Louder, we can't hear you

>> Tuesday, February 03, 2009

It seems there's a recent paper by one Reginald Smith suggesting a solution to the Fermi Paradox.1 "Broadcasting but not receiving: density dependence considerations for SETI signals" suggests that:

...it can be possible for many CCs [communicating civilizations] in the same galaxy to never contact one another. For example, even assuming the average CC has a lifetime of 1,000 years, ten times longer than Earth has been broadcasting, and has a signal horizon of 1,000 light-years, you need a minimum of over 300 CCs in the galactic neighborhood to reach a minimum density. For example, if there were only 200 CCs in our galactic neighborhood roughly meeting these parameters, probabilistically they will never be aware of each other. This finding can give pause to both those who predict no other CCs or those who predict a high number of CCs in our galactic neighborhood. Arguing that the lack of contact signifies the lack of CCs may be tempered with the fact that if there is a signal horizon, even a galaxy replete with life may have relatively isolated CCs in the absence of interstellar travel or extremely power signals. On the other hand, high estimates of CCs in our galactic neighborhood does not guarantee that there will ever be contact between them, especially reciprocal.


In other words, if two radio-using civilizations are far enough apart, it's safe to assume their broadcasts will dissipate before they can be detected by the other, so that they will never contact each other.2

Okay.

The main problem with this whole thing, of course, is that while it's an interesting explanation--and one that's a bit less fanciful than some other solutions to Fermi's Paradox3, it's still navel-gazing that basically proves that the Drake Equation is pretty much about pulling numbers out of your ass.

I mean, what Smith's paper really does is, really is sort of tweak the middle variables of the Drake Equation by imagining that instead of an even or random spread of planets, the number of planets (or perhaps the number of planets with life, or with intelligent life, etc.) are spread out over a volume of space so that radio waves from one might never reach another. And that's an interesting solution to the Fermi Paradox, but is it functionally that different from fudging those variables downwards to account for habitable-planet-population density?

I have to be honest: I don't know what to think of the Drake Equation except that I don't think much of it. I'd like to believe that space is swarming with interesting people who we'll eventually meet, sort of, or at least become pen-pals with. But the Drake Equation as a means of guessing how many alien civilizations we can "friend" in interstellar Facebook strikes me as nothing more than an attempt to quantify wishful thinking. I don't need Drake to hope space is teeming with intelligent life, and all the equation really does is force me to assume that the odds are probably lower than I'd like them to be since that's the simplest way to address Fermi's Paradox.

And it's not unwarranted. We're certainly discovering that Drake's fp--the frequency of planets--may be a bigger number than we could have hoped for. We're discovering new extrasolar planets every day and even taking pictures of them. But many of these worlds are beyond-exotic places. We happen to inhabit a Goldilocks planet--a perfect place in a perfect system. And it's possible we have this perfect place because of coincidences that are unlikely to be repeated: the interplanetary bang-up that produced the planetoid we style a moon, for instance, or the presence of a big brother like Jupiter to our rear where it absorbs, shepherds and deflects much of the detritus from the solar system's formation--reducing the number of catastrophic cometary and asteroidal impacts that would otherwise have ended life-on-Earth's long strange trip ages ago.

I want, like Fox Mulder, to believe. But I have yet to be convinced. And navel-gazing like Smith's doesn't quite cut it, though I will hand it to him that he's given us all something interesting to think about in the meantime.





1The Fermi Paradox, if you don't want to click the link to Wikipedia, simply asks why--if intelligent alien civilizations are as common as they seemingly ought to be given the number of stars and planets in the universe--we aren't crawling with alien visitors or awash in their broadcasts?

The reader might also consider the Drake Equation, which the Fermi Paradox is sort of a retort to. There's a link to Wikipedia for the Drake Equation up there, too, but for reference it's:


N = R* x fp x ne x f x fi x fc x L


  • N = the number of civilizations in our galaxy with which communication might be possible
  • R* = the average rate of stellar formation in the galaxy
  • fp = the fraction of those stars with planets
  • ne = the average number of planets that can support life per star with planet
  • f = the fraction of the above that develop life
  • fi = the fraction of the above that develop intelligent life
  • fc = the fraction of the above that develop a technology that releases detectable signs of their existence into space
  • L = the length of time such civilizations release detectable signals into space

2You're already thinking about what Smith briefly acknowledges in his conclusion:

Of course these strict constraints can be circumvented by interstellar travel or permanent automatic beacons.


