Drake Equation: simple equation that is used to summarize the factors that would determine
the number of communicating civilizations in our galaxy.
-Introduced at a conference in 1961
NHp = number of habitiable planets in our galaxy
F life= fraction of habitable planets that have LIFE
Fciv= fraction of the life-bearing planets with civilization capable of interstellar communication
N HpX f lifef civ Number of civilizations capable of interstellar communication.
Fnow is the fraction of civilization bearing planets that happen to have civilization now
NHp= number of habitable planets on which life can evolve
Flife =fraction of habitable planets in our galaxy that have life (close to 1)
Fciv=Fraction of life bearing planets on which a civilization capable of interstellar communication
has arisen at some time.
Fnow= fraction of these civ that happened to exist now.
The discussion is limited to the Milky way (our own galaxy) since there are 100 billion
Original Drake Equation: N = R x f planet x Ne x Flife x Fintell X Fciv X L
R=# of stars formed in galaxy each year
fplanet= refers to the fraction of stars having planets
ne= refers to the # of planets per system capable of supporting life
F =refers to fraction of life-bearing planets which develop intelligent life.
Fciv=refers to the fraction of planets in which intelligent life capable of inter-stellar
L= the lifetime over which such civilizations exist.
-We have been able to communicate interstellar since 1950.
-Intelligent civilization= one that is capable of radio communication Conservative: (Technological) intelligence Optimistic: Evolutionary mechanism
like our own is rare encourage an increase in intelligence
Some intelligent species would evolved on
Convergent evolution : the tendency of organisms of different evolutionary backgrounds to
resemble one another due to similar environment and common ecological niches.
Dolphin and shark body features are streamlined for faster speed
Eyesight within the mammals have evolved 18 different times.
-Intelligence is also subject to natural selection. If it enhances survival value, then convergent
evolution will occur.
- can be tested by measure the brain power of a variety of animal species over time.
-Heavier animals have heavier brains
-- In the graph, animals whose brain falls on this line are said to have encephalization
quotient (EQ) of 1.
-This means they have enough brain size for basic set of instructions.
EQ of 1 serves as the indicator of general intelligence
Human EQ is 7 which means our brain is 7 times more massive than average mammal. Higher
than any species known or alive.
-having a bigger brain is metabolically expensive (1/4 of our metabolism is for our brain) -competition between species also increases intelligence since when one animal catches
another; it allows other victim of species to be more aware.
-Intelligence is not merely required to make technology
(I) Physiological: hands are needed
(II) Sociological: societies that emerged from the ancient Greece have concept of science.
12.3 Searching for Intelligence
BEST WAY TO SEARCH FOR INTELLGENCE IS TO look/listen for EXISTENCE
Two Radio Pioneers (Marconi & Tesla)
-Guglielmo Marconi (made radio practical) & Nikola Tesla (made the first fluorescent lamp, used
AC to distribute power)said WRONGLY they head aliens on the airwaves.
-The alien sounds they heard were infact whistler’s ( electrical noise created by distant
Origins of modern SETI
Modern SETI began with a paper from Cocconi and Morrison in 1959
-Said that interstellar communication was p