Whether we are alone in the universe is one of the greatest mysteries facing
humankind. Given the >100 billion stars in our galaxy, many have argued that it
is statistically unlikely that life, including intelligent life, has not
emerged anywhere else. The lack of any sign of extraterrestrial intelligence,
even though on a cosmic timescale extraterrestrial civilizations would have
enough time to cross the galaxy, is known as Fermi's Paradox. One possible
explanation for Fermi's Paradox is the Zoo Hypothesis which states that one or
more extraterrestrial civilizations know of our existence and can reach us, but
have chosen not to disturb us or even make their existence known to us. I
propose here a proactive test of the Zoo Hypothesis. Specifically, I propose to
send a message using television and radio channels to any extraterrestrial
civilization(s) that might be listening and inviting them to respond. Even
though I accept this is unlikely to be successful in the sense of resulting in
a response from extraterrestrial intelligences, the possibility that
extraterrestrial civilizations are monitoring us cannot be dismissed and my
proposal is consistent with current scientific knowledge. Besides, issuing an
invitation is technically feasible, cheap and safe, and few would deny the
profound importance of establishing contact with one or more extraterrestrial
intelligences. A website has been set up (http://active-seti.info) to encourage
discussion of this proposal and for drafting the invitation message.Comment: 16 page