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

2) The Tour de France, first held in 1903, is one of the most prestigious and grueling cycling races, covering over 3,500 kilometers (2,200 miles) in three weeks.

3) The study of fossils is called paleontology, and it helps us understand the history of life on Earth and the process of evolution.

4) The Cuban Missile Crisis in 1962 brought the United States and the Soviet Union to the brink of nuclear war during the Cold War.