I'm one of the places where the earth axis intersects its surface.

我是地球旋转轴同地表的交汇之地。

The gravitational effect of the Moon keeps the degree of tilt on the Earth's rotational axis constant.

月球的引力使得地球的自转轴倾斜保持在一定的角度。

But there's something else about the Earth's axis: it isn't exactly straight up and down.

但地轴有些特别，它并不是上下垂直的。

The Earth's rotation helps organize this motion into huge cylindrical rolls that align with the Earth's axis.

在地球自转的帮助下，外核中产生了与地轴平行的滚筒式对流。

Imagine for a moment that the Earth's axis were exactly perpendicular to its orbit, straight up and down.

想象一下，如果地球自转轴与公转平面垂直。

See if you can I.D. me. I'm one of the places where the earth axis intersects its surface.

看你能不能认出我。我是地球旋转轴相交的地方。

As we spread out, a slight shift of the earth's axis Away from the sun cools the planet.

随着人类的分散，地轴相较太阳的轻微偏转，使得地球温度有所下降。

This discrepancy is due to the complications of the earth's orbit being elliptical and the earth's spin axis being tilted.

这种差异是由于地球的轨道是椭圆形的，而地球的自转轴是倾斜的。

Precession, basically is the change in the direction of earth’s axis of rotation.

进动，基本上是地球自转轴方向的变化。

It stabilised the famous tilt, the angle of 23 degrees by which Earth's axis is tilted in relation to its trajectory around the Sun.

它稳定了著名的倾斜角度(23度，地轴相对于绕太阳轨道倾斜)。

The equinoxes occur roughly halfway between those two times, when Earth's axis is pointed 90 degrees away from the sun.

春分点大约发生在这两个时间的中间，此时地轴与太阳呈 90 度角。

Which would explain why summer seems to zip by, except the seasons are a function of the tilt of the earth's axis, not its different distances from the sun.

这就解释了为什么夏天速度移动的飞快，当然是除去地球轴性导致的倾斜从而产生的季节因素，地球与太阳之间的距离也不是原因。

And if we look at the Sun-Earth system from afar we find that the Earth's axis maintains the same orientation regardless of its position in its orbit around the Sun.

如果我们从远处看一下太阳与地球的关系，我们可以发现地球的自转轴始终保持相同的方向，无论它在轨道位置的哪一个地点。

[MUSIC] Instead of being a whole day, the equinox is one very specific moment, when Earth's axis isn't pointing toward or away from the sun at all, which is also when the center of the sun crosses the equator.

而是一个非常特殊的时刻，当地轴根本不指向或远离太阳时，这也是太阳中心穿过赤道的时候。