9 | | The equation that governs the total radiative energy in the grid, E, |
| 9 | [[latex($\frac{\partial \rho e}{\partial t}<0$)]] |
| 10 | |
| 11 | which is interpreted as the matter losing energy via BB radiation. That is, the internal energy of that zone will decrease, thereby producing a concomitant increase in the radiation field's energy, or E, as we will see next. This equation also tells us that when [[latex($4 \pi B<cE$)]], there is more energy in the radiation field than in the BB, and so it gets absorbed by the matter. This causes the internal energy to increase, |
| 12 | |
| 13 | [[latex($\frac{\partial \rho e}{\partial t}>0$)]] |
| 14 | |
| 15 | Since the matter and the radiation are coupled in this way, the equation that governs the total radiative energy in the grid is the inverse of the internal energy, but with an added term for diffusion. Thus, E, can change in the grid either by acquiring energy from the blackbody radiation, and/or, by diffusion. |