Twitter tells scientists how the world feels

Hate mornings, especially on Mondays? You may be surprised to know that much of the world doesn't share that grumpy feeling.

Twitter shows people are more cheerful in the morning, get gloomier as the day wears on and rebound in the evening, with a peak right before bedtime. They're also happier from December to late June, when days gradually lengthen in the Northern Hemisphere.

Using the micro-blogging site Twitter as a gauge of global sentiment, social scientists studied 509 million tweets from 2.4 million users in 84 countries between February 2008 and January 2010, according to research reported on Thursday in the journal Science.

Bad news, even if it happens to a complete stranger, brings Twitter users down, research by scientists from Cornell University suggests.

Twitter, the five-year-old site that lets users communicate 140-character posts, offers an unprecedented chance to study human behavior and social networks, the scientists said.

Those brief posts get down to the nitty-gritty, showing that Twitter users prefer bacon to sausage and Cheerios to Frosted Flakes, Cornell sociologist and co-author Michael Macy said in a telephone interview on Friday.

"Twitter offers an unprecedented opportunity for social and behavioral scientists to study social behavior and interaction in real time with high temporal granularity -- hour by hour, day by day, over the course of the year -- and to do this at population scale with millions of people all over the world," Macy said.