  We point out that the intrinsic relationship between space and momentum in
quantum physics through the uncertainty principle has potential implications
for momentum anisotropy in heavy-ion collisions. Using a harmonic oscillator
potential we calculate the elliptic anisotropy and find it to be sizeable
compared to elliptic flow measurements in nuclear collisions. Our results
question the validity of the completely hydrodynamic interpretation of
anisotropic flow data, and highlight the importance of including quantum
physics in hydrodynamic calculations which has largely been neglected so far.
