GARY HINCKS / SCIENCE PHOTO LIBRARY GARY HINCKS / SCIENCE PHOTO LIBRARY
Redshift observation. Diagram illustrating how light from a distant star can appear shifted towards the 'red' end of the spectrum (an increase in wavelength) if the observer and star are moving away from each other (arrow). The converse effect, when objects are moving towards each other, is called a blueshift. Observations of redshift in distant objects (millions of light years away) are cosmological evidence for the general expansion of the universe. Here, the light shown passing between the star (left) and the observer (right) is shown with its wavelength increasing from the 'blue' end to the 'red' end of the spectrum.
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