Will the World's Largest Supercollider Spawn a Black Hole? (Op-Ed)

Cutting-edge science is an exploration of the unknown; an intellectual step into the frontier of human knowledge. Such studies provide great excitement for those of us passionate about understanding the world around us, but some are apprehensive of the unknown and wonder if new and powerful science, and the facilities where it is explored, could be dangerous. Some even go so far as to ask whether one of humanity’s most ambitious research projects could even pose an existential threat to the Earth itself. So let’s ask that question now and get it out of the way.

Can a supercollider end life on Earth? No. Of course not.

But it’s not really a silly question for people who haven’t thought carefully about it. After all, the Large Hadron Collider (LHC), the world’s biggest and most powerful particle accelerator, is explicitly an instrument of exploration, one that is designed to push back the frontiers of ignorance. It’s not so unreasonable to ask how you know something isn’t dangerous if you’ve never done it before. So how is it I can say with such utter confidence that the LHC is completely safe?

Well, the short answer is that cosmic rays from space constantly pummel the Earth with energies that dwarf those of the LHC. Given that the Earth is still here, there can be no danger, or so the reasoning goes.

And that could well be the final story, but the tale is much richer than that short (but very accurate) answer would lead you to believe. So let’s dig a bit deeper into what makes some suspect a danger, and then explore a fairly detailed description of the point and counterpoint involved in delivering a solid and satisfying answer to the question.

Can the LHC create an Earth-killer black hole?

Skeptics have proposed that the LHC would produce many possible dangers, ranging from the vague fear of the unknown to some that are strangely specific.

The most commonly mentioned is the idea that the LHC can make a black hole. In popular literature, black holes are ravening monstrosities of the universe, gobbling up everything around them. Given such a depiction, it’s not at all unreasonable for people to then wonder if a black hole created by the LHC might reach out and destroy the accelerator, the laboratory, then Switzerland, Europe and finally the Earth. This would be a scary scenario, were it credible — but it’s not.

What immediately follows are the weaker (but still compelling) reasons why this possibility is, well, not possible, and in the next section you will see the cast-iron and gold-plated reasons to dismiss this and all other possible Earth-ending scenarios.

The first question is whether a black hole can even be created at the LHC. Alas, when looking at all of the scientific evidence and using our most modern understanding of the laws of the universe, there is no way that the LHC can make a black hole. Gravity is simply too weak for this to occur.

Some skeptics protest that one explanation for the weakness of gravity is that tiny extra dimensions of space exist. According to that theory, gravity is really strong and just appears to be weak because gravity can “leak” into the extra dimensions. Once we start probing those tiny dimensions, the strong gravity could perhaps make a black hole. Sadly for black hole aficionados, no one has found evidence for the existence of extra dimensions, and if they don’t exist, the LHC can’t make black holes.

So the entire underlying idea of that particular possible danger is built on a long shot. Yet, even in the unlikely case that extra dimensions are real and a black hole can be created, there is a good reason to not worry about black holes damaging the Earth.

The shield against that hypothetical danger is Hawking radiation. Proposed in 1974 by Steven Hawking, Hawking radiation is essentially the evaporation of a black hole caused by its interactions with particles created in the vicinity of the hole. While black holes will absorb surrounding material and grow, an isolated black hole will slowly lose mass.

The mechanism is a quantum mechanical one, involving pairs of particles being made near the surface of the hole. One particle will go into the hole, but the other will escape and carry away energy. Since, according to Einstein’s theory of general relativity, energy and mass are the same, this process has the effect of very slowly decreasing the mass of the black hole. Even though one particle enters the hole, the loss of the other results in the hole slowly evaporating. This is a tricky point. Most people think of a black hole as the mass at the center, but it’s actually both the mass at the center and the energy stored in the gravitational field. The particle zooming down to the center is just moving around in the black hole, while the particle that moves out escapes the black hole entirely. Both the mass of the escaping particle and the energy it carries are lost to the black hole, reducing the energy of the entire black hole system.

And the rate at which a hole evaporates is a strong function of the hole’s size. A large black hole will lose energy very slowly, but a small one will evaporate in the blink of an eye. In fact, any black hole the LHC could possibly make, via any possible theory, will disappear before it can get near any other matter to gobble up.

Courtesy: Space News