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Moment of truth
The fastest man-made object that ever leave the Earth is the Pinoeer 10 spacecraft, launched in 1972, and attained a speed of more than 32000 mph.

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cgs system Metro.
A small-unit metric system of measurement which is based on three fundamental units: the centimeter (cm) for length, gram (g) for mass and second (s) for time. This is in contrast to the larger, standard metric system (SI) with meter (m) for length, kilogram (kg) for mass and second (s) for time. It was introduced by scientists in order to avoid confusion of unit conversions in the English units. Although the SI are the standard units, the cgs system is still used by some scientists such as astronomers or physicists that describe extreme scale phenomena. For instance, the unit debye, to quantify the molecular dipole moments.

chalk Min.
A white, amorphous mineral of calcium carbonate (CaCO3), similar in composition to limestone, but softer. Derived from the skeletal remains of microscopic sea creatures, such as plankton and foraminiferans. It is used in toothpaste and cosmetics. In building industry, it is used in cement, plaster and building stones. It can also be used as a blackboard chalk, although a more common substance of the latter is made of calcium sulfate.

Chandrasekhar limit Astron.
The upper limit, 1.44 solar masses (the mass of the Sun), for a white dwarf, as predicted by the electron-degeneracy theory. A mass that is greater than this limit will result in collapse of electrons into atomic nuclei, turning protons into neutrons.

chaperone Biochem.
A protein that protects other new or distorted proteins from undesired interactions to ensure the proteins fold properly, thus preventing misfolding that may lead to aggregates. Under normal biological conditions, chaperone does not form a component of these assembled proteins.

Charles' law Chem.
An ideal gas law which states that the volume (V) of a fixed amount of gas at constant pressure (p) is directly proportional to its absolute temperature (T). This is expressed as

Charles law

It was formulated by J. Charles in 1787. Kinetically this means that increase in temperature increases the average kinetic energy of the gas molecules and hence would normally leads to increase in pressure. But for a container with changeable volume, the original pressure will be maintained.

cheddite Chem.
A group of high explosive materials based on sodium or potassium chlorate or perchlorate. The names was derived from the town of Chedde, Savoy in France in early twentieth century. The explosive materials consist of a large proportion of chlorates mix with nitro compounds such as nitrobenzene, which improves flame propagation. Quite often, a little paraffin or castor oil is added as a moderant or desensitizer. Cheddite explosives are usually used in quarrying in mining. Since 1970s, cheddite has also become a commercial name for a compound used as an explosive charge (primer) in firearms' cartridges. It contains 90% chlorate, 7% paraffin, 3% petroleum jelly and traces of carbon black.

chemoautotroph Biol.
A subdivision of autotroph, it is a living organism that is capable to synthesize the necessary biological compounds and derive its energy directly from raw inorganic materials without the sunlight. This involves respiratory oxidation of inorganic materials such as ammonia, hydrogen sulfide and iron-containing compounds. For example, Beggiatoa, an Archaea that exists in deep sea hydrothermal vents, uses hydrogen sulfide as their energy source.

chondrite Space
A stoney meteorite that can be identified by the presence of chondrules. Chondrites are rich in silicates such as olivine, plagioclase and pyroxene. They are believed to be very old, probably as old as the age of the Solar System. Chondrites belong to the main meteorite group, the aerolites.

chondrules Space, Min.
Small nuggets or grains of rocky material that embeds in meteorites, usually in certain aerolites. They are rich in olivine and pyroxenes. Chondrules are believed to have formed in times during the birth of the Solar System about 5 billion years ago. Meteorites that contain chondrules are called chondrites.

chromophore Chem.
A molecular group that causes visual coloration in a compound such as dye. It generally consists of atoms having delocalised electrons, such as those p electrons on double bond conjugations. Examples of chromophores are azo (-N=N-), nitroso (-NO) and quinoid carbonyl (C=O).

chromosphere Astron.
The atmosphere layer of the Sun, between the surface of the Sun, photosphere, and corona. It is bright red in color and is where the solar energy begins its way out into space.

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