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Moment of truth
The Voyager I spacecraft is the most distant man-made object in the universe. It was launched in 1977 and as in 2002, it was more than 8 billions miles from the Earth.

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Goldschmidt process Min Ext., Chem
A method of extracting metals by reducing the oxide with aluminium powder. It was first developed by the German chemist Hans Goldschmidt (1861-1923) in 1898. By making use of aluminium being high in the electrochemical series, the process is used to extract metals from their oxides which are not easily reduced by carbon (coke). For example, chromium, manganese, molybdenum, uranium, zirconium, etc. can be obtained using this process. The reaction is highly exorthermic and the reaction mixture is often in fused molten state, in a temperature that can be much higher than the melting point of the extracting metal.

A more specific reaction, involving the Goldschmidt process is the Thermit (tradename) process which is a reaction between powdered aluminium and iron oxide, often achieve a temperature up to 2500C. This produces molten iron for joining or welding iron, railway lines and steel rails, pipes etc. The molten iron is poured into the joint to be welded, both for fusion and as a filler metal.

googol Math.
A name for the number 10100, or can be written in expanded form as 1 followed by 100 zeros. The name was derived by an American mathematician Edward Kasner's 8-year-old nephew, Milton Sirotta, who gave an answer 'googol', when asked what he would name for a really large number. The mathematician also coined the term googolplex which is equal to 10googol or 1 followed by a googol of zeros.

googolplex Math.
See googol.

Graham's law Chem.
A gas law which states that the rate of diffusion of a gas is inversely proportional to the square root of its relaive molecular mass. This was confirmed experimentally and named after Graham in 1829. Mathematically, this is expressed as

Graham's law

where Mr is the molecular mass of gass; R is the gas constant, T = temperature and c is the velocity of gas molecules, which relates to the rate of diffusion. Given that PV = nRT and Mr = Nm/n, where V = volume of gas, N = the number of molecules, m = mass of a molecule and n = number of mole of gas, the above equation can be written as

Graham's law

where the density, d = Nm/V. For this reason, the law is also sometimes defined as the rate of diffusion of a gas is inversely proportional to the square root of its density.

gravitational wave Phys., Astron
A ripple in the curvature of the space-time continuum due to mass acceleration. The wave was first theorized by Albert Einstein but never conclusively detect, yet. It is thought that a system will generate a gravitational wave flux if the mass changes shape as well as accelerates. This is because conservation of momentum stipulates that if a rigid mass accelerates will have another mass recoil whereby the gravitational waves from both masses cancel out each other.

Because of extremely weak nature of gravitational force, the waves are thought to be detectable in massive systems such as binary-star systems, pulsars or asymmetric collapse of a massive star to form a black hole. Gravitational waves emitted by these systems will travel across the universe at the speed of light and continually squeezing and expanding the space-time along their path. However, this ripple effect can be extremely small. The change in space-time is thought to be in the order of 1 part in 1022.

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