Mathematics — Introduction to Lebesgue Outer Measure + 5 more topics

You know how to measure the length of an interval, say $[a,b]$, which is simply $b-a$. But what about more complex sets? What if you have a set that's a union of many disjoint intervals, or even something much stranger like the Cantor set? Lebesgue outer measure, denoted $\mu^*(E)$, gives us a way to assign a size to any subset $E$ of the real numbers.