I don't think Smith should be faulted for simplifying the problem, regardless of any other issues with his article; it's almost a shame he has to state the obvious and there's no way he can cover every scenario--e.g. obviously two civilizations who have peppered their galaxy with Von Neumann machines might have routine contact. Duh.

3E.g. some have suggested a variable--call it "fs," say--to follow fi (fraction of planets to develop intelligent life) representing the odds of a civilization surviving its own technology: one pessimistic solution to the Fermi Paradox being that a number of alien civilizations fail to survive the invention of the atom bomb, or global warming, or some skiffyish scenario like grey goo.

I have to admit that I find those scenarios to be less the cautionary tale they're usually presented as ("What if we, too, end our species before we can introduce ourselves to the universe?" the scenarist usually closes) than an opportunity to imagine horror-SF movies in which hapless spacefarers land in desolate, haunted wastelands or find their ship swarming with some biological or technological plague that wiped out the ancient whatsits. Ideally, such a movie would star Sigourney Weaver and Donald Pleasance if the latter weren't dead and the former some kind of weird scary skeleton-woman who murdered Sigourney Weaver and stole her career. But one can still dream, no?



17 comments:

Jeri Tuesday, February 3, 2009 at 1:36:00 AM EST  

When you mentioned 'become pen pals with aliens' I had a vision of an intergalactic twitter feed. :)

vince Tuesday, February 3, 2009 at 8:55:00 AM EST  

The Drake equation is cool to look at, but it's wishful thinking disguised as science. Given the size of the Universe, I find it difficult to believe there isn't, hasn't been, or won't be other intelligent civilizations in the universe. But there is simply no way to predict if these civilizations exist or, if they do, when/where they exist.

There's two things that I think get missed in the whole "is there life out there" discussion. First is the often unstated assumption that life must meet the requirements of life on earth. On earth, life requires water and is carbon-based. There is no life on earth that we are aware of that doesn't meet, at a minimum, these two criteria. But is there any evidence that life must be carbon-based and must require water? Not that I'm aware of. This is the heart of Rare Earth hypothesis that argues that the circumstances required to develop and support life are so improbable that, if other civilizations exist, they would be few and far between - so few and far between that they are likely to be completely isolated from each other.

The second is the assumption that any radio waves generated by a civilization advanced enough to generate them would contain information that we would recognize as being intelligently-generated. Not understand - simply be able to accurately say "intelligent beings generated this, not known natural processes."

As for the Fermi Paradox, it's an interesting question, but it's also makes the previous assumption. Further, it implicitly equates "absence of evidence" with "evidence of absence."

Arguments concerning the likelihood of the existence of other intelligent civilizations and our ability to detect them rely to a great extent on assumptions that we cannot prove, and may never be able to prove. Worse, given what we actually know versus what we often assume, it's possible that another intelligent civilization would have developed so differently from us that we would not recognize them if we met them.

Nathan Tuesday, February 3, 2009 at 9:42:00 AM EST  

I'll go with Vince's take on this. First of all, we always seem to start with the idea that a "habitable" planet is located in an area a minimum and maximum distance from its star...a hollow sphere surrounding a star (of varying thickness depending on the size, energy, etc. of the star).

But that, as Vince points out, only applies to life that requires water, of life that has similar temperature requirements. We've seen, just on earth, life that exists deep in the sea where light is not a consideration; where temperatures and pressures we couldn't withstand are the norm.

To take Vince's concept a step further, if we encountered life that existed frozen in rock; which never moved or visibly consumed nourishment, and which communicated via decades long transfers of chemicals and elements through geological activity...would we recognize it as life?

(And if we didn't, would we be missing out on a whole lot?)

The existence of planets where sentient life could exist are either fairly limited in number, or astronomically difficult to predict.

Jim Wright Tuesday, February 3, 2009 at 12:29:00 PM EST  

I wouldn't dismiss the Drake Equation out of hand. It's an equation, a mathematical tool - its usefulness is dependent on the numbers that go in. Garbage In/Garbage Out of course, but also remember that the converse is true.

When all the numbers plugged into the equation are guesswork, the result may still be useful as an indicator of how good your guesses are - i.e. as an indicator if you're moving in the right direction. If the numbers you plug into the Drake indicate that every star should have communicating intelligence and yet direct observation indicates this is not so, it tells you something. Either your numbers are off or you're not observing properly (i.e. maybe nobody else uses modulated RF) or both. You need to adjust your numbers or you need to expand your observation techniques. So far the Drake tells us that the probability of intelligence that we can recognize is between 0 and n (which we can be positive is less than 100).

