More on Microscopic Black Holes

13 May 2008

(Not that we can really see black holes... Credit: Fernando Revilla)



While the production of black holes in the LHC is exciting for physicists who understand why they are harmless to life on Earth, some of the general public find the prospect rather alarming. We take these concernss seriously. Below, Michael Barnett of ATLAS Outreach writes to a worried citizen.

Thank you for writing to us about your concern with producing microscopic black holes. As you might guess, the physicists at the Large Hadron Collider have given considerable thought to this subject. The news media and others have speculated about possible danger associated with creating microscopic black holes. If there really were danger, we would be as concerned as anyone else. Of course, we would not consider starting an experiment if we thought there was the slightest risk.

According to some theoretical models, microscopic black holes could be produced in collisions at the LHC. Most people think it is very unlikely, but it would be fascinating if it were possible, and definitely harmless. They would decay into ordinary particles extremely quickly, and those particles would be detected by experiments (the tinier the black hole, the faster it evaporates).

How do we know that they are harmless? Cosmic rays are continuously bombarding Earth's atmosphere with far more energy than protons will have at the LHC, so cosmic rays would produce everything LHC can produce.

They have done so throughout the 4.5 billion years of the Earth's existence, and the Earth is still here. The LHC just lets us see these processes in the lab (though at a much lower energy than some cosmic rays).

We have read in the news media that a few people propose (despite the predications of physics) that black holes do not decay but are stable. Even if this speculation were true, a still more powerful piece of data rules out any concern. Such microscopic black holes would be produced by cosmic rays hitting neutron stars and be absorbed, and would turn the neutron stars into black holes. If this were true, we would not see any neutron stars, but of course we do.

In conclusion, no matter what assumptions one makes, microscopic black holes pose no concern to anyone. Also keep in mind that it is extremely speculative to imagine microscopic black holes being created, since it requires the existence of extra dimensions of space, and several other highly unlikely assumptions.

We hope this reassures you about the complete safety of the Large Hadron Collider. We also hope you will share with us the incredible excitement of great discoveries that the LHC may make over the next few years.

We do not know the exact start of the experiment, since there are many technical complications that make it very hard to determine.

Thank you.

Best regards,


Michael Barnett

ATLAS Outreach


Further Resources

CERN has devoted a web page to easing fears about black holes and strangelets.

For a more technical rundown, a fairly readable paper in the European Journal of Physics explains why LHC mini-black holes would be harmless (if produced at all).

However, not everyone is worried about black holes. Bob Park of the University of Maryland finds the lawsuit filed in Hawaii to be a bit...quixotic.

Muriel's Take (May 5)

Dear editor of ATLAS e-news,

I've a quick question - is there much discussion at CERN about the possibility of creating micro black holes when LHC turns on? I heard about it from another faculty member (apparently someone in Hawaii wants to file a lawsuit to delay the project), and then I heard it again on "The Daily Show" last night. And now, a student wants to study the issue for his semester research topic.

Have you, or Muriel been hearing about it?


Dear Paul,

I'm glad you ask the expert. I sure hope you haven't yet lost any sleep over this. Now talk about fussing about nothing: first of all, a hole, black to boot, and microscopic on top of that! If tiny, weeny little holes are going to get a big grown-up man like you all scared, holy banana, what would a big white bump do to you? And they tell me you used to play with dynamite in your youth?

At home, Fuzz and the gang have been asking me about it too, saying: "And what if one of them micro black holes was to hit us, right now?" My answer to them is: "No luck, kids. Finish your plate." If anything, humanity should be relieved. If only we could produce them and keep them is a micro black hole shaker. We'd have a means to get rid of villains or polluting cars in a flick. But no... They have to evaporate as soon as they are created. Bummer.

As my mother used to say: "If you ain't worth a law suit, you're ain't worth much!" Relax, spring is here, flowers are blooming, sun is shining, and out there in the vast universe, if a few of them microscopic black holes are being created as we speak, it means that they do exist but will create no harm. And the world will keep spinning and the LHC will go on as planned to bigger and better things: big, colourful and wonderful.

Yours, Muriel.



Muriel the Monkey



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