The Drake Equation Revisited

[TheBigDog]

The Drake equation states that:

 

[math]N = R^{\ast} \times f_p \times n_e \times f_{\ell} \times f_i \times f_c \times L \![/math]

 

where:

 

N is the number of civilizations in our galaxy in which communication might be possible;

 

and

 

R* is the average rate of star formation per year in our galaxy

fp is the fraction of those stars that have planets

ne is the average number of planets that can potentially support life per star that has planets

fℓ is the fraction of the above that actually go on to develop life at some point

fi is the fraction of the above that actually go on to develop intelligent life

fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L is the length of time such civilizations release detectable signals into space.[2]

I was looking up the Drake Equation the other day and I wonder if it is complete. As I am doing my work on the Prophesy Chronicles, I have been doing research on the idea of interstellar travel and settlement. The equation seems to assume that civilizations don't expand beyond their initial planet. But it is already in our technical capability (if not politically or economically feasible) to begin interstellar flight now. In a century or two we might be settling on other planets. But that is not part of the Drake Equation. The typical finding of those who use the equation determine that there are between 10 and 20 civilizations such as ours at any given time in our galaxy. But what about settlement? What does the ability to explore and settle other planets do the the Drake Equation?

 

It seems to me that it needs at least one other factor, perhaps two or three. I have created this thread to discuss how the Drake Equation would need to be modified based upon the idea of interplanetary settlement. If that is a possibility, then what are the likely number of civilizations in our galaxy?

 

Bill

[Boerseun]

Well, the equation attempts to approximate "the number of civilizations in our galaxy in which communication might be possible", so I suppose if you really want to be anal about this, you should first define what you mean with "civilization".

 

For instance, let's say the Prophesy pans out in real life, and humanity settles its second planet. Will humanity then count as one or two civilizations?

 

I would venture to say that it would still be only one civilization.

 

Then, I guess, the only amendment necessary would be the definition of L. Because "L is the length of time such civilizations release detectable signals into space", it can be said that if a civilization is spread across more than one planet, any possible event that would prevent that civilization from releasing signals to space should only happen on one of the civilization's planets. If a planet-terminating asteroid impact happened, only one planet will be blown up. Of course, trans-planetary politics (the rise of the Galactic Amish Armed Forces, for instance) might shun technology on more than one planet simultaneously. So, in hindsight, I guess that the definition of "L" can stand as is, but it should be kept in mind that it can be much longer than thought once a civilization spreads.

[TheBigDog]

I think the formula is planet centric by design, in that a civilization belongs to only one planet. When the equation tells me that there may be 100 civilizations, how many places can I point my radio waves and communicate with someone? I would think the answer is 100, even though there may be a million inhabited worlds among those 100 civilizations. So I think it needs to reflect at a minimum the planetary count.

 

The whole purpose of spreading out to other planets is to prevent extinction. All the eggs in one basket and all that.

 

Bill

[Moontanman]

I think there is a very good chance that civilizations dispense with planets very early on. The number of planets with civilizations may not be an indicate of anything but the starting points of civilizations. Artificial habitats could be spread out with no regard what so ever for inhabitable planets. One inhabited planet might seed civilizations around every star in the galaxy, so the variable of life bearing planets could very well be meaningless.

[Donk]

Larry Niven usually tries to get his science right, if controversial at times. He writes:

For protoplasmic life forms, there are not many habitable planets in the galaxy. Nature makes an unreasonable number of conditions. To insure the right composition of atmosphere, the planet must be exactly the right distance from a G type sun, must be exactly the right size, and must have a freakishly oversized moon in its sky. The purpose of the moon is to strip away most of the planet's atmosphere, generally around 99 percent of it. Without its moon a habitable world becomes shockingly uninhabitable; its air acquires crushing weight, and its temperature becomes that of a "hot" oven. ~ World of Ptavvs

He repeated the same theme in several other places. If true, it would cast grave doubt on the accepted figure for the number of life-bearing planets. Anyone here know whether he was talking sense?

[Moontanman]

Larry Niven usually tries to get his science right, if controversial at times. He writes:

 

He repeated the same theme in several other places. If true, it would cast grave doubt on the accepted figure for the number of life-bearing planets. Anyone here know whether he was talking sense?

