Why does cutting one wire sometimes take down the whole internet?

1What a network really is

Dots that need to reach each other, and wires between them

You only need two ideas. Watch each one:

Computers and wires

Each dot is a computer; each line is a wire. The whole internet is just dots joined by wires — billions of them, but the idea is this simple.

A message takes a path

A message hops wire to wire to reach the other side. A path is a chain of wires that gets you from here to there. No path = no message.

2Two ways to wire it up

The single road vs the web of streets

Same number of computers — but you can connect them in very different shapes:

One path

The single road

Everyone strung in a line, or hanging off one middle hub. Between two ends there is exactly one way through.

Many paths

The web of streets

Every computer wired to several others. Between two points there are lots of different ways through.

3Your turn — grab the scissors

Tap a wire to cut it, and watch the message find a new way

Here's one web of streets. The message wants to go from the green computer to the amber one. Tap any wire to snip it — then watch how the glowing path reroutes around your cut.

Wires you've cut: 0 · still connected

Keep cutting. How many wires before this message finally has nowhere to go?

4The fair test

Two networks, same number of computers. One random cut each. ✂️

Now a fair fight. Both networks have the same five computers and a message trying to cross from end to end. We'll cut one random wire in each. Guess first — then watch the snip.

Guess before you cut

You snip ONE random wire in each network. Which one keeps every computer reachable?

Why does cutting one wire sometimes break the whole internet — and sometimes nothing?