Why We Always See the Same Face of the Moon

Lab Brief #11

🎯 Your mission

Set it up. Test it. Be amazed.

⚡ The twist

Gravity is invisible — but it shapes everything.

What you'll learn

The Moon rotates once per orbit, so the same hemisphere always faces Earth — tidal locking. There is no permanently dark side: the far side gets just as much sunlight, we simply never see it from here.

Key words

tidal locking
When a body's rotation period equals its orbital period, so one face always points inward.
far side
The lunar hemisphere permanently turned away from Earth, which is lit like any other.

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

open floor space

⚠️ Safety first

Have an adult check your set-up before you start, and tidy everything away afterwards.

Step 1 of 4 · Read

Think about what you just learned: say what "tidal locking" and "far side" mean in your own words before you start.

Step 2 of 4 · Do

Walk one full circle around a partner who stays still, keeping your face towards them the whole time. Notice that you also turned once. Then repeat without turning, and describe what they saw.

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 same lunar face points at Earth because the Moon:

How sure are you?😐 maybe

Question 2 of 2

The lunar far side is:

How sure are you?😐 maybe

Mind = blown

🌌 If you could drive a car straight up at highway speed, you'd reach space in under an hour.

Nice work!

You got 0 of 2 right.

Next: Space Junk and Orbits We Have to Share All lessons

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✨ More to explore

🌍 Where you see this in real life: Every sunrise and every shadow is this idea in action.

🏆 Stretch challenge (try it 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?”

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Why We Always See the Same Face of the Moon

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