Zero on an absolute scale
The Celsius and kelvin scales have equal interval sizes but different origins, separated by 273.15. Absolute zero corresponds to 0 K, not to the freezing point of water. Ordinary negative Celsius temperatures consequently remain positive on the thermodynamic scale used in most physical calculations.
References: [1]
Cooling as a physical process
Cooling requires suitable transfers of energy or entropy to surroundings and depends on materials and equipment. Approximations useful at ordinary temperatures may fail near zero. Gas thermometry and other methods provide ways to compare temperature ranges, making extreme cold a matter of calibrated measurement rather than sensation.
The third-law limit
One statement of the third law rules out reaching absolute zero through a finite number of cooling steps. It complements energy conservation and the second law’s entropy constraints. Reporting an extremely small kelvin temperature describes approaching the limit rather than demonstrating that the limit has been attained.
References: [2]
States revealed at low temperature
Reduced thermal excitation can reveal collective properties obscured at higher temperatures, including superconducting transitions in suitable materials. Different systems have different transition conditions. Absolute zero supplies a common reference for temperature, not a guarantee that every material undergoes an identical transformation under one experimental arrangement.
References: [2]