Panes of transparent glass intersect and overlap. Starting anywhere, you can interpret what you see as part of a three dimensional object, but whose orientation is unclear. As your eyes continue along a path, you will find edges that force the panes to take a specific orientation. But if you try to extrapolate, you find contradictions: panes that looked horizontal now seem to be vertical, or vice versa. On a larger scale, it is impossible to perceive this scene as a definite physical object that can live in three dimensions.

*inconsistent histories*about what happens in the world. There is fundamentally no single objective reality on which all observers will agree.**

Glass is based on the premise that while here, the top group of panes looks vertical and the bottom group looks horizontal, ...

... if we see only a small subset of these clusters, we cannot distinguish them.

So the two states exist in superposition, until we reach an edge, where typically one particular orientation is favoured. This represents a measurement in quantum mechanics: the

*collapse of the wave function*.

* The Consistent Histories Interpretation, proposed by R.B. Griffiths (1984) and elucidated by the late Pierre Hohenberg in his Reviews of Modern Physics article (2009).

** This statement is shared by all interpretations of quantum mechanics.

Those with Waves show structure at the larger scales, representing the classical domain where indeed what we typically measure are waves.

( These effects can coexist, as here )

In contrast, those without any Shadow and without Flow are typically the most ambiguous.