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  2. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift , or negative redshift.

  3. Gravitational redshift - Wikipedia

    en.wikipedia.org/wiki/Gravitational_redshift

    In physics and general relativity, gravitational redshift (known as Einstein shift in older literature) [1] [2] is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well lose energy. This loss of energy corresponds to a decrease in the wave frequency and increase in the wavelength, known more generally as a ...

  4. Tests of general relativity - Wikipedia

    en.wikipedia.org/wiki/Tests_of_general_relativity

    It tested the gravitational redshift to 0.007%. Although the Global Positioning System (GPS) is not designed as a test of fundamental physics, it must account for the gravitational redshift in its timing system, and physicists have analyzed timing data from the GPS to confirm other tests. When the first satellite was launched, some engineers ...

  5. Tired light - Wikipedia

    en.wikipedia.org/wiki/Tired_light

    Tired light was an idea that came about due to the observation made by Edwin Hubble that distant galaxies have redshifts proportional to their distance.Redshift is a shift in the spectrum of the emitted electromagnetic radiation from an object toward lower energies and frequencies, associated with the phenomenon of the Doppler effect.

  6. Relativistic Doppler effect - Wikipedia

    en.wikipedia.org/wiki/Relativistic_Doppler_effect

    Given that, in the case where the inertially moving source and receiver are geometrically at their nearest approach to each other, the receiver observes a blueshift, whereas in the case where the receiver sees the source as being at its closest point, the receiver observes a redshift, there obviously must exist a point where blueshift changes ...

  7. Redshift quantization - Wikipedia

    en.wikipedia.org/wiki/Redshift_quantization

    Redshift quantization, also referred to as redshift periodicity, [1] redshift discretization, [2] preferred redshifts [3] and redshift-magnitude bands, [4] [5] is the hypothesis that the redshifts of cosmologically distant objects (in particular galaxies and quasars) tend to cluster around multiples of some particular value.

  8. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    The redshift z is often described as a redshift velocity, which is the recessional velocity that would produce the same redshift if it were caused by a linear Doppler effect (which, however, is not the case, as the velocities involved are too large to use a non-relativistic formula for Doppler shift).

  9. Pound–Rebka experiment - Wikipedia

    en.wikipedia.org/wiki/Pound–Rebka_experiment

    Gravitational redshift measurements provide a direct measure of LPI. Of the three hypotheses underlying the equivalence principle, LPI has been by far the least accurately determined. There has been considerable incentive, therefore, to improve on gravitational redshift measurements both in the laboratory and using astronomical observations. [11]