Heat has been found to behave like sound as it moves through graphite. Using a system of lasers, MIT researchers observed a wavelike motion in which heat travels through pencil lead at 120 kelvin. Points of the material that were warm were instantly left cold as heat waves travelled. The equivalent of this would be a kettle turning instantly cold as soon as the burner is turned off. Hard-to-control materials have previously exhibited this “second sound”, but at 20 kelvin – temperatures too cold to run practical applications.The findings, published in Science, suggest potential for removing heat in microelectronic devices that use graphite and its 2D equivalent, graphene.