The Drake equation is an attempt to provoke discussion about the possibility of alien civilisations contacting Earth. The equation is N = R* × fp × ne × fl × fi × fc × L, where N is the number of contactable alien civilisations and the other parameters are described below. Values are taken from estimates from the Wikipedia page.
The probabilistic calculator Caladis (also see associated paper) can be used to estimate and explore the probability distribution of the logarithm of N; the calculation is performed here. Probability density at log N > 0 (hence N > 1) could correspond to the probability that one or more alien civilisations are emitting detectable signals.
| Parameter | Description | Lower bound | Upper bound | Distribution of log(parameter) | Approximate mean from range | Approximate mean of log(parameter) |
| R* | Rate of star formation in our galaxy | 7 yr-1 | 7 yr-1 | log 7 | 7.0 | 2.0 |
| fp | The proportion of stars with planets | 0.4 | 1 | log U(0.4,1) | 0.7 | -0.4 |
| ne × fl | The average number of planets capable of supporting life, per star with planets, multiplied by the proportion planets capable of supporting life that actually develop life | 10-11 | 0.2 × 0.13 = 0.026 | U(log 10-11, log 0.026) ≈ U(-25.3, -3.7) | 0.013 | -14.5 |
| fi | The proportion of planets with life that develop civilisation | 10-9 | 1 | U(log 10-9, log 1) ≈ U(-20.7, 0) | 0.5 | -10.4 |
| fc | The proportion of civilisations that emit detectable signals into space | 0.1 | 0.2 | log U(0.1,0.2) | 0.15 | -1.9 |
| L | The length of time for which signal-emitting civilisations emit signals | 304 yr | 109 yr | U(log 304, log 109) ≈ U(5.7, 20.7) | 5 × 108 | 13.2 |