Absolute zero registers at how many degrees Celsius?

The idea of a coldest possible temperature is a fascinating one. As an object cools, its atoms and molecules slow down. Scientists in the 18th and 19th centuries observed that the volume of a gas would decrease linearly as it cooled, leading them to theorize that if you could cool a gas down far enough, its volume would eventually become zero. By extrapolating this behavior, they calculated the ultimate limit of cold, a point where all classical molecular motion would cease. This theoretical temperature, known as absolute zero, corresponds to -273.15 degrees on the Celsius scale.

This concept was formalized by the physicist William Thomson, later known as Lord Kelvin, who in 1848 proposed an absolute temperature scale that starts from this point. That is why temperatures are often measured in Kelvin, with 0 K being absolute zero. On this scale, water freezes at a much warmer 273.15 K. While the third law of thermodynamics states that reaching absolute zero is physically impossible, scientists have been able to get incredibly close, within billionths of a degree.

At these extreme temperatures, just above absolute zero, matter behaves in very strange ways. Elements can become superconductors, conducting electricity with zero resistance, or superfluids, which flow without any friction. In some cases, a new state of matter can emerge called a Bose-Einstein condensate, where thousands of individual atoms cool to a point where they behave as a single "superatom," displaying quantum phenomena on a macroscopic scale.