PM is a popular German magazine that reports in a usually entertaining way on science and engineering. I never much read it because to my taste there's always been too much engineering in it, but it makes for a nice read on the beach or so. The PM article about black holes at the LHC is unfortunately a) in German and b) not available online, but you can look at the two-page illustration here and read the first paragraphs here. You get the flavor I presume, we've all seen numerous articles of that sort during the last months. For an extensive discussion of the key points, see our previous posts on Micro Black Holes, Black Holes at the LHC - again, Black Holes at the LHC - What can happen, and Black Holes at the LHC - the CERN Safety report.
Regarding the PM article, we could not restrain from writing a letter to the editor that referred specifically to the last part of the article, in which they introduce the allegedly ingenious idea of how to supply the world's demand of energy with black hole relics. I commented on this previously in my post 'Micro Black Day'. The idea is roughly that in case the LHC produces black holes, and these happen to not evaporate completely but leave behind stable remnants (relics) one could use these relics to convert arbitrary matter in radiation energy. The picture, so I guess, I to collect the relics, shovel in garbage upon which they gain mass, radiate down again to the relic mass, thereby emitting clean energy with an average temperature of some hundred GeV.
Here is a rough translation of our letter that comments on this scenario:
- Letter to "Will a Black Hole swallow Earth?" PM 07 / 2008
As physicists who have worked for several years on the possible production of black holes at the LHC we were disappointed by your article. Instead of discussing the interesting aspects of the science involved, like Hawking-radiation or generally collider physics, you produce a sensational article about a constructed doomsday scenario.
Especially inappropriate is your mentioning of "Scenario No 3: Free energy in abundance," referring to a patent filed by Prof. Horst Stöcker. To begin with, it is completely wrong that "researchers find more and more hints that black holes do not completely evaporate". There are no hints whatsoever, and nothing changed about that recently. This possibility can just not be outruled.
Worse than this inaccuracy however is that your estimate about the "harvesting" of black hole radiation ignores the fact that one has to run a particle collider the size of the LHC to produce these black holes in the first place. The power consumption of CERN to run the LHC is about 240 Megawatt, about one fifth of a nuclear power plant. Even with the very optimistic estimate that the LHC produces about one black hole per second, this would then take about 70 kWh each - this is the mass equivalent of about 1018 protons or 1015 times the mass of the black hole itself. The black hole therefore has to convert about one billion billion protons into radiation in order to generate a net energy gain. In addition one has to take into account that even if these black hole relics can be produced, they have a very small cross-section and - similarly to neutrinos - will pass through all kinds of matter almost without interaction and will generally escape into outer space. Unless, that is, they carried electric charge, which could happen for purely stochastic reasons for about 2/3 of these black hole relics. However, if one "feeds" the black hole relics and lets them evaporate down to relic mass again, the end product will in one out of three cases be neutral again and escape. Therefore, it is practically impossible to reach only approximately the break-even-point of 1018 protons to be converted into energy: one had to constantly reproduce the black holes.
And with that we haven't even touched the question of how long it would take to get a "truck with only ten tons normal matter" to "cover the energy supply of the whole earth" into such a black hole with a cross-section of 10-32 cm2 - as mentioned, this cross-section is extremely small: the radius of the black hole of about 10-18 m stands in relation to the width of a needle with a diameter of about 1mm as the width of the needle to the average distance of the earth to the sun.
As far as we know, Prof. Stöcker's filed in patent was declined. The idea you are advertising here is scientifically complete nonsense.
To restore the scientific credibility (well, I'm not completely heartless) of Prof. Horst Stöcker and Prof. Marcus Bleicher who grin from a photo in that magazine, let me point you towards a very nice article by them that was on the arxiv today
- Exclusion of black hole disaster scenarios at the LHC
The upcoming high energy experiments at the LHC are one of the most outstanding efforts for a better understanding of nature. It is associated with great hopes in the physics community. But there is also some fear in the public, that the conjectured production of mini black holes might lead to a dangerous chain reaction. In this paper we summarize the most straightforward proofs that are necessary to rule out such doomsday scenarios.