May seem really daft but I don't know of any ways of detecting redshift in the rest of the EM spectrum, so was just wondering

  • 2
    $\begingroup$ If this shirt is blue you are moving too fast $\endgroup$
    – Paul
    Mar 4, 2017 at 14:14
  • $\begingroup$ @Sam Can you clarify your post? Your title asks something and the question content asks for something else. $\endgroup$
    – Yashas
    Mar 4, 2017 at 17:21
  • $\begingroup$ Can you explain why you seem to think that the frequency of light changes how you detect the redshift? $\endgroup$
    – Kyle Kanos
    Mar 4, 2017 at 20:30
  • $\begingroup$ You would use a radio telescope to detect redshift in the radio portion of the spectrum, and an X-ray telescope to detect redshift in the X-ray portion. $\endgroup$
    – Barmar
    Mar 4, 2017 at 22:38
  • $\begingroup$ Microwave spectroscopy, Infrared spectroscopy, UV spectroscopy (partially), X-ray spectroscopy, Gamma-ray spectroscopy. In any of these bands of the EM spectrum, a source moving away from an observer will be observed to have a spectrum shifted towards longer wavelengths. $\endgroup$ Mar 6, 2017 at 21:30

1 Answer 1


Redshift is said to have happened when the wavelength of electromagnetic radiation increases. Blueshift, a sister phenomenon of redshift, is said to have happened when the wavelength of electromagnetic radiation decreases.

In the visible light spectrum, the red color has a longer wavelength, around $700nm$, compared to other colors; Violet, for example, has a wavelength of $400nm$. When the blue light gets redshifted, i.e: its wavelength increases, it becomes redder. Hence, the name redshift. Though the word 'red' exists in the name, it has got nothing to do with red or visible light. This redshift phenomenon affects radiation of all wavelengths: gamma rays, x-rays, ultraviolet, visible light, infrared, microwave, radio waves and everything else in the electromagnetic wave spectrum.


Bonus: Redshift and the expansion of the universe (the big bang)

The redshift in different wavelengths of light measured from different galaxies is an indication that the galaxies are moving away from us. These observations not only indicate that galaxies are moving away from us but also indicate that the most galaxies are moving away from other galaxies. This hints at us that the universe is possibly expanding at every point.

However, it is important to note that these observations cannot stand on their own and prove that the universe is expanding. You'll need to take help from general relativity to conclude that the distant galaxies are moving away from us faster than light, or in other words, the universe is expanding.

The cosmic microwave background radiation and the cosmological redshift-distance relation are together regarded as the best available evidence for the Big Bang theory. Measurements of the CMB have made the inflationary Big Bang theory the Standard Model of Cosmology.

Source: Cosmic microwave background (wikipedia)

The cosmological redshift has played a very important role in our understanding of the universe.

Useful References:

  1. How does the Hubble redshift work?

  2. Interpretation of cosmological redshift

  3. Expanding space and redshift

  • 1
    $\begingroup$ You have your wavelengths mixed up. Red has longer wavelength, around 600-700 nm. $\endgroup$
    – nasu
    Mar 4, 2017 at 15:27
  • $\begingroup$ This redshift mush affect on the x-ray or gamma-ray of the furthest galaxies and turn them to visible light right? Also must turn the visible ray to infrared and lower wavelength. Do we have proof of them? $\endgroup$
    – imanzabet
    Mar 4, 2022 at 22:17

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