Single Planet Quotes
- Today the human race is a single twig on the tree of life, a single species on a single planet. Our condition can thus only… — Robert Zubrin
- There are too many accidents that can befall life on a single planet. — Stephen Hawking
- I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall… — Stephen Hawking