“Don't burn any bridges.” “Put a sock in it.” So many figures of speech evoke actions that, while physically possible, are not always good ideas. Others are harder to pin down. We may unsympathetically tell someone to cry us a river, but could they really do it? That’s what students at the University of Leicester decided to find out. They published their results this month in their school’s Journal of Interdisciplinary Science Topics.

These days, the words “cry me a river” are common parlance. But unlike many idioms, this one has a clear origin: a songwriter named Arthur Hamilton. Hamilton was working on a new tune in the early 1950s and wanted to evoke a certain vibe (bitter), but he needed the right words.

“I had never heard the phrase,” he told the Wall Street Journal in 2010. "I just liked the combination of words … Instead of 'Eat your heart out' or 'I'll get even with you,' it sounded like a good, smart retort to somebody who had hurt your feelings or broken your heart."

At first, the song seemed destined for failure; no fewer than 38 artists refused to record it. But in 1955, jazz-pop singer Julie London took it on, and it took over the charts. Since then, it’s been covered hundreds of times, and the phrase entered the American vocabulary. "Its general use as a put-down phrase has continued to delight and amaze me," Hamilton said. "Whenever my wife and I are watching a film or TV show, and the phrase is used, we laugh and gently punch each other." 

It must have crossed the pond, too, because two students at UL’s Centre for Interdisciplinary Science decided to put it to the test.

Leah Ashley and Robbie Roe started by identifying the shortest river in the world, in order to give their theoretical weepers the best chance of meeting the minimum tear production requirement. That title belongs to Montana’s Roe River, which is just 201 feet long and discharges between 156 and 193 million gallons of water per day. 

By comparison, the average human tear has a volume of 0.0062 milliliters. Ashley and Roe quickly realized that there is no way a single person could cry even the tiniest river. The entire of population of Earth couldn’t even do it, even if we were all really, really upset at the same time.

What about something a little smaller, like an Olympic-size swimming pool? That’s something we might be able to manage. A regulation pool, the authors write, is 50 x 25 x 2 meters, with a capacity of 2,500,000 liters. If each of the roughly 7.4 billion people on this planet cried 55 tears apiece, we could fill up that pool together, in a weird, sad triumph of international cooperation. 

Cheryl Hurkett, the authors’ instructor, was delighted with their paper. “I am always pleased to see my students engaging so enthusiastically with the subject,” she said in a press statement. “I encourage them to be as creative as possible with their subject choices as long as they can back it up with hard scientific facts, theories, and calculations!"