You might have heard this week that a new study proposed that there are something like 36 communicating alien civilizations in our galaxy.

That sounds like way too specific of a number for something that can't really be calculated right now. So what the heck is going on?

[1/n]

This number came from a paper by Tom Westby & Christopher Conselice ( @conselice) from the University of Nottingham that's titled "The Astrobiological Copernican Weak and Strong Limits for Intelligent Life".

Here's the paper from arXiv: https://arxiv.org/ftp/arxiv/papers/2004/2004.03968.pdf

[2/n]

One of the most famous ways to estimate possible numbers of alien civilizations that could be capable of communicating with us right now is The Drake Equation, formulated by Frank Drake in 1961.

https://www.universetoday.com/39966/drake-equation-1/

[3/n]

The equation is a thought experiment, allowing us to use the knowledge we have (and make some guesses at what might be possible) to consider how many civilizations might possibly be able to communicate with us right now.

https://www.seti.org/drake-equation-index

[4/n]

This interactive graphic from @infobeautiful is a fun way to play with the potential inputs from the equation and see the variations in the estimates in possible numbers of communicating alien civilizations out there.

https://informationisbeautiful.net/visualizations/the-drake-equation/

[5/n]

There've been lots of proposed ways to solve the Drake Equation, not to mention other equations in similar structures for considering the potential for alien life, but, on the whole, the equation isn't meant to be solved. However, that will never stop us from trying!

[6/n]

So what's going on in this new paper where they suggest that rather exact number? Co-author @conselice explains himself in this thread.

https://twitter.com/conselice/status/1248240486017634304

[7/n]

They proposed a new Drake-like equation, which they call The CETI Equation (where CETI is their acronym for Communicating Extra-Terrestrial Intelligent civilizations). Their equation is looking specifically at worlds in the Goldilocks Zone for liquid water around stars.

[8/n]

We don't know if the Goldilocks Zone will really turn out to be the best place to look for alien life. Maybe icy worlds like Europa and Enceladus in our solar system will be more commonly inhabited out there. But the Goldilocks Zone is a good place to start looking.

[9/n]

This new paper also assumes that it might take about as much time for a communicating alien civilization to evolve as it took us here on Earth (with their focus mostly in the range of 5 billion years in age).

[10/n]

We really have no idea how much time it might take on average for life to develop intelligent civilizations capable of transmitting signals into space. Maybe it happens a whole lot faster on most other worlds or maybe even slower.

[11/n]

But one thing that is cool in their paper is that they take the metallicity of star systems into consideration. The metallicity tells us how many elements heavier than hydrogen and helium may be available for forming planets. Life as we know it needs a bunch of elements.

[12/n]

Life here on Earth requires the CHNOPS elements (carbon, hydrogen, nitrogen, oxygen, phosphorous, & sulfur), but also might have required much heavier elements like iron and molybdenum and actually a bunch of others.

Gotta love @DrFunkySpoon in this GIF! The chemistry!

[13/n]

Still, I would definitely take that 36 number with a hefty "pinch of salt" (i.e., maybe don't take it too seriously).

As a fellow astrobiologist pointed out in a Facebook post: "eye roll to this highly specific number for something that is not calculable."

[14/n]

Also, as @SethShostak mentions in a post for @SETIInstitute, the presumptions in this 36 calculation also seem to assume that the lifetime of a communicating civilization will only be 100 years (yeah, roughly about the time that we've had radio).

https://www.seti.org/how-many-alien-societies-are-there?fbclid=IwAR1FBMe9XlPKtd4hpZNODLTHeNFH7Fs3fTVwBcBx3ecBcZpyaTMhocHdB_w

[15/n]

Even if it seems far too presumptive and specific, I definitely recommend checking out the paper all the same, and you can also watch an interview about it with @DrBrianKeating and one of the authors of the paper, @conselice, from just yesterday:



[16/n]

What do you think? Can we assume that other life takes about as long as it did here for transmission into space to begin, that most civilizations will only communicate for a century, or that advanced technological civilizations will only evolve within the Goldilocks Zone?

[17/n]

In the end, we may find that there are 1, 36, or maybe even millions of technologically advanced species in our galaxy. We've definitely learned a lot about the potential for alien life out there, but we really don't know yet if/how/where alien life may form and evolve.

[18/n]

Btw, I'll soon be jumping out of People of Space so that you can hear about some space awesomeness from more people. I didn't get to post much this week due to a hectic schedule, but it was still fun. Feel free to connect with me:

@cosmobiologist http://cosmobiota.com