Dark matter - that invisible stuff that is supposed to make up some 20% of the Universe - was thought up to explain a puzzling observation. The amount of mass we can see through our telescopes is not enough to keep galaxies from spinning apart. The existence of great quantities of hidden mass would provide the gravitational pull needed to form those galaxies and enable them to rotate in the way that they do.
But not everyone is willing to buy the idea that the Universe is cloaked in "invisible cloth." An alternate theory, first put forward by Weizmann Institute astrophysicist Prof. Moti…
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