But one should remember that this type of search is gaining speed in an exponential fashion, and that particular technical fact allows a crude estimate of when SETI might pay off. If we take — for lack of a better estimate — Frank Drake's opinion that there might be 10,000 broadcasting societies in the Milky Way, then we clearly have to examine at least one [million] – 10 million stellar systems to have a reasonable chance of tripping across one. That goal will be reached in the next two decades, but certainly not in 2020," Shostak said.但人們應該記住,這類蒐索正以指數級的速度增長,而且特定的科技事實允許粗略估計SETI可能在什麼時候獲得回報。如果我們接受弗蘭克·德雷克(Frank Drake)的觀點,即銀河系可能有10000個廣播社團,那麼我們顯然必須研究至少100萬到1000萬個恒星系統,才能有合理的機會穿越其中一個。這一目標將在未來20年內實現,但肯定不會在2020年實現,”肖斯塔克說。