DENVER — It’s a real-life threat no one wants to imagine, but one that many acknowledge is very real.An electromagnetic pulse is a short burst of electromagnetic energy that could shut down the nation’s power grid in a matter of seconds.The threat is so real there is a US Congressional EMP Leadership Caucus sponsored group called The EMP Task Force on National and Homeland Security studying the problem. Glenn Rhoades is the Colorado coordinator of that task force.”It would be so subtle, so silent, you would not know what was going on. It would just be a click. With an EMP device you wouldn’t hear any noise,” he said.Rhoades said most experts believe it’s a matter of when not if, and he believes it’s an event that could ultimately kill more than 200 million Americans.An EMP threat could come from several sources. A solar storm could hit Earth, overwhelming the power grid. North Korea could drop a bomb on the grid or a cyberterrorist could hack into the system and shut down the grid.Even more worrisome? Rhoades said the country is not prepared to respond to an EMP event.