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Winning the E.T. Lottery
Consul writes "Space.com has a cute story about the statistical probabilities that we have been visited by an alien civilzation. He seems to make a convincing argument."
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Or perhaps the aliens sent life-creating probes to thousands or even millions of star systems.
Imagine if we found that life is unique to Earth, but there are tons of planets out there capable of supporting life. Now we build a probe that will go to one such system. This probe determines what planet in the system has the best chance of supporting life, and it goes into orbit around it. Over time, it launches capsules with increasingly more complex life forms. This is done in conjunction with monitoring of the planet's atmosphere to encourage Earth-like development. We mass-produce said probes, and launch one to each of our neighboring star systems, expanding our definition of "neighboring" as we continue to produce the probes.
Now when we get around to colonizing the stars, we have planets ready for us.
If you read the article, you'd notice that he mentioned it really does not matter at what speed they would travel to us. In order to notice that our planet is generating signals, they would still have to notice and intercept our broadcast trasmissions, which have only been travelling at the speed of light.
Anyone can come up with all sorts of a sci-fi explanations to dispute this (let me try - aliens put a space beacon on any planet, which activates when there is life created, so that's how they knew about us so soon), but overall, the article makes several well-stated and well-supported points.
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Sometimes I feel as though one should need a license to practise maths.
It makes little sense to calculate the probability of something that has already occurred. If we have been visited (and as a self-described space nut, I'll admit I find the possibility positively knee-weakening), then that stands as evidence on its own that our being visited is possible.
I have heard similar arguments for why the end of the human race is very near. The reasoning goes, that since the human population is always growing, it is more probable that I would be born in the 20th century than in any century prior. But wouldn't it then be even more probable if I were born in the 25th century? In fact, the chances of my being born in the 20th century would be vanishingly small. Therefore, it is safe to assume that there will be no people in the 25th century.
You can prove nearly any crazy idea with this kind of "thinking."
"I'm a rocket man / Rocket man burning out his fuse up here alone." - Sir Elton John
It appears, depressingly, that modern physics is telling us that FTL travel is not possible, and never will be.
Actually, our existing understanding of physics suggests several interesting possible approaches to FTL travel. These are already being studied to some extent; time will show whether they're practical or not.
We also have enough gaps in our understanding to leave room for potential methods of FTL travel. We just know that it isn't terribly easy, if it is possible.
I think that is the most likely explanation. No civilizations make routine interstellar trips simply because it is so expensive.
That's one possibility.
Another is that life is uncommon enough that even frequent-FTL-travelling civilizations wouldn't be near enough to us to have found us.
Another is that the active lifetime of civilizations tends to be short enough that nobody happened to be alive (or at least interested in contacting people) during our history to contact us.
Or a combination of the above.
It will be interesting when we finally have enough information to be reasonably sure which is the case.