Life in the Universe

Abstract

For thousands of years our reflections on possible extraterrestrial life-forms have instinctively focused on beings not unlike those on Earth, and even on the idea of civilisations with which we might some day be able to communicate. If life has indeed begun on other worlds, including those within the solar system, there is nothing to indicate that it should in any way develop along the lines of the Earthly organisms with which we are familiar. So, before embarking upon any discussion on the subject of extraterrestrial life, we must define life.