- N is the number of civilizations in our galaxy with which communication might be possible;
- R* is the average rate of star formation in our galaxy
- fp is the fraction of those stars that have planets
- ne is the average number of planets that can potentially support life per star that has planets
- fℓ is the fraction of the above that actually go on to develop life at some point
- fi is the fraction of the above that actually go on to develop intelligent life
- fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
- L is the length of time such civilizations release detectable signals into space.
Code: Green Bank
Directive: Estimate number of extraterrestrial civilizations we may potentially come into contact with.
- Chien-Shiung Wu
- Frank Drake
- The Principles of Psychology (1890)
- Lee, T. D.; Yang, C. N. (October 1, 1956). "Question of Parity Conservation in Weak Interactions". Physical Review. 104 (1): 254. Bibcode:1956PhRv..104..254L.