The most impactful television events of the last 50 years, as measured in a survey conducted by Nielsen and Sony Electronics. The rankings are based on a questionnaire of consumers about events they had watched, if they remember where they were and if they discussed the events with others. 
 
 1. Sept. 11 terrorist attacks (2001). 
 
 2. Hurricane Katrina (2005). 
 
 3. The O.J. Simpson verdict (1995). 
 
 4. The Challenger space shuttle explodes (1986). 
 
 5. Death of Osama bin Laden (2011). 
 
 6. The O.J. Simpson White Bronco chase (1994). 
 
 7. The Japanese earthquake and tsunami (2011). 
 
 8. Columbine school shooting (1999). 
 
 9. BP oil spill in Gulf of Mexico (2010). 
 
 10. Princess Diana’s funeral (1997). 
 
 11. Death of Whitney Houston (2012). 
 
 12. Capture and execution of Saddam Hussein (2006). 
 
 13. Barack Obama Election Night speech (2008) 
 
 14. Wedding of Prince William and Kate Middleton (2011). 
 
 15. John F. Kennedy assassination (1963). 
 
 16. Oklahoma City bombing (1995). 
 
 17. Bush/Gore disputed election (2000). 
 
 18. Los Angeles riots, Rodney King beating (1992). 
 
 19. Casey Anthony murder trial verdict (2011). 
 
 20. John F. Kennedy funeral (1963). ||||| FILE - In this Sept. 11, 2001, file photo, the twin towers of the World Trade Center burn behind the Empire State Building in New York. The Sept. 11, 2001 terrorist attack is by far the most memorable... (Associated Press) 
 
 The Sept. 11, 2001 terrorist attack is by far the most memorable moment shared by television viewers during the past 50 years, a study released on Wednesday concluded. 
 
 The only thing that came close was President John F. Kennedy's assassination and its aftermath in 1963, but that was only for the people aged 55 and over who experienced those events as they happened instead of replayed as an historical artifact. 
 
 Sony Electronics and the Nielsen television research company collaborated on the survey. They ranked TV moments for their impact not just by asking people if they remembered watching them, but if they recalled where they watched it, who they were with and whether they talked to other people about what they had seen. 
 
 By that measure, the Sept. 11 tragedy was nearly twice as impactful as the second-ranked moment, which was the coverage of Hurricane Katrina in 2005. Minutes after the first airplane struck New York's World Trade Center on a late summer morning, television networks began covering the events continuously and stayed with them for days. 
 
 The other biggest TV events, in order, were the 1995 verdict in O.J. Simpson's murder trial, the Challenger space shuttle explosion in 1986 and the death of Osama bin Laden last year, the survey found. 
 
 Sony was interested in the study for clues on consumer interests and behaviors and found "that television is really the grandmother of all the social devices," said Brian Siegel, vice president of television business for the company. 
 
 Going into the study, Siegel said he had anticipated that entertainment events like the final episode of "M-A-S-H" (ranked No. 42), the Beatles' appearance on "The Ed Sullivan Show" (No. 43) and the "Who shot J.R.?" episode of "Dallas" (No. 44) would rank higher. Instead, television coverage of news events made the biggest difference in viewers' lives. 
 
 The Super Bowl is annually the most-watched TV event, with this year's game between the N.Y. Giants and New England Patriots setting an all-time record with 111 million viewers. The memories don't seem to linger, however: the top-ranked Super Bowl Sunday event in Sony's study came in 2004 and had nothing to do with football. It was Janet Jackson's wardrobe malfunction (No. 26). 
 
 Men and women agreed on the three most impactful television events _ Sept. 11, Katrina and Simpson. After that, some of the interests diverged. 
 
 For example, women ranked the 1997 funeral of Princess Diana as the fourth most memorable event, while men put that at No. 23. Women ranked last year's death of Whitney Houston at No. 5, with men judging it No. 21. 
 
 Similarly, the 2003 bombing of Baghdad at the start of the Iraq War was seen as the No. 14 most impactful moment by men, and No. 37 among women. Men were also far more struck by boxer Mike Tyson biting off a piece of Evander Holyfield's ear. 
 
 The passage of time has also diluted some moments once thought as unforgettable, simply because succeeding generations have no personal memory of them. Man's first moon landing in 1969 ranked No. 21. 
 
 Age also made a big difference in the survey. JFK's assassination was the second-most impactful TV event among people 55 and over, while for those between 18 and 34, it was the death of Osama bin Laden. 
 
 Young people also ranked Barack Obama's Election Night speech in 2008 at No. 3, while that didn't move older viewers quite as much (No. 24). 
 
 Simply because of their age, events like the JFK assassination, President Nixon's resignation and the moon landing didn't register at all among viewers 18 to 34. The oldest event to appear in their rankings was the 1980 shooting of John Lennon. 
 
 The study was based on an online questionnaire of 1,077 adults selected as a scientific sample from among Nielsen's panel of people measured for television ratings. It was conducted between Feb. 15-17 this year. 
 
 The study could be a good baseline for future looks at how television impacts viewers, said Paul Lindstrom, senior vice president for custom research at Nielsen. 
 
 "I'd like to see these done on a periodic basis going forward," he said.
– What moments are engraved most profoundly into the minds of television viewers in the past 50 years? Sony Electronics and Nielsen surveyed more than 1,000 adults and found that the 9/11 attacks are the easy No. 1, though OJ Simpson has the distinction of cracking the top 10 twice. The top vote-getters, from AP and the New York Post. 9/11 attacks Hurricane Katrina (2005) OJ Simpson verdict (1995) Challenger shuttle explosion (1986) Death of Osama bin Laden (2011) OJ Simpson's white Bronco chase (1994) Japan's earthquake and tsunami (2011) Columbine school shooting (1999) BP oil spill (2010) Princess Diana's funeral (1997)