1) Robert Downey Jr. is an American actor known for his portrayal of Iron Man in the Marvel Cinematic Universe. He has also starred in films such as "Sherlock Holmes," "Chaplin," and "Tropic Thunder," and has received critical acclaim and commercial success for his performances.

2) The Dead Sea, located between Jordan and Israel, is the lowest point on Earth's surface. Its saltwater is so dense that people can easily float on its surface.

3) The world's largest particle accelerator, the Large Hadron Collider, is located near Geneva, Switzerland, and spans a circumference of 17 miles (27 kilometers).

4) The first graphical web browser, Mosaic, was released in 1993 and played a key role in popularizing the World Wide Web.