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Comment by sevenless | Hacker News Reader

I always thought optical SETI makes more sense. With relatively inexpensive lasers we can send an extremely bright message, vastly outshining our sun, to every star within a few thousand light years. Surely that's how you'd say 'We're here' to aliens.

http://seti.harvard.edu/oseti/

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I'm not sure we could hit another star. They aren't stationary, at least not on the timescales needed for communication. We'd probably be ok out a few dozen light-years, but beyond that would require some trek-level 'stellar cartography' to predict both where the target will be in a thousand years and how our outbound light beam will interact with gravity on the way. And the fact that we don't really know where the target star is today but where it was a thousand years ago.

Sending seems a lot more risky than receiving.

Risky for what? Alien invasion? If interstellar travel were that easy or worthwhile they'd be here already, especially what with terrestrial radio broadcasts.

If your argument is that terrestrial radio broadcasts mean we don't need the laser... then why do we need the laser?

Re: interstellar invasion, perhaps not, but hard to rule out the possibility that the response we get to our broadcasts is something like a relativistic projectile.

The universe is a big place and we are a tiny planet. It's very likely we could remain unseen even in a highly active interstellar community. Announcing our presence could have consequences, or not.

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