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The problem with Fermi was not the logic, but the tools. Remember this was 1951. The only tool they had was radio astronomy. Radio astronomy can only look for technological life. Not intelligent, technological. If you are not blasting radio into space, in 1951 you are quite invisible.

So if the only purpose of life is to create technological civilization then there is a paradox. However that doesn't seem to be the case. The hominids are a uniquely unsuccessful branch of Earth's family tree. All but one species of hominids has died out (That is us by the way). And we cam within a few hundred breeding pairs after Toba, long before anyone picked up a radio transmitter.

In an earlier post I talked about the lunar lotto. But when Fermi died in 1954 they still thought Luna was a regular moon formed by accretion. It wasn't until they brought rocks back in 1969 that it became obvious that Luna was an irregular moon formed by collision.

Also in 1954 there had been a lot less research into what constitutes intelligence. Intelligent life meant technology. Well now we know that dolphins and whales communicate and have abstract concepts like names (or at least signals that identify an individual), chimps use simple tools. So we now have to draw a line between intelligent and technological. A line Fermi in 1954 would never have considered. You could have a highly developed civilization of squids. Communication, abstract though, use simple tools, but being an underwater race, no fire, no refined metals, and no radio. To Fermi they do not exist.

Finally in 1954 it was assumed that interstellar travel was easier that it turns out to be. This is critical to Fermi's argument because he postulated that if life exists it must colonize the entire galaxy. However in 1950 didn't have a good handle on cosmic rays and radiation. The Van Allen radiation belt wouldn't be discovered until 1958. Cosmic rays were not accurately measure until the year of Fermi's death, four years after the Paradox was proposed. So it might take much longer to travel from one side of the galaxy to the other, and just might not be worth the effort.

Again there is only a Paradox if the only type of life you consider is the kind with radio's and space ships. My definition is a bit broader than that.

But when Fermi died in 1954 they still thought Luna was a regular moon formed by accretion. It wasn't until they brought rocks back in 1969 that it became obvious that Luna was an irregular moon formed by collision.

How primitive are we, where we can't even determine what exactly it collided with, and can only speculate and throw out theories. Yet there are people here who claim there is no other life in the entire universe?

What a hoot.