We all know that the quantum world is weird, but just how weird is it that the future can affect the past?

Indeterminacy is the fact that in quantum mechanics, no matter how much you know about a quantum particle, you can't predict its quantum state until you measure it. Instead, what quantum mechanics provides is the statistical probabilities of a particular state.

This is best summed up by Schrodinger's famous cat in a box, who is in a superposition, being both alive and dead, until the box is opened.

A particle's state is not just unknown, it is truly undetermined until it is measured. It is the act of measurement itself that forces the particle, or cat, to collapse to a definite state.

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