Lesson 6 of 10 · Space
The Big Bang
🪐
🎯 Your mission
Run the experiment. Find out what really happens.
⚡ The twist
Gravity is invisible — but it shapes everything.
What you'll learn
Scientists believe the universe began about 13.8 billion years ago in an event called the Big Bang. Since then, space itself has been expanding, carrying galaxies farther and farther apart over time.
Key words
red shift
The stretching of light from a receding galaxy to longer wavelengths, the main evidence that space is expanding.
cosmic microwave background
Faint radiation filling all of space, left over from when the young universe first became transparent.
Make a hypothesis first
Before you check: which is closer?
Say your guess out loud — then find out if you were right.
Get ready
🧰 What you need
- balloon
- marker pen
- string
- ruler
⚠️ Safety first
- Balloon fragments are a choking hazard — keep them away from young children.
Step 1 of 4 · Read
Think about what you just learned: say what "red shift" and "cosmic microwave background" mean in your own words before you start.
Step 2 of 4 · Do
Draw galaxies on a deflated balloon, measure the gaps between three pairs, then inflate it and measure again. Show that every galaxy sees every other receding and that the most distant pair separated fastest — the pattern red shift actually records.
Step 3 of 4 · Observe
Record what actually happened, including anything that did not match what you expected.
Step 4 of 4 · Record
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Question 1 of 3
Question 2 of 3
Question 3 of 3
Mind = blown
🌟 The light from the closest star (after the sun) takes 4 years to reach you.
Nice work!
You got 0 of 3 right.
Next Smart Experiment
We'll pick an experiment that matches exactly how you're thinking right now.
✨ More to explore
🌍 Where you see this in real life: GPS, weather forecasts, and the seasons all rely on this.
🏆 Stretch challenge (try it this week): Find a constellation in the sky. Look it up. Tell someone its story.
👨👩👧 For the dinner table: “If you could visit any planet, which would you pick and why?”
Share this experiment
Send it to a parent who's looking for a 10-minute kitchen science win.
Ready?
The Big Bang
Run the experiment. Find out what really happens.
Full screen — no distractions
Done with science? Try something else
Print the whole Space track
All 8th Grade Space lessons as a printable PDF, with worksheets and answer keys.