#The Value of "g". This is a good [http://www.physicsclassroom.com/Class/circles/U6L3e.cfm resource] to study the variation of “g” at various distances above the Earth's atmosphere.
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#This [http://science.nasa.gov/science-news/science-at-nasa/2004/06may_lunarranging/ article] examines the Galileo experiment and discusses if there are other possible explanations.