The black hole is enormous, with a radius of roughly 9 billion miles... The concept of a black hole goes back to the 18th century, when the English astronomer-clergyman John Michell calculated that a sufficiently large star couldn't shine because light wouldn’t move fast enough to “lift off” and escape the star’s gravity. But Michell’s conjecture outran the physics of its time, which didn’t understand light, gravity or stars well enough to support it. The foundations for the modern understanding of black holes weren’t laid until the early 20th century, building on James Clerk Maxwell’s theory of electromagnetism and Albert...