# Changes

→Temperature: Added Surface Temperature calculation methods

===Temperature===

For each point on the surface map of the object, Universe Sandbox performs the following calculations in each time step. First, Universe Sandbox calculates the incoming energy from heat sources like nearby stars. Some of the energy will be reflected back into space and some will be absorbed. The fraction of incoming energy absorbed is calculated using the object's [[Average Albedo]].

Some of this absorbed energy will be re-radiated back into space. If the object has no atmosphere, the output power, or the rate at which energy is radiated away, is calculated from the temperature of the point using the [[https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law|Stefan-Boltzmann law]]. If the object does have an atmosphere, the output power is calculated from the temperature of the point and the [[Greenhouse Effect]] of the object <ref name="Kleeman">Kleeman, Richard (2017).[https://math.nyu.edu/faculty/kleeman/zero_dim_ebm.html Zero-Dimensional Energy Balance Model]</ref>.

The change in the temperature of the point, Δ''T'', is then calculated using the incoming power, ''P<sub>in</sub>'', the output power, ''P<sub>out</sub>'', the time step, Δ''t'', and the [https://en.wikipedia.org/wiki/Heat_capacity heat capacity] of silicate, ''C'' = 2.08×10<sup>8</sup> J/K, using

:<math>\Delta T = (P_{in} - P_{out})\Delta T / C. </math>

Heat flows from areas of high temperature to areas of low temperature, so the heat in a single point on the surface map of an object may spread or [https://en.wikipedia.org/wiki/Diffusion diffuse] into nearby points, and the heat in those points may spread to the first point. Universe Sandbox calculates this diffusion by using the [https://en.wikipedia.org/wiki/FTCS_scheme FTCS method] to solve the [https://en.wikipedia.org/wiki/Heat_equation heat equation]. The temperatures of each point on the surface map are then corrected based on the results of this diffusion calculation.

===Elevation and Displacement===