Unless: 1) The Drake Equation is wrong and its difficult to detect advanced civilizations. 2) We have detected other civilizations but we haven't recognized t

Unless: 1) The Drake Equation is wrong and its difficult to detect advanced civilizations. 2) We have detected other civilizations but we haven't recognized their signals properly. 3) We have detected other civilizations and the government is concealing it from us. 4) The UFO footage released recently by the Pentagon is proof of detection.