The headline caught my eye: “36 Intelligent Alien Races in our Galaxy, scientists say”. It also attracted a lot of rolled eyes from my fellow astronomers.

The work itself was actually perfectly reasonable. A recent paper in The Astrophysical Journal – which is the gold standard for the field – by Tom Westby and colleagues at the University of Nottingham, revisited the “Drake Equation”, which provides an educated guess of how likely it is that other intelligences exist in our galaxy. They used new assumptions and updated data to motivate a new formulation of the problem. To give the university credit, its original press release merely claimed “Research sheds new light …” but that obviously wasn’t hot enough for the papers that ran the story.

The idea behind the Drake Equation is straightforward enough. It starts by using the way that mathematicians calculate odds. Say half the people walking through a door are wearing a hat, and half of everyone walking through that door carry a newspaper. Assuming there’s no connection per se between wearing a hat and reading the paper, one can multiply one half times one half and conclude that the odds are one in four of someone coming in with both a hat and a newspaper. Multiplying the odds of each condition gives you the probability that all the conditions are met.