Over 5,500 planets have been discovered. Once we see clear biosignature gas spectra, we get much better estimate for f_l parameter in Drake's equation (the nu

Over 5,500 planets have been discovered. Once we see clear biosignature gas spectra, we get much better estimate for f_l parameter in Drake's equation (the number of active, communicative extraterrestrial civilizations in our galaxy) The current upper estimate is 10 million (set all unknown probability parameters in Drake's equation to 1.0 and L to infinite.) Setting unknown parameters to even slightly less optimistic numbers drops the estimate dramatically. For example: if you set life develops into intelligence = 0.5 , able to technologically communicate = 0.5, and lifetime = 100k years, you get N=30.