🧮 Drake Equation Results

Estimated Number of Detectable Civilizations

86,400

based on the current model parameters

The Drake Equation

N = R* × f(p) × n(e) × f(l) × f(i) × f(c) × L

where each term represents a probabilistic factor contributing to the number of detectable civilizations within the Milky Way galaxy.

📊 Parameters Used

Parameter Symbol Value Justification
Rate of Star Formation R* 2.00 ~2 new stars form per year in the Milky Way — midpoint of observed 1–3/year range.
Fraction of Stars with Planets f(p) 0.80 Most stars host planetary systems; Kepler data suggests ≥0.7. Value 0.8 chosen as reasonable.
Average Number of Habitable Planets per System n(e) 0.20 Exoplanet studies estimate 0.1–0.2 potentially habitable planets per star. Model uses 0.2.
Fraction of Habitable Planets Where Life Appears f(l) 0.50 Life may appear on ~50% of habitable worlds. Moderate optimism (0.5) used here.
Fraction of Life-Bearing Planets with Intelligent Life f(i) 1.00 Highly uncertain; used 1.0 for simplicity, assuming intelligence evolves on all life-bearing planets.
Fraction Developing Detectable Technology f(c) 0.10 Small fraction sustain detectable signals; conservative value 0.1 adopted.
Lifetime of Detectable Civilization (years) L 5,400,000 Weighted mean of 1961 (50×10⁶ years) and 2017 (1.0×10⁶ years) estimates, with 80% weighting on the newer data.
Computed as L = (0.2×50E6 + 0.8×1.0E6) ÷ 2 = 5,400,000.
🧩 Origin of Lifetime Estimates (L)

The values used for L—the expected lifetime of a communicating civilization—are derived from Impractical Python Projects by Lee Vaughan (No Starch Press, 2019), Table 10-1: Some Drake Equation Inputs and Results, p. 191. That table summarizes estimates originally discussed by Frank Drake, comparing his 1961 and 2017 parameter sets.

In this model, a weighted mean L = (0.2 × 50E6 + 0.8 × 1E6) ÷ 2 is used to balance early optimism with later, more conservative assumptions—producing a moderate expectation of how long technological civilizations may remain detectable within our galaxy.

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📚 References