l23 - Today Announcements: HW#9 is due Friday April 16 at...

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ISP209s10 Lecture 23 -1- Today • Announcements: – HW#9 is due Friday April 16 at 8:00 am – Exam #3 Thurs. April 29 – Final Exam will be on CAPA • Today: SETI loose ends • Atoms and Nuclei
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ISP209s10 Lecture 23 -2- Clicker Question If the Sun suddenly became a black hole, what would happen to the Earth’s orbit? A). The Earth would start a spiral into the Sun B). The Earth would fly off out of the solar system C). Depending of the mass of the Sun, the Earth’s orbit would approximately double or be approximately half of what it is now D). The Earth would join all the other plants at the same radius from the black hole E). Nothing
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ISP209s10 Lecture 23 -3- Clicker Question If the Sun suddenly became a black hole, what would happen to the Earth’s orbit? A). The Earth would start a spiral into the Sun B). The Earth would fly off out of the solar system C). Depending of the mass of the Sun, the Earth’s orbit would approximately double or be approximately half of what it is now D). The Earth would join all the other plants at the same radius from the black hole E). Nothing
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ISP209s10 Lecture 23 -4- Clicker question True or False. In principle, it is only possible for extremely large Masses to form a black hole. A) True B) False
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ISP209s10 Lecture 23 -5- Clicker question True or False. In principle, it is only possible for extremely large Masses to form a black hole. A) True B) False Given any mass M, if you squish it down to a sufficiently small radius (“Schwartzchild radius”), the escape velocity becomes equal to c, which signals that a black hole has formed.
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ISP209s10 Lecture 23 -6- Drake Equation # civilizations in Milky Way = N* f p n e f l f i f c f L N number of stars in the Milky Way (200 billion) F p fraction of stars with planets (0.2 to 0.4) n e number of planets where life may exist per star (1 to 5) f l fraction where life begins (0-1) f i fraction of life that develops intelligence (0-1) f c fraction of intelligent life that develops communication (0-1) f L fraction of a star’s life when intelligent life survives (0-1) The red factors are complete guesses, so the final answer can be billions or zero! Some critics say this makes the Drake Equation meaningless. Others say it still helps identify key factors.
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ISP209s10 Lecture 23 -7- Drake Equation # civilizations in Milky Way = N* f p n e f l f i f c f L N number of stars in the Milky Way (200 billion) F p fraction of stars with planets (0.5) n e number of planets where life may exist per star (2) f l fraction where life begins (1) f i fraction of life that develops intelligence (0.2) f c fraction of intelligent life that develops communication (1) f L fraction of a star’s life when intelligent life survives (3x10 -7 ) Drake’s guesses are shown in blue . His final answer is ~ 10,000
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ISP209s10 Lecture 23 -8- Fermi’s Question: Where is Everybody?
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l23 - Today Announcements: HW#9 is due Friday April 16 at...

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