The value of absolute zero on the Celsius scale is set at -273.15 °C. This temperature represents a theoretical point where molecular motion ceases, indicating the lowest limit of the thermodynamic temperature scale. At absolute zero, a system would contain minimal thermal energy, making it impossible for any physical process to occur. Although not achievable in practice, this concept is essential in understanding thermodynamics and the behavior of gases, leading to advancements in cryogenics and quantum mechanics.