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Comment by mseebach | Hacker News Reader

Why would an alien intelligence randomly throw a beam around so we're only in it for a few minutes? I think I've read that when we do the same, we pick out a likely place, and track that while broadcasting - exactly for this reason: the reception need to be long enough that you can confirm that it's an actual signal and tune to it so you can actually see what it says.

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If it is indeed extra terrestrial, it's possible that it wasn't deliberately broadcast to us.

Exactly, or maybe not broadcast by the dominant players! The speculative possibilities for this are huge - if we assume that the Zoo Hypothesis for the Fermi Paradox is correct (http://en.wikipedia.org/wiki/Fermi_paradox#Earth_is_purposel...) you could theorise that some renegade alien scientific faction tried to communicate with us before being obliterated by the dominant civilisation in our part of the Milky Way.

No proof, but a delicious tantilizing thought :)

Here's my problem with the Zoo Hypothesis:

You know how hard it is for us to find them in all that immense, inconceivable vastness of space? It's probably just about as hard for them to find us.

Space is not indexed. It's not made of octrees. To find something, you have to get within radio signaling range in 3D space, of which there is more than any being smaller than a solar system cannot realistically comprehend. If anything else intelligent out there is also bound to the same dimensions as us, and exists at a scale where they inhabit a planet of any type, there's pretty much no way we should ever know about each other unless we already get each others' radio pollution.

Perhaps space is not indexed - but our system of GPS satellites would seem magical to ancient sailors. We could speculate that if a civilisation has solved some of the problems of interstellar and possibly FTL travel, they may have an analogous system, subspace location beacons (to use Star Trek buzzwords).

With a system like that, marking out a piece of 3D space would be simple enough, like avoiding landing your plane on an island where the natives were less technologically advanced and hostile.

Von Neumann machines, set to disperse and report back, could search the galaxy in a fairly short amount of time - well, a few tens of thousands of years, but that's not inconceivably long for a civilization that would undertake this project.

I'd estimate it's more like millions of years. Our galaxy is (according to Wikipedia) 100000 light-years in diameter, and we live pretty close to the outer edge. Given that those Von Neumann machines would be limited to a velocity of less than c, that means fully exploring the galaxy will take a long time, indeed.

Well that's basically what we did.

http://en.wikipedia.org/wiki/Arecibo_message

Sure if you could have great certainty there was someone on the other side of your transmission then logically I think you are correct, but they might just be swinging for the fences like us.

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