"Physics provides the laws," I said. "Mathematics provides the language to predict the future before it happens. The fire at Notre-Dame was a tragedy. But the resonance was a lesson . And thanks to the general solution of the second-order linear differential equation, we can build a cathedral that will never fall again." The jury was silent for ten seconds. Then the physics professor smiled. The math professor adjusted his glasses and asked: "And what is the particular solution for a non-homogeneous term that is not sinusoidal, but a thermal shock function?"

I solved the homogeneous equation first: (x_h(t) = A e^{r_1 t} + B e^{r_2 t}), where (r_1) and (r_2) are roots of the characteristic equation (mr^2 + cr + k = 0).

"Léa, what is the link between your mathematics and physics specialities?"

I took a breath. I told them the story of the fire. Not as a tragedy—but as a differential equation.

Prologue: The Silence of Notre-Dame It is April 16, 2019. The morning after the fire. I am standing on the cobblestones of Paris, watching the last wisps of smoke curl from the charred skeleton of Notre-Dame Cathedral. The world is crying. But I am not crying. I am calculating.

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