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In Big Bang cosmology, the Planck epoch or Planck era is the earliest stage of the Big Bang, before the time passed was equal to the Planck time, t P, or approximately 10 −43 seconds. [30] There is no currently available physical theory to describe such short times, and it is not clear in what sense the concept of time is meaningful for ...
B λ (T) is the Planck function for temperature T and wavelength λ (units: power/area/solid angle/wavelength - e.g. watts/cm 2 /sr/cm) I λ is the spectral intensity of the radiation entering the increment ds with the same units as B λ (T) This equation and various equivalent expressions are known as Schwarzschild's equation.
For a black body, Planck's law gives: [8] [11] = where (the Intensity or Brightness) is the amount of energy emitted per unit surface area per unit time per unit solid angle and in the frequency range between and +; is the temperature of the black body; is the Planck constant; is frequency; is the speed of light; and is the Boltzmann constant.
According to Planck's distribution law, the spectral energy density (energy per unit volume per unit frequency) at given temperature is given by: [4] [5] (,) = alternatively, the law can be expressed for the spectral radiance of a body for frequency ν at absolute temperature T given as: [6] [7] [8] (,) = where k B is the Boltzmann ...
Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, [8] called the Planck spectrum or Planck's law. The spectrum is peaked at a characteristic frequency that shifts to higher frequencies with increasing temperature, and at room temperature most of the emission is in the infrared ...
The physical meaning of θ R is as an estimate of the temperature at which thermal energy (of the order of k B T) is comparable to the spacing between rotational energy levels (of the order of hcB). At about this temperature the population of excited rotational levels becomes important. Some typical values are given in the table.
The table "Planck temperature temperature conversion formulae" is a conversion table from and to Kelvin, not Planck temperature. Gulliveig ( talk ) 04:51, 23 August 2011 (UTC) [ reply ] Discrepency between this and "Orders_of_magnitude_(temperature)" page
By adjusting the tension to be small compared to the Planck scale, the Hagedorn transition can be much less than the Planck temperature. Traditional grand unified string models place this in the magnitude of 10 30 K, two orders of magnitude smaller than the Planck temperature. Such temperatures have not been reached in any experiment and are ...