Get the class to stand in a circle, all facing the same direction. Hand out cards, events in history, politics, geography, science ..... all these events are inter-dependent on each other. To show what you mean, slowly get the class to sit on the knee of the person behind them. Everyone must work together. Now while they are sitting on each others knees, get them to read off a few quotes. You show how it relates to another topic.... One big happy interconnected world. And they have fun too.