Absolute zero is the lowest possible temperature in the Kelvin scale, which corresponds to -273.15 degrees Celsius or -459.67 degrees Fahrenheit. It is defined as the point at which a substance has minimal thermal energy, and its particles possess the lowest attainable kinetic energy.
According to the laws of thermodynamics, reaching absolute zero is theoretically impossible without man's interference. This is due to the third law of thermodynamics, also known as the "Nernst heat theorem," which states that it is impossible to reach absolute zero through a finite number of operations in a finite time, as long as the system is in thermal contact with a finite-temperature reservoir.
In practical terms, it is incredibly challenging to cool a substance to absolute zero. As an object approaches absolute zero, its heat energy must be continuously removed, and the process becomes progressively more difficult. At extremely low temperatures, substances exhibit unusual behavior, such as superconductivity and superfluidity, which can be observed and studied.
Scientists have approached extremely low temperatures within a fraction of a degree above absolute zero using various cooling techniques, such as laser cooling, evaporative cooling, and magnetic cooling. However, actually achieving absolute zero is not possible due to the constraints imposed by the laws of thermodynamics. Therefore, absolute zero remains a theoretical concept that has not been experimentally realized.