Demons in the Details

On 25 May, the North Koreans conducted an underground test of a low-yield nuclear “device”, and the world trembled. I call it a “device” because I once made the mistake, when working at the Los Alamos National Lab in the US, of talking about the test explosion of a “nuclear bomb”. I was quickly and firmly told that a “bomb” is something you drop out of a plane and a “weapon” is something with which you attack someone else. If you detonate it under your own territory it is a “device”. 

Our experts on devices assure us that the North Koreans are only sort-of experts on devices and can still only make them large and crude and probably very difficult to transport, so we can relax a bit. But what if someone could make a whole new type of bomb the size of a milk bottle, which required no fiddly precision-timed explosives or big chunks of plutonium and which could blow up a city if you just left it alone until its batteries ran out? That is the terrifying prospect raised in Angels & Demons, the latest Dan Brown pseudo-religious schlockbuster to make it to the big screen. So should we be restocking the family air-raid shelter and practising duck-and-cover?

Given Hollywood’s history of scientific precision, you probably won’t be surprised to discover that the answer is no. The device depicted in A&D is a small amount (about one-eighth of a gram) of anti-matter harvested from the very first run of the Atlas experiment on the Large Hadron Collider (LHC) accelerator at Cern, near Geneva in Switzerland. The anti-matter is contained in a small vacuum flask by (presumably) magnetic and electric fields driven from a small battery. The scientists involved want to harvest the anti-matter because of its tremendous promise as an energy source, and through passionate conviction push ahead despite the danger that if the battery runs out, the anti-matter would drift away and contact the normal matter from which the bottle is made. When anti-matter meets matter they annihilate, releasing the rest of the energy of both; the annihilation of that much anti-matter would produce an explosion roughly one-third of the size of the one that destroyed Hiroshima. Of course, a gratuitously vicious Hollywood baddie shows up and steals the flask, which is then concealed in the Vatican as part of an elaborate plot against the Catholic Church. It all looks very slick and high-tech on the screen (right down to the shiny white lab coats that pretty much nobody at Cern actually wears), but could it really happen?

The short answer is: obviously not. The first reason is that unlike the makers of Hollywood blockbusters, Cern scientists understand elementary thermodynamics. Anti-matter does not occur freely in nature (which is in itself a major mystery, see my article in the March issue of Standpoint). You have to make it. By one of the most fundamental and experimentally well-tested laws of physics, the law of conservation of energy, you have to put as much energy into making it as you could possibly get back when you allow it to annihilate, so it can’t be a power source. It wouldn’t even work as a way to store energy, because the processes producing it are phenomenally inefficient, and only something like one part in 10 billion of the energy you start with ends up stored as anti-matter. It would even be unworkable as a weapon, if Cern scientists built weapons, which they most emphatically do not. 

It would be supernaturally expensive and difficult to produce anti-matter in any quantity and incredibly dangerous to handle (if you imagine a really good vacuum in the flask shown in A&D, the annihilation with the residual gas in the container would still produce enough radiation to kill anyone holding the flask in about five seconds). Therefore the motives of the physicists in the movie make no sense (an attribute they share with most of the rest of the characters in the movie, but that is a subject for a different review). 

That is not to say that they don’t make anti-matter at Cern. They do and they even trap some of it. When the proton beams of the LHC collide it will indeed produce particles of matter and anti-matter (as so dramatically depicted in A&D. I often wish we physicists had the graphics budget of a Hollywood studio). Physicists from all over the world have joined to build immense detectors (one of which, Atlas, was actually filmed for the movie, another one, called CMS, is led by my colleague Jim Virdee from Imperial College in London), which will study the detailed properties of the debris emitted from these collisions to extend our understanding of the most fundamental laws governing the universe. However, the anti-matter produced in those collisions is much too energetic to trap, so Cern has built another facility, called the Anti-proton Decelerator (or AD), to slow down and trap anti-protons produced from the collision of a proton beam with a target. These are then combined with positrons (the anti-matter equivalent of electrons) to produce neutral anti-matter, which must be cooled to temperatures near absolute zero in order to trap it in a bottle. This is much as depicted in A&D (but without the glass windows and plastic wires in the vacuum chamber), but in reality only a few million atoms can be trapped per day, at which rate it would take longer than the age of the universe to get one-eighth of a gram. The other main difference is the real motivation behind the Cern experiments, which is to make detailed studies of the properties of anti-matter and probe in another way those most fundamental laws of nature. 

