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 hibiscus flower is commonly associated with tropical regions and is the national flower of several countries, including Malaysia, South Korea, and Haiti.

4) Egyptian mythology centers around deities such as Ra, Osiris, Isis, Horus, and Anubis. It explores concepts of creation, death, and the afterlife, with elaborate rituals and beliefs shaping ancient Egyptian society. The mythology is richly depicted in temple reliefs, burial sites, and hieroglyphic texts.