Sean McKnight Profile picture
Feb 1 11 tweets 3 min read
1: Some industry buddies and I have been taking another crack at the Drake equation based on recent discoveries in astronomy and came away with an eerie conclusion:

There was less than a 50% chance for Earth to have developed an industrial civilization at this point (1) #space
2: For the unfamiliar, here's Carl Sagan running the Drake Equation in 1977.
3: Since Frank Drake came up with this thought experiment in 1961 we've learned quite a bit about the development of sentient life on our own planet, and more about exoplanets than can be summarized in a tweet.
4: Scientists are now pretty sure of the following:

Stars form planets as a rule, and life is all but guaranteed to arise on worlds capable of supporting it, given that it only took 500Myr for life to arise on Earth. So fp and fl both equal ~1.
5: We also now have a pretty good idea of how many planets are "Earth-like" (Sufficiently large/massive, and located in a goldilocks zone). Based on data from the Kepler observatory, ne is likely 40 Billion planets.…
6: The development of intelligence is tricky, and more of an equation within the Drake equation. Any star spewing out a lot of radiation (red dwarfs, blue and red giants) is disqualified, so that's at least 77% of all stars in our Galaxy.
7: We then have to disqualify any star that is much younger than our sun, as complex life has only existed on Earth for around 500Myr. That's about half of all stars.
8: That leaves us with around 11.5% of all Earthlike planets capable of hosting complex life of any kind.

Now we have to reduce it even more because tool using intelligent life took most of 498My to show up on Earth.
9: That ratchets us down to ~5.3 million worlds populated by Homo Habilis-level intelligences or greater.

5,000/2.3 million gets you to around 13,000 planets with a bronze age civilization or greater.

150/5000 gets you to 400 planets with radiocommunications...
10: Now here's the fun part. There are around 300 million stars within 5000 ly of Earth. That means, the model further reduces to where Earth itself has less than a 50% chance of harboring a radio using species.
11: So yeah, there's probably around 6400 cavepeople in that bubble, maybe a dozen or so planets with aliens swinging their equivalent of swords and halberds. But anybody who can talk to us is a long damn way off... if the model is right.

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