It was with you at the ATM, it was with you in your car; it’s probably right in front of you as you read this. Chances are you carry it in your pocket or purse, as well as having it strewn about your house. It helped create all those nifty things you like, too—plowed roads, sewer systems, mountain highways. It makes modern life possible.

It’s the Global Positioning System, and it’s only a matter of time until we have to live without it.

Although you might expect something with the benevolent ubiquity of GPS—which provides time-stamping as well as navigation—to be cherished and closely tended, the truth is, many businesses and individuals use it regularly without ever realizing what a key role it plays.

“The bad news is that people that use it, don’t know they use it,” Jim Caverly, of the Department of Homeland Security, told scientists at the Space Weather Workshop in Boulder last week. “Since the system has been so reliable, a lot of people haven’t had that aha moment to say this is important to me.”

That moment could come sooner than we think. Smooth delivery of GPS signals can be impeded by a number of on-the-ground threats, from handheld jammers to new wireless technology. Add to those worries an upcoming solar maximum, which can cause geomagnetic storms that interfere with GPS, and you have a recipe for… well, no one knows exactly what.

“I have been a proponent, rather facetiously, of shutting down GPS for two days and seeing what happens,” Caverly said. “It’s not a good policy decision but I have no way of knowing how else we’ll know what’s possible.”

Scientists know that disruptions can cause communication shutdowns, power failures, and navigation, traffic, and transport problems. What’s less clear is what it could mean to financial systems that use GPS time stamping to qualify transactions.

"A significant failure of GPS could cause lots of services to fail at the same time, including many that are thought to be completely independent of each other," Martyn Thomas, who recently led a Royal Academy of Engineering study that found countries “dangerously reliant” on GPS, told Agency France-Presse.

How emergency agencies might need to respond to such incidents is also murky, but the DHS and the Federal Emergency Management Agency are beginning to address how we can be better prepared for that eventuality, Caverly said. “This is like pandemic,” he said. “It’s going to happen, we just can’t tell you where or with what amplitude.”