So if you think of a shell, you can actually just think of an egg shell, that's probably the easiest way to think of it, where the yolk, if you really maybe make it a lot smaller might be the nucleus.

可以把它想成，个蛋壳，这也许是，最简单的思考办法,蛋黄如果，缩小非常多倍的话,就可以想象成核子。

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