Posted on 10/25/2001 9:13:53 AM PDT by RightWhale
Is there obvious proof that we could be alone in the Galaxy? Enrico Fermi thought so -- and he was a pretty smart guy. Might he have been right?
It's been a hundred years since Fermi, an icon of physics, was born (and nearly a half-century since he died). He's best remembered for building a working atomic reactor in a squash court. But in 1950, Fermi made a seemingly innocuous lunchtime remark that has caught and held the attention of every SETI researcher since. (How many luncheon quips have you made with similar consequence?)
The remark came while Fermi was discussing with his mealtime mates the possibility that many sophisticated societies populate the Galaxy. They thought it reasonable to assume that we have a lot of cosmic company. But somewhere between one sentence and the next, Fermi's supple brain realized that if this was true, it implied something profound. If there are really a lot of alien societies, then some of them might have spread out.
Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire Galaxy. Within ten million years, every star system could be brought under the wing of empire. Ten million years may sound long, but in fact it's quite short compared with the age of the Galaxy, which is roughly ten thousand million years. Colonization of the Milky Way should be a quick exercise.
So what Fermi immediately realized was that the aliens have had more than enough time to pepper the Galaxy with their presence. But looking around, he didn't see any clear indication that they're out and about. This prompted Fermi to ask what was (to him) an obvious question: "where is everybody?"
This sounds a bit silly at first. The fact that aliens don't seem to be walking our planet apparently implies that there are no extraterrestrials anywhere among the vast tracts of the Galaxy. Many researchers consider this to be a radical conclusion to draw from such a simple observation. Surely there is a straightforward explanation for what has become known as the Fermi Paradox. There must be some way to account for our apparent loneliness in a galaxy that we assume is filled with other clever beings.
A lot of folks have given this thought. The first thing they note is that the Fermi Paradox is a remarkably strong argument. You can quibble about the speed of alien spacecraft, and whether they can move at 1 percent of the speed of light or 10 percent of the speed of light. It doesn't matter. You can argue about how long it would take for a new star colony to spawn colonies of its own. It still doesn't matter. Any halfway reasonable assumption about how fast colonization could take place still ends up with time scales that are profoundly shorter than the age of the Galaxy. It's like having a heated discussion about whether Spanish ships of the 16th century could heave along at two knots or twenty. Either way they could speedily colonize the Americas.
Consequently, scientists in and out of the SETI community have conjured up other arguments to deal with the conflict between the idea that aliens should be everywhere and our failure (so far) to find them. In the 1980s, dozens of papers were published to address the Fermi Paradox. They considered technical and sociological arguments for why the aliens weren't hanging out nearby. Some even insisted that there was no paradox at all: the reason we don't see evidence of extraterrestrials is because there aren't any.
In our next column, we'll delve into some of the more ingenious musings of those who have tried to understand whether, apart from science fiction, galactic empires could really exist, and what implications this may have for SETI.
For example, it has been shown that the Earth's moon provides a stabilizing effect; without a moon of a given size and distance from Earth, the location of the poles would change every 100,000 years or so. In other words, any life that has developed in a temperate zone may suddenly find itself in a polar zone; thus any life that might begin may not have enough time to develop into a form that can relocate itself unless there is a properly sized moon associated with the planet on which life initiated.
The new factor that needs to be added to the Drake equation is the probability of a properly sized double planet system (which is essentially what the Earth-moon system is). You could argue that this is part of another term in the equation, but the other terms assume that if life can devekop, that it will be sustained. This term points out that while conditions might be favorable for the initiation of life at a given moment, that those conditions must remain favorable for the development of higher species.
We don't know yet, but I have a hunch that we're going to find out that there is a limit to how far away we can go, and for how long. Maybe there's something to that term, "Mother Earth".
An interesting read. (2 pages)
So far the U.S. and the U.S.S.R. made it to outer space. The U.S.S.R. is no more, and the U.S. just became involved in what may soon become WWIII.
Seems to me that those on our own planet tend to self destruct before we get advanced enough to do much space travel.
Would YOU want to spend almost all of your life totally isolated from earth, cooped up in what soon would seem to be a very small and very dull space craft, spending the vast majority of the time drifting through the void of space with nothing interesting to look at?
Go much further out and you are talking about multi-generational voyages. This opens up huge ethical questions. For example, is it ethical to condemn in advance the future generations born during the voyage to have no choice but to continue the mission? Doesn't this become something akin to slavery? Is it fair to condem a human born during the voyage to never having any chance of experiencing life on his or her home planet? What about the problems to which they will inevitably experience when they "return" to a "home" that they have never known? And what about the limited set of prospective mates that the children on the voyage will have? Furthermore, this will be an incredibly risky mission. No matter how much redundancy is built in, no matter how much every possible contingency is anticipated and prepared for, there will always be the risk of one thing going wrong and killing everybody. It is one thing for the original crew to accept that risk and to volunteer. But what gives them the right to impose that risk upon their children? Who would even want to?
It thus seems to me virtually certain that any space exploration beyond this solar system will be undertaken exclusively with robotic spacecraft. The only scenario that I can imagine where humans might travel to other star systems is a one-way voyage of colonization. This would involve a massive fleet of huge spacecraft, and probably multiple fleets. Such would come only after a suitable planet were located by robotic spacecraft, and the chances are that such would be truly rare.
Once such a colony was established, it would essentially be on its own. At a distance of ten or more light years away, whatever communications happened between earth and its colony would necessarilly be quite limited. Possibly a few pages of text each day could be exchanged, much more than that would require an investment in quantities of energy that neither planet could really afford.
