Consider this mathematician, with her standard-issue infinitely sharp knife and a perfect ball. She frantically slices and distributes the ball into an infinite number of boxes. She then recombines the parts into five precise sections. Gently moving and rotating these sections around, seemingly impossibly, she recombines them to form two identical, flawless, and complete copies of the original ball.
这是一位数学家。 她有一把绝对锋利的标准刀 和一个完美球体。 她手起刀落将球切分, 并把切片分别装入无数个盒子中, 然后将这些切片 分成完全平均的五份。 通过仔细地移动和旋转这些切片, 她竟然能将这些切片 重组为两个完整无缝的球体, 且与原本的球体完全一致。
This is a result known in mathematics as the Banach-Tarski paradox. The paradox here is not in the logic or the proof— which are, like the balls, flawless— but instead in the tension between mathematics and our own experience of reality. And in this tension lives some beautiful and fundamental truths about what mathematics actually is. We’ll come back to that in a moment, but first, we need to examine the foundation of every mathematical system: axioms.
这个结果在数学中 被称为巴纳赫-塔尔斯基悖论。 这里的悖论不是 因逻辑或证据产生的—— 毕竟它们就像 那些球一样完美无缺—— 而在于数学 与我们现实体验之间的矛盾。 于此矛盾之中,我们能够窥见 一些迷人的基本真理, 从而理解数学的本质。 这个问题先放在一边。 首先, 我们需要检视一下 所有数学系统的基础:公理。
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