“..The source of time travel speculation lies in the fact that our best physical theories seem to contain no prohibitions on traveling backward through time.
The feat should be possible based on Einstein’s theory of general relativity –
– which describes gravity as the warping of spacetime by energy and matter.
An extremely powerful gravitational field – such as that produced by a spinning black hole –
– could in principle profoundly warp the fabric of existence –
– so that spacetime bends back on itself..”
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