AberrationWith regards to physics, a discontinuity or distortion in an image produced by a lens.
Absorption SpectraThe spectra of electromagnetic radiation transmitted through a substance, with dark lines indicating the absorption of specific wavelengths.
Accelerating UniverseOne where distance increase faster with time, in contradiction to those where the gravitational attraction of ordinary matter slows down the expansion.
AccelerationThe right of the lender to demand payment on the outstanding balance of a loan.
Angular resolutionThe smallest angular size that the instrument can resolve.
Angular SizeThe size of an object as viewed from the earth. For example, the moon subtends (covers) an angle of 1/2 of a degree.
AnisotropyThe difference in the property of a system with changes in direction. In this case, anisotropy refers to the difference in the temperature of the cosmic…
Annihilated/annihilationA process in which a particle meets its corresponding antiparticle and both disappear.
AnomalySomething that is out of the ordinary. For example if in a set of 1000 two winged, two legged, one headed, (essentially normal) chickens, one of them had…
AntimatterMatter made up of elementary particles whose masses are identical to their normal-matter counterparts but whose other properties, such as electric charge…
Antiparticle/antiquark/antielectronFor most particle types there is another particle type that has exactly the same mass but the opposite value of all other charges.
Apparent luminositiesThe brightness of an object as it appears from the earth. The apparent luminosity does not take into account the distance from the earth to the object…
AtomsThe smallest unit of matter that possesses chemical properties. All atoms have the same basic structure: a nucleus containing positively charged protons…