Is fracking dangerous?
That has yet to be definitively determined. In hydraulic fracturing, a slurry of water, sand, and chemicals is blasted at high pressure through a well pipe that reaches a mile or more into a layer of shale. There, the high-pressure fluid cracks open the porous rock, unlocking trapped oil and gas and releasing it to flow back up the well. Like all energy extraction methods, fracking has a multitude of environmental impacts, but one critical question will determine fracking's future: Does fracking contaminate drinking water? The oil and gas industry insists that it does not, but environmentalists and some scientists say gases and toxic chemicals can escape from the well pipe or percolate up into aquifers located above the shale layer. So far, the evidence on that question is mixed. A Department of Energy study in Pennsylvania determined that fracking has had no impact on the safety of drinking water. But a larger study of the region by Duke University found that some wells have higher concentrations of methane and ethane, suggesting "that drilling has affected some homeowners' water."

How will that question be answered?
By ongoing scientific studies conducted by state and federal governments. The most important one is being conducted by the Environmental Protection Agency, and it will help determine official federal policy and regulations on fracking. But the study, which began in 2010 and was supposed to be completed by 2014, won't be concluded until 2016. Steve Hvozdovich, an anti-fracking activist in Pennsylvania, said the Obama administration "is trying to promote natural gas as an energy supply," and is worried that the EPA may find that fracking does, in fact, contaminate groundwater.

What is Obama's position on fracking?
So far, it's been largely positive. In his "all of the above strategy," the president has lauded fracking for promoting American energy independence, economic growth, and reduction of greenhouse gases. (In electrical power plants, natural gas produces roughly half the carbon dioxide emissions that coal does.) Largely because of fracking, the U.S. last year became the largest producer of oil and gas in the world, passing Russia and Saudi Arabia. Petroleum imports last year fell to their lowest level since 1999. All that makes the EPA's decision enormously fraught. At a meeting of business executives, U.S. Chamber of Commerce President Thomas Donohue recently warned that the EPA study on drinking water "could short-circuit America's absolute explosion in energy opportunity that is creating millions of jobs.''

What does the public think?
As with so many other issues, Americans are sharply divided. In 2013, Pew Research found a big swing in public opinion against fracking, with 49 percent now opposed to fracking and 44 percent in favor. The volatility of the issue — and the enormity of what's at stake — may explain why Obama and state governors such as New York's Andrew Cuomo (see below) and Maryland's Martin O'Malley keep postponing decisions on fracking. Amy Mall, a senior policy analyst with the Natural Resources Defense Council, says fracking has become the "third rail" of energy policy.

What do the states say?
Their policies vary dramatically from state to state, and even within states, with many rural residents generally clamoring for the jobs and economic development that fracking brings, and urban "greens" adamantly opposing it. Fracking is booming in Pennsylvania, Colorado, and North Dakota, where abundant deposits and depressed economies created an incentive to drill. Other states are more cautiously accepting fracking. Illinois and California both passed regulations last year that allow fracking to expand. Why California? It sits atop the vast Monterey Shale. Tapping it, a University of Southern California study estimated, could bring in $25 billion in taxes and create 2.8 million jobs by 2020. "Anybody who stands in the way of the fracking boom," says Ohio Democratic state Rep. Robert Hagan, "is seen as standing in the way of jobs."

Do all municipalities agree?
No. So far, fears that fracking will pollute groundwater and turn rural areas into industrial wastelands have led to more than 100 fracking bans or moratoriums in cities, counties, and states nationwide. Four predominantly liberal Colorado communities voted last year to ban fracking, though the state as a whole has embraced it. To the frustration of some rural residents, New York state imposed a moratorium on fracking in 2008 and ordered a study on its effects on groundwater and the environment. There, upstate residents with rich natural gas deposits under their property anxiously wait for the state and the EPA to render a decision, with the issue dividing longtime neighbors and friends into vehement camps. "On an issue like this, there is no gray area," said Alice Diehl, who owns a dairy farm with her husband in Callicoon, N.Y. — potential fracking territory. "People are either for it for an important reason, or against it for a reason they think is as important."

New York state: A fracking microcosm
No state better sums up the politically fraught debate than New York. Upstate New York desperately needs jobs, and fracking could sustain 62,000 new ones, according to the Public Policy Institute of New York State. But New York is solidly blue, and home to many vocal liberals. "Artists Against Fracking," founded by Yoko Ono and her son, Sean Lennon, includes such celebrities as Lady Gaga, Paul McCartney, and Alec Baldwin, and has voiced its opposition in everything from billboards to a celebrity-heavy music video. Overall, 45 percent of New Yorkers now oppose fracking, while 37 percent support it, according to a recent Siena poll. Democratic Gov. Andrew Cuomo, who is up for re-election in November and is widely believed to have presidential ambitions, keeps punting the study's release date. Last May, he said it was weeks from completion; he now says it will probably be done after he is presumably re-elected. "I want the right decision," he said. "Not necessarily the fastest decision."