> I suppose that's all "environment" you need for a large number of degrees of freedom. No. The 100 atoms is the largest molecule that we can do experiments on

> I suppose that's all "environment" you need for a large number of degrees of freedom. No. The 100 atoms is the largest molecule that we can do experiments on without having decoherence happen and ruining our attempts to observe interference. The number of degrees of freedom in the environment is many orders of magnitude larger, something like 10^30 or more for a typical experiment.