The metadata that the National Security Agency collects on all calls in the U.S. is not just what's on a phone bill, as the program's supporters have claimed. Your phone bill lists some of the same things the NSA's collecting — numbers dialed, length of all — but does not list the geolocation of each of your calls. It is that final piece of data — where you made your calls — that tells the government everything about your life. "Nobody's listening to the content of people's phone calls," President Obama said last week. "The only thing taken, as has been correctly expressed, is not content of a conversation, but the information that is generally on your telephone bill," Sen. Dianne Feinstein said on Sunday. "We don't know anything that's in there, we won't search that," said Gen. Keith Alexander, the NSA's director of Cyber Command, at a Senate hearing today. But it doesn't matter. The government doesn't need to listen to your calls. Because it already knows where you are, and that does matter.

In a paper published in Nature's Scientific Reports last year, MIT researchers found that with cell phone call metadata from 1.5 million anonymous people, they could identify a person easily with just four phone calls. As Foreign Policy's Joshua Keating explains, they didn't need names, addresses, or phone numbers. They only used time of the call and the closest cell tower.

"We use the analogy of the fingerprint," said [MIT professor 

Yves-Alexandre] de Montjoye in a phone interview today. "In the 1930s, Edmond Locard, one of the first forensic science pioneers, showed that each fingerprint is unique, and you need 12 points to identify it. So here what we did is we took a large-scale database of mobility traces and basically computed the number of points so that 95 percent of people would be unique in the dataset."

And it's not just that metadata easily identifies us. Where we go and who we talk to tells a story. Mathematician and former Sun Microsystems engineer Susan Landau explained to The New Yorker's Jane Mayer. "If you can track [metadata], you know exactly what is happening—you don’t need the content." As a New York Times editorial explains, metadata can reveal "political leanings and associations, medical issues, sexual orientation, habits of religious worship, and even marital infidelities." Have you ever called in sick — from the beach? The NSA would know. Just check your daily metadata.

Or think, for example, of cell phone metadata showing a senator and her intern were both in the same hotel in the middle of the night. That is exactly how a rogue NSA agent used it once, according to former NSA director Michael Hayen. As The Daily Beast's Eli Lake reports, "Hayden said he remembered a collector who was fired for trying to snoop on his ex-wife overseas." So when Fox News' Brit Hume says, "I don't think there have been any abuses, frankly," he is wrong. The former head of the NSA says so.

In the cancelled sci-fi Fox show Fringe, evil genetically-modified humans from the year 2609 travel back to our time to oppress normal humans and rule our not-yet-polluted-beyond-all-hope Earth. In one episode, the bad guys eavesdrop on human rebels' cell phone calls with an elaborate device that measures the imprint sound waves left on glass. This was dumb. The bad guys did not need technology from 600 years in the future to figure out who or where the rebels were. They did not even need to eavesdrop. They just needed the metadata collected on all of us by the NSA.

It goes without saying that the NSA is not staffed by cruel humanoids who time-traveled from the future. However, the agency's surveillance power is so amazing that writers on a cheesy sci-fi shows failed to anticipate it. And, a week after The Guardian revealed the program, some politicians who are supposed to be in charge of oversight of the program still fail to grasp it. As one of the other NSA whistleblowers, Thomas Drake, writes in The Guardian today: "The problem is that in the digital space, metadata becomes the index for content. And content is gold for determining intent.."

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Top photo by Fire At Will via Flickr. Bottom photo via Fox. Inset diagrams via Nature(A) Trace of an anonymized mobile phone user during a day. The dots represent the times and locations where the user made or received a call. Every time the user has such an interaction, the closest antenna that routes the call is recorded. (B) The same user's trace as recorded in a mobility database. The user's interaction times are here recorded with a precision of one hour. (C) The same individual's trace when we lower the resolution of our dataset through spatial and temporal aggregation. The user's interaction are recorded with a precision of two hours.