Personally, I think an answer to the Fermi Paradox belongs in Science, not New Scientist:
So much space, so little time: why aliens haven't found us yet | Science | Guardian Unlimited
... It ranks among the most enduring mysteries of the cosmos. Physicists call it the Fermi paradox after the Italian Nobel laureate Enrico Fermi, who, in 1950, pointed out the glaring conflict between predictions that life was elsewhere in the universe - and the conspicuous lack of aliens who have come to visit.
Now a Danish researcher believes he may have solved the paradox. Extra-terrestrials have yet to find us because they haven't had enough time to look.
Using a computer simulation of our own galaxy, the Milky Way, Rasmus Bjork, a physicist at the Niels Bohr institute in Copenhagen, proposed that a single civilisation might build eight intergalactic probes and launch them on missions to search for life. Once on their way each probe would send out eight more mini-probes, which would head for the nearest stars and look for habitable planets.
Mr Bjork confined the probes to search only solar systems in what is called the "galactic habitable zone" of the Milky Way, where solar systems are close enough to the centre to have the right elements necessary to form rocky, life-sustaining planets, but are far enough out to avoid being struck by asteroids, seared by stars or frazzled by bursts of radiation.
He found that even if the alien ships could hurtle through space at a tenth of the speed of light, or 30,000km a second, - Nasa's current Cassini mission to Saturn is plodding along at 32km a second - it would take 10bn years, roughly half the age of the universe, to explore just 4% of the galaxy. His study is reported in New Scientist today.
Like humans, alien civilisations could shorten the time to find extra-terrestrials by picking up television and radio broadcasts that might leak from colonised planets. "Even then, unless they can develop an exotic form of transport that gets them across the galaxy in two weeks it's still going to take millions of years to find us," said Mr Bjork. "There are so many stars in the galaxy that probably life could exist elsewhere, but will we ever get in contact with them? Not in our lifetime," he added. ...
He gets a different answer from Fermi because there’s no exponential growth. The 8 probes have 8 subprobes, so it’s only 64 probes exploring the galaxy. Fermi assumed the travel of sentient organisms that then launched new exploration from each “residence”, so there were long residence times but there was exponential “probe” growth. Exponential growth conquers all.
Most modern formulations of the paradox assume self-replication of abiologic entities — the probes have the capability to construct copies of each other, so in a few generations there are trillions of probes.
If we find there’s some immense obstacle to self-replication then this result stands. If not the paradox stands. The most common resolution to the paradox is that technologic civilizations do not sustain an interest in travel, so Bjork’s answer is (to me) very enticing — it suggests a more optimistic answer. I’d describe Bjorks’ answer as “self-replicating machines cannot be created within the lifetime of technological civilizations”. So the difficulty of creation would set an upper bound on the lifetime.
The Guardian is misleading about where he published, btw. He published in an online repository, New Scientist just reported on it. This is interesting enough to merit updating my Fermi Paradox page however.
PS. This Slashdot comment is hilarious. The low rating is why I don't usually read Slashdot comments -- the raters are dysfunctional. (Comments are often good, it's the ratings system that's broken)
.. Negative. I find your argument untenable. I am in agreement with the Danish monkey-being. Probabilities of non-human life spreading through the Galaxy and discovering primitive monkey-beings in Sol System are minimal. Probability is on the same order of probability of a F'narthag slime-weasel evolving wings and taking flight. It is also highly improbable that extraterrestrial beings would colonize the pathetic planet Earth and blend into the primitive monkey-being society. They would be forced to hide in internet discussion groups and the tech sector so that they are mistaken for geeks when they display lack of monkey-being social skills....The Slashdot commentators had the same response I did -- ignoring self-replication is nonsensical. The author came up with a silly reason why self-replication wouldn't work; he said the probes interfere with one another. Duh.
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