3. Gravitational Wave Detection (2015) (20/20)

In 2015, scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first-ever detection of gravitational waves, ripples in spacetime caused by massive cosmic events like black hole mergers. Announced in 2016, this groundbreaking discovery confirmed a prediction made by Einstein over a century ago and opened a new window into the study of the universe, allowing astronomers to observe events invisible to traditional telescopes.