1) The Southern Ocean surrounds Antarctica and is the coldest and least-visited ocean.

2) The first sound film, "The Jazz Singer," was released in 1927 and marked the transition from silent movies to "talkies."

3) Serena Williams is an American professional tennis player widely regarded as one of the greatest athletes in the sport. She has won numerous Grand Slam titles and Olympic gold medals and has become an influential figure both on and off the tennis court.

4) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.