This is the map of the whole course. Today only the ends are lit: a person sends something, and a person receives it. Everything between those two is what we spend the year on.
2
The Hook
One second.You just sent a photo to a friend across town and it arrived in about a second. Nothing about that felt remarkable. So what actually happened in that second? Take a guess before you read on — wrong guesses are genuinely useful here, and you will get this page back in December to see how far you have come.
3
The Idea
A photo does not travel the way a letter does. Nothing physical leaves your phone. What leaves is a description of the picture, converted into a form that can be sent as a signal, copied through machines nobody in the conversation owns, and rebuilt on the other end.
Here is the trip, in the roughest possible terms:
The camera measures light and turns it into numbers
The numbers get stored as a file, and made smaller
The file leaves as a radio signal — Wi‑Fi or cellular
It is broken into pieces that travel separately
The pieces cross a lot of cable and a lot of other people's computers
Your friend's phone puts them back in order and turns numbers back into a picture
Every unit this year explains one step of that trip. By May you will be able to defend every arrow on this board.
You are not expected to understand any of these steps yet. You are expected to notice that there are steps.
4
Try It
Trace it yourself
With a partner, draw the trip on paper. Six boxes, arrows between them. For each box, write your best guess at what is happening.
Rules: no phones, no searching, guesses only. Argue about it. Two questions you must answer somewhere on the page:
If someone cut a cable in the middle while you were sending, what would happen?
Besides your friend, who or what could possibly see this photo along the way?
Keep this sheet. You will redo it in December and again in April.
5
Vocabulary
You only need to recognize these today. Every one gets taught properly later.
computing devicerecognition
A physical thing that runs programs and handles data — a phone, a laptop, a smart watch, the computer inside a car.
computing networkrecognition
Two or more computing devices connected so they can send data to each other.
computing systemrecognition
A group of devices and programs working together to do a job.
6
Think About It
Before you go
Which step of the trip do you think you understand least?
Write one question about this trip you would actually like answered this year.
Bring your question to class — good ones become future lessons.
Sign in first if you want Mr. Muller to see it.
7
Connections
This whole year — every unit fills in one arrow of this diagram.
Next lesson — step 1: how a picture becomes numbers in the first place.
Unit 6 — steps 3 through 5, the part where your photo crosses the planet.
Unit 7 — your second question above. Somebody else can see it, unless something stops them.