"A wave is a deformation in the surface of a liquid that moves at a speed that is independent of that liquid," the researchers explain. For example: in the waves that are formed when a rock is thrown into a pond, the water remains still while the waves move away from the center at their own speed. "In our case, what occurs is actually the opposite: the water moves very rapidly (at several meters per second), but the wave moves at a speed of zero. That is, it remains still, "frozen" in time for any observer who sees it from outside of the water," explains one of the authors of the research report, Javier Rodríguez, of UC3M's Fluids and Thermal Engineering Department.
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