  We use wrapped D-brane probes to measure position dependent perturbations of
compactification moduli. Due to the backreaction of the D-branes on the local
geometry, we suspect that measuring the fluctuations of one modulus to high
precision will generically affect the others. These considerations lead us to
conjecture a novel uncertainty principle on the Calabi-Yau moduli space. We
begin our investigation with a gedanken experiment on a torus.
