CHRIS BUTLER / SCIENCE PHOTO LIBRARY CHRIS BUTLER / SCIENCE PHOTO LIBRARY
Red shift. Illustration of galaxies distributed in Space, with the furthest galaxies red due to red shift. This effect was discovered by amateur astronomer William Huggins in 1868, who noticed that the light from some stars was further towards the red end of the spectrum. Huggins realised this was due to the Doppler effect: just as the noise of a moving vehicle changes as it passes, so light from a star changes in wavelength as the star moves towards or away from us. Stars moving away more quickly are more red. In 1929 another astronomer, Edwin Hubble, used red shift to show that the fastest receding galaxies are also the most distant, indicating that the Universe is expanding.
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