1) The Internet of Things (IoT) refers to the network of physical devices, vehicles, appliances, and other objects embedded with sensors, software, and connectivity.

2) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.

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

4) The United Nations (UN) is an international organization founded in 1945 with the goal of promoting peace, security, and cooperation among nations through diplomatic and political means.