What is absolute zero?
Absolute zero is the lowest possible temperature, −273.15°C (−459.67°F), or 0 kelvin. At this point particles have the minimum possible energy and cannot get any colder.
Temperature measures how fast atoms and molecules move. As something cools, its particles slow down. Absolute zero is the theoretical point where they reach their lowest possible energy. The Kelvin scale, named after Lord Kelvin, starts at absolute zero, so it has no negative numbers.
Absolute zero can be approached but never actually reached, according to the laws of thermodynamics. Scientists have cooled atoms to within a billionth of a degree of it in laboratories using lasers and magnetic traps.
Strange things near absolute zero
Near absolute zero, matter behaves strangely. Some metals become superconductors, carrying electricity with no resistance, and liquid helium becomes a superfluid that can climb up the walls of its container. These effects are used in MRI scanners and quantum computers.
Did You Know?
The coldest natural place known in the universe is the Boomerang Nebula, a cloud of gas about 5,000 light-years away, at about one degree above absolute zero.