The Drake Equation: The number of technological civilizations that might exist among the stars

THE DRAKE EQUATION This equation expresses the number of technological civilizations that might exist among the stars. R * FP * NE * FL * FI * FC * LN = N = number of advanced technical civilizations emitting detectable radio signals. R = mean rate of star formation averaged over the lifetime of the galaxy. FP = fraction of stars with planetary systems. NE = mean number of planets per system with environments suitable for the origin of life. FL = fraction of such planets on which life does develop. FI = fraction of such planets on which intelligent life rises during the lifetime of the local sun. FC = fraction of planets on which advanced technical civilizations rises. L = lifetime of this technical civilization. When explaining this equation, Carl Sagan once said the formula means that at least 1 million of the 100 billion stars in our Milky Way galaxy have planets which have developed advanced intelligent civilizations. Now, if we consider the astronomical fact that there are over 10 billion galaxies in the universe, each holding at least another million solar systems, one may start to think that we may not be the only life in the universe.

I think the Drake equation makes sense. Given the size of our Galaxy, not even considering all the other Galaxies in the whole Universe (!), it would seem that the cosmos would be teeming with life. Of course, not all life would be sentient and have communications technology, but there would be plenty of those too.

www.activemind.com...

According to this calculation of the Drake equation, there should be about 1000 sentient species out there in our Galaxy with communications technology developed. That's a lot of species to try to contact!

www.seti.org...

From a seven page pdf appearing in Astrobiology in 2004, titled,
"The Temporal Aspect of the Drake Equation and SETI"

Interesting read for those wondering about the scientific theory that, since we exist, other life has to as well. . . .

In 4 decades of SETI projects there have been no results, in spite of the prevailing “contact optimism” of 1960s and 1970s, motivated largely by uncritical acceptance of the Drake equation. Conventional estimates of that period spoke about 10(6)–10(9) advanced societies in the Milky Way forming the “Galactic Club” (Bracewell, 1975). Today, even SETI optimists have abandoned such fanciful numbers, and settled on a view that advanced extraterrestrial societies are much rarer than previously thought. One of the important factors in this downsizing of SETI expectations has been demonstration by “contact pessimists,” especially Michael Hart and Frank Tipler, that the colonization—or at least visit—of all stellar systems in the Milky Way by means of self-reproducing von Neumann probes is feasible within a minuscule fraction of the galactic age.

[edit on 22-11-2007 by anhinga]

Since we don't know the actual figures for any of the variables in the Drake Equation, that means the total number of advanced alien civilizations could be anywhere from zero to billions. That really narrows it down.

Both Drake and Sagan seriously, seriously, serously underestimated the number of advanced technological civilizations, in the known universe, in my humble opinion, by a factor of bazillions.

Happy Thanksgiving!

Happy T-day to you too.

Hate to rein in anyone's enthusiasm, but the OP mis-stated the Drake Equation.

It's not the number of civilizations 'among the stars'. It's the number of communicating civilizations in our Galaxy.

Basically it doesn't include those simply able to Listen, or passively receive communications (like Earth does). It requires an ability to Send or actively communicate by sending out a something like a multi-giga-watt signal.

Now, that has NO impact on a wild guess of the numbers of basic sentient (planet bound) life forms, say at least at the level of the chimp or dolphin, tool-using, etc.

That number may very well be quite large. But we'll probably never know since the distances are too vast for radio transmissions to arrive in a normal lifetime - conversations would probably be impossible.

What is probably very, very rare is a civilization which:
1. is highly sentient, and
2. is able to use technology, and
3. is able to reach a Type I civilization, and
4. is able to become a truly space faring civilization (requires more than just building an orbiting space station), and
5. has sufficient natural resources or energy to go to another Star System in the same Galaxy, and
6. has sufficient capability that they have colonized at least one other planet to the level of their home world (anti-catastrophic), and
7. is able to find us and come here in person (as opposed to a nano-mechanical visitation). Surely reaching the level of a Type II civ. would be required for all seven conditions.
*8. are temporally concurrent - they have to be dominant in our time scale (not have died off or not yet occurred until years into the future.