 

It's now known as the Rare Earth Hypothesis, basically it's the idea that conditions on the Earth depend on so many variables that are connected and interdependent that the idea of complex life one another planet is all but impossible.

 

There are other schools of thought, one big if, the formation of the moon, is thought by some to not be all that unusual. Both Venus and Mercury are not thought to have been affected by huge impacts of the type that formed Earths moon and in those cases either no moon was formed (Mercury) or the moon formed orbited in retrograde fashion and impacted the planet (Venus). If this idea of the way terrestrial planets formed is true then large moons may not be all the rare. Until we actually see other planets it is difficult to really know.

 

Rare Earth hypothesis - Wikipedia, the free encyclopedia

 

Rare earth: why complex life is ... - Google Books

[Moontanman]

I think this is also relevant,

 

Hypothetical types of biochemistry - Wikipedia, the free encyclopedia

[Boerseun]

I don't think biochemistry would have any bearing on the Drake Equation.

 

It's fundamentally about calculating the odds for how many civilizations we can communicate with, in other words, how many civilizations have stumbled upon radio astronomy.

 

What their biological make-up would be to get to that point should be irrelevant, because the fundamentals of radio astronomy is universal.

 

I guess there could be vast numbers of civilizations that never get past our version of Roman times, where you have a big, well-structured and well-ordered civilization, which simply never gets around to inventing electricity or never go through a whole Industrial Revolution because the entrenchment of slavery simply does not make labor-saving a priority.

 

But that's not what the Drake Equation attempts to calculate, either.

 

I think what might make matters more complex, however, is that we have invented radio astronomy and we assume that its the way to go. What wonders still lie waiting for discovery as far as communication goes? We simply don't know. We assume that Pulsars are what they are, because it makes sense in the context of our current knowledge. For all we know, Pulsars can be stars that have been intentionally imploded by a super-advanced civilization to serve as galactic navigation beacons (okay - forget that they exist in the early years of the universe, far far away, but it illustrates my point). Assuming that radio astronomy is the ticket might as well be the same as a guy who invented writing and is casting bottles with notes into the ocean because that is the epitome of communication in his context, and everybody else will communicate with him in the same way. His entire life passes by without him receiving a single note. On his deathbed, he assumes that he was the only guy in the world. Yet, all around him, every second of every day, billions of radio signals criss-cross his island and fly over his lonely head. He dies, sad and alone, writing his final note. Maybe there's some other medium of communication just one step up from our current technological paradigm, and we're merely casting bottles into the ocean of space.

 

Consider for instance, that today, in the age of optical storage media where laser diodes are taken for granted, the only physical communications that we've ever cast into the void is phonograph records on Voyagers 1&2 - a mere few decades ago. That was the technological paradigm of the day. A needle scratching a platter.

 

So I guess if the Drake Equation is to be updated, current technological truths on Earth should be kept in mind, and we should remember that if we apply it as it is, we'll only find other civilizations who hold radio astronomy in the same esteem as we do.

 

Let's say a civilization stumbles on radio astronomy, and starts beaming its message to the universe - only to find out a mere ten or twenty years later that there's a much better system, which would achieve much better results for much less energy spent. On Earth, we would see their signal for twenty years and then silence. Would we assume that they've destroyed themselves? Who's to say that our technology would branch into the necessary direction to follow them to be able to listen to them using the new technology? There's still two civilizations, perfectly capable of communicating using radio astronomy, but the one branched into using nooglefetzers as the de facto universal communications medium, and the other branched off into using lobbleputzers. Nooglefetzers and lobbleputzers are incapable of communicating with each other, but both civilizations make excellent arguments as to why their particular technology would be the equipment of choice for other distant civilizations whom they wish to communicate with.

 

If there is a way to jump directly from the invention of electricity to the invention of nooglefetzers and bypass radio astronomy altogether, then we would never hear from that particular civilization at all. Which makes an excellent case that in employing the Drake Equation, we will only find civilizations very much like ourselves and we scrap all those that follow much different technological paths.

 

This whole argument rests very heavily on what nooglefetzers and lobbleputzers might be, and what limitations there might be on technology. But then again, the entire Drake Equation rests on guesswork in any case. It might be that radio astronomy is the end-all and be-all of galactic communication. But using the Drake method of employing your own numbers for the variables, it very well might be not, too. In which case there is a definite cause for an extra variable in the Drake Equation which might cater for this argument.

