A second look at supernovae light: Universe’s expansion may be understood without dark energy

Light disperses from a supernova explosion (yellow) to a site of detection (blue). As the universe expands, the light energy becomes diluted as it travels from its past, dense surroundings to its present, sparse surroundings. The light’s wavelength increases as a result of the decrease in surrounding energy density. IMAGE/Arto Annila/©2011 Royal Astronomical Society

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