absolute zero

American  

noun

1. the temperature of −273.16°C (−459.69°F), the hypothetical point at which all molecular activity ceases.

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absolute zero British  

noun

1. the lowest temperature theoretically attainable, at which the particles constituting matter would be in the lowest energy states available; the zero of thermodynamic temperature; zero on the International Practical Scale of Temperature: equivalent to –273.15°C or –459.67°F

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absolute zero Scientific  

1. The lowest possible temperature, at which all molecules are have the least possible amount of kinetic energy. Absolute zero is equal to 0°K, −459.67°F, or −273.15°C. At temperatures approaching absolute zero, the physical characteristics of some substances change significantly. For example, some substances change from electrical insulators to conductors, while others change from conductors to insulators. Absolute zero has never been reached in laboratory experiments.

2. See also Bose-Einstein condensate zero-point energy

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absolute zero Cultural  

1. The lowest temperature that can be attained by matter, corresponding to the point at which most motion in atoms stops. Absolute zero is about –273 degrees on the Celsius scale and about –460 on the Fahrenheit (see also Fahrenheit) scale.

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Closer Look

The temperature of a substance is determined by the average velocity of its molecules: the faster they move, the warmer the substance. At absolute zero molecules have minimal kinetic energy (or zero-point energy) and heat energy cannot be extracted from them. The molecules are not motionless, however, due to the uncertainty principle of quantum mechanics, which entails that the atoms cannot have both a fixed position and zero momentum at the same time; instead, the molecules of a substance at absolute zero are always “wiggling” in some manner. Absolute zero is zero degrees Kelvin, equal to −273.15 degrees Celsius and −459.67 degrees Fahrenheit. The coldest known place in the universe is the Boomerang Nebula, where the temperature is −272° Celsius. Scientists at Massachusetts Institute of Technology have gone much lower than that by using laser traps and other techniques to cool rubidium to 2 × 10^null degrees Kelvin.

Example Sentences

Superconducting circuits use metals cooled to near absolute zero; trapped ions are suspended in vacuums and manipulated by lasers.

From Barron's • May 21, 2026

These devices trap single ions such as aluminum or ytterbium, cool them to temperatures near absolute zero, and control their quantum states using lasers.

From Science Daily • May 18, 2026

Scientists can observe these arrangements by cooling materials to temperatures close to absolute zero.

From Science Daily • Apr. 22, 2026

The newly observed sequence involves two important changes in magnetic behavior that occur as certain materials are cooled toward absolute zero.

From Science Daily • Mar. 7, 2026

On the other hand, Kelvin’s discovery of absolute zero told physicists what they couldn’t do.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife