Wednesday, December 15, 2010

The Drake Equation

I did enjoy the program on BBC4 last night The Search for Life: The Drake Equation. If you can use I-player then I suggest you go take a look. But what is the Drake Equation? This explanation lifted from SETI lays it out nicely:

Is there a way to estimate the number of technologically advanced civilizations that might exist in our Galaxy? While working at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake conceived a means to mathematically estimate the number of worlds that might harbor beings with technology sufficient to communicate across the vast gulfs of interstellar space. The Drake Equation, as it came to be known, was formulated in 1961 and is generally accepted by the scientific community.

N = R* fp ne fl fi fc L


N = The number of communicative civilizations
R* = The rate of formation of suitable stars (stars such as our Sun)
fp = The fraction of those stars with planets. (Current evidence indicates that planetary systems may be common for stars like the Sun.)
ne = The number of Earth-like worlds per planetary system
fl = The fraction of those Earth-like planets where life actually develops
fi = The fraction of life sites where intelligence develops
fc = The fraction of communicative planets (those on which electromagnetic communications technology develops)
L = The "lifetime" of communicating civilizations

Frank Drake's own current solution to the Drake Equation estimates 10,000 communicative civilizations in the Milky Way. Dr. Drake, who serves on the SETI League's advisory board, has personally endorsed SETI's planned all-sky survey.

Moving no from the Drake Equation you then get to the Fermi Paradox:
The Fermi Paradox is the apparent contradiction between the high probability extraterrestrial civilizations' existence and the lack of contact with such civilizations.
In this program, I like how these two are covered. Consider how much of the EM spectrum there is to cover, how much our usage of radio has changed in just a few decades (AM to FM for example). Consider too a simple calculation: 100 billion (the number of stars in our galaxy) divided by that number of civilizations above.


Ryan said...

Ive always wondered about the likelyhood of discovering other tool-users though. our sense of self is born out of a weird aspect of our evolution that relied on us being able to better model the world around us until eventually we could model ourselves and the minds of our peers. add a dash of curiosity and an ability to tool use and we became what we are now. How likely is that though? its not a question we can really answer without seeing a bit more of the universe. perhaps other tool users would have evolved completely differently and be far more alien than we could ever realise...

Neal Asher said...

The Drake Equation exists, but things start to get dodgy when inputting numbers that are, at best, guestimates. Yes, the whole point about the alien is that it is ... alien.

Ryan said...

The fermi paradox is fascinating to think of. If we don't up wiping ourselves out through war or massive economic collapse (then war)or destroying the ecosystem (through war) then I don't see why eventually we wont spread out further than this system. Even with no FTL over millions of years its plausible that our descendents could colonise a healthy portion of the galaxy. Which begs the question of why it hasn't been done before.

Neal Asher said...

It has been done before but, as we well know, those expanding civilizations always eventually run into Jain Technology. And of course, in Alastair Reynolds' books the Inhibitors serve the same purpose.

Ryan said...

My mistake, I humbly apologise and shall submit myself to the nearest bell I can find for gabbleisation

alibaba said...

I can recommend Paul Davies' The Eerie Silence for an in-depth analysis of the whole subject. Not only might we be looking in the wrong EM wavelength, we might be looking at the wrong things entirely - what about modulation of gravity waves as a form of communication?

billd said...

The program was good. Surprised they didn't mention the WoW signal:!_signal. There is an interview with Davies on the Grauniad Science Weekly podcast from earlier this year I only just came across here:

He talks about Drake and some of the stuff from his book, including the possibility an ETI may have come this way before we evolved and left messages in the DNA sequences of organisms on Earth.

Neal Asher said...

Ryan, no need yet, just wait until someone picks up a meteorite with interesting cubic patterns on its surface...

I'll take a look at that alibaba. It's just like the AM FM thing. Just maybe the civilizations out there are instantly communicating using some form of quantum entanglement (to be found in Zero Point).

More for me to look at billd. But of course they've been here before. They moved in a convenient moon to strip off atmosphere and create tides so as to speed up the evolution of life. They positioned Jupiter to suck up incoming asteroids, then visited again to deposit starter life here during the Cambrian explosion (Cowl). Then they came back later, realized the dinosaurs weren't up to much and dumped an asteroid on them.

Neal Asher said...

Enjoyable podcast, billd, but quite a lot to argue with. I think there's a bit of a failure of imagination when he cites journeys centuries long as a reason why no one would embark one them. Very human-centric. If you're a member of a super-civilization with quite likely a life extended to eternity, century-long journeys wouldn't be such a problem. Also, aliens would not just by physically different, their minds would probably operate in ways we couldn't fathom.

Also his contention that religions would be killed by the discovery of an alien civilization is a bit naive. Religions had always adapted and changed - they're a difficult meme to kill. And I'm sure something like scientology would upsurge.

Hitch said...

Finally manage to see this, we don't get iplayer access here so had to take alternative routes.

Good program, not overly popsci and covered the bases well.

Loved the little story about Carl Sagan, but more than that, the idea that a second form of intelligent life could arise here on Earth.

The Dolphins seem to be the best example. Just recently they have proven that wild Dolphins can be taught by previously captive ones too. Another few hundred years and we may get quite a shock :)