Physics Buzz: Naked Singularities Have Permanent Clothes

The center of a black hole is a mysterious place - a singularity where matter is concentrated into an infinitesimally small point and the laws of physics break down making anything possible. A year ago, a couple physicists said that we might be able to see into a black hole, to see a "naked singularity." Today, three physicists say that's not possible.

In October 2009, Ted Jacobson and Thomas Sotiriou published a paper theorizing that under the right circumstances it could be possible to see the center of a black hole. Now, in a new paper due to appear in Physical Review Letters, three physicists argue the Jacobson/Sotiriou theory, saying that no real-life circumstances would ever allow a singularity to be revealed.

To understand what we're talking about, we first have to understand a black hole's anatomy. A black hole's outer edge - called the event horizon - is defined as the "point of no return" where gravity is strong enough to trap objects traveling at the speed of light, not to mention any passersby going slower.

At the center of the black hole is a singularity, the area where matter is densely packed. We can't see beyond the event horizon, though, because everything inside is gravity-bound. No light can escape. That makes the singularity invisible to us.

But what if there was a way to destroy the event horizon, Jacobson and Sotiriou asked? Then we could see a naked singularity.

The duo said that if a spinning object collided with a black hole spinning in the same direction their combined momentum would allow the spinning force to counteract gravity enough to overcome the event horizon. No more trapping of light. We could see inside a black hole.

What would happen then is anybody's guess. It could mean the destruction of the universe. Because of that, scientists like Stephen Hawking believe in a cosmic censorship conjecture that requires singularities to be shielded by indestructible event horizons.

To come to their conclusion that an event horizon could be destroyed, Jacobson and Sotiriou used a mathematical simulation of a black hole. To do the difficult calculations, though, they had to discard some of the variables.

To understand what Jacobson and Sotiriou did, imagine that instead of simulating a black hole, they were simulating the Earth. To make the math easier, they effectively said the Earth was round, even though we know it is not. In reality, it is covered with small bumps like mountains and trees that, though small relative to the size of the Earth, do affect its gravity. Jacobson and Sotiriou ignored those bumps and their results told them that an object colliding with a black hole could disrupt the event horizon.

Enrico Barausse, Vitor Cardoso and Gaurav Khanna - the physicists with the latest paper - spent the last year adding some of those bumps back into the equation. Their results showed that as the object approached the black hole, the object's gravity would be enough to cause it to be deflected away from the black hole, keeping the event horizon intact.

Their research confirms the cosmic censorship conjecture, keeping any would-be naked singularities under wraps.

via physicsbuzz.physicscentral.com