The simplistic portrait masks a mind-bendingly complex realityby Philip Ball / April 12, 2019 / Leave a comment
The groundbreaking picture of a black hole that graced most newspaper front pages on 11th April must be one of the most deceptive scientific images ever. That’s not to impute any intentional deceit to the international team of 200 or so astronomers who created it—it’s just that nature conspires here to produce something that looks archetypally, almost simplistically black-holeish, but which in reality is a mind-bendingly complex sight.
What we got was a bright yellow-orange blob with a black void in the middle: a cosmic doughnut in which the voracious gravitational field of the light-gobbling entity in the centre had apparently chomped out a perfect circular gap. If you ever imagined staring through a telescope at a black hole, you might have thought this is just what you’d find. But you’re not seeing what you might think you are, partly for reasons that are deeply strange.
The reason for all the excitement is that this is the first time a black hole has ever been imaged directly by any telescope. Black holes are stars—or in this case, vast conglomerates of many stars—that have collapsed under their own gravity. Albert Einstein’s theory of general relativity, published in 1916, predicts that in some circumstances this collapse becomes a runaway process that continues until the objects shrinks to an infinitely small point, called a singularity, where its mass becomes infinitely dense. The gravitational field created by such a dense object is so strong that, within a certain distance (called the event horizon), nothing can escape from being sucked in—not even light. What, according to Einstein’s theory, is really happening here is that the unthinkably dense mass warps time and space itself, so that there are simply no paths for the light inside the event horizon that can lead back out. This is the key to the oddness of the new image: what it’s really showing is not simply a sphere that absorbs all the light falling on it, but a place where time stops and space is curved in on itself.
Black holes were thought at first to be too absurd to be believed. But from the 1960s, when research on general relativity came back into fashion in physics, it became gradually accepted that…