AcademoSpeed of Light Visualizer
An interactive demo showing how long a signal travelling at the speed of light takes to get across the world
The demo above shows two markers on a map of the world. The markers are connected by a geodesic, which is the shortest path between the two locations. If the Earth was flat, it would be a simple straight line, but since the Earth is round, the geodesic looks curved. The markers can be dragged to any location you wish.
The sidebar contains a button with the title "Send Pulse". This allows you to send a pulse (represented by a yellow circle) at the speed of light from one marker to the other. Below the button, there is some information revealing the distance between the two markers, and the time taken for the pulse to arrive at it's destination, given that the pulse is travelling at 299,792,458 m/s. As you can see, the signals reach their destination in the blink of an eye, even when travelling from one side of the Earth to the other.