For decades, the phrase "energy independence" was an aspirational slogan all Americans could get behind, like "E pluribus unum" or "Have a Coke and a smile."

Now, practically overnight, the thing itself is upon us. The U.S. first became the world's largest natural gas producer in 2009 and could become the biggest oil producer in the next few years. The question, “where in the world are we going to buy natural gas?” has become “where in the world can we sell it?”

Other questions have popped up, too, as economists, companies, politicians, scientists, environmentalists and communities catch up. Here’s what we fight about when we fight about fracking.

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