Pop CSI: How Science Conquered TV

The show has a few rules about the use of math. For starters, Charlie won´t use the same device twice. (Principal-components analysis might be better at profiling houses, but they used it last year.) That means that, after 50 episodes, Charlie´s got a mighty big toolbox-much bigger than any single real-world mathematician would have. â€Most working mathematicians are quite narrow in their focus,†Falacci says. Early in the series, the math advisers pointed out that it would be more realistic if Charlie called in an expert or two each week. But in television, audiences like the show´s problems to be solved by the hero, not some day-player they´ll never see again. â€Charlie has to be a superhero in his breadth of knowledge,†Falacci says.

As a superhero, Charlie often applies mathematics developed for a different problem than the one facing him. Multi-attribute compositional modeling isn´t used for houses. Charlie has to improvise, Heuton says, because there aren´t enough validated crime-solving math applications to cover all the show´s episodes. She argues that such improvisations are in keeping with the spirit of math. â€Mathematics is just a language-a language that´s fundamental and universal-and if you´re smart enough, you can do anything with it.â€

Later in the episode, Charlie determines that all the murder-scene houses are in â€hot zones,†where Megan´s Law predators are prohibited near schools and playgrounds. This finding bolsters the FBI agents´ suspicion that the serial killer´s motive is to punish child abusers (a suspicion they couldn´t confirm because none of the victims had adult criminal records). The math Charlie uses here is actually geoprofiling, Black says, but, cheating the no-repeat rule, they don´t call it geoprofiling on the show.

Geoprofiling has its critics. With data sets from only a few crimes, it´s hard to draw statistically strong conclusions. Numb3rs hears the same criticism from mathematicians. Charlie frequently comes to precise conclusions using scant data.
A related sleight of hand is time compression: Charlie solves huge problems in short order. On CSI, tests come back in hours; in real life, they would take weeks. â€We get bagged on a lot for that,†says CSI executive producer Naren Shankar, possibly the only writer in television with a Ph.D. in applied physics. (Shankar´s first Hollywood job was as a science researcher for Star Trek: The Next Generation.)

â€If you want to mock us, go ahead,†says Hart Hanson, who created Bones. â€In television, we compress 10 steps into one.†To maintain dramatic appeal, writers must distill a story down to its most important events. In real life, lawyers sit and read in silence for hours. Most cops pass the day either making endless phone calls or driving in circles. Marriages can go for years without much in the way of drama. But the mundane details of reality don´t make for good television.

HOLLYWOOD + MATH = EYE-ROLLING EXPERTS

In the middle of â€Killer Chat,†the FBI discovers that the murderer is luring victims to the empty houses by posing as an underage teen in online chatrooms. To cover his tracks, he employs â€onion routing,†a sophisticated real-world hack that uses randomly selected servers to obscure routing information. At this point, McGill wanted Charlie to use a â€trawling algorithm,†a cryptographic net to catch the killer´s true online identity. It´s an idea that has no mathematical basis, says Wolfram consultant Eric Weisstein. It comes straight from the writer´s imagination. Despite the dictum that the math be real, this objection caused Black only minor alarm. He had begun a weeks-long conversation with Caltech computer-science professor Steven Low, who was helping him come up with mathematics that, Black says, â€could plausibly work†as McGill´s trawling algorithm.