Why the Sky Is Blue

Lab Brief #6

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

The opposite of what you expect is often what happens.

What you'll learn

Air molecules scatter short wavelengths far more strongly than long ones. Blue light is therefore scattered across the whole sky while red passes through. At sunset the light travels further through the atmosphere, so even more blue is removed and the Sun looks red.

Key words

scattering
The redirection of light in many directions by small particles.
atmosphere
The layer of gases surrounding Earth, through which sunlight must pass.

Make a hypothesis first

Predict: what happens if you double the force?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

clear tank or bottle
water
milk
bright torch
dark room

Get ready

⚠️ Safety first

Keep the torch and any electrical items clear of the water.

Step 1 of 4 · Read

Think about what you just learned: say what "scattering" and "atmosphere" mean in your own words before you start.

Step 2 of 4 · Do

Add a few drops of milk to a tank of water and shine a torch through it. View from the side and from the far end, and record the colours you see. Add more milk to lengthen the effective path and note the shift.

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 2

The sky looks blue because air scatters:

How sure are you?😐 maybe

Question 2 of 2

Sunsets look red because the light travels through:

How sure are you?😐 maybe

Mind = blown

🔥 A bolt of lightning is 5 times hotter than the surface of the sun.

Nice work!

You got 0 of 2 right.

All lessons

🎯

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✨ More to explore

🌍 Where you see this in real life: This is why airplanes can fly and why rockets reach space.

🏆 Stretch challenge (try it this week): This week, find one thing in your house that turns one kind of energy into another.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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