It's a beautiful thing to watch people tweet. Especially when you try to figure out what they're tweeting about, how they feel, and where they're tweeting from then put that all on a map and animate the changes over time.

Researchers from Northeastern University and Harvard College recently built a pretty and captivating visualization of U.S. Twitter users' moods, as determined by sentiment analysis. You can watch two days worth of tweeted moods in this video:

Watching the cartogram pulse as it indicates the proportional volume and sentiment of tweets is probably more interesting than the researchers' conclusions about their data: people are happier on weekends than weekdays; West Coast happiness trends are usually about three hours after East Coast happiness trends. Still, it's neat to learn that Thursday evening aka just about the time I'm posting this is the time of the week Twitter users tend to express the most negative sentiment.

Meanwhile, over at Betaworks, they've just posted a visualization of the record-setting sustained volume of tweets from around the world during the World Cup. There's no sentiment analysis here just counting of relevant hashtags but you can see the volume of tweets corresponding with the occurrence of games that people in a country are interested in.

People seem to tweet less about being frustrated than being triumphant; for the championship game, Betaworks noted an immediate lack of traffic in the Netherlands after losing while the attention in Spain persisted through the next morning. Or it could be that disappointed tweeters just left off the proper hashtag formulation when lamenting their team's loss.

These aren't the first Twitter geography-plus-time visualizations videos, of course. Here's one from last year that maps tweets with the words just landed and just arrived in:

Just Landed 36 Hours from blprnt on Vimeo.

Here's another of tweets from people who were pleased about Barack Obama's inauguration. And here's one from the New York Times depicting tweets during the Super Bowl. (Those two aren't embeddable, so you'll have to click through.)

Perhaps the data geeks who made these were too busy thinking about the visuals, but for some reason or another none of them include a soundtrack. So it's up to you to put some trippy music on, chill out, and watch the Twitter visualizations.