How can we prove the world is really quantum mechanical?

I ALMOST didn’t write this column because I worried that it might give people the wrong impression about quantum mechanics. So let me start by saying that I wholeheartedly believe that quantum mechanics is a correct description of reality on a micro scale. If there are limits to how correct it is, those are likely to involve questions about how to combine quantum mechanics and gravity, which we have so far been unable to do with a testable model.

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