So I have to ask. What does it matter if every single star in the Galaxy has a planet with sentient species? If they can not come here (i.e. fulfill all of the above conditions at minimum), then what does it matter?

It's really as though they don't exist if:
1. we are never able to communicate with them (and FTL theory says we can't)
2. they never become truly space faring.
3. existed but died off a long time ago. (etc.)
......

The inevitable conclusion, imo, is that if there really were billions and billions of civilizations in our Galaxy, and countless trillions in our Universe, then almost by some law of averages (luck?) -if they were able to come here, they'd already be here-. AND, they'd be blatantly obvious. IOW, once one civilization succeeded to Type I or Type II, then lots of them would start making it as contact was made and advancements shared.

The fact that they are not (barring the Borg Scenario), then ergo, they are extremely rare to the point of less than one civilization per galaxy.

I'd estimate per Galaxy:
Life: a certainty (including simple organisms);
Non-sentient higher life forms: almost a certainty;
Type 0 civilizations (planet bound) - probably millions, to billions per galaxy;
Type I civilizations (solar system bound) - maybe tens per galaxy
Type II civilizations (space faring) - none.
Type III civilizations (galaxy faring) - none.

2 cents.


(of course the above is a non-science fiction approach. It may be that some civilizations are of an incredibly strange type that they can transcend normal physics. Those would have to be outliers which no theory can encompass).

PS - the "Borg Scenario" referenced above would be a situation where a galaxy-wide threat caused a type of 'radio silence' among the other advanced civilizations. There might be other reasons for radio silence also.

Surely anyone who examines the evidence in a genuine spirit of open-minded skeptical inquiry will discover that we have been visited by civilizations from elsewhere for millenia. They are still here, and are encountered somewhere on Earth every day by airline pilots, the world's military, and ordinary folks.

Some of us have had very close experiences which make intellectual arguments a la 'Drake' pretty much irrelevant.

Question is, what are the SETI fools playing at? Willfully ignoring the evidence? I suppose if disclosure happens, as promised by some, they'll be out of a job. Maybe use of radio frequencies as a communication medium is something a civilization goes through in the blink of an eye - 20 or 30 generations, before graduating to another level of technology. No wonder they don't detect much.

Whatever the propulsion technology, or the space-time-bending physics utilized, some of them get out here to this little yellow star on the edge of the galaxy for sure. And they keep on visiting. Our system is quite young in the galactic time-frame, so it's reasonable to postulate that the galaxy teems with life of all kinds.

No matter how many zeros are on the end of a 'bazillion' John, I could buy into that thesis. Seems reasonable to me.

reply to post by Badge01


An excellent use of logic, though without any greater reason to be accurate than any other. Since we have no numbers to work with except the number one, we human, then the rest is just whatever we wish to think.

I favor life, simply because life finds a way to thrive, as is evident here on Earth in some rather nasty conditions like thermal vents in the ocean. Now how much life, and at what stage, is the question.

Because it seems that life is a force, much like gravity or time, I feel that the galaxy must be crawling with it. The leap from planet to space should be a logical expression of expansion. The stars will not seem so far away when we reach Pluto.

Considering that we have gone from the speed of a horse to many times the speed of sound in less than 300 years, a veritable eye blink in cosmic timekeeping, another 300 years would not seem to long to attain star flight using some form of FTL speeds.

I think that one of the things left out of the above equations may be location. We orbit an insignificant star far out on a spiral arm of a rather ordinary galaxy. There seems to be little in our area to attract scientists from some alien system, such as massive black holes, or interesting quasars, and the like. And we cannot know if commerce is such a universal concept for others as it is for us. Since we know nothing of the others, we cannot know what might be a motivator for them to explore into our rural area.