The trick is to determine the value of n to a higher degree of confidence than we so far have achieved.

Up until recently, the numbers plugged into the Drake were pure speculation for the most part. Ten years ago we could not, with any confidence, determine the frequency of planet formation in systems outside Sol. We had one data point upon which to base fp. But as you mentioned in the post - we have now found extra-solar planets, and in fact have found that stars as a general rule are more likely to have planets than not. That gives us a hell of a lot higher statistical confidence upon which to base fp numbers.

However, note that the method used to detect extra solar worlds works best with large, super jovian sized gas giants - the ones least likely to produce an intelligence we can recognize and communicate with. The process is being refined and has detected worlds as small as 2x earth mass. At this point it's speculation to say that because a system has a detected jovian, it is also likely to have a rocky earth-sized world as well (and by extension, that rocky world is inside the star's biosphere).

The process of extra solar planetary detection is evolving rapidly, new tools and techniques are coming online all the time. The fp variable is an aggregate value which breaks down into planetary systems, planetary systems with proper sized worlds, proper sized worlds in the right orbits - around the correct type of star. So far, our ability to refine the overall variable is limited to making a reasonable guess at planetary systems based on super-jovian detection, the rest of the sub-variables are unknowns. However, within the next ten years, it should be possible to fill in the blanks, especially after the JWST comes on-line, and especially now that we've got a science orientated administration.

Now, as Vince mentioned, we only have one type of life to base ne and fi on. However, astronomers are developing the tools and techniques to classify the planets detected via gravitational displacement around other stars. Sooner or later we'll be able to perform spectral analysis and then we'll be able to make more accurate estimates of what those numbers are - i.e. the number of worlds that could produce carbon based life and potentially an intelligence most likely to recognized as such.

Which is the long way around of saying that while currently the actual value of N is a complete WAG, the Drake provides useful guidance for determining what we need to know next, what tools we need to develop, where we need to look.

Refining information such as the RF/information propagation issues postulated in the article you linked also provide useful boundaries for limiting the scope of the search.

The basic Drake Equation is useful as a tool for research development, it is simple and elegant - just as E=mc(2) is. But just as with Einstein's mass/energy equation, there's a whole shitload of math underneath that people often forget about. The difference being that most of the constants and variables underlying E=mc(2) are understood through observation and experimentation. The constants and variables underlying the Drake have barely begun to be validated - which is pretty damned cool. Especially when you confront those who seem to think science has about run its course and we know everything worth knowing.

Random Michelle K Tuesday, February 3, 2009 at 1:56:00 PM EST  

become pen pals with aliens

Dear Beetlejuice,

How are you? I am fine. Today in school we learned about asstroids. Do you have asstroids where you are?

Yesterday my mom caught me putting my brother's GI Joe in the toaster. She was pretty mad, which I thought was totally unfair, because I didn't have anything else to use as the fiery pits of hell. Do they have hell where you are?

OK. The teacher says we have to finish our letters now. Write back soon.

Sincerely,
Nathan

Nathan Tuesday, February 3, 2009 at 2:41:00 PM EST  

Dear Nathan,

Our pits of Hell are Icy, but supremely uncomfortable, nonetheless. Your use of the toaster was inspired and I can have a hit team at your house to take out your mother sometime in the next millennium if you'd like. Please let me know.

Sincerely,

BeetleJuice, Jr.

P.S. your notes take quite some time reaching us and each one will, most likely reach us in our next generation. Fear not. We pass on all previously gained knowledge during gestation, so communication should appear seamless.

P.P.S. I thought G.I.Joe was worshiped on your planet. Please explain his sacrifice.

Eric Tuesday, February 3, 2009 at 3:13:00 PM EST  

Dear Beetlejuice, Jr. (did we do that correctly?),

We were very very excited to receive your message, even if it took us several weeks to decode it and we still don't understand much of it. The Elder Minds tell us that the "Hell" of the Ancient Ones was something like the Roa'otel, into which many of us will enter but none may leave. But they also thought that maybe this Hell that was mentioned was a time, not a place, the time when the Great Fires burned across our world and left behind the Holy Illumination from which (according to the Holy Song Of Songs) we gained our collective soul, our ability to speak and write, and fingers. That confused us, because the Great Fires purged the unfit and the Holy Illumination made us what we are, but the Elder Minds' chitterings often confuse us. Some of us think we might be dumb, but we think it's really the Elder Minds' fault.

