Planck temperature

Planck temperature, denoted by TP, is the unit of temperature in the system of natural units known as Planck units. It serves as the defining unit of the Planck temperature scale. In this scale the magnitude of the Planck temperature is equal to 1, while that of absolute zero is 0. Other temperatures can be converted to Planck temperature units. For example, 0 °C = 273.15 K = 1.9279×10−30 TP.

In SI units, the Planck temperature is about 1.417×1032 kelvin (equivalently, degrees Celsius, since the difference is trivially small at this scale), or 2.55×1032 degrees Fahrenheit or Rankine.[1]

## Contents

* 1 History
* 2 Definition
* 3 Significance
* 4 See also
* 5 Notes and references
* 6 External links

## History

What today is known as the Planck temperature was first introduced in 1899 by Max Planck together with his introduction of what today is known as the Planck length, the Planck mass and Planck time.[2][3]

## Definition

The Planck temperature is defined as:

TP=mPc2k=ℏc5Gk2≈ 1.416808(33)×1032 K where:

* mP is the Planck mass,
* c is speed of light in a vacuum,
* ℏ is the reduced Planck constant defined as ℏ =h2π,
* k is the Boltzmann constant,
* G is the gravitational constant.

The two digits between the parentheses are used to denote the standard error of the last two digits of the estimated value.[4]

## Significance

As with most of the Planck units, a Planck temperature of 1 (unity) is a fundamental limit of quantum theory, in combination with gravitation, as presently understood. In other words, the wavelength of light emitted by an object can be calculated by its temperature. If an object were to reach the temperature of 1.42×1032 kelvin (TP), the radiation it would emit would have a wavelength of 1.616×10−35 m (Planck length), at which point quantum gravitational effects become relevant. At temperatures greater than or equal to TP, current physical theory breaks down because we lack a theory of quantum gravity.[5]

## See also

* Absolute hot
* Hagedorn temperature
* Orders of magnitude (temperature)
* Natural units
* Planck constant
* Planck units

## Notes and references

1. ↑ TranslatorsCafe.com \- Unit Converter
2. ↑ Tomilin, K. A., 1999, "Natural Systems of Units: To the Centenary Anniversary of the Planck System", 287–296.
3. ↑ M. Planck. "Natürliche Einheiten." Königlich-Preußische Akademie der Wissenschaften, pp. 479–480, 1899.
4. ↑ "CODATA Value: Planck temperature". The NIST Reference on Constants, Units, and Uncertainty. NIST. http://physics.nist.gov/cgi-bin/cuu/Value?plktmp. Retrieved 2011-10-12.
5. ↑ Nova: Absolute Hot

## External links

* NIST reference: Planck temperature
* What is the opposite of absolute zero?

* v
* t
* e

Scales of temperature

* Celsius
* Delisle
* Fahrenheit
* Gas Mark
* Kelvin
* Leiden
* Newton
* Planck
* Rankine
* Réaumur
* Rømer
* Wedgwood

Conversion formulas and comparison

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