Light Travel Time Worksheet
Goal: Use the speed of light to describe distances in the solar system and beyond, and explain why seeing far away means seeing the past.
What to do
- Check that Distance unit is set to Astronomical units (AU). Press each of the three presets and record the readouts.
- Type 5.2 into Distance (Jupiter’s distance from the Sun) and record the readouts.
- Change Distance unit to Light-years and type 4.24 (Proxima Centauri, the nearest star after the Sun). Record the readouts.
Record your results
| Setting | Light travel | In minutes | In years |
|---|---|---|---|
| Sun to Earth (1 AU) | |||
| Earth to Moon (0.00257 AU) | |||
| Sun to Neptune (30.18 AU) | |||
| Sun to Jupiter (5.2 AU) | |||
| Proxima Centauri (4.24 light-years) |
Questions
How long does sunlight take to reach Earth? Give your answer in seconds and in minutes and seconds.
Predict how many minutes sunlight takes to reach Jupiter (5.2 AU), then check with the lab.
If the Sun suddenly went dark, how long would it take people on Earth to notice? Explain.
Radio signals travel at the speed of light. About how long does a message take to reach a spacecraft near Neptune? Why can’t engineers steer it live?
The Moon is about 1.28 light-seconds away. Is a light-second a unit of time or of distance? What about a light-year?
Light from Proxima Centauri takes 4.24 years to reach us. When you look at it, are you seeing it as it is today? Explain.
Free from The Astronomy Lab · theastronomylab.com · MS-ESS1-3: Analyze and interpret data to determine scale properties of objects in the solar system.