And we can ask all those questions because there has been a revolution in our understanding of what a habitable planet is, and today, a habitable planet is a planet that has a zone where water can stay stable, but to me this is a horizontal definition of habitability, because it involves a distance to a star, but there is another dimension to habitability, and this is a vertical dimension.
我们之所以能够提出这些问题 是因为我们对于“可居住星球”的理解 有了革命性的发展， “适居行星”如今的定义是 一个具有可储存稳定状态水地域的行星， 但是对我来说，这是 可居住性的横向定义， 因为这可以涉及到另一个星球， 其实可居住性 还有另一个维度的定义， 一个纵向的维度。