Hey you! Yes, you! Thank you for adding beauty to the world!
Definitions of blue flash:
noun: (meteorology, astronomy) A very rare phenomenon observed in the morning or evening when the sun is crossing or immediately below the horizon, in which a momentary flash of blue light appears above the upper rim of the solar disk, caused by refraction of light in the atmosphere.
noun: (nuclear physics) A phenomenon sometimes observed when a criticality incident occurs in nuclear materials, inducing a discharge of radiation into the environment.