Black holes remain one of the biggest mysteries of the cosmos even 103 years after physicist Karl Schwarzschild first predicted their existence. Black holes cannot be seen or measured in conventional methods, and until recent developments, remained a hypothetical scenario. In 2015, scientists detected the side effect of two black holes merging together, which seemingly proved right one of the brightest minds of the 20th century – Albert Einstein. Black holes locked into an orbit around one another – binary black holes – will eventually fall towards each other and merge.