Why might the Earth be the only inhabited planet in our galaxy? Out of the planets in our solar system (Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Pluto), Earth seems to be the only one that can sustain life. Also, is the Earth or planets mentioned in the Torah?
From what we know, earth is the only planet that can sustain physical life, however spiritual life is not dependent on the physical properties of earth, therefore it does exist in places besides for this planet. The planets are mentioned numerous times in the oral torah, and in kabbalah.