*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.