Alternative Theories
Although dark matter is the most popular theory to explain the various astronomical observations of galaxies and galaxy clusters, there has been no direct observational evidence of dark matter. Some alternative theories have been proposed to explain these observations without the need for a vast amount of undetected matter. They broadly fall into the categories of modified gravity laws and quantum gravity laws. The difference between modified gravity laws and quantum gravity laws is that modified gravity laws simply propose alternative behaviour of gravity at astrophysical and cosmological scales, without any regard to the quantum scale. Both posit that gravity behaves differently at different scales of the universe, making the laws established by Newton and Einstein insufficient.
Read more about this topic: Dark Matter
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