Kepler's laws of planetary motion
[ kĕp′lərz ]
Three laws devised by Johannes Kepler to define the mechanics of planetary motion. The first law states that planets move in an elliptical orbit, with the Sun being one focus of the ellipse. This law identifies that the distance between the Sun and Earth is constantly changing as the Earth goes around its orbit. The second law states that the radius of the vector joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse. As such, the planet moves quickest when the vector radius is shortest (closest to the Sun), and moves more slowly when the radius vector is long (furthest from the Sun). The third law states that the ratio of the squares of the orbital period for two planets is equal to the ratio of the cubes of their mean orbit radius. This indicates that the length of time for a planet to orbit the Sun increases rapidly with the increase of the radius of the planet's orbit.
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New law bans use of confusing words and sentences in government documents. Read the resultsOn October 13, 2010, President Obama signed into law the “United States Plain Writing Act of 2010.” Thirteen years after President Clinton issued his own “Plain Writing in Government” memorandum, the revised set of guidelines states that by July of this year all government agencies must simplify the often perplexing bureaucratic jargon used in documents produced for the American public. Gone are the grammatically longwinded sentences, …
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