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Longevity of Civilizations

Longevity of Civilizations. ASTR 1420 Lecture 22 from a Nature paper. SETI Debate. Drake Equation (Carl Sagan’s version). N = N * × f planet × f E × f life × f intell × f civ × f L. ×. ×. ×. ×. N number of transmitting civilizations. f planet. f Earth. f life. N *. ×. ×.

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Longevity of Civilizations

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  1. Longevity of Civilizations ASTR 1420 Lecture 22 from a Nature paper SETI Debate

  2. Drake Equation (Carl Sagan’s version) N = N* × fplanet× fE× flife× fintell× fciv × fL × × × × N number of transmitting civilizations fplanet fEarth flife N* × × = fintell fciv flong N

  3. Δtargument (Richard Gott 1993, Nature, 363, 315) Past Future Tbegin TNow TEnd If there is an End, where do we stand now in the time axis?

  4. Delta t argument (Richard Gott 1993, Nature, 363, 315) Past Future Tbegin TEnd • t will range between 0 and 1. • Calculates a probability of t being in the first or last 2.5%. • Probability of 0.025 ≤ t ≤ 0.975 ? •  95% • At the 95% confidence level, t will NOT be in the beginning 2.5% or in the ending 2.5% range.

  5. Delta t argument (Richard Gott 1993, Nature, 363, 315) • 0.025 ≤ t ≤ 0.975  • Similarly, at the 99% confidence level Past Future Tbegin TEnd

  6. Delta t argument At 95% confidence! • the length of time something has been observable in the past is a rough measure of its future observability…

  7. History of Human • Homo Sapiens : ≈200,000 years. • 200,000 / 39 < Future < 39*200,000 • 5128 years < Future < 7.8 million years • For our human civilization of 10,000 years • 10,000 / 39 < Future < 39 * 10,000 • 256 years < Future < 390,000 years • Our industrial civilization of ≈200 years • 200 / 39 < Future < 39 * 200 • 5 years < Future < 7,800 years

  8. If aliens are like human 6,400 ≤ N ≤ 9.8 million

  9. In summary… Important Concepts Important Terms • Delta t argument • Statistical approach to the longevity of civilizations • Chapter/sections covered in this lecture : Longevity of Civilization • UFOs : next class!

  10. SETIWill it succeed? ASTR 1420 Section 12.2 + ?

  11. Ernst Mayr • Bioastronomy News (1995, V7, No. 3) • German/American biologist • Harvard Biology Prof. • 7/5/1904 – 2/3/2005

  12. Carl Sagan • Bioastronomy News (1995, V7, No. 4) • We need “functional equivalent of human” not “prevalent humanoids”… • Radio technology  If Aztec civilization survived, would they develop radio technology in several millenia? • We, humanoids, are very young, but we have ~5 billion years to spare in the future. • American Astronomer • Cornell Professor • 11/9/1034 – 12/20/1996

  13. SETI debate Ben Zuckerman Seth Shostak SETI Astronomer • UCLA Astronomy professor

  14. Drake Equation (Carl Sagan’s version) N = N* × fplanet× fE× flife× fintell× fciv × fL × × × × N number of transmitting civilizations fplanet fEarth flife N* × × = fintell fciv flong N

  15. In summary… Important Concepts Important Terms • Logics behind each SETI arguments • Mayr vs. Sagan • Zuckerman vs. Shostak • Statistical approach to the longevity of civilizations • Chapter/sections covered in this lecture : SETI debate

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