From a distance, the Matterhorn looks fixed in place, a giant wedge of rock planted above Zermatt and unchanged by time. New measurements show that the famous Alpine peak is in constant motion, rocking back and forth in a slow, nearly imperceptible rhythm driven by seismic energy moving through the Earth. An international research team found that the mountain vibrates roughly once every two seconds, with motion so slight that people cannot feel it. Yet the signal is there, and on the summit it can grow much stronger than at the base. “The movements of the underground cause every object to vibrate, which we fortunately cannot feel, but detect with sensitive measuring instruments,” Donat Fäh of the Swiss Seismological Service at ETH Zurich said in a statement. That idea is familiar in bridges and tall buildings. The striking part here is scale. The same kind of resonant behavior can be picked up in one of the Alps’ most iconic mountains. Oblique aerial image showing the east flank of the Matterhorn with the Hörnli ridge on …