Earth's average surface temperature is about 288 K. If we had a hypothetical exoplanet with a surface temperature of 300 K, this would be about 4% higher than Earth's.

Because we say Earth radii and Earth masses, would we refer to this as 1.04 Earth temperatures? Or, how about 1.04 Earth's temperature? $1.04 \cdot T_⊕$? Is there a standard in astronomy to use?


1 Answer 1


Possible, but rare. The reason is that many things are not linear with respect to temperature.

Volume of gas is in direct proportion to temperature (at given pressure) but we rarely need to consider this.

But, for example, the density of water is markedly non-linear with temperature.

Moreover our physiometric response to temperature is also non linear. We dont experience 300K as being 4% higher than 288K.

As such, planetary temperatures are usually described in Kelvin, Celcius or Fahrenheit (or even Rankin if you look hard enough) rather than being referred to Earth temperaturees.

  • 2
    $\begingroup$ Phase changes are the ultimate example of "not linear with temperature". In or out of "goldilocks zone" is an alternative metric but it's absolute and boolean, the opposite of relative. $\endgroup$
    – uhoh
    Mar 1, 2021 at 2:10

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