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

2) Ryan Reynolds is a Canadian actor, producer, and entrepreneur known for his roles in films such as "Deadpool," "The Proposal," and "Detective Pikachu." He has gained recognition for his comedic timing and charismatic performances on-screen.

3) The President of the United States serves as the head of state and the head of government, responsible for leading the executive branch and representing the nation domestically and internationally.

4) The speed of light is approximately 299,792,458 meters per second.