Absolute zero, defined as 0 Kelvin (−273.15 °C), represents a theoretical limit where all thermal motion of particles ceases. However, the laws of quantum mechanics and thermodynamics make it impossible to reach this temperature. In particular, Heisenberg’s uncertainty principle prevents particles from coming to a complete stop, and zero-point energy remains unattainable.
Despite these constraints, scientists have achieved record-breaking low temperatures. In 2000, researchers at Helsinki University of Technology cooled nuclear spins to 100 picokelvins (pK). In 2014, the CUORE experiment at Gran Sasso cooled a 1 m³ copper vessel to 0.006 K, and in 2015, MIT physicists lowered the temperature of sodium-potassium gas molecules to 500 nanokelvins (nK).
Further advancements have come from space-based research. In 2018, NASA’s Cold Atom Laboratory (CAL) on the ISS began experiments with Bose-Einstein condensates, reducing thermal disturbances through microgravity. In 2021, a new record was set at 38 pK—the lowest temperature ever achieved in an experiment.
The average temperature of the universe, measured from cosmic microwave background radiation, is 2.73 K and will continue to decline, but it will never reach absolute zero. Research into ultra-low temperatures continues to confirm fundamental quantum physics principles while opening new frontiers in technology and astrophysics.
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