There is absolutely, positively, definitely no chance of the LHC destroying the planet when it eventually switches on some time later this year. Right?

Err, yep. And yet a few niggling doubts are persuading some scientists to run through their figures again. And the new calculations are throwing up some surprises.

One potential method of destruction is that the LHC will create tiny black holes that could swallow everything in their path including the planet. In 2002, Roberto Casadio at the Universita di Bologna in Italy and a few pals reassured the world that this was not possible because the black holes would decay before they got the chance to do any damage.

Now they’re not so sure. The question is not simply how quickly a mini-black hole decays but whether this decay always outpaces any growth.

Casadio have reworked the figures and now say that: ” the growth of black holes to catastrophic size does not seem possible.”

Does not seem possible? That’s not the unequivocal reassurance that particle physicists have been giving us up till now.

What’s more, the new calculations throw up a tricky new prediction. In the past, it had always been assumed that black holes would decay in the blink of an eye.

Not any more. Casadio and co say: “the expected decay times are much longer (and possibly ≫ 1 sec) than is typically predicted by other models”

Whoa, let’s have that again: these mini black holes will be hanging around for seconds, possibly minutes?

That doesn’t sound good. Anybody at CERN care to clarify?

Ref: arxiv.org/abs/0901.2948: On the Possibility of Catastrophic Black Hole Growth in the Warped Brane-World Scenario at the LHC