And if that is the extent of any exchange between the planets, then one has to start to wonder why earth would even want to mount such a massively expensive colonization venture in the first place. We would be looking at pure cost, no economic exchange that amounted to anything. The only convincing reason that could be suggested for mounting such a venture would be to provide something of an "insurance" policy to assure the survival of the human species should something catastrophic happen on earth. But how many people would want to sacrifice for themselves and ALL their descendants any possibility of living on earth, FOREVER, just to serve as an "insurance policy" for those that stay behind? Life on the new planet would have to offer attractions that would almost unimaginably surpass anything that earth could offer. The opportunity to establish one's own kingdom on an idylic tropical island, perhaps? It would take something of that magnitude to attract any volunteers for the venture.
Even just sending out robitic exploration spacecraft becomes technically problematic. To go out much beyond ten light years or so requires energy supplies that will last for centuries. To expore the farther reaches of the galaxies would require energy sources that would last for millenia. The craft would be too far from stars for most of its voyage to make solar panels an option. The half lives of any fissile materials rules out atomic energy. Massive storage tanks of O2 and H2 for fuel cells or rocket combustion would be an option for voyages up to a few decades, I suppose. However, sooner rather than later one is drawn to the logical conclusion that fusion must be the energy supply of choice. Presuming that the engineering problems can eventually be overcome, this also presumes that we can also eventually locate sufficient extra-terrestrial sources of deuterium and tritium within our solar system, and can economically develop the infrastructure needed to develop these resources both for our own terrestrial use and for the interstellar exloration project.
Then there is the problem of building in not only extreme multiple redundency, but also of developing the science of artificial intelligence to the point where such a robotic spacecraft can become fully self-operating and self-repairing. It is wastefully expensive enough to send a couple of simple little spacecraft to mars and not have them work. For an interstellar exploration project, we are talking about spacecraft that are at least a thousand times more expensive, and probably many tens of thousands of times more expensive. The risk of failure will also be of comparably greater magnitude. It is not likely that we can afford to send out more than a few of these spacecraft just to see the mission fail. Thus, they will have to be engineered for assured success, and that will be very difficult and expensive.
Then there will be the problem of communications between earth and the spacecraft. When it is light years away, it must necessarilly be on its own, and able to control itself and deal with any contingencies. Not only must it carry sufficient energy to accelerate and then de-accelerate as it approaches the target, but also to keep its systems warm and operable, and also to keep up some minimal communications with earth so that we do not "lose" it. Presumably solar panels could be deployed once the craft has entered orbit around its target, but the craft would need sufficient AI competency and robotic skills to fix the inevitable panel that failed to deploy properly, etc. Even with an energy boost from solar power, transmission of data back to earth from a distance of many light years is going to be a slow process. At best, we are probably looking at perhaps one photograph per day, plus a few pages of data. Positioning a network of communication relay nodes in deep space would help a little bit.
Bottom line: Sometime by perhaps the end of this century at the earliest, or perhaps the century after, we might be ready to begin to send the first interstellar exploration robots. We (or our descendents, rather) should start seeing images of the Alpha Centauri system possibly as early as the middle of the next century, if all goes well. Perhaps another dozen or two star systems might have probes sent to them over the course of the next millenium. In the extremely rare possibility that one of the planets explored is habitable, another millenium of intensive follow-up exploration and preparation would insue. The first colonization voyage might take off as early as 2000 years from now, perhaps. More likely, it will never happen.
It's true we don't have a random sample taken from all the stars in our galaxy. But this arm of the galaxy is fairly representative, AFAIK, and we've looked at thousands of stars in the vicinity of the sun. That's a pretty good statistical start, at least when it comes to saying something about the prevalence of advanced civilizations in the galaxy.
See the ca. 1750 British Empire for a counter example. Travel times were measured in months then, true, but there was still incredibly poor communication from, say, India to London. The Governor is on his own...
They were "complex," perhaps, but they weren't what we would consider a technological society. By that I mean the ability to exploit the electromagnetic spectrum, and to use energy sources other than animals, wind, water, and fire. We're the first technological society on earth. Perhaps we're the first in the whole galaxy.
If I live on an island, and I use drums to communicate across the island... how do I try to determine if other life is out there beyond the island? I can either sit quietly and order all drums on the island quiet and wait for years to see if I hear anything... or I can make as big a drum as I can and bang it to hopefully signal others off island and wait for their drum response...
If none comes, I then assume there is no live outside of the island... Obviously this is a false test. Why haven't we detected them? Perhaps they don't exist, perhaps they communicate using technologies beyond our own.. or perhaps our little blue ball in our small uninteresting solar system has not been worth the time to come close enough for us to notice... or perhaps, just perhaps... they were already here long ago, and had an impact in some way on life on earth today....
All are just as valid hypothesis as Fermi's....
But there are a few hundred billion stars in our galaxy! If we've searched a few thousand of them, there could still be a hundred million civilizations in our galaxy, with only a 63% chance of our having seen one to date. If there are only one million civilizations in our galaxy, the chances of our having seen one in a few thousand stars searched is near zero.
Somebody had to be first. The other species won't ponder Fermi's paradox; instead they'll wonder about us, "where the hell did they come from?" ;-)
Now whether it's useful information, I don't know. Probably not, since we cannot do the probabilty calculations yet, precisely because we don't have a random sample. Still my intuition is that the data contain very revealing information, even at this early stage. It's kind of disappointing to me in a way because I used to think the universe was teaming with life, and advanced civilizations were a dime a dozen (and they may still be; we could just be in a dead spot -- literally).
Cheers! (I always enjoy reading your comments.)
Here's what I think:
The limits to empire are not willpower and climate. The true limits are economic. Look at the USSR. What finally did them in was economics. All those resources were there in Siberia, and still are, but distances threw the economic equations out of balance. Even the train system couldn't balance the annual report. Extend the economic equations to interstellar distances and see how willpower has any effect at all.
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