I guess we'll have to go to "town" and see why the "city slickers" never come out to the sticks and say howdy. Then we'll know, if there is no town, that we're the first.

reply to post by bovarcher


Unfortunately, every single sighting, every single encounter documented thus far, could be explained by prosaic, non-fantastic explanations. I'm not saying it was, but so far, despite good evidence that -something- odd is occurring, there's no proof that it's non-terrestrial.

As long as there has not been at least one irrefutable documented sighting that is not dis-info or due to a terrestrial, though here-to-fore unknown reason, then we can't say we have been visited.

There has been a lot of strange, even compelling evidence, but, unfortunately, none of it rises to the level of even the barest proof.

Radar traces of objects, reported abductions, sightings, crashed saucers - they are all just stories at the present time.

When you try to scientifically examine the plausibility of not just any kind of life somewhere, but that a sentient spacefaring species has come -here-, it seems extremely implausible. It's just too difficult at almost every step.

Originally posted by bovarcher
Surely anyone who examines the evidence in a genuine spirit of open-minded skeptical inquiry will discover that we have been visited by civilizations from elsewhere for millenia.

I doubt that. They will come to the conclusion that there is little solid evidence and no facts to back up a scientific answer.

All sightings, abduction stories, alien crashlandings or whatever requires ALOT of faith because we do not have the absolute answers. And that is where the science would break apart. Proof cannot live on faith alone.

Until we can show the definitive end-all-arguments proof that aliens either have been on Earth or we can find a civilization in space and confirm its presence, I personally wont even recognize the Drake equation as anything of value. Its utterly unscientific since there is nothing to base it on but Earth... And you cant even make a simple line diagram from that, that's how little data there is.

reply to post by anhinga




SETI is looking for electromagnetic broadcasts.

Silly humans... That's not what they use.

But we don't understand THAT yet.

reply to post by NGC2736


I agree that as we prove each step, planets, Earth-sized solid planets, life possibly on Mars, it makes everything else a little more plausible.

My central thesis though, is that any full-sized, in person Alien visitation would be -extremely- obvious. Uh, not to call on authority, but Stephen Hawking also feels this way.

I give a tiny possibility that ET may have sent a nano-probe here. In fact I'm pretty sure that a robotic probe would always be sent prior to a full sized visit - it's simple economics - you can't launch a full-sized expedition to every potentially habitable planet.

It may have been that we were visited once by a robotic probe, but it might have been during the age of single celled organisms - so the probe reported back negatively. (this is the temporal requirement I mention in a previous post).

It's surely fun and compelling to talk about it, but when you get right down to the nitty gritty, like I said, it's just too difficult.

Space faring civilizations don't just arise out of nothing. There has to be a LOT more terms to satisfy than just the Drake equation to postulate a full-size visit by non-terrestrials. (planet size, minerals, stable society, economics, durable organisms, mental set (curiosity), etc.).

That build up would be visible, imo, by astronomers in the form of Dyson Spheres and other structures. We'd see them populating other stars before they got here, I think. If they had the technology to come here, they could spell out 'we are here' by lining up nearby stars, for instance.

I just can't get past the difficulty and the fact that they've had time enough that if they existed, they'd be here.

Probably tons of planet-bound sentients out there, though, but doubt we'll ever find out about them.

Originally posted by dionysius9
reply to post by anhinga

 

SETI is looking for electromagnetic broadcasts.

Silly humans... That's not what they use.

But we don't understand THAT yet.

If you were trying to communicate with someone from a distance, say a bunch of boy scouts setting up tents in a valley below, would you use a microwave transmitter sending binary code?

No. You'd send smoke signals or use a mirror to flash the sun, or use a campfire at night.

It's the responsibility of the SENDing civilization to use sufficiently common or low tech signalling. They'd have to be pretty ignorant to use a 'too sophisticated' method'.

