To the Editor: In 1960, an astronomer proposed a mathematical model for determining whether extraterrestrial life exists  It was based on the assumptions that life as we know it could exist only on a planet and that many stars are, like our Sun, orbited by planets  On the basis that there are nine planets in our solar system and one of them has life as we know it, the astronomer predicted that there are as many as one million extraterrestrial civilizations across all solar systems  Yet astronomers to date have not detected even one planet outside our solar system
This indicates that the astronomer' s model is wrong, and life as we know it exists only on the planet Earth
Detecting planets outside our solar system requires more sophisticated instruments than are currently available.