When you’re in an unexplored wilderness, you’d better be quiet, because you never know whether there might be dangerous predators lurking. Unfortunately, Earth has not been following this cautionary principle so far: we’ve been broadcasting radio waves into space for more than a century. If there are technological civilizations within a hundred light-years that monitor their sky with radio telescopes similar to ours, then they may already know about our existence. We could hear from them in the future. Our saving grace might be that chemical rockets, similar to those used in the Voyager or New Horizons missions, would take a million years to traverse that hundred light years. And so, we might be out for prolonged suspense before encountering our cosmic neighbors.

If extraterrestrials eventually arrive at our doorstep, the question is: how should we respond? Clearly, interstellar affairs are not an imminent policy concern for any nation at this moment, so there is no international protocol issued by the United Nations for what to do. We should keep in mind that within a million years, humans might reside on the moon, Mars or free-floating space platforms, and each community might choose to respond differently. It is premature to contemplate a global policy long before it is required.

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