This artist's impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus. M. Kornmesser/ESO hide caption

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M. Kornmesser/ESO

British cosmologist Stephen Hawking gives a talk to workers at Cedars-Sinai Medical Center in Los Angeles on April 9. Eric Reed/Cedars-Sinai/AP hide caption

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Eric Reed/Cedars-Sinai/AP