Are macroscopic objects self-collapsing ?

[jshrager]

Are macroscopic objects "self-collapsing"?

For fun (and classroom demos) we we regularly calculate the diffraction and time evolution dispersion of macroscopic things like viruses, bullets, and elephants. But it would seem to me that this is actually a pretty misleading. Anything larger than a fundamental particle has structure, so wouldn't anything of any complexity at all, let's say an H2 molecule (or actually, even just a proton!) be self-stabilizing via self-collapse of one another objects' wave functions? Yes, you COULD write down the combined wave function, but in reality wouldn't each object's time-dependent wf be constantly being reset to the initial (delta) state by virtue of the influence of the other object? That is, doesn't the field that holds anything at all together effectively co-collapse the wave functions of each subpart?

 

[The_Duck]

No, objects cannot "self-collapse." Given an arbitrarily large object, we can write down a wave function for it and this wave function will evolve smoothly, without collapse, unless and until the object interacts with something external to itself. Of course, almost all objects of any significant size are constantly interacting with their environment so practically speaking their wave functions do not last long before collapsing.

However, under controlled conditions we have for example done diffraction experiments on buckyballs-molecules consisting of 60 carbon atoms. The buckyballs do not "self-collapse." They demonstrate the same sort of interference pattern as electrons, as long as you are careful not to let them interact with their surroundings. For example, I imagine you would need a good vacuum to do this experiment, so that the buckyballs would not interact with any air molecules.

 

[jshrager]

Terrific; and perfect example; Thanks!