# Distances in Space

Distances to objects in space are very, very large. The nearest star (excluding the Sun), Alpha Centauri, is 41.23 trillion km, or 41,320,000,000,000 km!!

Therefore, astronomers use a unit called a light-year, which is the distance that light can travel in a year. Knowing the speed of light, we can calculate the distance of a light-year.

In this activity, you will use the speed/distance/time equation to calculate the length of a light-year in metres, then use this information to calculate how far away Alpha Centauri is in metres!

**By the end of this resource you will:**

- Have used the speed/distance/time equation
- Have rearranged an equation
- Know that the speed of light is a constant
- Have used the speed of light to determine astronomical distances

**To complete this resource you will need:**

- To read the instructions on this page
- The worksheet
- A calculator