On September 2, 2022, Frank Drake, the American astronomer, and astrophysicist (b. May 28, 1930) died at his home in Aptos, California, from natural causes at the age of 92.

Frank Drake is considered one of the pioneers of the modern field of the search for extraterrestrial intelligence (SETI). He was the creator of the Arecibo Message, an interstellar radio message carrying basic information about humanity and Earth that was sent to globular star cluster M13 using the Arecibo radio telescope in Puerto Rico on 16 November 1974.

Using the radio telescope at Green Bank, Drake mapped the center of the Milky Way Galaxy for the first time. He also discovered the ionosphere and magnetosphere of the planet Jupiter and made significant observations of the atmosphere of the planet Venus.

But his most famous contribution to SETI was the Drake equation without a doubt.

## Drake Equation

Are humans unique and alone in the vast universe? This question is summed up in the famous Drake equation, formulated in 1961 by Frank Drake. It is a probabilistic argument used to estimate the number of intelligent, active, and communicative (you can’t communicate with civilization if it doesn’t want to, or if it hides from the Universe, or if it is not in our current past light cone) extraterrestrial civilizations in the Milky Way Galaxy.

The Drake equation is:

N = R x fp x ne x fl x fi x fc x L

where

• N: The number of technologically advanced, communicable civilizations in the Milky Way galaxy
• R: The average star formation rate in our Galaxy
• fp: The fraction of those stars which have planets that are orbiting them
• ne: The average number of planets that can potentially support life per star that has planets orbiting them
• fl: The fraction of planets that could support life that actually develops life at some point
• fi: The fraction of planets with life that actually go on to develop intelligent life
• fc: The fraction of civilizations that develop a technology that releases detectable signs of their existence into space
• L: The length of time for which such civilizations release detectable signals into space

Please note that all item on the list above is actually a “fraction of the above”, which means that all the previous conditions have been satisfied. For example, when we consider fc we assume that intelligent life has already
developed.

The context of this equation was that Drake and others were considering how likely it would be that if we observed, say, radio waves from various stars we might detect signals of intelligent origin.

The general idea is that by breaking down the big question into various sub-questions, it is ultimately possible to make a reasonable estimate of the final answer.

In doing it this way it is also implicitly assumed that no factor is so small as to render the others meaningless. For example, if you think that fi is equal to 10-10, then no amount of optimism about the other factors will compensate.

## Interview with Frank Drake: Why Aren’t Aliens Already Here?

Here’s an interview with Frank Drake titled “Why Aren’t Aliens Already Here?” published by the Closer to the Truth channel.