Breaking Newton’s Law

In the quantum world, our intuition for moving objects is strongly challenged and may sometimes even completely fail. Experimental physicists of the University of Innsbruck in collaboration with theorists from Munich, Paris and Cambridge have found a quantum particle which shows an intriguing oscillatory back-and-forth motion in a one-dimensional atomic gas. A ripe apple falling from a tree has inspired Sir Isaac Newton to formulate a theory that describes the motion of objects subject to a force. Newton's equations of motion tell us that a moving body keeps on moving on a straight line unless any disturbing force may change its path. The impact of Newton's laws is ubiquitous in our everyday experience, ranging from a skydiver falling in the earth's gravitational field, over the inertia one feels in an accelerating airplane, to the earth orbiting around the sun. In the quantum world, however, our intuition for the motion of objects is strongly challenged and may sometimes even completely fail. What about imagining a marble falling through water oscillating up and down rather than just moving straight downwards' Sounds strange.