[Moontanman]

One of the fundamental factors in the Drake equation is "earth like planets" Alternate biochemistries expand that concept considerably.

[Larv]

This is my first exposure to the Drake equation. At first blush, it appears to me to be a logical extension of Isaac Asimov’s “Extraterrestrial Civilizations” (1979), in which he is makes one critically false assumption: biological life leads improbabilistically but nevertheless stochastically to intelligent life and civilization as if there were a natural driving force toward higher complexity. No such driving force exists in natural that I know of.

 

What I think is wrong with the Drake Equation is the absence of what I will call the “one-off factor.” The one-off factor would allow for the assumption that nature often produces just single events—ones arising from an infinitely rare set of circumstances—that produces a completely unpredictable emergent property. As such, the one-off factor would render the Drake Equation all but useless. So far as we know, abiogenesis was such an event. Add to that the improbably emergence of intelligence humans and eventually civilization on Earth, which seems to me to be much more one-off-ish than statistically predictable.

 

Like Asimov’s speculation, the Drake equation relies on large numbers of event opportunities that have no statistical basis for validity. They are simply saying that because there are so many planet-bearing star systems—“billions and billions and billions” (Carl Sagan)—that it is fair to expect that what happened on this planet will likely happen somewhere else.

 

Hasn’t the SETI experiments already proven one thing? If there were other civilized planets with our level of technology then we should be hearing from them by now. Where are the messages from space that beckon us to communicate with them? We seem to be awfully alone, don’t we?

 

Do all life-bearing planets eventually go through a transition from prokaryotes to eukaryotes? Do they eventually have their own versions of the Cambrian Explosion? Do they have the same kinds of environmental stresses and mass extinctions that we have had here on earth? And will they eventually adopt civilizations to cope with their vicissitudes?

 

Frankly, I don’t think we know nearly enough about the course of biological evolution from abiogenesis to civilization to make any judgments on the likelihood of extraterrestrial civilizations. I think the safest assumption is that we are uniquely intelligent and uniquely civilized, no matter how many “billions and billions and billions” of stars are out there.

[Moontanman]

This is my first exposure to the Drake equation. At first blush, it appears to me to be a logical extension of Isaac Asimov’s “Extraterrestrial Civilizations” (1979), in which he is makes one critically false assumption: biological life leads improbabilistically but nevertheless stochastically to intelligent life and civilization as if there were a natural driving force toward higher complexity. No such driving force exists in natural that I know of.

 

This is thought to be true.

 

What I think is wrong with the Drake Equation is the absence of what I will call the “one-off factor.” The one-off factor would allow for the assumption that nature often produces just single events—ones arising from an infinitely rare set of circumstances—that produces a completely unpredictable emergent property. As such, the one-off factor would render the Drake Equation all but useless. So far as we know, abiogenesis was such an event. Add to that the improbably emergence of intelligence humans and eventually civilization on Earth, which seems to me to be much more one-off-ish than statistically predictable.

 

 

I'm not sure why you can say abiogenisis is a one off deal, most schools of thought think that abiogenisis will occur naturally when ever conditions allow it. Some even think it occurs on almost all planets as they form only later becoming extinct as conditions change. See the book "Rare Earth"

 

Like Asimov’s speculation, the Drake equation relies on large numbers of event opportunities that have no statistical basis for validity. They are simply saying that because there are so many planet-bearing star systems—“billions and billions and billions” (Carl Sagan)—that it is fair to expect that what happened on this planet will likely happen somewhere else.

 

I happen to agree it makes little sense until we can actually nail down more of the variables, so far we are trying to plot a trend with one point.

 

Hasn’t the SETI experiments already proven one thing? If there were other civilized planets with our level of technology then we should be hearing from them by now. Where are the messages from space that beckon us to communicate with them? We seem to be awfully alone, don’t we?

 

Actually no, SETI pretty much depends on a signal intentionally being beamed to get our attention, when it comes to accidentally detecting an Earth like civilization SETI comes up very short. There is some doubt if we could detect accidental signals from a close as Alpha Centari much less hundreds if not thousands of light years away. Our own radio leakage is now thought to be completely swamped by interstellar static with in just a few light years of the earth.

