karmaplus:This collapse [of the civilisation of Easter Island] speaks powerfully to the last factor

karmaplus:This collapse [of the civilisation of Easter Island] speaks powerfully to the last factor in the Drake equation. The length of time a civilisation lasts. Imagine there are, and have been thousands or millions civilisations in the history of the Milky Way galaxy. Imagine their lifetimes are short.No matter how they’re distributed in space and time.. They never overlap. And I think this is quite a sobering thought. The reason we have never and will never hear from any other civilisation is because none of them ever last long enough to contact each other. But I don’t think that’s necessarily the answer. I think the story of the Rapa Nui people hints at something else.Their island was the final destination of the human colonisation of Earth. A journey that took us from our origins in East Africa to across the planet in less than 60.000 years. And I think a sufficiently advanced alien civilisation would mirror this process of colonisation.In the 1940s, the mathematician John von Neumann thought about the possibility that we could build self-replicating machines, he called them Universal Constructors. So these would be space probes that could fly out to a solar system, land on an asteroid, or a moon, or a planet, and then mine the resources they needed to copy themselves. In This way von Neumann’s replicating machines could spread across the entire galaxy, just as humans spread across the Earth.Think about how the Polynesians colonised the Pacific islands, they sailed across the ocean, they landed on some uninhabited rock like Easter Island, and they used the resources they found there to make copies of themselves. We call it breeding. Now, modern computer models suggest that such a strategy a would allow an advanced alien civilisation to colonise the entire Milky Way galaxy in only ten million years - the blink of an eye in cosmic time.All this sounds like science fiction, but if they’re possible in principle then you have to construct some kind of argument as to why we don’t see them, and I can’t construct one. It bothers me.It follows that if such an advanced civilisation had existed, we’d know about it. We’d have encountered one of von Neumann’s machines. And I think that suggests that there is only one technologically advanced civilisation in the Milky Way, and there only has ever been one - and that’s us. We are unique.Could it be that we alone have passed through the evolutionary bottlenecks that seem to have prevented civilisations from arising elsewhere? If the answer is yes, we are the only intelligent civilisation in the galaxy, and that makes us indescribably precious and valuableWe are the only island of meaning in an infinite sea of lonely stars. And without wishing to be overly romantic of sentimental about it, that would seem to me to confer on us a responsibility, the responsibility to act together as a civilisation to survive, and, ultimately, to explore those stars.— Professor Brian Cox, Human Universe -- source link

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