchor cable, 120 fathoms.
cal: An abbreviation of calorie, a unit of energy in the British system of units.
Calendar Year: 1 calendar year = 31.536x10⁶ seconds
Caloric: A postulated elastic fluid associated with heat.
Calorie: A unit of energy in the British system of units. Still used to define the amount of energy amount of energy contained in foods.
Calorimeter: An insulated vessel for measuring the amount of heat absorbed or released by a chemical or physical change.
Calorimetry: The science of measuring heat flow.
Calutron: A device that separates isotopes by ionizing the sample.
Camera Obscura: A room with a small hole in one wall used by artists to produce images.
Candela: The SI unit of luminous intensity.
Capacitance: The capacitance is defined as the total electric charge on a body divided by its potential.
Capacitor: An electrical component that passes alternating currents but blocks direct currents.
Capillary Action: A phenomenon whereby the narrower the tube the higher the liquid will climb above it's normal bulk level in the container.
Carat Gold: Measure of parts of gold per 24 parts of an alloy and equal to 41.667 milligrams of gold per gram of alloy.
Carat Precious Stones: A standard measure of weight for precious stones.
Carbon-Nitrogen-Oxygen Cycle: In stars more massive than the sun this cycle is the primary process which converts hydrogen into helium.
Carnot's theorems: No engine can be more efficient than a reversible engine working between the same limits of temperature. All reversible engines working between the same two limits of temperature have the same efficiency.
Carrier Particle: A fundamental boson associated with quantum excitations of the force field corresponding to some interaction.
Carrington Longitude: A system of fixed longitudes rotating with the sun.
Casimir Effect: A quantum mechanical effect, where two very large plates placed close to each other will experience an attractive force, in the absence of other forces.
Cassegrain Telescope: Two-mirror reflecting telescope.
Cathode: Electrode where electrons are gained (reduction) in redox reactions.
Cathode Ray: An electron emitted from the negative electrode in an evacuated tube.
Cathode Ray Tube: An evacuated tube containing an anode and a cathode that generates cathode rays when operated at a high voltage.
Causality Principle: The principle that cause must always preceed effect. More formally, if an event A ("the cause") somehow influences an event B ("the effect") which occurs later in time, then event B cannot in turn have an influence on event A.
Cavendish, Henry: English physicist and chemist, discovered hydrogen.
Cavitation: A condition which can occur in liquid handling machinery where a system pressure decrease in the suction line and pump inlet lowers fluid pressure and vaporization occurs.
cd: An abbreviation of candela, the SI unit of luminous intensity.
Celsius Temperature Scale: The centigrade scale of temperature was defined as 0°C at the ice point of water and as 100°C at the boiling point of water (at 1 standard atmosphere).
centi: Prefix representing a multiplication of 10^-2
Centigrade: The centigrade scale of temperature was defined as 0°C at the ice point of water and as 100°C at the boiling point of water (at 1 standard atmosphere).
Centigrade Heat Unit: The amount of heat necessary to raise one pound weight of water through 1° C.
Centimetre: The centimetre is a unit of length and is one hundredth of a metre by definition.
Centimetre Gramme Second: A system of units in which the fundamental units are centimetre, gramme and second.
centipoise: One hundredth of a poise, the CGS derived unit of dynamic viscosity of a fluid.
Centre: A point or axis around which anything revolves or rotates.
Centre European pour Rechearche Nucleaire: The major European International Accelerator Laboratory located near Geneva, Switzerland.
Centre Frequency: Frequency to which an amplifier is tuned. The frequency half way between the cut-off frequencies of a tuned circuit.
Centre of Mass: The balance point of an object. The location in an object that has the same translational motion as the object if it were shrunk to a point.
Centre of Pressure: The point at which the aerodynamic forces on a body appear to act, and at which there is no aerodynamic movement.
Centrifugal Force: A fictitious force arising in a rotating reference system.
Centripetal: An adjective meaning 'centre-fleeing.'
Cepheid Variable: A type of variable star which exhibits a regular pattern of changing brightness as a function of time.
Cerenkov Radiation: A charged particle emits Cerenkov radiation in a cone around its direction of travel when it travels through any medium faster than the speed of light through that medium.
CERN: The major European International Accelerator Laboratory located near Geneva, Switzerland.
CGS Units: Abbreviation for centimetre-gramme-second.
Chadwick, James: English physicist who discovered the neutron.
Chain: The chain is a unit of length.
Chain Reaction: A process in which the fissioning of one nucleus initiates the fissioning of others.
Chandrasekhar Limit: A limit which mandates that no white dwarf can be more massive than about 1.4 solar masses.
Change of State: The change in a substance between solid and liquid or between liquid and gas.
Characteristic X-ray: An X-ray having a unique energy that is emitted by an atom during its de-energization after ionization of one of its electrons.
Charge: The excess or deficiency of electrons resulting in the body having negative or positive charge.
Charged: Possessing a net negative or positive charge.
Charged Particles: Particles with positive or negative charge, for example electrons, protons or ions.
Charles Gas Law: For a fixed mass of gas at constant pressure the volume is directly proportional to the temperature.
Charm: The flavor of the fourth quark.
Charon: Pluto′s double.
Chemical Energy: Energy stored in the bonds of atoms and molecules eg coal, petrol, biomass.
chi: A letter of the Greek alphabet.
Chirality: Handedness, the quality of having non-superimposable mirror images.
Chromatic Aberration: A defect in lenses that causes different colors (wavelengths) of light to have different focal lengths.
Chromophore: A group or substructure on a molecule that is responsible for the absorption of light.
Chromosphere: The layer of the solar atmosphere above the photosphere and beneath the transition region and the corona.
Chronology Protection Conjecture: The concept that the formation of any closed timelike curve will automatically be destroyed by quantum fluctuations as soon as it is formed.
Chu: Abbreviation of centigrade heat unit.
Ci: Abbreviation of curie, a unit of radioactivity.
Circuit: Interconnection of components to provide an electrical path between two or more components.
Clark Cell: A voltaic cell that is used as a reference emf.
Clausius statement: No process is possible whose sole result is the transfer of heat from a colder to a hotter body.
Clerk-Maxwell, James: Clerk-Maxwell′s greatest work was his initial contribution to electromagnetic radiation.
Closed System: A system which can exchange only energy with its surroundings.
cm: The centimetre is a unit of length and is one hundredth of a metre by definition.
CNO Cycle: Abbreviation for Carbon-Oxygen-Nitrogen Cycle. In stars more massive than the sun this cycle is the primary process which converts hydrogen into helium.
Coanda Effect: The effect that indicates that a fluid tends to flow along a surface, rather than flow through free space.
Coefficient: A coefficient is a constant multiplicative factor of a certain object.
Coefficient of Performance: The ratio of cooling or heating to energy consumption.
Coercive Force: Magnetizing force needed to reduce residual magnetism in a material to zero.
Cohesive Force: The attractive force exerted on a liquid molecule by the neighbouring liquid molecules.
Cold Junction: The reference junction of a thermocouple which is kept at a constant temperature.
Collector: One terminal of a transistor.
Collider: An accelerator in which two beams traveling in opposite directions are steered together