The shortest distance between the sun and a planet is called perihelion.

太阳和一颗行星最短的距离叫作近日点。

Aphelion is the farthest orbital point from the sun and perihelion is the closest.

Aphelion（远日点）是离太阳最远的轨道点，而Perihelion（近日点）是指最近的。

The closest point is known as perihelion and occurs around the 3rd of January.

而最近点被称为“近日点”，大约出现在1月3日。

So, at one perihelion pass, one side of Mercury faces the Sun.

所以它第一次经过近日点时，有一面面相太阳。

Then, 88 or so days later, it approaches perihelion again.

然后在88天左右之后，它会第二次靠近近日点。

However, its motion around the Sun is faster at perihelion than aphelion.

然而，它在近日点比在远日点时公转更快。

The second law tells us that the Earth moves fastest when it's closest to the Sun, or at its perihelion.

第二定律告诉我们，当地球在离太阳最近的时候，或者说在近日点，运动得最快。

At the calculated acceleration, the head of the meteor-stream must very soon pass perihelion.

以计算出的加速度， 流星流的头部必须很快通过近日点。

(Laughter) And this is essentially what that clustering in argument of perihelion was telling us.

（笑声） 这基本上就是近日点参数的聚集告诉我们的。

These objects really did all share a common value of argument of perihelion, and they shouldn't.

这些天体确实都具有共同的近日点角角值，但它们不应该如此。