Henrik Andersen Sveinsson

Ice slips away from under a skate blade like a bar of soap in wet hands. For a hundred years, scientists argued about where this slipperiness comes from. Some said there is already a thin layer of water on top: it acts as a lubricant. Others countered that water only appears when you start moving, due to friction.

A thin crack runs through glass. At first glance, the fracture line simply reflects the material's brittleness. But if you zoom in to the atomic level, the picture gets more complex: glass starts to resist differently when the crack accelerates.