Outside the range of a spectrum, especially the visible light spectrum or range of analyzed wavelengths.
From Latin 'extra' (outside) + 'spectral' (relating to a spectrum, from 'spectrum' meaning appearance or image, from 'specere' to look).
Infrared cameras see extraspectral light that our eyes can't detect—animals like pit vipers evolved to see extraspectral heat radiation, giving them superpowers in the dark that humans without technology can only dream of.
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