In 1961, Frank Drake, one of the founders of the SETI Institute (Search for Extra Terrestrial Life) came up with his famous equation representing the number of intelligent alien civilisations in our galaxy. Since there are so many variables, whose values we can only guess at, it’s no surprise that everyone comes up with a different result. In the course of some recent research, I revisited the Drake Equation and thought I’d publish my own results.
The Drake Equation:
N = R* . Fp . Ne . Fl. Fi . Fc . L
Where:
• R = average rate of star formation per year in our galaxy
• Fp = fraction of those stars that have planets
• Ne = average number of planets per star that can support life
• Fl = fraction that actually develop life
• Fi = fraction that develop intelligent life
• Fc = fraction that develop enough technology for us to detect their existence
• L = length of time in years that these civilisations release detectable signals into space
Drake’s own numbers worked out as follows:
N = 10/yr . 50% . 2. 100% . 1% . 1% . 10,000 years, or
N = 10 x 0.5 x 2 x 1 x 0.01 x 0.01 x 10000
Therefore, Drake imagined 10 detectable, intelligent civilisations in our galaxy. Wow. No wonder it’s an empty place out there – our galaxy covers an immense volume of space.
My results:
N = 10/yr . 60% . 4 . 100% . 1% . 50% x 5000
OK, so this isn’t good science, just my own guesses. My basis is the speculation that Earth, Mars, Titan and Europa all have (or had) life, and that half of all civilisations become technologically advanced, but don’t stay that way for long. I’m not suggesting they necessarily fail, just that they evolve means to hide themselves, such as Dyson Spheres.
So what did I come up with:
N = 10 x 0.6 x 4 x 1 x 0.01 x 0.5 x 5000
N = 600 intelligent civilisations in our galaxy.
If the galaxy fills 39 million million cubic light years, there ought to be a civilisation every 65 thousand million cubic l.y, or within 4000 l.y. of us. OK, so now my book needs a pretty fast superluminal propulsion system to travel that distance.
That was all a bit of fun. Want to make your own guesses?