Search for a border between classical and quantum worlds

The effects of environmental decoherence on a mass-center position of a body consisting of many atoms are studied using a kind of linear quantum Boltzmann equation. It is shown that under realistic laboratory conditions these effects can be essentially eliminated for dust particles containing ${10}^{15}$ atoms. However, the initial velocity distribution and certain geometrical conditions make standard interference-type measurements extremally difficult beyond the nanometer scale. The results are illustrated by the analysis of the recent experiments involving fullerenes. Applications of decoherence effects to precise monitoring of environment or to separation of molecules are suggested.