This press release is available in German. What is normal to most people in winter has so far been impossible in physics: a minus temperature. On the Celsius scale minus temperatures are only ...

The most accurate thermometer in the known universe looks nothing like a thermometer. It is a copper vessel the size of a large cantaloupe, filled with ultrapure argon gas and studded with microphones ...

Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to ...