Here we have a new treatment of the Drake Equation in this paper: A Numerical Testbed for Hypotheses of Extraterrestrial Life and Intelligence. From the preamble:
This paper outlines a means for applying Monte Carlo Realisation techniques to investigate the parameter space of intelligent civilisations more rigorously, and to help assign errors to the resulting distributions of life and intelligence.
The Monte Carlo method, from what I can gather from Wikipedia, involves:
…a large and widely-used class of approaches. However, these approaches tend to follow a particular pattern:
- Define a domain of possible inputs.
- Generate inputs randomly from the domain, and perform a deterministic computation on them.
- Aggregate the results of the individual computations into the final result.
There’s a lot of complex maths in the paper, and author Duncan H. Forgan says that when it comes to biological parameters the figures are basically guesswork, given that there is only one known biosphere.
Forgan applies his methods to different theories concerning the likelihood of life, including Panspermia, the Rare Life Hypothesis (life is rare, but life is likely to become intelligent), and the Tortoise and Hare Hypothesis (we assume civilizations that develop rapidly are more likely to destroy themselves) with the following scores:
- Rare life: 361 advanced civilizations
- Tortoise and Hare: 31,573 advanced civilizations
- Panspermia: 37, 964 advanced civilizations
Read the paper – if it demonstrates anything it is how much more there is to find out about our galaxy.