1) The Great Barrier Reef in Australia is the largest living structure on Earth and can be seen from space.

2) The word "computer" contains three vowels: O, U, and E.

3) The first successful human heart transplant was performed by Dr. Christiaan Barnard in 1967.

4) Oprah Winfrey is an American media mogul, television host, actress, and philanthropist. She is best known for hosting "The Oprah Winfrey Show," which became the highest-rated talk show in TV history, and for her influential role in the entertainment industry.