Temperature Temperature Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. It is unachievable in practice but it exists as a limit for real physical phenomena, and it was inferred by extrapolation from kinetic theory, and from other considerations in theoretical physics. One would like to define it as the temperature at which all motion ceases, but even at absolute zero some motion remains due to the requirements of quantum mechanics. Alternate definitions are that absolute zero is the temperature at which no further energy can be extracted from a physical body, or the temperature at which the entropies of perfect crystals vanish, or the temperature at which the entropy change of an adiabatic process vanishes. ...more on Wikipedia about "Absolute zero"
The International Temperature Scale of 1990 (ITS-90) defines international Kelvin and Celsius temperatures and facilitates the comparability and compatibility of temperature measurements internationally. The ITS-90 defines thermodynamic temperature from 0.65 K on up and is subdivided into multiple temperature ranges which in some instances overlap. Many different thermometer designs are required to cover the entire scale. These include Helium Vapor Pressure Thermometers, Helium Gas Thermometers, Standard Platinum Resistance Thermometers and Monochromatic Radiation Thermometers. The scale is made up of defining temperature fixed point values over a wide range of temperatures. Although the kelvin is defined using absolute zero (0 K) and the triple point of water (273.16 K), it is impractical to use this definition at temperatures very different from the triple of water. Thermometers calibrated on the scale can be used to interpolate among defined temperature fixed points over a wide range of temperatures. The temperature fixed points are based on the thermal properties of phase changes in materials (melting or freezing) or their triple point values. For example the triple point of water is realized in a triple point cell which is a closed glass container with pure water of specific isotopic composition and a specific partial pressure of water vapor. When the triple point is realized all three phases of matter coexist: liquid, vapor, and solid. The temperature at the triple point is defined to be exactly 0.010°C or 273.16 K. The table below shows some defining fixed points of the scale. ...more on Wikipedia about "International Temperature Scale of 1990"
Lambda point is the temperature (approximately 2.19 kelvins) at which helium I transitions to superfluid helium II ** . ...more on Wikipedia about "Lambda point"
Mean Radiant Temperature ( MRT) is the uniform surface temperature of a black enclosure with which an individual exchanges the same heat by radiation as the actual environment considered. It describes the radiant environment for a point in space. Distance to a source affects the temperature that is felt. For instance, if they sun is setting, turning to night, you may feel a coolness, although the temperature is unchanged at that moment. ...more on Wikipedia about "Mean radiant temperature"
In physics, negative temperature is a concept that occurs in some systems and specific definitions of temperature. A system with a negative temperature is not colder than absolute zero, but rather it is, in a sense, hotter than " infinite" temperature. ...more on Wikipedia about "Negative temperature"
Sub-zero temperatures are those below zero degrees. ...more on Wikipedia about "Sub-zero (physics)"
Thermodynamic temperature (formerly called absolute temperature) is a measure, in kelvins (K), of temperature for thermodynamics. The ( unattainable) temperature of 0 K is called " absolute zero", and coincides with the minimum molecular activity (i.e., thermal energy) of matter, which is zero, except for the residual quantum mechanical zero-point energy. ...more on Wikipedia about "Thermodynamic temperature"
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