PURPOSE: To demonstrate regelation.

DESCRIPTION: A thin wire with weights on the ends is looped over an ice cube. In a few minutes the wire will cut through the ice cube and the weights fall with a bang onto the stand. The ice re-freezes after the wire passes, leaving a single cube of ice.

The photograph at the right shows the wire cutting through the ice cube.

SUGGESTIONS: There is a lot of discussion about whether this really demonstrates regelation, but rather simply conduction of heat by the wire to the ice cube so that it will melt, followed by freezing over of the cut due to conduction of heat away from the cut to the surrounding ice.

It seems clear from the literature (but disappointing) that regelation is not the cause of the ice being slippery when you ice skate. A paper published in Physics Today in December 2005 and listed in the references for this demonstration, discusses the concept, initially proposed by Faraday, that a microscopic layer of water, found on ice even at very low temperatures, is responsible for ice being slippery. On the other hand, regelation apparently is a primary contributing cause for the motion of glaciers, as discussed in one of the references.

REFERENCES: (PIRA 4C20.30) For further information on this question see the Demonstration Reference File.

EQUIPMENT: Regelation stand, wires, weights and ice cube.

SETUP TIME: 5 min.