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The Universe to Scale Worksheet
By the end you will: use light-years and the speed of light to compare distances from the Moon to the edge of the observable universe.
A. Explore with the simulation
Use “Jump to” for each stop. Write how wide the view is and how long light takes to cross it.
Stop View is Light crosses it in Earth & Moon Solar System Nearest stars Milky Way Why do astronomers switch from km to AU to light-years as you zoom out?
B. Calculate
Light travels 3 lakh (300,000) km every second. How far does it go in a minute? In a year?
Proxima Centauri is 4.2 light-years away. How far is that in km?
The fastest spacecraft travel at about 190 km/s. How long would one take to reach Proxima Centauri?
C. Think it through
“Looking far away is looking back in time.” Explain with an example.
Answer key (for teachers and parents)
- Earth & Moon: about 12.6 lakh km, about 4 seconds · Solar System: about 134 AU, about 18 hours · Nearest stars: about 33 light-years, 33 years · Milky Way: about 2 lakh light-years, 2 lakh years.
- Numbers in km get far too big to handle. An AU (Earth–Sun distance) suits the Solar System; a light-year suits stars and galaxies.
- In a minute: 18 million km. In a year: 300,000 × 31.5 million s ≈ 9.5 trillion km (1 light-year).
- 4.2 × 9.46 × 10¹² ≈ 4 × 10¹³ km (40 trillion km).
- 4 × 10¹³ ÷ 190 ≈ 2.1 × 10¹¹ s ≈ 6,700 years.
- Light takes time to reach us. We see the Sun as it was 8 minutes ago and Andromeda as it was 2.5 million years ago.
Free to print and share for teaching. Made with the interactive simulation at jugnix.com/simulations/universe-scale.