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
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