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.
Even worse the funds to to the exploration. When I was at JPL we always had funding issues. And that was for planetary exploration.
Actually I don't think they (if they exist) even know we are here.
How do we know we are taking the correct samples?
Most SETI searches ar at the 21cm band. We have international treaties to not broadcast at this frequency at all. So here we are looking for signs of a narrowband signal heralding the fact that intelligent life is not wholly constrained to this little dirt ball at this frequency. Now if any intelligent race develops radio and radio astronomy, they too will recognize the importance of this 21cm band. And they also may instigate a SETI search using this frequency. So here is the question. Would they hear us at that frequency? It is the one that we are not transmitting on at all. I could just see 500 races all looking for each other at the very frequency none of them are transmitting on due to the very nature of the importance of that frequency to the exploration of the universe.
Good one.
One of the many things of radio astronomy I have no clue on is the ability of the telescopes to pick up signals on single planets within a solar system at any given moment. For example, if you point your telescope near a star does it have to be pointed exactly at the spot where a planet is to pick up a signal or do the telescopes have a wide enough signal berth in that area to pick up any signal from the entire expanse of that solar system while scanning one place?
By random sampling. That's why we like to have a random sample, which, of course, we know we don't have in this case. You can actually show mathematically that the "best" sample is a random sample.
But what we have might be good enough.
My hunch, based on doing a zillion inference problems in grad school, is that the sample is good enough right now to at least point the way; i.e., violation of the model assumptions in this regard isn't going to hurt us very much.
I read a couple of articles by astronomers not too long ago that essentially make the same points, and I've been trying to find them so I could quote from them . . . But no luck so far. :-(
Perhaps an occasional ping would be permitted?
We actually have done that with Aricebo. The reply time though is longer than civilization has existed on this planet.
No problem. Just keep good notes, and write legibly. We can hope that the Little Gray Guys are occasionally pinging too.
Except we are not looking for information, modulation or any other encryption/coding schemes. We are only looking for that vary narrow band carrier signal.
Man-made radio signals such as the strongest military RADAR systems radiate 14,000 megawatts into a bandwidth of 0.1 Hz. Even ordinary TV carriers concentrate about half their power in a very narrow band of 0.1 to 1 Hz
He's also assuming that we've never encountered aliens. Much as I hate Van Daaniken if you take his rather bizaar view of the world we clearly have. If Van Daaniken is right (God I hope not, not that the implication bothers me, I just don't like the idea of that pinhead being right about the time of day, much less having his "theories" proven) all of our "supernatural beings" through out recorded mythology and history were actually aliens.
There's also an assumption that were aliens to stop by they'd decide we were worth dealing with at all. Again cosmosological centrism shows us through China's history that's it's entirely possible to go someplace, even a great distance that would be difficult to travel, and decide it was a complete waste of time, go home and never come back.
Finally, he's assuming this empire would develop unopposed, or even want to expand that wide in the first place. Looking at how we've performed in 20th century wars (Patton's 3rd Army being a wonderful example) you could draw a very logical conclusion that a civilization as advanced as our could easily conquer an earth sized planet in just a few decades. The fact that America is not a globe spanning nation with total ownership of the planet does not disprove that America exists; it means that we were opposed and really not into that whole globe spanning empire thing.
This is all an example of assigning experts too much knowledge. No one challenges that Fermi was a brilliant man, within his field. But this assertion of his shows that clearly he lacked understanding of sociology and psychology (much like Einstein with his line, very popular amung liberals, that you cannot prepare for war and peace at the same time; clearly demonstrating his lack of understanding on how to achieve peace by scaring those who would make war against you), not to mention clear misses in understanding how technology advances and the rates at which it happens.
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