科学家们知道：只有在中子撞击原子的原子核时，中子才可能处于游离状态。这种碰撞会改变原子核的运动轨迹。

Scientists know that a neutron is loose only when the neutron hits the nucleus of an atom. The collision changes the path of the nucleus.

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MRI是将患者置于某一强磁场中，该磁场可让患者机体原子核（其运动类似于磁化的陀螺）顺着磁场方向排列。

In MRI, the patient is placed in a strong magnetic field that causes some of his body's atomic nuclei, which act like tiny magnetised spinning tops, to align themselves with the field.

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这就解释了为什么我们不担心，原子核运动起来，因为原子核和电子的质量比约为2000 ？

That is why we don't worry about the motion of the nucleus 1 because the ratio of mass is about 2,000 to one.

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That is why we don't worry about the motion of the nucleus 1 because the ratio of mass is about 2,000 to one.

这就解释了为什么我们不担心,原子核运动起来,因为原子核和电子的质量比约为2000：

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