The idea of messaging to extraterrestrial intelligence (METI) suggests that a possible way to establish contact with civilizations on other planets is to first send transmissions ourselves. The search for extraterrestrial intelligence (SETI) has traditionally followed a passive listen-only mode to detect any alien transmissions headed our way. If everyone is listening and nobody is transmitting, then METI might be the way to attract attention.

But is attracting attention from extraterrestrial civilizations necessarily good? We have no idea if contact with extraterrestrial beings would benefit or harm humanity, or even be completely neutral in its impact. Some scientists are unconcerned about possible risks and suggest that METI transmissions should occur whenever they are viable. Others worry that METI transmissions could expose Earth to significant risk and argue in favor of a moratorium on METI activities.

I recently published a paper titled “Policy options for the radio detectability of Earth” in the Futures special issue on the Detectability of Future Earth. In this paper, I argue that the METI risk problem cannot be conclusively decided until contact with extraterrestrial intelligence actually occurs. This implies that any moratorium on METI activities cannot be based on the requirement for new information, as the only new information that would actually suffice is the actual discovery of alien life. Following from this conclusion, there are three possible policy options for proceeding with SETI and METI:

  1. Precautionary malevolence – alien contact is likely to be harmful, so we should not engage in METI until SETI succeeds.
  2. Assumed benevolence – alien contact is likely to be helpful, so we should engage in METI along with SETI.
  3. Preliminary neutrality – alien contact is unlikely to occur at all, so we may as well do SETI and METI if funds are available.

All three of these policies remain viable options until we actually discover extraterrestrial intelligence and learn the actual risks to humanity. Precautionary malevolence would imply that human civilization should reduce all of its transmission activities so as to minimize its detectability by alien observers. Likewise, assumed benevolence implies that greater transmissions from Earth would increase the chances of contact. But both of these policies are optimistic about the likelihood of contact with alien life. Perhaps a more pragmatic approach is preliminary neutrality, which would remain consistent with business-as-usual on Earth and would not recommend any significant changes to Earth’s future detectability.