In December 2016, William Akley sat down in his sprawling headquarters for the biggest gas utility in Massachusetts, Eversource. Across the table were three women from a group that had become increasingly troublesome to his company. The group was Mothers Out Front, and it had been doing things like dressing up in orange costumes depicting gas flames and putting big signs where the company's natural gas lines leaked into the air. As the meeting started, Zeyneb Magavi and each of the other mothers calmly explained their passion to Mr. Akley: "I have three kids," Ms. Magavi said. "I'm worried about climate change. And I'm worried about their future." It was the start of an unlikely partnership that eventually became an audacious idea: to use heat from underground instead of natural gas " to both cool and heat homes and buildings. The test of that idea is now blinking on in Framingham, Massachusetts. Eversource workers have buried a mile-long loop of plastic pipe underground ... to collect geothermal energy. They are now connecting the loop to heat and cool 36 buildings " homes, a fire station, and businesses. It is the first U.S. trial of this innovative technology being provided to an entire neighborhood by a major utility. It's the kind of scaled-up model that could bring a wholesale change to the nation's infrastructure, replacing natural gas just as natural gas supplanted coal and oil in much of the United States.