A reader of my end-of-the-world column from last June

“One of the potential disasters described by Rees has a higher probability

than he estimates. He mentions the possibility that particle colliders might

create mini black holes. However, he estimates the risk as low because he

concurs with the idea that they will dissipate via Hawking radiation.

However, Hawking radiation is a theoretical model that has never been seen.

It may not work as expected. In order to demonstrate that there is question

about this within the physics community, we sent a questionnaire to chairmen

of thirty university physics departments that have a concentration on high

energy physics. The five who responded estimated the probability that

Hawking radiation would work as expected at 50%, 70%, 98%. 99%, and 100%, an

average of 83.4%.

“Another supposed reason not to worry is that cosmic rays in the energy

range of upcoming colliders have been hitting the earth (and the moon, where

they are more likely to hit heavy atoms) for billions of years without

adverse effect. But there is reason to think that a mini black hole would be

about as reactive as a neutrino. Most neutrinos pass completely through

earth without hitting a single atom. A mini black hole created by a cosmic

ray would retain the momentum of the cosmic ray, distributed over the cosmic

ray particle and the earth particle it impacted. It would be moving faster

than escape velocity from earth. It would have to accrete many particles to

slow below escape velocity, impossibly far out on the Poisson distribution

in one pass through earth at neutrino-like rates of impact. On the other

hand, a mini black hole created by two particles moving in opposite

directions would (sometimes) be moving at less than escape velocity from

earth. Depending on its momentum, it would orbit or oscillate within the

earth. It would accrete matter at a rate that would be slow initially, but

that would increase exponentially.

“For references, see www.risk-evaluation-forum.org.”