In physics, absolute zero is defined as the lowest possible temperature, where the thermal energy of a substance is at its minimum. It is equal to 0 Kelvin (K) or approximately -273.15 degrees Celsius (-459.67 degrees Fahrenheit). At absolute zero, particles have minimal kinetic energy, and all molecular motion ceases.
According to the laws of thermodynamics, it is not possible to achieve temperatures below absolute zero in a classical system. However, in recent years, researchers have explored the concept of "negative absolute temperature" in certain quantum systems.
In these quantum systems, such as certain atoms or particles with specific energy levels, the temperature scale can be extended beyond absolute zero. In such cases, the temperature is considered negative on a Kelvin scale but still higher than zero on an energy scale. It is important to note that this concept of negative absolute temperature is distinct from temperatures below absolute zero in a classical sense.