A light-day from home.
The farthest thing we ever made, in ten drawings. Follow the light: it is the spacecraft. Scroll, or let it roll.
Something we built is about to be a whole day away. At the speed of light.
It left in 1977. It has never stopped, and it still phones home.
It has less memory than a single photo on your phone.
About 70 kilobytes, a tape recorder for most of its life, and a dish that always points back at us. It runs on the warmth of plutonium.
It stole its speed from giants.
Fall towards Jupiter, swing behind it, and leave faster than you came. That is a gravity assist, and the planets only line up for this one about every 175 years.
In 1990 it turned around and took our picture.
From six billion kilometres, Earth is a tenth of a pixel. Carl Sagan called it “a mote of dust suspended in a sunbeam.” At JPL they kept having to replace the print: everyone touched the dot.
How long would it take you to get this far?
Guess first. Then pick a way to travel.
One light-day, travellingIn 2012 it left the Sun’s bubble.
The Sun blows a wind that holds back the thin gas between the stars. Where that wind gives out is the heliopause. Voyager 1 was the first thing we made to cross it.
It calls home with the power of a fridge bulb.
Twenty-three watts when it leaves. Almost nothing when it arrives, nearly a day later. We built dishes 70 metres wide to hear it, at 160 bits a second. Two of its instruments are still on, listening to the space between the stars.
And it carries a mixtape.
A golden record: hello in 55 languages, 27 pieces of music, a kiss, rain, a heartbeat, and drawn instructions for playing it. It should last a billion years.
We are the kind of species that sends a mixtape.
The power runs out in the 2030s. The journey does not. In 40,000 years it drifts past another star, still carrying Bach, Chuck Berry and hello.
Ten drawings. 49 years. One light.
A Lightline film by Bolted.
Five things you now know.
Try to answer each one before you open it. Pulling a fact back out of your head is what makes it stay.
| How far | How far is a light-day? Open |
|---|---|
| How fast | Where did it get its speed? Open |
| The dot | How big was Earth in the 1990 photograph? Open |
| The edge | What did it cross in 2012? Open |
| The cargo | What is on the golden record? Open |
| The format | A Lightline film: one long drawing, one light, the scroll as the camera. Here the light is the spacecraft, and the number that travels with it is the year, the distance and how long its signal takes to get home. |
|---|---|
| How it teaches | A question to open. One idea a chapter. Nothing drawn before it is reached. A guess before the answer. Plain words behind the dotted ones. And the five questions above. |
| The facts | From NASA and JPL. Not to scale: nothing this far apart can be. Sources in LIGHT-DAY.md. |
| The controls | Roll plays it. The chapter bar, 1 to 9 and the arrow keys jump. Space rolls, N opens the director’s notes, G opens every dotted word. |