Twitter is either an indispensible professional and personal tool, or the downfall of humanity, depending on who you believe. But to Scott Golder and Michael Macy from Cornell University, it is something more: an unparalleled source of data. The duo has used the popular social networking site to eavesdrop upon the world’s moods, as they rise and fall throughout the day and across the week. By analysing half a billion tweets from 2.4 million people in 84 different countries, they turned Twitter into a giant global mood ring.

They found that, on average, people wake up in a good mood, which falls away over the course of the day. Positive feelings peak early in the morning and again nearer