## Saturday, February 23, 2008

### LHC alarmists

When LHC was getting started on September 10th, 2008, there was an embedded Sky News Live video here.
After some time, I was led to web pages of the LHC alarmists again:
LHC defense
LHC concerns
The most catastrophic man-made phenomena that they are afraid of - and that might be caused by the new accelerator at Franco-Swiss CERN, the Large Hadron Collider (LHC) - are microscopic black hole production, gigantic strangelets, and the tunneling into another vacuum in the landscape. These things may create a growing volume whose interior is incompatible with life and they may destroy our planet: the LHC is therefore irresponsible, they say.

Just like the alarmists of all kinds, these people are using a very contrived - and in this particular case, extremely contrived - combination of common sense, emotional, obsolete scientific, and cutting-edge scientific arguments that are connected exactly in the "right" way to justify the conclusions that they determined at the very beginning. The similarity with other forms of religion is obvious.
If they followed one of the approaches - common sense; phenomenology; classical physics; cutting-edge theoretical physics - consistently, they would know that it is extremely unlikely that there exists any threat. Without a loss of generality, let us talk about the microscopic black holes.

Anthropogenic global blackholing

The hypothetical threat discussed below is that the LHC produces a small black hole that will grow and eat the whole planet, after some time. Is it possible?

In the world of movies, it is. ;-) But what about the real world?

According to classical general relativity, one may create a black hole if he squeezes a sufficient amount of mass (=energy, as special relativity implies) into a small enough region. One can see that if we assume that there are always 3+1 dimensions only, as most people still do, it is technologically impossible to get enough mass in the form of elementary particles to create a black hole.
See a preprint by Koch et al. that rules out the black hole threats at the LHC, too...
The elementary particles are simply too light, even if they are accelerated to high energies. Even if you wanted to create a black hole that it as small as the Planck length, about 10^{-35} meters, you would need to concentrate the Planck energy, 10^{19} GeV or so, into one or two particles. The LHC with its 10^{4} GeV clearly can't do it. The elementary particles themselves have a "size" and you can't squeeze them into too small volumes anyway, certainly not the Planck length.

So if the alarmists followed general relativity as a classical theory, they would have no reason to be afraid because a black hole simply couldn't be produced.
See Giddings & Mangano for a more technical refutation of the LHC black hole alarm
In order for them to have a reason for alarm, they need a theory where the dimensional analysis above is modified, namely theories with additional dimensions, ideally the Randall-Sundrum-like warped compactifications. In such theories, one important additional dimension of space exists, it is highly curved, the normal elementary particles are stuck to a brane (localized in the extra dimensions), and small black holes might be produced by the LHC with some assumptions about the parameters of the theory.

That's great. So do we have a reason to be worried now? No, we don't because these black holes rapidly evaporate. (Even if they didn't evaporate, a black hole produced by the LHC would be too small to eat the planet in a foreseeable future. If it were created in the rest frame, it might sit at the center of the Earth and stay there for eons. But let us assume that the evaporation is the only savior here.)

So the alarmists need to say that they accept the Randall-Sundrum models (1999) as a real possibility but they are going to believe that the Hawking black hole evaporation (1974) doesn't work. It hasn't been experimentally tested, after all, they will tell us - a popular and populist argument frequently applied to brainwashed laymen these days.

Now, this is a really bizarre combination of scientific assumptions. A scientist at the cutting edge of course knows that the existence of black hole evaporation is indisputable. It can be derived in completely different frameworks such as Hawking's semiclassical treatment of general relativity as well as microscopic descriptions of black holes represented by string theory, including the holographic AdS/CFT correspondence. A good physicist knows that whether or not the effect has been experimentally tested is secondary. Only laymen who don't understand the math can have doubts about these matters.

The Hawking radiation is pretty much a fact but the Randall-Sundrum scenario is a relatively unlikely possibility. Every well-informed high-energy physicist including Raman Sundrum and Lisa Randall knows that. The alarmists have to believe that an unlikely theoretical possibility (warped braneworld) is real while an established and universal theoretical result (Hawking radiation) is wrong. That's a very contrived, and I would say inconsistent, position. Why?

Well, the Randall-Sundrum description of our Universe hasn't been experimentally tested either. The only reason why high-energy physicists say that it is a conceivable feature of our Universe that can be tested by the LHC is the respect that they pay to the quantum field theories describing particle physics at very short distances, including the consequences of these theories that haven't been observed directly. But the very same theories and methods imply that black holes evaporate.

So the alarmists are really cherry-picking results to create their fantastic possibility of a judgement day. A peasant would have no reason to believe any black hole production because he has no idea what a black hole is and why it should be produced. He might correctly argue that if the world has survived for so many years, it will survive the year 2008, too. God will stop those CERN guys anyway, if they wanted to do something really bad.

A more educated peasant who is familiar with classical general relativity would conclude that even though black holes may exist, we won't be able to produce them. And a physicist who knows the effective field theory up to Randall-Sundrum phenomenology knows that small black holes at the LHC are conceivable but they quickly evaporate.

