$$\mathrm{d}s^2 = \left(1 - \frac{2M}{r}\right) \mathrm{d}t^2 - {\left(1 - \frac{2M}{r}\right)^-}^1 \mathrm{d}r^2 - r^2 \mathrm{d}Ω^2$$ that’s not a black board, that’s the black hole! this isn’t the university of life, this is the university of you! – James Martin and The Guest, ‘GOOD DOG’