and provided us with the magnetic field that shields us from cosmic radiation. 还为我们提供了磁场，保护我们不受宇宙辐射。

　　It also gave us plate tectonics, which continually renews and rumples the earth. 它还给了我们板块构造，不停的更新地面和使地面褶皱。

　　If Earth were perfectly smooth, it would be covered everywhere with water to a depth of four kilometers. 要是地球完全平坦，到处都会覆盖着4公里深的水。

　　There might be life in that lonesome ocean, but there certainly wouldn't be baseball. 那寂寞的海洋里也或许有生命，但肯定不会有足球比赛。

　　In addition to having a beneficial interior, we also have the right elements in the correct proportions. 除了有个大有好处的内部以外，我们还有合适数量的合适元素。

　　In the most literal way, we are made of the right stuff. 我们完全是以合适的材料组成的。

　　This is so crucial to our well-being that we are going to discuss it more fully in a minute, 这对我们的健康是极其重要的，我们过一会更加充分地讨论这个问题，

　　but first we need to consider the two remaining factors, beginning with another one that is often overlooked: 但我们先来考虑以下剩下的两个因素，首先是我们往往忽略的那个因素：

　　We're a twin planet. 我们是个双子行星。

　　Not many of us normally think of the Moon as a companion planet, but that is in effect what it is. 通常，把月球看成是伴星的人为数不多，

　　Most moons are tiny in relation to their master planet. The Martian satellites of Phobos and Deimos, for instance, are only about ten kilometers in diameter. 但它实际上就是——火卫一和火卫二——直径只有大约10公里。

　　Our Moon, however, is more than a quarter the diameter of the Earth, 然而，我们的月亮的直径是地球直径的四分之一以上。

　　which makes ours the only planet in the solar system with a sizeable moon in comparison to itself 这就使得我们的行星成为太阳系里独一无二的行星，拥有一个与自身相比称得上是很大的月球

　　(except Pluto, which doesn't really count because Pluto is itself so small), and what a difference that makes to us. （除了冥王星，但冥王星其实不算，因为它本身很小）——这对我们来说至关重要。

　　Without the Moon's steadying influence, the Earth would wobble like a dying top, with goodness knows what consequences for climate and weather. 没有月球的持久影响，地球会像个快要停转的陀螺那样摇摇摆摆，天知道会对气候和天气产生什么后果。