(this is less surprising when you realise the equations describe facts about geometry, rather than physics[-as-beyond-geometry].)
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Only two of Maxwell's Equations can be derived from varying the action of QED (eq. 1)
To obtain the others, we need Fμν to satisfy the Bianchi Identity (eq. 2)
This implies that Fμν represents a 𝒄𝒖𝒓𝒗𝒂𝒕𝒖𝒓𝒆
This curvature is in a space called a "vector bundle" pic.twitter.com/qlflapqh0G
