1) The speed of a sneeze can reach up to 100 miles per hour (160 kilometers per hour).

2) The Great Wall of China is a UNESCO World Heritage site and one of the most iconic man-made structures in the world. It stretches over 21,196 kilometers (13,171 miles) and was constructed to protect the Chinese empire from invasions during ancient times.

3) Democracy is a system of government in which power is vested in the people, who exercise it through elected representatives. It allows for political participation, freedom of speech, and protection of individual rights and liberties.

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