If you recall, we had used the concept of joint probability to explain the swiss cheese models of viral infection. That the probability of someone getting infected by a virus is a joint probability of several independent events.
In 1961, Frank Drake made the following equation to invoke some thoughts on estimating the probability of life outside earth.
N = R* x fp x ne x fl x fi x fc x L
- N: number of civilisations in the galaxy with which communication might be possible
- R*: average rate of star formation in the galaxy
- fraction of those stars having planets
- fraction of those planets that could support life per star
- fraction of those that could go on to make intelligent life
- fraction of that civilisation that could develop technologies
- the length of time they could release detectable signals into space
Choice of parameters
The choice of the parameters is the difficult part and what invited criticisms of the equation.
