One possibility for communicating across the vast distances of space is the use of radio or other electromagnetic waves. Human civilization already posses the technology to broadcast and receive signals at many wavelengths. If other extraterrestrial civilizations exist in the galaxy, then it is possible that they could develop similar capabilities. Based on this premise, the search for extraterrestrial intelligence (SETI) has scanned the sky for over fifty years now to look for any such signals. Along similar lines, a handful of attempts at messaging to extraterrestrial intelligence (METI) have been undertaken in recent years, with hopes of being picked up by an extraterrestrial listener. The content of these messages has increased in complexity and content, though, which may produce cryptic messages that are disorganized or difficult to decipher.
In a recent paper published in the journal Space Policy, my co-authors Dimitra Atri and Julia DeMarines and I propose the development of a METI protocol in order to guide the construction and transmission of messages to extraterrestrials. A METI protocol would include technical considerations such as the method of signal encoding, message length, and transmission strategy. This protocol would also provide guidelines for the content of messages, which includes limits on culturally-dependent, anthropocentric, or sense-dependent information. This will help ensure that a message into space is more representative of Earth as a whole and may also increase the likelihood that the message is understood by potential listeners.
As a way of testing messages and promoting educational outreach, we will implement an interactive website in which users can attempt to submit or decrypt messages according to a METI protocol. This will allow messages to be tested across cultural borders, which arguably is a minimum requirement for a message that would be sent to unknown extraterrestrial listeners. Such an exchange will also help users of the website to gain insight into cultures other than their own by discovering success or failure at effectively communicating a message to unknown receivers on Earth.