We May Have Dramatically Misunderstood the Shapes of Black Holes

By Annalee Newitz on at

Even if you didn’t see Interstellar, you’ve probably heard about how black holes have an “event horizon” — and once you pass it, you’re mashed into multi-dimensional mush. But now, some physicists believe we got it all wrong. Black holes are more like fuzzy balls of cotton, with no event horizons at all.

Over at Quanta, Jennifer Ouellette explains:

In the late 18th century, the scientist John Michell pondered what would happen if a star were so massive, and its gravity so strong, that its escape velocity would be equivalent to the speed of light. He concluded that any emitted light would be redirected inward, rendering the star invisible. He called these hypothetical objects dark stars.

Michell’s 1784 treatise languished in quiet obscurity until it resurfaced in the 1970s. By then, theoretical physicists were well acquainted with black holes — the dark star idea translated into Albert Einstein’s theory of gravity. Black holes have a boundary called an event horizon that represents the point of no return, as well as a singularity, a point of infinite density within.

Yet Einstein’s description of the world is inconsistent with quantum mechanics, driving physicists to seek a complete theory of quantum gravity to reconcile the two.String theory is a leading contender, presenting yet another potential picture: Black holes may be reimagined as “fuzzballs,” with no singularity and no event horizon. Rather, the entire region within what was envisioned as the event horizon is a tangled ball of strings — those fundamental units of energy that string theory says vibrate in various complicated ways to give rise to space-time and all the forces and particles therein. Instead of an event horizon, a fuzzball has a “fuzzy” surface, more akin to that of a star or a planet.

Samir Mathur, a string theorist at Ohio State University, believes fuzzballs are the true quantum description of a black hole and has become a vocal champion of his own self-described “fuzzball conjecture” expanding on the concept. His version of fuzzballs provides potential mechanisms to resolve the knotty problem of reconciling the classical and quantum descriptions of a black hole — and, ultimately, the rest of our universe. But to make it work, physicists will have to abandon long-held notions of singularities and event horizons, a sacrifice many are unwilling to make.

In some ways, this hypothesis makes a lot more sense. Instead of a black hole being a kind of nothingness, it’s more like a star or planet covered in strings. That means when a star becomes a black hole, it retains something of its old shape instead of being converted into the bizarre gravitational phenomenon whose shape is difficult to represent other than as a kind of funnel.

Read the rest of the article at Quanta, to find out how all of this could change our understanding of the universe.

Illustration via Quanta