The article, she explains, uses rules of probability to conclude that airport screening, which relies on profiling passengers based on ethnicity and nationality, is largely ineffective in predicting who is and isn’t a terrorist. Given these findings, Leah says, "It seems like any kind of screening is a waste of time."

"I don’t think that was exactly the point," Bill says. "The conclusion I came to was that screenings should be proportional to the square root of the likelihood." In other words, as the article explains, "If the profile suggests certain people are 10 times more likely than average to be terrorists, they would be screened only three times, or the square root of 10, more than average."

"What does that mean, though?" asks a social science student sitting next to him.

"When you’re running an airport," Bill explains, "rather than have a list of names of people you detain with the probability of 100 percent, the math suggests that if you were being more systematic with the data you wouldn’t use the numbers directly. Instead, you should modify them based on likelihood and assign people in clumps." He looks around to make sure that everyone is following. "Investigate the probabilities is what the math seems to conclude."

A senior, Oren Vinogradov, has been listening and Joy asks him what he thinks. Oren smiles, "I do music now," he says. But, he immediately offers some airport insight. "Did you know that most of the screenings at the airport are computerized and completely random? It’s very unlikely that you’ll get stopped."

He continues with other airport factoids. Most of the airport rules, like turning off your laptop in flight, are completely unnecessary, but enforced to condition us to respond to commands in an emergency situation. Also, "They’re getting rid of business class," Oren says. "It will just be first and economy classes soon."

Alec quips, "Just like our social classes."

Everyone laughs.

Although this gathering seems like a Simon’s Rock tradition—with all its familiar banter and passionate back-and-forth discussions—it is not. The café just began meeting this year. "This is what an open discussion facilitates," Joy says. "When we talk about science socially, in a way that isn’t absolutely directed, it’s so easy to see just how much our students have to offer." She says she’s meeting students she hasn’t had in class yet, and getting to better know and learn from her own students. Not surprisingly, she says, the kind of conversation, interdisciplinary interest, and investment in the discussions is impressive: "Every week I am blown away."

Despite having an official start and end time, the conversations tend to end when the ideas are exhausted. Sometimes the discussions go on so long the dining hall staff is forced to kick the café out when it’s time to shut down.

It’s approaching the official end point, but still, the group transitions. They’re onto thinking about ocean fertilization. This calls on a question that came up in last week’s café gathering about science and values. The group discussed whether or not scientists have an obligation to ask both whether something could be done and also whether it should be done. Other topics seed—terrestrial bias, human overpopulation, animal tagging, Google maps and the ocean, and logistics of farm waste transport. In the end, the last three remaining readers at the table pick up where the café began, quantum entanglement—this time zooming in on quantum computing.