longevity of civilizations
DESCRIPTION
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 *. ×. ×. - PowerPoint PPT PresentationTRANSCRIPT
Longevity of Civilizations
ASTR 1420
Lecture 22
from a Nature paper
SETI Debate
Drake Equation (Carl Sagan’s version)
N number of transmitting civilizations
N = N* × fplanet × fE × flife × fintell × fciv × fL
× × × ×
× × =
N
N* fplanet fEarth flife
fintell fciv flong
Δt argument (Richard Gott 1993, Nature, 363, 315)
Tbegin TEnd
Past Future
If there is an End, where do we stand now in the time axis?
TNow
Delta t argument (Richard Gott 1993, Nature, 363, 315)
Tbegin TEnd
Past Future
• 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)
Tbegin TEnd
Past Future
• 0.025 ≤ t ≤ 0.975
• Similarly, at the 99% confidence level
Delta t argument
• the length of time something has been observable in the past is a rough measure of its future observability…
At 95% confidence!
History of Human• Homo Sapiens : ≈200,000 years.
o 200,000 / 39 < Future < 39*200,0005128 years < Future < 7.8 million years
• For our human civilization of 10,000 years
o 10,000 / 39 < Future < 39 * 10,000256 years < Future < 390,000 years
• Our industrial civilization of ≈200 yearso 200 / 39 < Future < 39 * 2005 years < Future < 7,800 years
If aliens are like human
6,400 ≤ N ≤ 9.8 million
R* 20 stars/yr
fplanet 1
nE 0.5
flife 0.5
fintell 0.5
fciv 0.5
L 5100 yrs
R* 20 stars/yr
fplanet 1
nE 0.5
flife 0.5
fintell 0.5
fciv 0.5
L 7.8 million yrs
In summary…
Important Concepts• Delta t argument
• Statistical approach to the longevity of civilizations
Important Terms
Chapter/sections covered in this lecture : Longevity of CivilizationUFOs : 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• UCLA Astronomy professor
Seth Shostak• SETI Astronomer
Drake Equation (Carl Sagan’s version)
N number of transmitting civilizations
N = N* × fplanet × fE × flife × fintell × fciv × fL
× × × ×
× × =
N
N* fplanet fEarth flife
fintell fciv flong
In summary…
Important Concepts• Logics behind each SETI argumentso Mayr vs. Sagano Zuckerman vs. Shostak
• Statistical approach to the longevity of civilizations
Important Terms
Chapter/sections covered in this lecture : SETI debate