Cold Running Hot
By the classical laws of thermodynamics, the void of vacuum must be infinitely cold. The 0th law posits an absolute temperature, which is conventionally expressed by the Kelvin scale.
Scottish mathematical physicist William Thomson, better known as Lord Kelvin, imagined a temperature so low as to be absolute zero. That chilling concept sets the floor of the Kelvin temperature scale.
The notion of drop-dead thermodynamics at 0 K was upturned when minus-K was discovered: add more energy after maximum entropy and a quantum system shifts into negative temperature, where a high-energy state is the only way to accommodate the extra energetic input.
In an environment with negative temperature, the laws of thermodynamics work in reverse: particles prefer to populate high-energy states instead of low-energy ones. In minus K, the laws of physics are completely overturned.