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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
Longevity of Civilizations

ASTR 1420

Lecture 22

from a Nature paper

SETI Debate

drake equation carl sagan s version
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

t argument richard gott 1993 nature 363 315
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?

delta t argument richard gott 1993 nature 363 315
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.
delta t argument richard gott 1993 nature 363 3151
Delta t argument (Richard Gott 1993, Nature, 363, 315)
  • 0.025 ≤ t ≤ 0.975 
  • Similarly, at the 99% confidence level

Past

Future

Tbegin

TEnd

delta t argument
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…
history of human
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
if aliens are like human
If aliens are like human

6,400 ≤ N ≤ 9.8 million

in summary
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!
seti will it succeed
SETIWill it succeed?

ASTR 1420

Section 12.2 +

?

ernst mayr
Ernst Mayr
  • Bioastronomy News (1995, V7, No. 3)
  • German/American biologist
  • Harvard Biology Prof.
  • 7/5/1904 – 2/3/2005
carl sagan
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
seti debate
SETI debate

Ben Zuckerman

Seth Shostak

SETI Astronomer

  • UCLA Astronomy professor
drake equation carl sagan s version1
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

in summary1
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