The alarmists are gluing pieces of a cutting-edge Randall-Sundrum physicist with pieces of a peasant. Whether you take modern theoretical physics - including semi-classical general relativity - seriously or not, theirs is a very problematic and unlikely position from a rational point of view. They could be afraid of the growing black holes if they believed classical general relativity with extra dimensions but kind of discarded some of the basic consequences of quantum mechanics.

But quantum mechanics is established and I find it difficult to create a psychological setup to estimate probabilities in which very modern features such as extra warped dimensions are accepted but the existence of quantum phenomena is not. The quantum phenomena have been crucial for physicists to figure out whether various extra-dimensional models are acceptable or not. If you give up the Hawking radiation, you must also denounce the methods that are used to decide which models beyond the Standard Model are semi-realistic.

I don't know where it ends - a kind of "anything goes" situation? - but you probably end up close to the peasant who must still use some methods to decide what he thinks about various risks and their probability. I think that he will either realize that the world has survived worse things than the LHC, or he will decide to trust more educated people than he is. If he does something else, he is a conspiracy theorist.

Cosmic rays insurance

There also exists a very general "historical" reason why these catastrophic events, regardless of any details, are a very unlikely possibility for the LHC or any other doable experiment, for that matter. The LHC is going to be more powerful than any previous accelerator but the events it will create are not unprecedented in comparison with the events that have occurred in the Universe - and even on the Earth - billions of times.

Very high-energy cosmic rays are constantly hitting the Earth. The center-of-mass energy of such collisions is often higher than the energy at the LHC. If we believe special relativity for a while - a subtlety discussed below - the only new feature of the LHC is that these collisions will occur repeatedly at the same place that happens to be surrounded by detectors and physicists who will look at them.

Just like in all cases, you might find a loophole. You might decide not to believe special relativity. So the center-of-mass energy won't be the only relevant parameter of a collision for you. You may say that in order to mimick the LHC collisions naturally, we would need two natural 7 TeV cosmic rays to collide with each other - something that doesn't happen too often in the vicinity of Earth.

Now, special relativity is not only pretty but it has been tested. Upper bounds on possible known Lorentz-violating effects have been determined and if you stay within the mantinels, even a slightly Lorentz-violating theory will imply that the LHC collisions are harmless and the calculation involving the center-of-mass energy only is an extremely good approximation.

Fine. So as an alarmist, you might choose to believe that the world is violating the Lorentz invariance in a new way that hasn't been considered. A way that is ultimately compatible with the experiments but that still allows the LHC collisions to be catastrophic. Needless to say, you won't be able to present any coherent theory how it might be possible but you might still believe that yours is a rough sketch of the state of the affairs.

If you do so, it is not necessary to provoke you and say that you are being dishonest: it is enough to neutrally state that the combination of the assumptions that you are making is just extremely unlikely. So unlikely, in fact, that the risk that the LHC is dangerous because of your worries - something that is proportional to the risk that your assumptions are correct - remains safely acceptable. Indeed, the risk can't be exactly zero. But if it is smaller than 10^{-20}, I am ready to okay the LHC without any hesitation. The actual risk is much smaller.

Walter Wagner and the velocity

Walter Wagner, a nuclear physicist in the LHC alarmist NGO, argues that even if he believes special relativity, there is one new thing about the LHC in comparison with the collisions that have occurred for a long time: that the new objects are created at rest relatively to the Earth and they have therefore better conditions to eat our blue, not green planet.

Well, I agree that the relative velocity is different. But if you assume that the black holes or other dangerous objects don't decay, then it also means that these objects produced at very different places of the Universe might still be wondering around. We would be immersed in a sea of such things, some of them would be slow, and it would still be strange that we haven't observed any catastrophe - on the Earth or elsewhere - that these objects have caused.

Tunneling into another vacuum

The most catastrophic event that the LHC could cause is the tunneling of our Universe into a completely different point of the configuration space or the landscape, if you wish. A new spherical bubble in the Universe - where the composition and properties of elementary particles differs from ours and life of our type is clearly impossible - would start to grow. The bubble would quickly start to grow by nearly the speed of light and it would eventually swallow the whole Universe.

This possibility is the most fantastic one but it is also the least likely. Because of its global character, such a catastrophe could have been started anywhere in the Universe. Because the Universe has survived for 13.7 billion years, it follows that no collision in its long history was enough to start such a cataclysmic evolution. But there have been many collisions in the Universe, including collisions of 7 TeV particles going in the opposite directions.

The LHC is clearly nothing new in this sense and we are safe.

Strangelets

Similar comments apply to the production of strangelets - a gigantic nucleus with a lot of strange quarks that may be produced as that may swallow the whole Earth (but stop afterwards, unlike the bubble above).

