Lesson 5 of 6 · Spacetime
Lesson⭐ 30 XP🚀 StarbaseCosmic Microwave Background Radiation
Spacetime.
🎯 Your mission
Learn the rule. Then catch nature using it.
⚡ The twist
Gravity is invisible — but it shapes everything.
Mind = Blown
🌟 The light from the closest star (after the sun) takes 4 years to reach you.
Make a hypothesis first
Before you check: which is closer?
What You'll Learn
The universe is filled with faint microwave radiation, almost identical in every direction, left over from about 380,000 years after the Big Bang when it first became transparent. Its temperature of 2.7 K and its tiny ripples match the model's predictions closely.
Key Words
Tap a word to see its definition.
Steps
Read the explanation above and note the two key terms before you start.
Research the 1965 Penzias and Wilson discovery and write a short account of how they ruled out equipment faults, including the pigeons. Identify what made the signal impossible to explain locally.
Record what actually happened, including anything that did not match what you expected.
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Check Your Understanding
Question 1
1 of 2The cosmic microwave background has a temperature of about:
Where you see this in real life
Every sunrise and every shadow is this idea in action.
Stretch Challenge
Try this in real life this week.
Look at the moon tonight. Notice its shape. Look again in 3 days.
For the dinner table
“If you could visit any planet, which would you pick and why?”
Next Smart Experiment
We'll pick an experiment that matches exactly how you're thinking right now.
Share this experiment
Send it to a parent who's looking for a 10-minute kitchen science win.
Ready?
Cosmic Microwave Background Radiation
Learn the rule. Then catch nature using it.
Full screen — no distractions
Checkout complete lesson on Spacetime for 9th Grade
Get the full Spacetime track as a printable PDF — all lessons, worksheets, and answer keys.