In fact, the truth is the planets don't follow close orbits at all

事实上行星完全不是按闭合轨道运动
but that the ellipse,

而且这个椭圆轨道
instead of starting out this way and staying this way forever,

不会从始至终保持这个状态
slowly rotates,

它会慢慢地旋转
and that's called the procession of the orbit.

这叫作轨道的进动
And one of the biggest mysteries was Mercury had a procession.

最神奇的事情之一是水星的进动现象
In other words, the orbit was not closing

换句话说轨道不是闭合的
but like a Rosetta Stone it is doing this --

而是像罗塞塔石碑那样
not at this rate but very, very slowly.

只是没有这样的速率而是非常非常慢
The majority of that procession was fully understood

我刚才提到的效应
by the effects that I mentioned to you,

基本解释了进动现象
namely the fact there are other forces on it.

也就是其它作用力的存在