Abiotic

Non-biological in origin, or not derived from living organisms.

Ablation

Gradual removal of the successive surface layers of a material through various processes.

  1. The gradual removal and loss of meteoritic material by heating and vaporization as the meteoroid experiences frictional melting during its passage through the atmosphere. The resulting plasma ablates the meteor and, in cases where a meteor achieves stable flight, the meteorite may develop regmaglypts, roll-over lipping, and other features associated with oriented flight. The particles released during ablation will ionize the surrounding atmospheric molecules, which later de-excite to produce the glowing trails commonly associated with this type of object.
  2. Terrestrial ablation processes include reduction of a glacier by surface melting/sublimation and rock weathering by hydraulic or aeolian (wind) erosion. Ventifacts are beautiful examples of rocks ablated by sand and wind creating aerodynamic shapes reminiscent of some oriented meteorites.

Abrasion

Type of erosion process in which rocks and/or rock fragments scrape and grind away each other’s surface. The fragments may be carried by rivers, wind, ice, or the ocean currents. Smooth river rocks are the result of abrasion. process of scraping or wearing something away

Absolute Magnitude

Magnitude an object would have if placed at a distance of exactly 10 parsecs (= 32.6 light years). A supergiant star might have an absolute magnitude of -8 whereas a dim red dwarf might have an absolute magnitude of +16. The Sun has an absolute magnitude of +4.8 – about half way between the two extremes. To convert the observed brightness of a star (the apparent magnitude, m, to an absolute magnitude, we need to know the distance in parsecs d, to the star. Alternatively, if we know the distance and the apparent magnitude of a star, we can calculate its absolute magnitude. Both calculations are made using:

The quantity m – M is known as the distance modulus.


Some or all content above used with permission from J. H. Wittke.


Absolute Zero

Lowest possible temperature, according to the kinetic theory of gases, attained when a system is at its minimum possible energy, equal to 0 K (-273.15° C and -459.67 F). Temperature is a reflection of molecular energy, thus there must be a point at which no further energy can be extracted from a system. Although it is possible to approach absolute zero, the “third law” of thermodynamics holds that it is impossible to attain absolute zero in a system.


Some or all content above used with permission from J. H. Wittke.