Historical Estimates of The Parameters
Considerable disagreement on the values of most of these parameters exists, but the values used by Drake and his colleagues in 1961 were:
- R* = 1/year (1 stars formed per year, on the average over the life of the galaxy; this was regarded as conservative)
- fp = 0.2-0.5 (one fifth to one half of all stars formed will have planets)
- ne = 1-5 (stars with planets will have between 1 and 5 planets capable of developing life)
- fl = 1 (100% of these planets will develop life)
- fi = 1 (100% of which will develop intelligent life)
- fc = 0.1-0.2 (10-20% of which will be able to communicate)
- L = 1000-100,000,000 years (which will last somewhere between 1000 and 100,000,000 years)
Drake states that given the uncertainties, the original meeting concluded that N ≈ L, and there were probably between 1000 and 100,000,000 civilizations in the galaxy.
Read more about this topic: Drake Equation
Famous quotes containing the words historical, estimates and/or parameters:
“In public buildings set aside for the care and maintenance of the goods of the middle ages, a staff of civil service art attendants praise all the dead, irrelevant scribblings and scrawlings that, at best, have only historical interest for idiots and layabouts.”
—George Grosz (1893–1959)
“Writing a book I have found to be like building a house. A man forms a plan, and collects materials. He thinks he has enough to raise a large and stately edifice; but after he has arranged, compacted and polished, his work turns out to be a very small performance. The authour however like the builder, knows how much labour his work has cost him; and therefore estimates it at a higher rate than other people think it deserves,”
—James Boswell (1740–1795)
“Men have defined the parameters of every subject. All feminist arguments, however radical in intent or consequence, are with or against assertions or premises implicit in the male system, which is made credible or authentic by the power of men to name.”
—Andrea Dworkin (b. 1946)