Black holes are one of the most naggingly peculiar objects in the universe. Beyond the event horizon of a black hole, our equations are turned upside down; they also get turned inside out when we attempt to fathom the singularity at its center when using the equations given to us by Einstein. To make life simpler, what if we removed the singularity all together? There is some math for that.
Quantum gravity is an attempt in theoretical physics to explain gravity and the behavior of gravitational fields at the quantum scale. In other words, quantum gravity is one possible 'Theory of Everything' scientists are considering. When you apply the framework of quantum gravity to a black hole, some very interesting things happen, among the most interesting is the vanishing singularity.
Instead of a singularity, quantum gravity replaces the center of a black hole with science-fiction’s best friend – a portal to another universe. How many times have we seen our hero (or the villain) fall into a black hole and avoid a crushing death by being transported to another universe? That might not be so far from the truth. Disregarding the fact that our favorite sci-fi movies get a boost of scientific accuracy, such a model immediately helps physicists resolve the black hole information paradox.
The paradox basically addresses two parts of scientific theory that are butting heads with each other. On one hand, general relativity combined with quantum mechanics seems to suggest that information can permanently vanish when it’s devoured by a black hole. In contrast, a common tenet of science states that information cannot be permanently destroyed.
OK, back to the singularity, or lack thereof. As most of you are aware, flying into a black hole is a very poor life choice. According to relativity, tidal forces from the black hole will elongate you in a process affectionately called 'spaghettification' – and all of this happens before you cross the event horizon. After you pass the point of no return, you’ll continue to fall to the singularity (the point at the center of the black hole where gravity is infinitely strong and all matter is crushed into an infinitely dense point--fun times). What happens next? We have no idea. General relativity simply stops working and breaks down when trying to describe the singularity.
Singularities aren’t the only thing relativity has problems with. Einstein’s crowning achievement also breaks down when describing the big bang. In 2006, a team of physicists used loop quantum gravity in an attempt to explain the big bang; their results were very interesting. Again, the singularity commonly thought to exist at the start of the universe disappeared and was replaced with something the team described as a “quantum bridge” that brought the team into an older universe that existed before ours.
Relativity is a fascinating theory that is nothing short of remarkable, but maybe it’s playing with an incomplete deck when it comes to black holes and their inner singularities. Perhaps a comprehensive theory of everything will reveal hidden portals within one of nature’s most fearsome creations.