from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An increase in the wavelength of radiation emitted by a celestial body as a consequence of the Doppler effect.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Light spectra shifted towards red, as by elongation of light waves from a source moving away from the detector.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum); generally interpreted as evidence that the universe is expanding
From the fact that the longer wavelengths of light are at the red end of the visible spectrum.(American Heritage® Dictionary of the English Language, Fourth Edition)