the behaviour of matter at temperatures close to absolute zero −273.15 °C (−459.67 °F). At such temperatures the thermal, electric, and magnetic properties of many substances undergo great change, and, indeed, the behaviour of matter may seem strange when compared with that at room temperature. superconductivity and superfluidity can be cited as two such phenomena that occur below certain critical temperatures; in the former, many chemical elements, compounds, and alloys show no resistance whatsoever to the flow of electricity, and, in the latter, liquid helium can flow through tiny holes impervious to any other liquid.