The document provides an overview of metric and scientific units used in astronomy, including prefixes, fundamental SI units of length, mass, and time. It lists several special units used to measure large astronomical distances and objects, such as astronomical units, light-years, and parsecs. It also gives examples of metric equivalents for units like years, kilograms, and seconds. Finally, it mentions two resources that demonstrate relative sizes of objects in the universe on a scale of powers of ten.