from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A decrease in the wavelength of radiation emitted by an approaching celestial body as a consequence of the Doppler effect.
From the fact that the shorter wavelengths of light are at the blue end of the visible spectrum.(American Heritage® Dictionary of the English Language, Fourth Edition)
This is the gift that age brings: even as the sirens' blue shift unsteadies her, her palms are tender as talc.