Prof. Dan Stinebring, Physics

Could the Earth really get swallowed up by a black hole created by the Large Hadron Collider?

Walter Wagner is worried. In fact, he is so worried that he filed a lawsuit in a Hawaii court in March to try and stop the world's largest particle accelerator from starting operation. So far his legal approach hasn't worked, but he's generating lots of press and getting people talking to any physicist or astronomer they know. "Could the Earth really get swallowed up by a black hole created by the LHC?" a friend wrote me recently. Hmmm. I'm not sure on that one. I'll flag it in my inbox and get back to him after grading lab exercises and writing that overdue departmental report. (By the way, the LHC started up on schedule a few weeks ago, but then some magnets burned out, and a months-long repair is underway.)

Are we all going to die? Yes. But are we all going to die in a flash of glory as we get sucked down a micro black hole created by the Large Hadron Collider? Probably not, but, ouch, that would hurt. As I tell my Intro Astronomy students, "It's not the gravity that gets you, it's the tidal forces!" Free-falling feet-first into a black hole wouldn't even be noticeable if the gravitational pull on your feet wasn't hugely greater than the pull on your head. The result is not pretty. You get stretched well beyond the breaking point and eventually disintegrate into individual molecules. It's a good way to recycle, but not an easy way to say goodbye to friends.

What is Walter Wagner worried about? From his vantage point as someone who minored in physics in college and now tends his botanical garden in Hawaii when he's not filing legal briefs, here's the problem: the LHC has the energy to create micro black holes, particularly if the universe we live in has the 10 dimensions that some physicists think that it may have. And we all know that black holes suck matter into them. So wouldn't that create a runaway effect - the black hole that ate Manhattan and Oberlin and Peoria? Nope. Saved by evaporation! At least that's what Steven Hawking has taught us. Nothing is permanent, not even a black hole. Through a tricky quantum mechanical process, black holes absorb one of a pair of virtual particles at their boundary, with the other particle flying out into space. The particle that is absorbed has negative energy, hence the black hole has less mass than it started out with before the quantum nibble.

And, the less massive the black hole, the faster it evaporates. For example, at the full energy of the LHC, if a micro black hole was created - not at all a certainty - it would have a mass of only 10-23 kilogram. That would evaporate in about 10-84 seconds, which even Walter Wagner would agree is a short time.

So, why worry? Well, it's that old bugaboo "it's only a theory." No one has seen a black hole evaporate, although there are certainly people searching. So, if it's only a theory, maybe it could be wrong. And, of course it could be, although it would radically change much of the foundation of modern physics.

Are you still skeptical, having been brought up on various swindles in public life? Well, it turns out that John Ellis, a thoughtful physicist at the LHC, realized that there are plenty of observations about this very thing. He realized that ultra high energy cosmic rays, which are produced by sources like pulsars, pack a lot more wallop than the LHC particles, and they are constantly bombarding the Earth, the Moon, and the Sun. None of the cosmic rays has yet produced a micro black hole that went berserk and started gobbling up everything around it.

Was Walter Wagner silly to think about this? No. It's good to think, and it's good to try out wild ideas on friends and professors. But, it's also good to do some calculations to check your wild ideas and to see if there is any simple evidence that might rein in your imagination. Walter Wagner didn't do that.

He went to court instead. That's going to cost a lot of money and take a lot of time, and that's not great. But, at least it got a lot of people talking and thinking about the LHC and black holes, and maybe that will pay back the negative energy with something positive.

Hurry and get those magnets fixed!