📏 Light-years

Space is so big we measure it with light. A light-year is the distance light travels in one year: about 9.46 trillion km.

• The Moon is 1.3 light-seconds away; the Sun 8.3 light-minutes.
• The nearest star, Proxima Centauri, is 4.2 light-years away.
• Voyager 1, our farthest probe, would need about 75,000 years to get there.
• When you look at a star you see old light — you are looking into the past.