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Mathematics

Compactness in Metric Spaces and Its Consequences

Quick fact

In a metric space, compactness is equivalent to the property that every infinite set has a limit point — a far-reaching generalization of the Bolzano-Weierstrass theorem.

Why this is interesting

You know that every continuous function on a closed interval attains a maximum and a minimum. But why does that work, and what happens when we leave the familiar real line?