Humans pumped so much groundwater out of the Earth that the planet has begun to wobble detectably on its axis, a new study has found. On its own terms, the magnitude of the new wobble is slight — a matter of millimeters, which puts it in the same approximate speed category as Earth’s slowly drifting continents. But the findings published earlier this month in Geophysical Research Letters show the extent to which human action — in the form of dam construction, groundwater drilling and the burning of fossil fuels — are impacting the very position of the Earth. They also...