Aliens Among Us

摘要

For scientists, few questions inspire as heated a debate as, What is life? You'd think we'd have that one down by now. But it turns out that defining life is really difficult. Go too narrow and it's arbitrary, like you're drawing a line in the sand. Go too broad and it's meaningless, like there's no line at all. A lot of scientists say they would prefer to leave the business of a precise definition up to philosophers.