In this online interactive challenge, learners choose items to represent the Earth or solar system, then determine other items to represent the Moon, or Milky Way based on their relative size. The question mark button in the bottom right corner provides learners with useful background information and definitions like "What is a planet?" Learners can also see relative distances by using an online map and typing in their own addresses. Use this activity to introduce learners to elements of the universe (planets, moons) as well as size and scale. The activity also features several informative videos.