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| cosmological redshift | Slipher | A few galaxies show blueshifts, the most famous being Andromeda galaxy, but most show redshifts, due to the expansion of the universe. | 1926 | The redshift due to the expansion of the Universe. Contrary to popular belief, this is not a Doppler shift. Most galaxies move away from us, but this is not the cause of their redshifts. Instead, as a light wave travels through the fabric of space, the universe expands and the light wave gets stretched and therefore redshifted. | z | the cosmological redshift as observed is the ratio of the radius of the Universe at the present epoch to the radius of the Universe at the time the radiation left the distant object. | | | wavelength shift is directly proportional to distance |
| Doppler shift | | | | The shift in the received frequency and wavelength of a sound wave or electromagnetic wave that occurs when either the source or the observer are in motion. Approach causes a shift toward shorter wavelengths and higher frequencies, called a blueshift. Recession has the opposite effect, called a redshift. | | the amount of shift is directly proportional to relative velocity | | | |
| gravitational redshift | | | | Displacement of spectral lines toward longer wavelengths due to the effects of gravity. | | | | Einstein effect | |
| isomer shift | | | | Displacement of an absorption line due to the fact that the absorbing nuclei have a different s-electron density from that of the emitting nuclei. | | | | | |
| Lamb shift | | | | A tiny change in the energy of an electron orbiting the nucleus of an atom, caused by the interaction of the electron with other particles that appear and quickly disappear in "quantum fluctuations". (See quantum fluctuations.) | | | | | |
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