The Speed of Light in Space

Lab Brief #1

🎯 Your mission

Master the concept. Use it tomorrow.

⚡ The twist

The light you see now started its trip a long time ago.

What you'll learn

Light from the sun takes about 8 minutes to reach Earth. A light-year is the distance light travels in one year—about 9.5 trillion kilometers.

Key words

light-year
A unit of distance, not time: the roughly 9.5 trillion kilometres light covers in one year.
light travel time
The delay between light leaving an object and reaching the observer, which means every image of space shows the past.

Make a hypothesis first

Guess: how big does that look from here vs. from there?

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

Step 1 of 4 · Read

Think about what you just learned: say what "light-year" and "light travel time" mean in your own words before you start.

Step 2 of 4 · Do

Calculate the light travel time to five objects, from the Moon at 384,000 km to Proxima Centauri at 4.2 light-years, and tabulate how old each image is when it reaches your eye. Mark which of them could show an object that no longer exists.

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

A light-year is a measure of:

How sure are you?😐 maybe

Question 2 of 3

Sunlight takes about 8 minutes to reach Earth, so the Sun you see is:

How sure are you?😐 maybe

Question 3 of 3

One light-year is roughly:

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 3 right.

Next: Nebulae: Where Stars Are Born 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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