Sheffield is going to have a happiness clock. All being well – the organisers are negotiating this bit – it will be beamed on to the side of City Hall and the cathedral via an HD projector. Passersby will be able to glance up (or visit happysheffield.co.uk) and tell how happy the city is. Users from elsewhere can enter their Twitter handle on the site for their own happiness reading. The “clock” is the brainchild of researchers at Sheffield University, as part of the city’s upcoming Festival of the Mind.

But can you really hope to measure a city’s happiness? Chris Blackmore, one of the academics behind the #HappySheffield project, hesitates. “Well, I suppose it would be about more than that … Maybe calling it Angry Sheffield wouldn’t have flown as well. But, actually, it is about the diversity of emotional experience.”

The project will collect its data from all tweets known to have come from Sheffield. The display will indicate not only the current mood but plot the emotional map of recent tweets (Blackmore says around 20% of the city’s 570,000 inhabitants use Twitter). “You can put any text through affect-analysis programs and they will give you a readout of how many happy words are in there. Pretty much every word you can think of is emotionally logged,” Blackmore explains. Computers can’t read irony, but Blackmore says that’s not a big problem for the city where he moved as a student in the early 1990s and has never left.

Sheffield has a history of featuring in happiness studies. In 2013, it was named the UK’s happiest city. “That was one of our motivations,” Blackmore says. “To query that, to get underneath it. In some parts of the country, do people use more happy language and how does that map on to the experience of everyday life?”

But will all this talk of happiness, the watchful eye of the clock, make people fret? “Some will think we are forcing happiness down their throats,” Blackmore admits. But happiness, and the jaunty emoji-style readouts of the city’s mood, he says, are just a way into a conversation. He imagines people, “in private, will almost take the next step: ‘I’ve realised there is a big gap between what my Twitter is saying about me and what I think about me, and I know I need to do something about that … to live authentically.’”

Blackmore has spent the past nine months studying the city’s tweets and knows, for instance, that the city is at its happiest between 6am and 8am – “the waking up, the early-morning commute, the first hour or two of the day”.

So after 8am it’s all downhill? That’s so sad. (Analysis of my own tweets suggests I am happy, excited, tired and a bit angry: that sounds like an average day.)

“If you read the unexpurgated Twitter feed from anywhere, it’s really depressing,” Blackmore agrees. Although his feed suggests he is pretty happy, satisfied and just a bit tense, he has started to sound dejected. “People [are] being quite horrible on there, tweeting about the most banal things. But that’s human life, I suppose,” he says, brightening. “In all its glories.”