Mathematics
Set Theory
Quick fact
Set theory reveals that the set of all real numbers is much larger than the set of all natural numbers—even though both are infinite. This was a groundbreaking discovery by Georg Cantor in the late 19th century.
Why this is interesting
You've probably grouped objects into collections before—like your favorite books or a bag of groceries. But what happens when you try to compare the size of two infinite collections, like all even numbers and all whole numbers? Are they the same size? Set theory provides the surprising answer.