3 ms·

I'd like to know where that value comes from, is there any scientific basis to it?

• PixelRobot 16y ago
  It seems to be just speculation. There's not much data you can use to guess those numbers with the current scientific knowledge.
• rflrob 16y ago
  When the equation was first proposed, I'd guess they assumed Sol is an "average" solar system, and given that we have Earth, which is by definition Earth-like, and Mars, Venus, and several of the Jovian moons, which could all fit a suitably loose definition of "earth-like", Drake might even have thought he was being conservative.