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In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a medium, but is characterized by an abrupt, nearly discontinuous, change in pressure , temperature , and ...
Shock waves are common in astrophysical environments. [1]Because of the low ambient density, most astronomical shocks are collisionless.This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system.
The defining criterion of a shock wave is that the bulk velocity of the plasma drops from "supersonic" to "subsonic", where the speed of sound c s is defined by = / where is the ratio of specific heats, is the pressure, and is the density of the plasma.
Also amphidrome and tidal node. A geographical location where there is little or no tide, i.e. where the tidal amplitude is zero or nearly zero because the height of sea level does not change appreciably over time (meaning there is no high tide or low tide), and around which a tidal crest circulates once per tidal period (approximately every 12 hours). Tidal amplitude increases, though not ...
Also actiniform. Describing a collection of low-lying, radially structured clouds with distinct shapes (resembling leaves or wheels in satellite imagery), and typically organized in extensive mesoscale fields over marine environments. They are closely related to and sometimes considered a variant of stratocumulus clouds. actinometer A scientific instrument used to measure the heating power of ...
A meteor or "shooting star" is the visible streak of light from a heated and glowing object falling through the Earth's atmosphere. A meteoroid is a small rocky or metallic body travelling through outer space.
Bolide from the French astronomy book Le Ciel; Notions 'Elémentaires d'Astronomie Physique (1877). The word bolide (/ ˈ b oʊ l aɪ d /; from Italian via Latin, from Ancient Greek βολίς (bolís) 'missile' [2] [3]) may refer to somewhat different phenomena depending on the context in which the word appears, and readers may need to make inferences to determine which meaning is intended in ...
Achondrite – a differentiated meteorite (meaning without chondrules). Aerolite – an old term for stony meteorites. ALH – an abbreviation used for meteorites from Allan Hills. Allan Hills 84001 – is an exotic meteorite from Mars that does not fit into any of the SNC groups and was thought to contain evidence for life on Mars.