The Planck temperature Tplanck is the temperature having Planck energy Eplanck associated with it in this way:
Eplanck = kTplanck.
Planck energy was typical of the light filling the universe at its beginning and Planck temperature is commonly given as the Big Bang temperature.
Every temperature T has associated with it a characteristic amount of energy kT which is present in surroundings with that temperature at the quantum and molecular levels. At any given temperature the characteristic kT energy serves as a kind of keynote in the mix of energies in thermal radiation and gives a handle on the distribution of molecular kinetic energies. Temperature can be seen as an alternative scale for measuring that characteristic energy.
Planck temperature is related to the Planck mass and energy. The natural mass unit Mplanck is mite-sized, a flea with that mass would look like a speck, not too different the period in some type-fonts. The natural energy unit Eplanck is what would result from converting that mite-sized bit of mass into energy.
The natural mass unit is simply SQRT ( h-bar c/G) and the energy unit Eplanck is what you get by multiplying by c2, namely SQRT ( h-bar c5/G). So the temperature Tplanck is just that divided by k. It comes to around 1.417 x 1032 kelvin.
h-bar, c, and G are not going away. They'll be here when our species has evolved into something else or vanished and Planck energy and temperature, because they're the energy and temperature which arise from those things, will not go away either. It's the unit of energy and the temperature scale which are intrinsic to light and gravity.
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