When two senators warned that the Patriot Act is being interpreted in a secret way that would alarm Americans if they knew the details, civil liberties activists could only speculate about what they meant. The activists' fear: that the government is using the anti-terrorism law to collect vast troves of personal information, including cellphone records, on Americans who have no link to terrorism. Sens. Ron Wyden of Oregon and Mark Udall of Colorado, both Democrats, proclaimed that the Patriot Act's surveillance powers are being used far more expansively than most Americans realize. Today the American people do not know how their government interprets the language of the Patriot Act," Wyden said. "Someday they are going to find out, and a lot of them are going to be stunned. Some of them will undoubtedly ask their senators: 'Did you know what this law actually did? Why didn't you know? Wasn't it your job to know, before you voted on it?'" The warnings by two lawmakers with access to secret information underscore the extent to which government surveillance is shielded from view, in an age when nearly every American leaves a digital trail through the Internet and mobile devices. A clue about Wyden's concerns may be found in a separate bill he is proposing, to forbid the government from tracking, without a court order, the location of Americans through the GPS signals given out by their cellphones.