It comes from measuring the velocity distribution of the atoms. A narrower distribution corresponds to colder temperatures.widderjoos said:How are ultra cold temperatures measured? For example, sometimes I see things measured in nanoKelvins. I'm thinking there has to be direct contact since the vacuum is already hotter than this, but how is it actually done?
That does not address the question, which is, how are these cold temperatures measured?shawl said:It requires ultra high vaccum.
And the cooling technology can be utilized is "Laser cooling" and "Magnetic refrigeration".
I'm more familiar with measurements in the μK range that were common 20-or-so years ago. I'm not 100% sure if they still work in the nK range -- I believe they do, or some variation of them -- but here is a brief explanation:widderjoos said:Thanks, but how do they measure the velocity distribution without significantly heating the system up?
In cold environments, temperature can be measured using a variety of methods, including thermometers, thermocouples, infrared sensors, and resistance temperature detectors (RTDs). These instruments use different principles to measure temperature, such as expansion of liquids or gases, change in electrical resistance, or emission of infrared radiation.
The coldest temperature that can be accurately measured depends on the type of instrument used. Some thermometers can measure temperatures as low as -200 degrees Celsius, while other instruments, such as infrared sensors, can detect temperatures as low as -273.15 degrees Celsius, which is absolute zero.
To ensure accurate measurements in cold temperature environments, scientists must use instruments that are specifically designed for these conditions. These instruments are calibrated to account for the effects of extreme cold on their readings. Scientists also follow proper measurement techniques, such as allowing the instrument to reach thermal equilibrium with the environment before taking a reading.
Cold temperature measurement has many important applications in scientific research, industry, and everyday life. Some common uses include monitoring the temperature of refrigerators and freezers, measuring the temperature of cryogenic fluids used in medical and scientific applications, and studying the effects of cold temperatures on materials and organisms in extreme environments.
Yes, cold temperature measurement can be combined with other measurements to provide a more complete understanding of a system or process. For example, scientists may combine temperature measurements with pressure, flow rate, or chemical concentration measurements to study the behavior of a chemical reaction at low temperatures or the efficiency of a cryogenic cooling system.