1) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.

2) The universe is estimated to be around 13.8 billion years old.

3) The highest-grossing film of all time is "Avengers: Endgame," which has earned over $2.79 billion at the global box office.

4) The blue whale is the largest animal to have ever existed, with an average length of about 82 feet (25 meters).