 Banach–Tarski paradox

The Banach–Tarski paradox is a theorem in set-theoretic geometry that demonstrates a counterintuitive property of infinite sets. Formulated by mathematicians Stefan Banach and Alfred Tarski in 1924, the paradox states that it is possible to take a solid ball in three-dimensional space, decompose it into a finite number of disjoint non-overlapping pieces, and then reassemble those pieces using only rotations and translations to create two identical copies of the original ball.