  Deliberate and unintentional radio transmissions from Earth propagate into
space. These transmissions could be detected by extraterrestrial watchers over
interstellar distances. Here, we analyze the harms and benefits of deliberate
and unintentional transmissions relevant to Earth and humanity. Comparing the
magnitude of deliberate radio broadcasts intended for messaging to
extraterrestrial intelligence (METI) with the background radio spectrum of
Earth, we find that METI attempts to date have much lower detectability than
emissions from current radio communication technologies on Earth. METI
broadcasts are usually transient and several orders of magnitude less powerful
than other terrestrial sources such as astronomical and military radars, which
provide the strongest detectable signals. The benefits of radio communication
on Earth likely outweigh the potential harms of detection by extraterrestrial
watchers; however, the uncertainty regarding the outcome of contact with
extraterrestrial beings creates difficulty in assessing whether or not to
engage in long-term and large-scale METI.
