Mosh:
Oishan se aikamoista tilanhukkausta, jos ei olisi!
Ja siis jos kaikki muuttujat on äärettömiä... eikös oo todennäköistä että jossai tampataan konemusiikin tahtiin yhtä intohimosesti ku meilläkin?
Toki jos ois ääretön määrä planeettoja niin kaikki mahdolliset vaihtoehdot toteutuisivat, itse asiassa äärettömän monta kertaa. Mutta kun ei ole.
The Drake Equation was was devised by Dr. Frank Drake in the 1960s in an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. The main purpose of the equation is to allow scientists to quantify the uncertainty of the factors which determine the number of extraterrestrial civilizations.
The Drake equation states that
N = R^{*} * f_{p} * n_{e} * f_{l} * f_{i} * f_{c} * L
where:
N is the number of extraterrestrial civilizations in our galaxy with which we might expect to be able to communicate
and
R* is the rate of star formation in our galaxy
fp is the fraction of those stars which have planets
ne is average number of planets which can potentially support life per star that has planets
fl is the fraction of the above which actually go on to develop life
fi is the fraction of the above which actually go on to develop intelligent life
fc is the fraction of the above which are willing and able to communicate
L is the expected lifetime of such a civilization
Current estimates of the Drake equation parameters
This section attempts to list best current estimates for the parameters of the Drake equation. Please list new estimates for these values here, giving the rationale behind the estimate and a citation to their source.
R*, the rate of star creation in our galaxy
Estimated by Drake as 10/year
fp, the fraction of those stars which have planets
Estimated by Drake as 0.5
ne, the average number of planets which can potentially support life per star that has planets
Estimated by Drake as 2
fl, the fraction of the above which actually go on to develop life
Estimated by Drake as 1
In 2002, Charles H. Lineweaver and Tamara M. Davis (at the University of New South Wales and the Australian Centre for Astrobiology) estimated fl as > 0.33 using a statistical argument based on the length of time life took to evolve on Earth. Lineweaver has also determined that about 10% of star systems in the Galaxy are hospitable to life, by having heavy elements, being far from supernovas and being stable themselves for sufficient time. [1] (
http://www.newscientist.com/news/news.jsp?id=ns99994525)
fi, the fraction of the above which actually go on to develop intelligent life
Estimated by Drake as 0.01. Solar systems in galactic orbits with radiation exposure as low as Earth's solar system are more than 100,000 times rarer, however.
fc, the fraction of the above which are willing and able to communicate
Estimated by Drake as 0.01
L, the expected lifetime of such a civilisation
Estimated by Drake as 10 years.
A lower bound on L can be estimated from the lifetime of our current civilization from the advent of radio astronomy in 1938 (dated from Grote Reber's parabolic dish radio telescope) to the current date. In 2004, this gives a lower bound on L of 66 years.
In an article in Scientific American, Michael Shermer estimated L as 420 years, based on compiling the durations of sixty historical civilizations. Using twenty-eight civilizations more recent than the Roman Empire he calculates a figure of 304 years for "modern" civilizations. Note, however, that the fall of most of these civilizations did not destroy their technology, and they were succeeded by later civilizations which carried on those technologies, so Shermer's estimates should be regarded as pessimistic.
Näillä parametreilla meidän galaksissamme olisi 0,42 ehdot täyttävää sivilisaatiota, eli ei yhtään lisäksemme. Tietenkin noiden parametrien valinta on paikoin aikamoista arvontaa, joten tuota voi pitää korkeintaan yhtenä mahdollisena ohjeellisena arvona.
http://en.wikipedia.org/wiki/Drake_equation