For ten points, identify this increase in wavelength as light moves away from the observer, most famously manifested in the relativistic Doppler effect.
The Sachs-Wolfe effect observed in the cosmic microwave background is an example of one form of this phenomenon. The Friedman-Robertson-Walker metric can be used to derive the cosmological form of this phenomenon, which was measured by Vesto Slipher, resulting in a famous law. The Ives-Stillwell experiment demonstrated the special-relativistic form of this effect by measuring time-dilation, and in astronomic applications it is usually given as a dimensionless number equal to one plus the emitted frequency over the observed frequency. For ten points, identify this increase in wavelength as light moves away from the observer, most famously manifested in the relativistic Doppler effect.
The Sachs-Wolfe effect observed in the cosmic microwave background is an example of one form of this phenomenon.
{redshift} (accept {gravitational redshift} before “cosmological”)