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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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phagocytosis Biochem.
Meaning cellular eating. See endocytosis.

phase diagram Chem.
A graph showing the relationship between solid, liquid and gaseous states over a range of condition such as temperature and pressure.

phase space Phys.
The state of a classical system that contains all the information about the system at an instant. In a three-dimensional space, the system occupies one point in phase space at an instant and contains all the positions and momenta of the particles. This phase space point can be mathematically presented as

  X = (q, p)   q = (x1, y1, z1, ...)   p = (px1, py1, pz1, ...)

where q contains all the coordinates of particles in the system, and p contains all the corresponding momenta components. Hence, each particle is associated with 3 position coordinates and 3 momentum coordinates and the system is said to occupy 6N-dimensional phase space, where N is the number of particles in the system.

phenolphthalein Chem.
An organic compound of general formula C20H14O4, use in the laboratory as an acid-base indicator, involving in titrations of a weak acid and a strong base. Its full scientific name is 3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranore. It is colorless below pH 8 but turn to redish pink above it. It is more soluble in alcohol and in water and hence the indicator is usually dissolved in alcohol where only a few drops are required in a titration. It is also used in pigment and also as a laxative. However, its use in laxatives has been restricted due to its possible carcinogenic effect.

phenotype Biol.
The outward physical or observable characteristics of an organism as results from interaction of the genotype with the environment.

Phillips process Chem.
An industrial process introduced by Phillips Petroleum Corporation in 1961 for making high-density polyethylene by using a catalyst as an active site for the polymerization of ethylene. The process is carried out at a temperature of 150C and 30 atmospheric pressures, using chromium oxide (supported on silica) as a catalyst.

philosopher's wool Chem.
Common name for zinc oxide, due to formation of white fluffy appearance when zinc is burnt in air to give zinc oxide.

phishing Comp.
The practice of sending out e-mail messages with an intent to trick people into handing over confidential details such as bank account numbers and pin codes. The email often employ means to deceive people as if it is originated from a legitimate financial institution but when click on a link can often direct to another web site that looks like that of the bank or financial institution.

phosphor bronze Eng.
A bronze alloy containing 4% to 13% tin and up to 1% of phosphorus. It is used in harsh conditions that exposes to heavy wear, as in gear wheels, bearings for aero engines and pressure vessels for chemical plants.

photoautotroph Biol., Bot.
A subdivision of autotroph, it is a living organism that obtain its energy directly from sunlight. Green plants are phototrophs.

photochromism Phys.
Property of a color change in certain materials when exposed to light or ultraviolet, which reverting to its original color (or colorless) when the light source is removed. For instance, such materials are used in sunglasses which darken in bright sunlight.

photon Phys.
A virtual particle carrier (gauge boson) of electromagnetic radiation (light) with a quantized energy of E=hn where h is the Planck's constant and n is the frequency of the radiation. It has zero rest mass and no charge but carries a momentum hn/c where c is the velocity of light.Quantum electrodynamics is the study of theoretical descriptions of photons.

photonics Elec.
Concept or technology for computing, data transmission and energy generation using photons (lights and other forms of radiation) instead of electrons. A good example is the fiber optics used in high-speed data transmission.

photosphere Astron.
The surface of the Sun that appears luminous yellow and corresponds to a temperature of about 5500C. It defines the upper surface of a convecting layer of gases originated deep within the Sun.

phylum Zoo.
A group of related forms constituting one of the major subdivisions of the animal kingdom, or a division in plants. The phylum Chordata (vertebrates) and the phylum Mollusca (invertebrates) are two examples of major subdivisions of the animal kingdom.

phylogeography Geo.
Study concerned with the processes and principles governing the geographic distribution of genealogical lineages. This usually involves analysis and research into mitochondrial DNA in order to study both macro- and micro-evolution. In Greek, phylo- means race

phytosanitary Bot.
Pertaining to regulartory health for plants or parts of plants for export. For example, phytosanitory inspection and certification.

pinocytosis Biochem.
Meaning cellular drinking. See endocytosis.

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