  Spectra of various particle species have been calculated with the Quantum
Molecular Dynamics (QMD) model for very central collisions of Au+Au. They are
compatible with the idea of a fully stopped thermal source which exhibits a
transversal expansion besides the thermal distribution of an ideal gas.
However, the microscopic analyses of the local flow velocities and temperatures
indicate much lower temperatures at densities associated with the freeze-out.
The results express the overall impossibility of a model-independent
determination of nuclear temperatures from heavy ion spectral data, also at
other energies e.g. CERN or for other species (i.e. pions, kaons, hyperons)!
