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

2) 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.

3) The insurance industry employs a wide range of professionals, including underwriters, actuaries, claims adjusters, and insurance agents.

4) Mountains are formed through various geological processes, including tectonic plate movements, volcanic activity, and erosion.