The cosmos may have something in common with a doughnut.
In addition to their fried, sugary goodness, doughnuts are known for their shape, or in mathematical terms, their topology. In a universe with an analogous, complex topology, you could travel across the cosmos and end up back where you started. Such a cosmos hasn’t yet been ruled out, physicists report in the April 26 Physical Review Letters.
On a shape with boring, or trivial topology, any closed path you draw can be shrunk down to a point. For example, consider traveling around Earth. If you were to go all the way around the equator, that’s a closed loop, but you could
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