There's a slight misunderstanding in your question. Temperature isn't *measured* at -273K, rather, -273.15°C (or -459.67°F) is considered absolute zero on the Kelvin scale.

Here's why:

* Kelvin Scale: The Kelvin scale is an absolute temperature scale, meaning it starts at absolute zero, where all molecular motion theoretically ceases.

* Absolute Zero: At absolute zero, there is no thermal energy, and particles are in their lowest possible energy state.

* Relationship to Celsius: The Kelvin scale is directly related to the Celsius scale: 0°C = 273.15K. This means that each Kelvin degree is the same size as a Celsius degree.

* Why -273.15°C? This value is derived from the relationship between temperature and the volume of an ideal gas. As temperature decreases, the volume of an ideal gas also decreases linearly. Extrapolating this relationship to zero volume would theoretically correspond to -273.15°C.

Key Points:

* Temperature is measured using various scales, including Kelvin, Celsius, and Fahrenheit.

* The Kelvin scale is the only absolute scale, meaning it starts at absolute zero.

* Absolute zero is a theoretical limit where all molecular motion ceases.

Let me know if you have any more questions!