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.
That may not be a problem a couple of billion years from now. Our galaxies are on a collision course. In 2-3 billion years the MW and Andromeda will be one mega galaxy.
That, and the second-hand cosmic dust.
Well said. However most SETI searches are not looking for the information, they are looking for that very narrowband CW carrier that contains most of the energy. I am fully aware of spread spectrum suppressed carrier communications, but Radar and other such RF emanations will still retain that carrier.
Sure it does. Nobody's talking about decoding the suckers. If you find a radio-bright planet, it's a civilization. Planets and stars are naturally pretty dim in the radio bands, that's why we're able to make use of them.
I understand the sentiment, but this is only true under certain strict conditions. Systems that have built-in error correction and fault tolerance (like our brain), can be slowly migrated to new hardware via incremental component replacement, using the built-in error correction and fault tolerance facilities to "recover" bits of the brain on new hardware. Eventually, you could be completely migrated to artificial hardware without interrupting your normal thought patterns or even really copying yourself in the conventional sense. Much like how on high-end fault-tolerant hot-swappable servers you can pretty much replace the entire machine while it is running, as long as you do it component at a time.
I don't think anyone is looking for radio-bright planets.
In any case, this falls under the same reasoning. A civilization that is maximizing its use of the EM spectrum isn't going to look "radio-bright". Efficient use means lower power and much wider spectrums for a single channel. It also means much higher frequencies. Most new technology long-range RF links use less than one watt of power, and even satellite is hopping on board. The days of the old C-band transmitters and high power microwave links is fading. Which is wonderful, as most of that technology really sucks from an efficiency standpoint. It is probably safe to assume that any other advanced civilization will follow a similar trajectory towards increased bandwidth and efficiency in their communication infrastructure as well.
I wonder if this is a legitimate way to look at things: Imagine a caveman who knows absolutely nothing about mathematics or mathematical logic; i.e., he is totally incapable of rigorous deductive and/or inductive reasoning (therefore, any conclusions he reaches are based only on his eyeballing of the data, and not on his ability to derive any logical consequences).
Now, I believe if you gave this caveman a sample of several hundred positive integers selected randomly from the first, say, 1015 positive integers (far more than the number of stars in the galaxy), and he were willing to stick out his neck for his hypercritical caveman buddies to lop off his head if he is wrong about anything, he would absolutely be able to make a whole bunch of valid conjectures about the first 1015 positive integers, indeed, about all integers in general.
That's the power of sampling. It doesn't hurt us one bit that our sample is almost vanishingly small in comparison to the larger population. The only thing that matters is, is our sample representative? That's all I'm saying.
Our SETI data constitutes a very small sample relative to the larger population. But it doesn't matter. We can live with that. The only question is, is the data representative? I think there is a good chance the data are representative.
Make sense, or nonsense? :-)
1: Is there a random chance of life, or does it arise only from divine inspiration?
2: If the answer to (1) is randomness, how large is the Universe?
If the answer to 1 is divine inspiration, we will each have to look to our Creator for the answer to the great question "Are we alone?". If the answer is that life arises at random intervals, then question 2 tells us all we need. Remember, in an infinite universe, the least likely thing happens an infinite number of times.
The formulas assume random generation of life, of course. They also seem to be either assuming a finite universe, only considering a part of an infinite universe, or only considering likelihood of contact in a given time frame.
This is essentially a case study of trying to predict what an alien civilization may do based on our current understanding of science and historical development. My speculation is that a highly advanced civilization would likely operate under different constructs than us because of their success in solving problems that we have yet to even contemplate. Kind of like our own development over the centuries. But just because our only very recent attempts to pick up ET signals have not yielded results so far does not mean that intelligent ET life does not exist or we won’t detect their signals in the future. With any luck, people like the Radio Astronomer with ever more sensitive equipment and detection techniques will one-day pick out ET signals from the noise of space. Fermi's arguments are too one dimensional to take seriously.
I would wager my life savings that we DON'T have a billion years, or even tens of millions of years, to work with. If a large comet or asteroid doesn't cause a mass extinction before then, an all-out war almost certainly will.
This kind of explanation for the Fermi Paradox has been considered. It may be that some aliens are guided by the Prime Directive, and they won't interfere with us. But in a galaxy of thousands -- or perhaps millions -- of intelligent species, all it takes is one rogue culture to breach the protocol and go out conquering. One species can occupy the galaxy in a relatively short time, even if each "hop" from one star to the next takes centuries. Once a species' expansion begins, it's surprisingly rapid. The occupied sphere of colonized space grows very rapidly (again, relatively speaking). There's been time for the galaxy to have been colonized many times, by a whole succession of species. So the Fermi Paradox is still very valid.
My implicit assumption in this is that the "protecting" civilizations are substantially more advanced than the "conquering" kind and thus able to control them or if necessary destroy them. Perhaps by design of God a natural hierarchy like this exists to protect emerging life forms.
If they aren't afraid of us, maybe they ought to be. In spite of our ludicrously short lifespans, we are mighty beings.
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