Thomas Hales is a mathematician known for his work in the field of geometry and for solving the Kepler Conjecture. This conjecture, proposed by Johannes Kepler in 1611, concerns the most efficient way to pack spheres in three-dimensional space. Hales proved that the densest arrangement of spheres is the face-centered cubic packing. In addition to his work on the Kepler Conjecture, Hales has contributed to various areas of mathematics, including formal verification and computer-assisted proofs. His approach often involves using computer algorithms to verify complex mathematical proofs, which has influenced how mathematicians tackle difficult problems today.