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Meteoroids-Asteroids-Comets
Meteoroids-Asteroids-Comets

... • Not that we know of! • None of the asteroids or comets discovered so far is on a collision course with Earth. • However, we can't speak for those that are not yet discovered. In principle, one of those could hit any time, but statistically the chances are very small. ...
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Meteroroids! Asteroids! Comets!

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... using a conception of the habitable zone that extrapolates directly from that of our own Solar System. The habitable zone is a star-specific concept, however. Stars exist in a variety of sizes and masses. More massive stars tend to burn more brightly, but have shorter lifetimes. The most common type ...
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THE COSMIC CRASH

Answers
Answers

February 2012
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... along the sequence of the Zodiac. However, as the Earth moves around the Sun, our view of planets occasionally makes them appear to reverse their motion. Mars will have appeared to stop moving on January 24th, and a backing up motion will proceed until mid-April. Careful observers can use Regulus, t ...
Report - WordPress.com
Report - WordPress.com

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Chapter 2 - Cameron University

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... 12. The distance from the Sun to Neptune, the farthest known planet, is about (a) * 30 AU. (b) 30 light years. (c) 30 parsecs. (d) 30 kWh. 13. The Sun is (a) significantly larger than average stars. (b) significantly smaller than average stars. (c) * an average-sized star. (d) not a star. 14. The pl ...
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... 21. Kepler’s second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that A) a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun. B) a planet’s period does not depend on the eccentricity of its orbit ...
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... Therefore, the statement given makes sense, since we need heavier stars to make the chemical elements upon which our lives are based. In fact, only the most massive stars, greater than about 10 solar masses, will ever form the chemical elements of iron and those more massive than iron, up to and inc ...
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... Therefore, the statement given makes sense, since we need heavier stars to make the chemical elements upon which our lives are based. In fact, only the most massive stars, greater than about 10 solar masses, will ever form the chemical elements of iron and those more massive than iron, up to and inc ...
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Rare Earth hypothesis



In planetary astronomy and astrobiology, the Rare Earth Hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth (and, subsequently, human intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare. The term ""Rare Earth"" originates from Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the University of Washington.An alternative view point was argued by Carl Sagan and Frank Drake, among others. It holds that Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Given the principle of mediocrity (also called the Copernican principle), it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: that planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the Solar System, and our region of the Milky Way are very rare.
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