Black Holes From the LHC Could Last For Minutes

KentuckyFC writes "There is absolutely, positively, definitely no chance of the LHC destroying the planet (or this way either) when it eventually switches on some time later this year. And yet a few niggling doubts are persuading some scientists to run through their figures again. One potential method of destruction is that the LHC will create tiny black holes that could swallow everything in their path, including the planet. Various scientists have said this will not happen because the black holes would decay before they could do any damage. But physicists who have re-run the calculations now say that the mini black holes produced by the LHC could last for seconds, possibly minutes. Of course, the real question is whether they decay faster than they can grow. The new calculations suggest that the decay mechanism should win over and that the catastrophic growth of a black hole from the LHC 'does not seem possible' (abstract). But shouldn't we require better assurance than that?"

Comments

Re:cosmic rays

[secPM_MS]

Small black holes are far less dangerous than made out to be. I wouldn't like to be very near one due to its Hawking radiation (virtual photon creation near the event horizon where one of the virtual photons is absorbed and the other turns real as it escapes), but the fear mongers of black holes forget the limiting factor. Matter falling into a black hole is compressed and gets hot. The hot matter radiates light / gamma rays. While in some cases this radiation might be captured as well, it is far more likely that the radiation pressure will limit the rate of matter absorption by the black hole. The radiation pressure effect is known as the Eddinton effect and is a major factor in stellar stability. In the case of a small black hole, the size of the black hole is far smaller than the absorption length of gamma rays, preventing advection of the gammas. Since a non-rotating black hole is likely to convert on the order of 1% of the absorbed mass into gamma radiation, such a source would be more than capable of creating a near vacuum of hot matter about itself.

If such stable black holes were creatable / existed, we should see rather remarkable things with old white dwarfs and neutron stars, which would be greatly affected by such energy sources.

Re:cosmic rays

[John Hasler]

> What happens if one of these black holes happens to intercept a spacecraft as it leaves
> or re-enters the atmosphere? Does it do significant damage?

No. Try to understand how small these holes would be. They are so tiny that in the unlikely event that they hit the nucleus of an atom they would almost certainly pass through with out interacting at all with any of the subatomic particles there. Your spacecraft is going to be hit by cosmic rays with far more energy and with a far higher probability of interacting.

Re:Bogus

[blueg3]

Actually, cosmic rays, which regularly (read: constantly) enter our atmosphere, have energies up to 10^20 eV. The LHC uses 7 TeV protons and ~500 TeV lead nuclei. That's on the order of 10^12 to 10^14 eV.

So, you have it backwards. We don't produce particle at anywhere near the energy they're produced in nature.

Re:Advanced Alien Civilizations

[ball-lightning]

Actually, a black hole at mars orbit wouldn't do any damage (to us) because if it swallowed up Mars, it would have the same mass as mars, thus leaving everything else untouched. A black hole on earth would well, not be enjoyable for us.