The Personal Blog of Stephen Sekula

We Created the Monster

An article in today’s NY Times, forwarded to me by a friend, notes that the LHC may face a threat other than the realities of a slipping schedule when building a one-of-a-kind, frontier physics experiment: the law. That’s right! THE LAW. [1]

Specifically, a lawsuit brought in a Hawaiian court seeking to stop the turn on of the LHC. Why? Because the LHC could destroy the world. That’s the argument – specifically, that the LHC may create micro black holes that, if stable, would devour the Earth.

Let’s step back from the details of the article for a second and really think about this. Are we surprised? I mean, are we shocked that a few citizens of the U.S. are bringing suit to stop the formation of micro black holes in Geneva after years of touting how the LHC could produce black holes? The physics and astronomy community has spent decades sexing up the destructive force of cosmic black holes, dead stars forever feeding on whatever might pass into their gravitational arms. Rightly so, those things are terrifying!

But we failed to do a good job of communicating the relationship between black hole size and danger. A big black hole can live along time, but a small one suffers from a serious problem: thermodynamics. In fact, one of the first problems that I had to solve in graduate level statistical mechanics was the problem of the micro black hole. Let me see if I can dig up my notes on this . . .

Yep, here it is: legendary LD3!

LD3: Hawking radiation and the lifetime of black holes

(a) It was observed by J. Bekenstein, Phys. Rev. D. 7, 2333 (1973), that the entropy of matter falling into a black hole should increase the entropy of the black hole, and that the entropy of the hole should be proportional to the area. The resulting temperature of a black hole of mass M or energy Mc^2 is T = hbar c^3/(8 pi k G M), where G is Newton’s constant.

Determine the entropy S assuming that S = 0 for a zero-mass black hole, and find the dependence of the area A = 4 S L^2_{Pl} on M. Here, L_{Pl} is the Planck length, L_{Pl} = sqrt(hbar G/c^3) ~ 1.6 x 10^{-33} cm. Estimate the size of a black hole of solar mass, M = 2 x 10^{33} gm.

(b) A black hole with T > 0 will radiate photons (and neutrinos) with a thermal spectrum [S. W. Hawking, Nature 248, 3 (1974); Comm. Math. Phys. 43, 199 (1975); Phys. Rev. D 13, 191 (1975)]. The power radiated per unit area in this “Hawking Radiation” is given by the expression for blackbody radiation, P = sigma T^4, up to a factor of order unity. Here, sigma is the Stefan-Boltzmann constant sigma = pi^2 k^4/(60 hbar^3 c^2). Use this result to estimate how massive a black hole formed in the big bang must be if it is to have survived the ~ 15 x 10^9 yr to the present.

In the comments on the problem set, Dr. Durand (LD = Loyal Durand) asked the following: “How long would a black hole of your mass last?” The answer to the last problem is as follows: for a person of mass 100 kg, compressed into a black hole, the lifetime of the black hole is just 8.4 x 10^{-11} s. That’s so far below the blink of an eye that it might as well not even exist. All of the energy would be released in the form of particles (photons, neutrinos, probably some other stuff).

Putting this in perspective, the collision energy of the LHC is 14 TeV. We can convert energy (trillions of electron volts, or TeV) to mass using E = mc^2, to find the mass equivalent. That turns out to be 2.5 x 10^{-23} kg – far smaller than little old 100 kg me – and therefore far shorter lived.

But all of this is academic – quite literally. To this date, there is no evidence that black holes evaporate, although it would mean abandoning several hundred years of well tested thermodynamics if they behave differently than other blackbodies. Making black holes in the lab would teach us a hell of a lot about them, and assuming they obey thermodynamics (in the same way we assume gravity will pull us down when we jump and that water will go down the toilet when we flush) there is no doubt we’ll make them safely in the lab, watch them evaporate, and leave behind beautiful images of their deaths.

Setting aside the science for a second, there is a societal issue here. Physicists have a knack, it seems, for telling the public to “f**k off”. Sorry for the language, but that’s how it comes across boys and girls. Of course, it’s only slightly veiled. Take Nima’s comment:

“There is some minuscule probability, he said, ‘the Large Hadron Collider might make dragons that might eat us up.'”

I can translate that for you – get lost, go away, f**k off.

Instead of making these belittling comments, why not invite the two plaintiffs in the suit to come to CERN, ask as many questions as they like and see anything they like? Why not invite the community into the lab and let them decide when they’re satisfied. If they feel their suit needs to go forward, so be it. Heck, why not even invite them to participate in the safety oversight committee? If people are skeptical, why not bring them closer to the process than further away? After all, it’s a good chance for people to see the process in action. They might not be able to do all the math, if math is involved (although one of the plaintiffs should have no trouble at all with it, by the description), but they can at least feel a part of the conversation and decide whether there is wool being pulled over eyes.

After all, we created this monster. We sexed up the physics with flashy graphics and simplified language. We did the right thing – we communicated the science and got a whole bunch of people interested in it. Now we have to accept that this comes at a price, since free thinking people will come up with ideas. However, in science there is a way to test those ideas (including turning on the LHC), and we shouldn’t discourage people from such thinking after telling them they have every right to get excited. Our job now is to encourage the exploration of that thinking within the rigor of the scientific method.

Getting people excited about science is easy, when you think about it. Getting them to practice it when they start wielding it as a tool – that’s a helluva lot harder.

[1] Asking a Judge to Save the World, and Maybe a Whole Lot More

P.S. Want the solutions to the above problems? Let me know!