We use roads to drive about, but imagine someone builds a handy shortcut that everyone uses.  The shortcut works but causes traffic jams which will slow rather than speed up traffic. Analysing the network beforehand might have suggested a different shortcut, or several shortcuts. File photograph: Cyril Byrne/The Irish Times

What do social media, the street outside your door, your blood vessels and the number of people who catch the flu have in common? All involve connect(...)