In an analysis in Physics Letters B of the motion of particles entering a black hole, published in March, Nikodem Poplawski of Indiana University in Bloomington showed that inside each black hole there could exist another universe. “Maybe the huge black holes at the center of the Milky Way and other galaxies are bridges to different universes,” Poplawski says. If that is correct — and it’s a big “if” — there is nothing to rule out our universe itself being inside a black hole.

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— Cosmologist’s theory about black holes puts a new spin on the universe