How close have scientists got to absolute zero?

Scientists had made significant progress in reaching extremely low temperatures, but achieving absolute zero (0 Kelvin or -273.15 degrees Celsius) is theoretically impossible due to the third law of thermodynamics. This law states that it is impossible to reach absolute zero in a finite number of steps. However, researchers have come remarkably close to this temperature.

One approach to achieving ultra-low temperatures involves the use of laser cooling and evaporative cooling techniques. Laser cooling involves using lasers to slow down the motion of atoms, reducing their kinetic energy and consequently lowering the temperature. Evaporative cooling, on the other hand, is a process where a cloud of atoms is allowed to expand, and the most energetic atoms escape, leading to a decrease in temperature.

Scientists have successfully cooled gases such as rubidium and sodium to within a few billionths of a degree above absolute zero. In 2019, a team of researchers reported reaching a temperature of 500 trillionths of a degree above absolute zero using a combination of laser cooling and evaporative cooling with potassium-potassium (K-K) molecules. This achievement represents one of the coldest temperatures ever recorded.

While absolute zero remains a theoretical limit, the advancements in cooling techniques and technology have allowed scientists to explore the fascinating and often strange behaviors of matter at temperatures extremely close to absolute zero, unlocking new insights into the fundamental nature of physics.