How does a message cross the world in a blink?
Your message does not travel as one piece. It is chopped into tiny packets, each finds its own way across the planet, and they snap back together at the far end. No one is steering the whole trip.
Your message does not travel as one piece. It is chopped into tiny packets, each finds its own way across the planet, and they snap back together at the far end. No one is steering the whole trip.
You send a message, and a heartbeat later it is on a screen on the other side of the world. It crossed oceans and continents and dozens of computers to get there. The astonishing thing is how. It did not travel as one neat letter. It was torn into pieces first.
Cut it into packets
Before your message leaves, it is chopped into many small pieces called packets. Each packet is stamped with the address it is going to and a number saying where it belongs, packet one, packet two, packet three. Then they are let loose, and here is the surprise: they do not have to travel together, or take the same road.
Passed hand to hand
The internet is a vast crowd of computers, called routers, each connected to a few neighbors. A packet arrives at a router, which glances at the address and passes it to whichever neighbor is a step closer to the destination. That neighbor does the same. Hand to hand, hop by hop, the packet makes its way across the world, and no single computer ever knows the whole route. Each one only knows the next step. Your different packets might take different paths, and that is fine. At the far end they are put back in order by their numbers, one, two, three, and your whole message appears.
No one knows the whole route. Each computer only knows the next step.
Why it was built this way
It would be simpler to have one master computer directing all the traffic. But then, if that master ever failed, the whole world would go dark. So the internet was built with no boss on purpose. Every router only has to know its own neighbors. If a road floods, packets just flow around it. This is why the internet is so hard to break: there is no single heart to stop. It keeps working because no one part is in charge of all of it.