Imagine it like this: If you spin something, the direction of the axis tends to wobble.

这样想一下：如果你旋转什么东西，这个轴的方向将会变化。

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For example, you can try to measure how hard it is to spin this sheet of paper about an axis that is in the center of it.

比如，试着让一张纸绕其中心轴旋转，看看有多困难。

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For the sake of his life, Galileo recanted his views in 1633, admitting that the earth did not spin on its own axis.

为了保住性命，1633年，伽利略被迫宣布放弃日心说，承认地球并不是绕着地轴旋转的。

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One way to think about it, if we want to use a classical analogy, which often helps to give us an idea of what's going on, is the spin of an electron, we can picture it rotating on its own axis.

如果我们用一个，经典的比喻来考虑它的话，这经常会帮助我们建立起一些概念，就是我们可以把电子的，自旋想象是它绕着轴自转。

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In particular, every electron has its own magnetic field aligned with the axis of its spin.

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