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On the other hand, we don't understand the theory too completely, and because of this fuzziness of spacetime, the very concept of spacetime and spacetime dimensions isn't precisely defined.

另一方面，我们对这个理论的理解还不是很全面，而且由于时空的这种模糊性，时空和时空维度的概念本身并没有得到精确的定义。

— Edward Witten 爱德华·维特恩