February 1: Space Shuttle Columbia Disaster: The Space Shuttle Columbia disintegrated as it re-entered Earth's atmosphere during its return flight, resulting in the death of all seven crew members onboard.
March 20: Invasion of Iraq Begins: The United States and its allies begin military operations in Iraq to overthrow the regime of Saddam Hussein, citing concerns over weapons of mass destruction.
April 4: SARS Outbreak: The severe acute respiratory syndrome (SARS) outbreak begins in China and spreads to several countries, causing over 8,000 infections and hundreds of deaths globally.
April 15: Human Genome Project Completed: The Human Genome Project (HGP), an international scientific effort, announces the completion of the first draft of the human genome sequence.
July 3: EU Expansion: Ten countries join the European Union, the largest expansion in the organization's history.
August 14: Northeast Blackout: A power outage affects multiple states in the northeastern United States and Canada, leaving over 50 million people without electricity.
October 31: Turkey Earthquake: A magnitude 6.2 earthquake hits the city of Bingöl in southeastern Turkey, causing extensive damage and leaving hundreds of people dead.
December 15: Capture of Saddam Hussein: Former Iraqi President Saddam Hussein is captured near his hometown of Tikrit by United States forces.
Throughout the year, there were also developments in technology, entertainment, sports, politics, and various other fields.