Whether we are alone in the universe is one of the greatest questions facing humankind.
Because the time it takes for a civilization to emerge and spread across the galaxy is much shorter than the age of our galaxy, one would have expected other, older extraterrestrial civilizations to have reached us by now. The fact that none have been detected in spite of search for extraterrestrial intelligence (SETI) efforts for over half a century 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 remain committed not to disturb us or make their existence known to us.
Here we propose a proactive test of the Zoo Hypothesis. Specifically, we propose to send a message to any extraterrestrial civilization(s) that might be listening stating that we are ready to communicate with them and inviting them to respond. Even though we accept this is unlikely to be successful in the sense of resulting in a response from extraterrestrial intelligences, few would deny the profound importance of establishing contact with one or more extraterrestrial intelligences.