In some discussions here about quantum effects in the macro world, ZapperZ will only admit that things like superconductivity, Bose Einstein condensates etc. are good examples. But these are just macroscpic quantum coherent phenomena. Of course, if you have a flux qubit, you can directly demonstrate certain types of non-classical behavior that cannot be reproduced using ordinary macroscopic objects. But then a baseball is ultimately also described by a many particle wavefunction (that is, of course, completely entangled with the rest of the world). The fact that macroscopic objects like a baseball are described by quantum mechanics and not by classical mechanics can be readily demonstrated using interference experiments. Consider doing a two slit interference experiment. Behind the slits there are floating mirrors that reflect the light in some direction toward a screen. On the screen an interference pattern will be visible, despite the fact that there will be some momentum transfer from the photons to the mirrors. This means that the momentum transfer to the mirrors is not suficient to determine the which path information. This is explained by the fact that due to rapid decoherence of the mirrors in the position basis, the wavefunction of the mirrors in momentum space is much broader than the momentum transfers to the mirrors by the photons. Any attempt to prepare the mirrors in states with a sharply defined momentum is doomed due to rapid decoherence. Now, according to classical physics, the mirrors always have a well defined center of mass position and momentum. But then you would always have precise which path information and you could not see an interference pattern. The fact that we do see an interference pattern can only be explained by the fact that the mirrors do not have a well defined momentum which violates classical mechanics for the macroscopic center of mass motion of the mirrors. So, why isn't this considered to be experimental proof of the validity of the formalism of quantum mechanics in the macro world?