The Scale of Space

Light-years and looking back in time

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A light-year is the distance light travels in a year: about 9.5 trillion km.
• Sunlight takes about 8.3 minutes to reach Earth. The nearest star is 4.2 light-years away.
• Looking farther away means seeing further back in time.

Steps

1. Sunlight’s journey
2. Light-years
3. A scale model
4. Messages from Voyager
5. A logarithmic journey
6. A star that is gone?