Einstein published his Theory of General Relativity on November 25th, 1915, in which he also predicted the existence of gravitational waves. In 1974, physicists discovered two neutron stars orbiting each other, getting closer and closer in a way that Einstein predicted would happen. Despite this discovery, it wasn’t until September 15th, 2015 that scientists were finally able to detect the presence of actual gravitational waves, when LIGO’s instruments were upgraded and became more sensitive. Finally, 72 days shy of exactly 100 years, Einstein’s theory was verified.