The methodology would have to be in the style of a 'Billboard' or a 'Searchlight', easy to pick up, based on some common item, like the frequency of Hydrogen or Helium, the most common elements.

Or were you just trying to pretend be 'mysterious'?

Vaguely surprised not many people have more 'hope' in the Drake Equation. In 1961, when Frank Drake came up w/ the equation, he estimated the amount of communicating civilizations to be ten, since then the number has obviously risen w/ the amount of 'galaxies' found and the universe better understood.

Actually, the Wiki page has some interesting results/theories on their page:

en.wikipedia.org...

Other assumptions give values of N that are (much) less than 1, but some observers believe this is still compatible with observations due to the anthropic principle: no matter how low the probability that any given galaxy will have intelligent life in it, the universe must have at least one intelligent species by definition otherwise the question would not arise.

Some computations of the Drake equation, given different assumptions:

R* = 10/year, fp = 0.5, ne = 2, fl = 1, fi = fc = 0.01, and L = 50,000 years
N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 50,000 = 50

Alternatively, making some more optimistic assumptions, and assuming that 10% of civilizations become willing and able to communicate, and then spread through their local star systems for 100,000 years (a very short period in geologic time):

R* = 20/year, fp = 0.1, ne = 0.5, fl = 1, fi = 0.5, fc = 0.1, and L = 100,000 years
N = 20 × 0.1 × 0.5 × 1 × 0.5 × 0.1 × 100,000 = 5,000

[edit on 22-11-2007 by anhinga]

over the next few years we will be able to accurately fill in FP=fraction of stars with planetary systems. In fact on december 10th CoRoT scientists will release their 1st paper on what they have found.

Originally posted by Badge01

Unfortunately, every single sighting, every single encounter documented thus far, could be explained by prosaic, non-fantastic explanations...

When you try to scientifically examine the plausibility of not just any kind of life somewhere, but that a sentient spacefaring species has come -here-, it seems extremely implausible. It's just too difficult at almost every step.

I can't agree, but then I may have an unfair advantage in this debate.

Have you had an encounter? Because if you have one, nothing will then convince you that what happened to you did not happen. It kind of makes it irrefutable. You can't argue about experience.

Had I not had my particular history, I don't know what my position on this issue might be. But I can tell you, having been through what I've been through I know they ain't from here. And for whatever reasons, they absolutely do not want to be 'open' about their presence, which is why we are able to have this debate and the 'Silly Effort to Investigate' continues to get gov funding.

The evidence is very extensive, and good enough for me to convict world govts beyond reasonable doubt of covering it up.



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Well, my whole point is, should we use Earth as a model, philosophically, then the theory has to go forward, w/ 'best guesses' to fill in the blanks, and recent scientific discovery, like the 'fraction' amount one poster mentioned helps narrow the equation down.

... article at space.com about this topic.... at the end of the article is a video player where they calculate the odds w/ Drake equation. Interesting watch:

"A Cosmic Evolution"
www.space.com...

Originally posted by Badge01

The inevitable conclusion, imo, is that if there really were billions and billions of civilizations in our Galaxy, and countless trillions in our Universe, then almost by some law of averages (luck?) -if they were able to come here, they'd already be here-. AND, they'd be blatantly obvious. IOW, once one civilization succeeded to Type I or Type II, then lots of them would start making it as contact was made and advancements shared.

Thanks for the post Badge01. Regarding your statement "-if they were able to come here, they'd already be here." And how do you think you would know this? Do you think that the President of the United States would make an announcement? Or do you think it would just go straight to CNN? Just asking.

They're might be other reasons for radio silence also.

Do you think? Maybe they don't feel like getting blasted. Or maybe they don't want to get Democratized. You know what I mean?

Thanks for the post.

reply to post by johnlear


John, can you tell me a little about the Martians? Are they technologically advanced at all? I'm starting to believe what you say about them living underground... the Drake Equations seems like a good reference point for skeptics to wonder about universal life.