Redshift

n. shift toward the longer wavelengths in the spectral lines emitted by a heavenly body (caused when an object is moving away from an observation point)

This article is about the physical phenomenon. For the photochemical usage, see bathochromic shift. For other uses of the phrase "red shift" or "redshift", see redshift (disambiguation).In physics and astronomy, redshift occurs when the electromagnetic radiation, usually visible light, that is emitted from or reflected off an object is shifted toward the (less energetic) red end of the electromagnetic spectrum. More generally, redshift is defined as an increase in the wavelength of electromagnetic radiation received by a detector compared with the wavelength emitted by the source. This increase in wavelength corresponds to a decrease in the frequency of the electromagnetic radiation. Conversely, a decrease in wavelength is called blue shift.
See more at Wikipedia.org...

n. การเปลี่ยนความยาวคลื่นของคลื่นแสง (ทางดาราศาสตร์)