1) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.

2) Insurance policies often contain exclusions, which are specific events or circumstances that are not covered by the policy.

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

4) 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.