This
image ought to show one of the hemispheres marked red.
The blue was a mass, a single particle, sitting onto the inner lining within the hemisphere. Let's think the hemisphere has got it's counterpart at the other side and the air was pumped out so they are firmly tight.
The yellow circle was an other, bigger, free moving, floating mass (particle), within the hemispheres.
The green arrow points to the spot were the magic will happen. There, both masses (the blue and the yellow circle) would have an alleged common place where, caused by their incompatibility in motion, I think the zero room comes into being. Therefore, the blue, the smaller mass will want to move the hemisphere to the right a bit, caused as well as of the less inertia of the less weight, the restructured form after the zero room has made his way into being, as well as the position of the mass onto the metal surface.
The same will happen at the other side that was not in the image, of course moving the other hemisphere to the left. And is gonna happen millions, billons, trillion? of times making this hemispheres attempts, experiments possible.
Please notice, the sizes of the the single unities in the sketch are not in proper dimensions but I think they visualise the text's content.