A team at the MIT-Harvard Center for Ultra-Cold Atoms has devised a method for measuring extremely cold temperature. How cold? How about 1 nK? That stands for one billionth of a degree above absolute zero.
Absolute zero, the coldest temperature theoretically possible, is defined as 0 Kelvin and is equivalent to negative 273.15° Celsius or negative 459.67° Fahrenheit. Extremely low temperatures are useful for using and creating superconductors (materials with no electrical resistance or interior magnetic field).
The team used something called ‘spin gradient thermometry’. Simply put, the system to be measured is placed in a magnetic field gradient. The mean magnetization of the atoms can then be used to determine their temperature.
This method has been successfully used to measure temperatures as low as 1 nK. However, scientists are confident that the method could be used for materials as cold as 50 pK, or 50 trillionths of a degree above absolute zero.
Now that's cold!