Longevity of Civilizations

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# Longevity of Civilizations - PowerPoint PPT Presentation

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

ASTR 1420

Lecture 22

from a Nature paper

SETI Debate

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

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)

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, 315)
• 0.025 ≤ t ≤ 0.975 
• Similarly, at the 99% confidence level

Past

Future

Tbegin

TEnd

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
• 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

6,400 ≤ N ≤ 9.8 million

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!
SETIWill it succeed?

ASTR 1420

Section 12.2 +

?

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

Ben Zuckerman

Seth Shostak

SETI Astronomer

• UCLA Astronomy professor
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 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