Some exobiologists believe that if there were any other civilizations in the universe, they would probably be much older than ours and would thus have knowledge of radio signals and use them to contact earth.
Osa eksobiolooge arvab, et kui eksisteeriks muid tsivilisatsioone, oleksid need arvatavasti tublisti vanemad kui meie oma ning seega raadiosignaalide ja nende kasutamisega sedavõrd kursis, et saaksid kontakteeruda Maaga.