Again, there are cosmic ray bounds on this threat and there is a detailed phenomenological theory of such things where a fine-tuning of some parameters is necessary to agree with the survival of the Sun (to stop the nucleus from growing when it reaches a certain size comparable to the Earth) but to admit a room for worries about the fate of the Earth (or at least the European Union). Again, you will be able to combine your assumptions about the validity of various theories and about the values of various important parameters in such a way that a catastrophe is still possible.

But if you quantify the probability that your assumptions needed for the catastrophe are satisfied in our Universe, you must honestly conclude that the risk is completely negligible. The main logical fallacy that the LHC alarmists use in order to create alarm is to discard the effects such as the Hawking radiation - to identify them as uncertain or even unlikely - which follow from the same theories that are needed to create the possibility of a threat in the first place.

It is very unlikely that the real Universe agrees with some a priori unlikely conclusions of a very sophisticated theory but completely disagrees with others.

Other alarmists such as the catastrophic global warming alarmists are also combining a lot of assumptions, pretending that their combination is likely. But because of the sheer number of these assumptions, the combined probability (the product) is pretty low. They need to believe that the feedbacks are at the upper end of all estimates, that all individual but numerous effects that contradict the greenhouse explanation of the recent trends will go away, that one or a few degrees of warming will cause certain catastrophes even though they didn't mean anything bad in the past, that changes in our use of fossil fuels will make a difference, and so on, and so on, in order for their policies to be justified.

Even if the probability of each of the assumptions was 80%, and it is much less, if you need to assume ten independent assumptions whose probability is 80%, the combined probability of your assumptions is around 10%. In other words, it is unlikely that your assumptions are reasonable.

We should avoid the logical fallacies that assign spuriously high probabilities to a collection of assumptions, especially an inconsistent one.

And that's the memo.

The energy 14 TeV that the LHC pumps into a pair of protons is not too high: it is roughly 2 microjoules, a tiny energy. Recall that "tera" means "10^{12}", a trillion, and an electronvolt is 1.602 x 10^{-19} Joules. The only new aspect of this energy is that it is pumped into just two elementary particles. There are, in fact, billions of protons that get this dose of energy every minute. This huge concentration of energy is something new and you really need high-energy physics to know what happens. That's why the collider is build to study high-energy physics.

1. This comment has been removed by the author.

2. someone should k1ll Luboš Motl for endangering our damb planet/universe with his damb retarded theoretical bull shit mouth head hole ehm...

3. This is a very lucid set of arguments debunking the LHC "defense" crackpots. Unfortunately, there are few arguments against such foolishness that pop up on Google. On the other hand, the search term "LHC defense" yields only 108 results in on Google. At least few people are paying attention to these dingbats.

4. Talking about dingbats, I wonder how you people know for sure that a mini black hole created at rest in the laboratory will not be harmful? Just think about it. How do YOU know? Well the answer is, you don't, but you just "believe" it's harmless. Just like all the pros at CERN believe in the theoretical model of black hole evaporation. This is unknowon territory and black hole evaporation has never been demonstrated. After \$8B and 15y of effort, what else can we but create one and see what happens? This is called instrumental reason, it's foolish, irresponsible and wrong. It's all about being self-righteous while playing God.

5. CERN judging their own LHC is safe is like a drunk deciding he's all right to drive... with 6,700,000,000 passengers.
Who cares about a Higgs Boson particle or some quark gluon goop except a handful of frustrated geeks who have run out of ideas and have to experiment with forces they don't even understand. These freaking physicists waste money and energy time and time again building atom smasher after atom smasher and end up with more questions, not answers. Now they've built one so powerful they say themselves it will create mini black holes at the rate of one per second! Which would change your life more; knowing they found some particle or getting crushed and sucked into a black hole along with everyone and every thing you ever cared about?
That sound like a good risk vs. benefit to you?!? Just because you can't wrap your mind around it does not mean it can't happen.
See for yourself;
http://www.risk-evaluation-forum.org/anon1.htm
http://www.LHCDefense.org/
http://www.LHCFacts.org
http://www.SaneScience.org/
Popular Mechanics - "World's Biggest Science Project Aims to Unlock 'God Particle'" - http://www.popularmechanics.com/science/extreme_machines/4216588.html"

6. I find it interesting that people comment on here about "These freaking physicists waste money and energy time and time again building atom smasher after atom smasher" when the Collider in Waxahachie, TX was cancelled. So where are all of those atom smashers that we "keep wasting money on"?

Also, there seem to be a few folks who don't understand the true nature of science. They throw words around like "know" and "believe". You never believe anything in science. You only have evidence for or evidence against.

This whole discussion all sounds remarkably like 1945 and the folks who were worried that the first atomic bomb might annihilate the planet. Honestly, it was a possiblity, I suppose. So is the black hole danger with the LHC.

The mathematics notwithstanding, (I teach physics, but this stuff is over my head) I have to trust that the most brilliant minds on Earth are not going to do something that will endanger myself and the rest of the human race. Why would they? What do they have to gain? What is their motivation? Be careful about that whole playing God thing in a scientific discussion. Religion is based on faith, science is based on evidence.