According to our current understanding of physics, the lowest possible temperature in the universe is absolute zero, which is equivalent to 0 Kelvin (K) or approximately -273.15 degrees Celsius (-459.67 degrees Fahrenheit). At absolute zero, particles possess the least amount of thermal energy and are in their lowest energy state.
Absolute zero is considered the theoretical limit because it represents the absence of any remaining heat energy in a system. As temperature decreases, the kinetic energy of particles decreases, and they approach a state of minimal motion. However, reaching absolute zero is not practically achievable due to the third law of thermodynamics, which states that it is impossible to reach absolute zero through a finite number of steps.
Experiments conducted on various systems, such as atoms and molecules, have approached extremely low temperatures, but none have reached absolute zero. These experiments have achieved temperatures very close to absolute zero, such as fractions of a billionth of a Kelvin.
In summary, based on our current understanding, absolute zero represents the lowest possible temperature in the universe.