Physics: why is it cold in space?

Self-tutoring about thermodynamics: the tutor imagines the temperature in space and why it’s meant to be so cold.

The temperature in space, away from any heat-producing features, is meant to be around 2.7K. By comparison, 0°C is 273K.

Temperature, as I’ve been taught since grade 10 physical science, is a measure of the kinetic energy of the resident particles. With no resident particles, how can one achieve a temperature? Moreover, why does “no temperature” mean “cold”?

A post at explains that an area’s temperature can be thought of as its impact on the temperature of a body that enters it. Therefore, space is cold because anything that enters it will radiate heat until it’s cold.



Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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