1) The concept of sovereignty refers to the supreme authority and power of a state to govern itself, make decisions, and control its own territory without interference from external forces.

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

3) The Olympic Games, originating in ancient Greece, were revived in 1896 and are now held every four years, bringing together athletes from around the world.

4) The World Wide Web, developed by Tim Berners-Lee in 1989, revolutionized the way information is accessed and shared on the internet.