On this day in 1998, telecommunications companies MCI Communications and WorldCom completed their $37 billion merger to form MCI WorldCom.
On this day in 2001, Historic National Prayer Service held at Washington National Cathedral for victims of the September 11 attacks. A similar service was held in Canada on Parliament Hill, the largest vigil ever held in the nation's capital.
On this day in 2003, in a referendum, Estonia approved joining the European Union.
On this day in 2015, the first observation of gravitational waves was made, announced by the LIGO and Virgo collaborations on February 11, 2016.