As for gijo, we don't know why the Ancient Ones would have worshipped a shapeless blob of green and beige melted hydrocarbons, but then we don't understand why they set themselves on fire, either. Sorry we can't be more helpful.

-Neoroach Collective Consciousness #129,392,037,429.

P.S.

We really liked getting mail, almost as much as we like eating flakes of dead skin! Please write again soon!

Random Michelle K Tuesday, February 3, 2009 at 3:13:00 PM EST  

Dear Beetlejuice,

How are you? I am fine.

Why do you want to send baseball to my house? I think this is what the teacher called cultural disconnect.

I got in trouble again with my mom. She got my brother a new GI Joe after I put his old one in the toaster, and she was mad when I put this one in the blender.

I just wanted to see what a maelstrom was like.

Dad says it's Mom's own fault and she should stop taking me to see that damned preacher.

I don't think Dad should use such naughty words.

Write back soon.

Sincerely,
Nathan

Eric Tuesday, February 3, 2009 at 3:20:00 PM EST  

Oh noes, a temporary animalimy has fractured the space-time contimium! Halp!

;-)

John the Scientist Tuesday, February 3, 2009 at 3:58:00 PM EST  

In order for sentience to evolve, it will have to evolve in a milieu of competing organisms that force one of their number to develop intelligence as a defense.

Intelligence is not going to form spontaneously on some rock. Even if the energy transport mechanism in those organisms is not water (highly unlikely given water's extremely unusual and favorable properties as a solvent), the molecules of life that correspond to proteins in those organisms will have to be quite varied. There are only a few elements that fit the bill, Carbon and Silicon being the chief two, with Carbon far and away the winner in the complexity of compounds that can be made, especially in its ability to incorporate heteroatoms.

Silicon-based life forms would not jerk me out of an SF story, there's still a lot of chemistry that can be done there.

You have to be a really, really good salesman to convince me of Boron or Phosphorous-based life forms. Even more so for Sulfur.

There just ain't much else to build life with.

Random Michelle K Tuesday, February 3, 2009 at 6:59:00 PM EST  

You have to be a really, really good salesman to convince me of Boron or Phosphorous-based life forms. Even more so for Sulfur.

"Night of the Living Farts"

neurondoc Tuesday, February 3, 2009 at 9:24:00 PM EST  

"Night of the Living Farts"

That happens frequently in my house.

Nathan Tuesday, February 3, 2009 at 10:19:00 PM EST  

Dear Nathan,

Tell us more of these farts. They intrigue us. Are they truly malevolent?

Beetlejuice, IV

P.S. I read that Scientist guy's comments. We personally have knowledge of a system where the prevalent life-form is Argon-based. But don't tell him. He seems so confident and we wouldn't want to spoil his day.

John the Scientist Thursday, February 5, 2009 at 11:45:00 AM EST  

Yeah the Scientist guy is pretty sure. If you tell me you know about life from dark matter, I might believe you. Argon? Pull the other one, it's got bells on.

Now if you'd said that you knew of one that was based on a combination of sulphur and phosphorous (Night of the Living Farts That Light Themselves), then I'd believe you.

:p

Eric Thursday, February 5, 2009 at 12:09:00 PM EST  

Oh yeah? Well I have a lifeform from argon for you right here! Booyah! Score! Take that!

Also, there's this guy. He's totally argon.

I win!

John the Scientist Thursday, February 5, 2009 at 12:16:00 PM EST  

Eric, I'm Argon to come after you with an ICP. :p

Random Michelle K Thursday, February 5, 2009 at 1:48:00 PM EST  

Dear Beetlejuice,

How are you? I am fine. My teacher said somebody con-fuh-skated your last message. So I am writing you another letter so you no I didn't forget you.

We have had a lot of excitement at home. Before I could use my brother's GI Joe to see what would happen when the demons with their knife-like talons tormented sinners, Dad and me and my brother moved and we now live in an apartment near the school.

Do they have demons where you are?

Mom has been having sleep-overs with the preacher, and we now go to another church. They have a kids room where we have Action Hero Jesus and his 12 apostles and everything. The preacher there says it is not very polite to talk about Hell. I hope you do not think I was rude in my last letters.

Write back soon.

Sincerely,
Nathan

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