General Relativity just turned 100 years old. Quantum Mechanics is 10 years younger. They both enjoy excellent health and, together, have produced a prolific offspring of black holes that populate the Universe, which is also their child. They hold irreconcilable differences and yet, they are condemned to understand each other. At what price?

The talk is based on "Causality constraints on corrections to the graviton three-point coupling”, written with Xián Camanho, Juan Maldacena and Alexander Zhiboedov, JHEP 1602 (2016) 020.