 

Do all life-bearing planets eventually go through a transition from prokaryotes to eukaryotes? Do they eventually have their own versions of the Cambrian Explosion? Do they have the same kinds of environmental stresses and mass extinctions that we have had here on earth? And will they eventually adopt civilizations to cope with their vicissitudes?

 

Very good question, the Rare Earth theory would suggest no they do not and that single celled prokaryotes may be the main life form in the universe.

 

Frankly, I don’t think we know nearly enough about the course of biological evolution from abiogenesis to civilization to make any judgments on the likelihood of extraterrestrial civilizations. I think the safest assumption is that we are uniquely intelligent and uniquely civilized, no matter how many “billions and billions and billions” of stars are out there.

 

I agree with the first point but assumptions are always a bad idea.

[TheBigDog]

Actually no, SETI pretty much depends on a signal intentionally being beamed to get our attention, when it comes to accidentally detecting an Earth like civilization SETI comes up very short. There is some doubt if we could detect accidental signals from a close as Alpha Centari much less hundreds if not thousands of light years away. Our own radio leakage is now thought to be completely swamped by interstellar static with in just a few light years of the earth.

This is an interesting point. It is even possible that transmissions which make perfect sense to an alien communication system would only look like random static to us. Who's to say that they don't encrypt their messages for privacy, or they use digital encoding in such a fashion that without the knowledge of the protocol it is meaningless. Someone receiving signals from earth, even without distortion, may only be able to read them as random static.

 

Imagine you are sending a picture. Not so long ago the only way to do that was to deliver a hard copy of the picture. Then we got television and we broadcast pictures, but without a technical understanding of the broadcast protocol it would be a huge challenge to turn those radio signals back into a picture. Now we are in the digital age. We send a JPEG into space. Who do we expect to take those ones and zeros and turn them into coordinates and colors unless they know the protocol ahead of time.

 

We are also biased to sight and sound. Other life may have sensory bias that is totally out of context with what we are communicating.

 

But lets throw all that out and look at math. The concepts of math and counting are universal. We often see examples of prime numbers being used to indicate that a civilization has a concept of math. This is logically sound to me. What I don't know is the frequency that we expect to receive these signals. There are algorithms used by SETI which look for patterns, but we are looking for patterns that necessarily make sense to us. If someone was tapping out a series of prime numbers to us what is our realistic expectation of the interval that we receive those signals? We could be throwing out alien communications simply because our cultural assumptions dictate a specific range of time to receive information.

 

And that brings us to the types of waves used for the communications. On earth we still have AM and FM for radio. Amplitude modulation and Frequency modulation are two different beasts when if comes to how you read them. Now digital is taking over and it gets even more complicated as we are not interpreting analog streams anymore, but taking packets of compressed data and expanding them into information. And we have hundreds or thousands of these data streams intermingled in the same range with protocols used for sifting one out from all the rest. I can't imagine trying to make sense of them without prior knowledge of the system.

 

Do all life-bearing planets eventually go through a transition from prokaryotes to eukaryotes? Do they eventually have their own versions of the Cambrian Explosion? Do they have the same kinds of environmental stresses and mass extinctions that we have had here on earth? And will they eventually adopt civilizations to cope with their vicissitudes?

 

Frankly, I don’t think we know nearly enough about the course of biological evolution from abiogenesis to civilization to make any judgments on the likelihood of extraterrestrial civilizations. I think the safest assumption is that we are uniquely intelligent and uniquely civilized, no matter how many “billions and billions and billions” of stars are out there.

As for development of life. I think that our one point of reference makes a strong argument for the likelihood of life being pretty much anyplace capable of supporting it. Everywhere we go on earth we find life. In the heights of the atmosphere we find life. In the depths of the sea we find life. In boiling water around volcanic vents we find life. In caves without sunshine or circulating air we find life. In the driest desert we find life. In the coldest winters at the poles of the earth we find life. Where the oceans batter the shores we find life. After nuclear explosions and irradiation we find life. After the most cataclysmic global disasters we find life. Life as we know it finds a way to survive and to thrive. There is no reason to believe that this is a unique phenomena to our planet.

