Absolute zero

Absolute zero is the lowest possible temperature in the universe: −273.15 degrees Celsius (0 Kelvin). At this theoretical point, all subatomic particles would cease thermal motion entirely, giving matter zero entropy.

Though absolute zero cannot be reached in practice—the second law of thermodynamics forbids it—physicists have cooled matter to within billionths of a degree of it. These extreme conditions reveal strange phenomena: quantum effects dominate, superfluids flow without Friction, and materials exhibit bizarre electromagnetic properties.

The concept emerged from studies of gas behavior in the 1600s and was rigorously formalized by Lord Kelvin in the 1850s. It anchors the Kelvin scale, the standard measurement in science.

Absolute zero remains unreachable because removing heat requires work, and that work generates heat—a paradox intrinsic to thermodynamics. Yet laboratories worldwide pursue ever-closer approaches, unlocking insights into quantum behavior and enabling technologies from superconductors to quantum computers.

Related

Kelvin scale, Thermodynamics, Quantum mechanics, Superconductivity, Entropy, Temperature