Temperature scientists measure temperature using the Celsius scale and thermodynamic temperature using the Kelvin scale, which is the Celsius scale offset so that its null point is = , or absolute zero. Many engineering fields in the U.S., notably high-tech and US federal specifications (civil and military), also use the Kelvin and Celsius scales. Other engineering fields in the U.S. also rely upon the Rankine scale (a shifted Fahrenheit scale) when working in thermodynamic-related disciplines such as combustion. The basic unit of temperature in the International System of Units (SI) is the kelvin. It has the symbol K. For everyday applications,
Absolute hot Absolute hot Absolute hot is a concept of temperature that postulates the existence of a highest attainable temperature of matter. The concept has been popularized by the television series "Nova". In this article, absolute hot is assumed to be the high end of a temperature scale starting at absolute zero, which is the temperature at which entropy is minimal and classical thermal energy is zero. Contemporary models of physical cosmology postulate that the highest possible temperature is the Planck temperature, which has the value . Above about , particle energies become so large that gravitational forces between them would become