 

Each individual life form is unique and leads a unique existence. While they may be from a macro perspective very similar to all the others of their species, they are still unique and represent a potential new path for genetic adaptation and diversity. Even something like a horseshoe crab, which appears to have been essentially stable for hundreds of millions of years still has the potential to adapt and evolve given the proper circumstances to drive that happening. The only one-offs are the individuals. It is a statistical impossibility that parallel paths of development do not happen given enough time and opportunity. That is the purpose of the Drake Equation. To try and figure out the odds of parallel development. If you want Earth to be a one off, then simply rationalize the variables to come up with an answer of near zero. But even then all you are doing is satisfying your own preconceptions rather than following a more investigative route.

 

Then there is the practical side of things. What if we found out today that there was life on another planet. It is likely that nobody alive today would live to experience an encounter with that life other than something as simple as tapping out number sequences and then waiting decades for a response of the same or the next numbers. Actually visiting would take centuries even for the closest stars unless there is a fictional leap to faster than light travel in our future. Should we come up with an equation to predict the likelihood of that?

 

Bill

[Larv]

I'm not sure why you can say abiogenisis is a one off deal, most schools of thought think that abiogenisis will occur naturally when ever conditions allow it. Some even think it occurs on almost all planets as they form only later becoming extinct as conditions change. See the book "Rare Earth."

Moontan, I happen to be impressed by the fact that abiogensis remains only an untested theory. I would expect abiogenesis to be high-school lab experiment by now, for the hoopla made over it. This makes me suspicious that abiogenesis did not happen on Earth, but instead in some other place of unknown character. Panspermia offers a vehicular theory for Earth habitation, but it does not account for the original event. I would regard such an occurrence as a one-off event…if we actually knew anything important about it. We certainly do NOT know enough about it to call it a recurring event.

 

And yet there are renowned scientists who make very bold assumptions, such as Stuart Kauffman (in “At Home In The Universe,” 1995, p. 45). I call it his “order-for free-miracle-garden assumption”:

 

There are compelling reasons to believe that whenever a collection of chemicals contains enough different kinds of molecules, a metabolism will crystallize from the broth. If this argument is correct, metabolic networks need not be built one component as a time; the can spring up full-grown from a primordial soup. Order for free, I call it. If I am right, the motto of life is not We the improbable, but We the expected.

Peter Ward (“Rare Earth”) ostensibly makes the same assumption. But I’m not ready yet to make it, not until we learn how abiogenesis actually occurred and reproduce it in the laboratory.

[Moontanman]

Reproducing abiogenisis in the lab will only be practical when we have a lab as big as a planet and millions of years of lab time.....

[Larv]

Reproducing abiogenisis in the lab will only be practical when we have a lab as big as a planet and millions of years of lab time.....

If that is what you think will be required to produce an artificial abiogenesis then you are admitting that abiogenesis cannot be effectively understood.

[Moontanman]

If that is what you think will be required to produce an artificial abiogenesis then you are admitting that abiogenesis cannot be effectively understood.

 

Just because something cannot be reproduced in a test tube doesn't mean it cannot be understood. We have a pretty good handle on star formation and evolution but we cannot make a star in a test tube. Abiogenesis is a complex process, we understand many parts of it, have theories about some of it and small bits of it are still undetermined. You have an unreasonable desire for cut and dried answers, yes/no, right/wrong, white/black, man/eunuch, a great many people think this way, they are called fundamentalists, possibly you should join them for your answers.....

[Larv]

Just because something cannot be reproduced in a test tube doesn't mean it cannot be understood. We have a pretty good handle on star formation and evolution but we cannot make a star in a test tube. Abiogenesis is a complex process, we understand many parts of it, have theories about some of it and small bits of it are still undetermined. You have an unreasonable desire for cut and dried answers, yes/no, right/wrong, white/black, man/eunuch, a great many people think this way, they are called fundamentalists, possibly you should join them for your answers.....

Stars are big and hot and dangerous. Life is small and cool and molecular. You ought be able to do abiogenesis in any pot, once you have the right recipe. After all, it’s only the basic primordial soup you’re brewing there, waiting for those metabolisms to crystallize. I’ll very interested when you get to the part where your molecules invent the genetic alphabet.

 

What does this have to do with the Drake equation? The Drake equation assumes necessarily that abiogenesis is a ubiquitous process. I question that assumption.