1) The phenomenon known as "black holes" occurs when matter is crushed into an infinitely small space, creating a gravitational pull so strong that nothing can escape.

2) The assassination of Archduke Franz Ferdinand of Austria in 1914 triggered the start of World War I.

3) The national animal of Australia is the kangaroo.

4) Mount Everest, located in the Himalayas, is the highest mountain on Earth, reaching a peak elevation of 29,032 feet (8,848 meters).