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Index (C)
CA - CC
CD - CF
CG - CJ
CK - CN
COA - CON
COO - CR
CS - CV
CW - CZ
Moment of truth
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The Sun, with a diameter of 1,392,000 km, is made of 94% hydrogen atoms. |
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COO - CR
corona Astron.
The outermost atmosphere of a star, consists of very hot gas heated to temperatures millions of degrees.
The Sun's corona is clearly visible when the Moon completely covers the sun during total solar eclipse (left).The temperature of the surface of the sun is about 6000°C, whereas corona temperature can reach up to a million centigrade. There is still no satisfactory explanation
why the corona is so much hotter than the sun's surface.
cosmic ray Astron.
High-speed particles with an energy range of 109 GeV to more than 1020 GeV and originate from space. Most of these particles consist of protons (~80%) and alpha particle (~12%) while the remainder can be electrons, nuclei of oxygen, carbon, nitrogen and other
heavier elements. Most of these particles are thought to originate with the Milky Way but those of extremely high energy (above 1018 GeV) are believed to have created at even more distant sources. The rays was first discovered by Viktor Hess in 1912 and these particles often
interact with air molecules in the atmosphere to produced scattered paths and short-lived particles.
cosmic year Astron.
The time it takes the Sun to complete an orbit around the center of the Milky Way (galatic rotation). This is approximately equal to 225 million years.
coulombic interaction Chem., Phys.
Energy interaction between two point charges, acting along the line connecting the two charges and defines as:
where r is the distance between two ions, q1 and q2 are the corresponding electric charges (in Coulombs) and e0 is the dielectric constant of a medium (electrical permitivity of space).
Two opposite charged species will give an attractive interaction (negative U), while similar charged species give repulsive interaction (positive U).
counterion Chem.
An ion that is of opposite charge to another ionic species. A counterion is often necessarily present in a system in order to maintain the overall charge neutrality of the system. For example, sodium cation is a counterion for the chloride anion (and vice versa)
in the sodium chloride solution.
covalent radius Chem.
Measure of the size of atom which forms part of a covalent bond. Usually the sum of two covalent radii should be the covalent bond length between two similar atoms. For instance, the covalent radius of hydrogen atom in the hydrogen gas (H2) is 37.07 pm (picometer) which is half of the H-H bond length.
However, the covalent radius of an atom is not the same depending on its chemical environment and its covalent bonding with the other atom. Covalent radii can usually be measured by X-ray diffraction.
CPT symmetry Phys.
Abbreviation for Charge, Parity and Time Reversal symmetry, the hypothesis of the Standard Model of particle physics which states that the laws of physics do not change if all the interacting particles are replaced by their
antiparticles of opposite charge (C), all the directions are reversed (P) and the time is reversed (T).
COO - CR
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