The Risk of Transmitting to Space

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.

Should We Transmit Into Space?

Deliberate and unintended radio transmissions from Earth propagate into space. Deliberate transmissions are intended as attempts to send messages to potential extraterrestrial watchers (known as “Messaging to Extraterrestrial Intelligence”, or METI). Unintended radio leakage includes television and radio broadcasts, cell phone networks, and high-power military and astronomical radars. This radiation gives evidence of our technological civilization to any extraterrestrial watchers.

Do radio transmissions pose a risk and should they continue? I recently published a paper with a team of BMSIS scientists in the journal Space Policy that examines the various benefits and harms that could arise as a result of human transmissions into space. In general, we think that the value of radio communication on Earth today is too large to justify ceasing all radio transmissions in order to reduce the risk of being found by a hypothetical harmful extraterrestrial civilization.

Most deliberate METI transmissions are detectable over much smaller volumes than the radio leakage. These transmissions are either short in duration or use a high bandwidth, in contrast to television carrier waves or high-power radars. These transmissions do not increase the probability of contact with extraterrestrial civilization. Such METI attempts are also valuable for education and public outreach efforts on Earth and for developing scientific groundwork for future METI projects. Given the modest costs associated with METI at low levels of detectability, we think that such projects should continue.

In contrast, high-power and persistent METI projects could have detectable volumes greater than the radio leakage, and would have a greater probability of being detected by any extraterrestrial watchers. The consequences of contact with extraterrestrials are highly uncertain, so we cannot say with confidence whether or not such attempts at METI should proceed. One additional benefit of transmitting messages into space at high power is that they serve a purpose analogous to digital time capsules, preserving the knowledge of human civilization, should our species become extinct. This may provide an additional justification for engaging in METI; however, the cost of maintaining such a long duration beacon must be weighed against the long-term benefits.

Existing governing structures or treaties are currently lacking for METI. Active engagement in long-term METI would benefit from international cooperation in order to accurately represent Earth and humanity and to better understand how to communicate effectively with an unknown observer.