# Number of Alien Civilizations ( Extraterrestrial Life ) In Our Galaxy

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Extraterrestrial life is life originating outside of the Earth. It is the subject of astrobiology and its existence remains hypothetical, because there is no credible evidence of extraterrestrial life which has been generally accepted by the scientific community.

The Drake equation is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence. It can be used to predicate (read as calculate) the number of advanced civilizations in our galaxy right now. But the result are not accurate and lots of criticism involved.

Disagreement (ie general ignorance) over these numbers leads to estimates of the number intelligent civilisations in our galaxy that range from 10^-5 to 10^6.
i. panspermia predicts 37964.97 advanced civilisations in our galaxy with a standard deviation of 20.

ii. the rare life hypothesis predicts 361.2 advanced civilisations with an SD of 2

iii. the tortoise and hare hypothesis predicts 31573.52 with an SD of 20.

And the number of intelligent civilisations in our galaxy isâ€¦

1 ExtropicPacifist November 4, 2011 at 1:58 pm

he odds of Extraterrestrial Intelligence in our Galaxy and Known Universe:

The Frank Drake equation:

N = R* x F x N x F x F x F x L
p e l i c

extended formula:

N = R* x F x N x N x N x F x F x F x F x L x L
p e g m l i c s E

N= the number of extraterrestrial civilizations

R* = the number of stars formation/year
F(p) = the fraction of stars with orbiting planets
N(e) = the fraction of habitable planets
F(l) = the fraction of planets able to develop life
F(i) = the fraction of planets where intelligent life developes
F(c) = the fraction of planets capable of interstellar communication
L= the life expectancy of civilization

extended part of the formula:

N(g) = the fraction of planets having geotectonic activity
N(m) = the fraction of planets having heavy elements
F(s) = the fraction of planets capable of (interstellar) space travel
L(E) = the fraction of planets having a sufficient energy production level

for our Galaxy the number N = ~5.25 to 525

R* = ~ 7
F(p) = .3
N(e) = .1
F(l) = .5
F(i) = .1
F(c) = .05
L = ~10^4 to ~10^6

N(g) = .1
N(m) = .3
F(s) = .2
L(E) = .3

then N = ~ 0.00945 to ~ 0.945

however,if we assume a higher number for L = ~ 10^9,then
N= ~ 945

extrapolated to the known universe this means:

(assuming the number of galaxies existing in the known universe to
be as much as 7 x 10^10)

N= ~ 3.675 X 10^11 to ~3.675 x 10^13 according to the Frank Drake
formula

N= ~ 6.615 x 10^8 to ~ 6.615 x 10^10 according the extended formula

assuming an interstellar/intergalactic extraterrestrial civilization would
last for approx. 10^9 years, N= ~ 6.615 x 10^13

the latter value for N would indicate the possible existence for a cosmic
(type IV or V beyond the Kardashev-scale) extraterrestrial civilization

Not into account being taken is the possibility of colonized worlds orbiting
other stars by an extraterrestrial,starfaring civilization

By introducing the new variable F for the extended formula we assume the
C*

rate of colonization of other worlds during the lifetime of such a civilization.

Let’s assume F(C*) = ~ 10^1 to ~10^6 in the Drake Formula,this would mean
N= ~5.25 x 10^1 to ~ 5.25 x 10^7 colonized worlds within our galaxy

according the findings of the extended Drake formula:
N= ~ 0.0945 to ~ 9.45 x 10^5 within the galaxy

assuming the life expectancy to be 10^9 y N= ~ 9.45 x 10^8

On the scale of the known universe this would mean N= ~ 6.615 x 10^9 (lower
estimate) to ~ 6.615 x 10^19 (upper estimate).

The number of stars,assuming the galaxy is approx. 1.3 x 10^10 y old,being
formed thus far: ~7 x 1.3 x 10^10= ~ 9.1 x 10^10