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| Asteroids and Meteors |
1. Smaller meteors burn up and are fragmented in the thick atmosphere.
3. Statistical arguments can only be used to predict what will happen on average when things are repeated many times; they can never be used to predict individual events.
5. Let's assume for estimates a lifetime of 100 years. Then the probablility in that lifetime of an event that happens on average every one hundred million years is 102 / 108 = 1/1,000,000. Thus, there is one chance in a million, statistically, of such a catastrophe in a single human lifetime if our estimate of the rate is correct.
7. Since aten asteroids by definition are Earth-crossing asteroids with semimajor axes less than 1 AU, they must have orbital periods shorter than that for Earth, by Kepler's third law. The asteroid 1995 CR shown in this animation is an aten with an orbital period of 322 days.
9. Using the formula from chapter 2 for superior planets, if the periods are given in years P = S / (S -1). Inserting S = 466.6 days = 1.278 years gives a sidereal period P = 4.604 years. From Kepler's third law, a = P2/3 =2.77 AU.