One piece of science that the LHC is really built for is mentioned in A&D, which is the search for the Higgs boson. The Higgs is a curious beast that was first proposed to solve a tricky problem at the heart of the Standard Model of Particle Physics, a supremely successful group of theories describing the different forces between particles at the smallest scales we have probed so far. On the surface, these theories appear to suffer from the minor drawback that they predict infinity as the answer to any question you pose, which is not a terribly useful property for a theory since experiments most definitely don’t measure infinity for everything. In the 1940s, a way around this problem was discovered, called renormalisation, which removed the infinities and left predictions, which agreed with experiments to an amazing degree of precision. Unfortunately this renormalisation trick only works for forces carried by massless particles (like electromagnetism). For forces like the weak force, which are carried by massive particles, another solution was needed. The Standard Model solves this problem by assuming that the really fundamental particles which we would see at very high energies really are massless, with the mass we see at “low” energies (ie, the energies we see around us in nature today) being a consequence of the particles “sticking” to an all-pervasive field called the Higgs field. This may sound crazy, but one consequence of the model was a prediction that there should exist an entirely new type of force, called the weak neutral current, which had never been seen before. 

Subsequent experiments not only found the weak neutral force but also found that it had exactly the properties predicted for it by the Standard Model, which makes physicists believe that this was not just a lucky guess. However, if the model is right you should be able to make real Higgs bosons if you collide particles with enough energy, and the energy needed must be within the range of the LHC. So we are quite certain that either 1) the LHC will make the Higgs, or 2) the LHC will make something even weirder and more complicated than the Higgs, or 3) we don’t know what we are talking about (which would perhaps be the most interesting outcome, although somewhat uncomfortable to explain to the funding agencies). 

So the Higgs may be scientifically fascinating, but what does it have to do with blowing up the Vatican? Not much, really. It is mentioned in the film as a bit of scientific window-dressing to try to give a portentous feel of Great Ideas being debated in what is really just a pretty standard body-count whodunit. There is some mention of the conflict between science and religion, but only in clichés. The search for the Higgs is dubiously claimed to be science intruding into religion by touching the actual moment of the Creation, and on this point you can forgive the filmmakers, because it was the Nobel Prize-winning physicist Leon Lederman who engaged in a bit of poorly-considered hyperbole when he coined the term “The God Particle” for the Higgs (to sell books). In reality, the Higgs field is just one of many fields in the Standard Model, and a Higgs boson has no more spiritual significance than an electron (and we are far from the energies needed to probe the earliest physics which took place at the beginning of the Big Bang, so we are not touching the moment of creation). 

On the whole, the science presented in A&D is actually no worse than in the average Hollywood movie, and quite a bit better than some. The typical Star Trek film has many more basic scientific flaws, but they get away with it because lots of scientists were closet Trekkers when growing up so they keep their mouths shut. So I guess the question we should ask is: “Why is the science in most Hollywood movies so ridiculous?” 

I got some insight into that years ago when I actually helped make a Hollywood movie — The Saint. Central to the plot of that film was “The Secret of Cold Fusion”, a set of formulas written on a piece of paper conveniently stored in Elisabeth Shue’s bra. Through a path too tortuous to go into here, my colleague Victor Christou and I ended up equipping a set with old nuclear physics and chemistry lab equipment. While we were working, the art director brought us the version of the secret of cold fusion that one of their artists had drawn up. It was intended to look like complex physics equations, and it did indeed consist of mathematical symbols, but it was total gibberish, ignoring all the meanings implicit in those symbols. It would be like showing a note in Latin supposedly written by Julius Caesar that said “EVCXO MNLFOEI“. All those letters are indeed used in Latin, but that combination can’t possibly be a meaningful Latin phrase, just as the symbols I was shown could not possibly encode any meaningful physics. When I complained, the art director pointed out that nobody watching the movie would notice or care. I told him that anybody with any knowledge of science would, so he let Victor and I rewrite the Secret of Cold Fusion into the form actually used in the film. I can prove this because I buried a mistake in the formulas (the constant in front of Fermi’s Golden Rule #2 is the wrong way up), which the keen-eyed will notice. 

I tell this story partly to point out that I am probably the only scientist on earth who has had a publication concealed in a top Hollywood actress’s bra, but mainly because it shows the real reason that there are so many science errors in Hollywood films. Film-makers are telling stories, they aren’t teaching science, and they only worry about factual errors when they think that these will bother the viewers. That doesn’t just apply to scientific errors, it applies to everything (as any historian will tell you about Braveheart). 

Of all the scientists I have heard complain about the scientific errors in A&D, I haven’t heard a single one complain about the timeline. The hero, after all, is shown in his office at Harvard talking to a Vatican official after a morning swim, and there are plenty of students walking around the campus, so it is at least 8am. He then watches the sun set in Rome that very evening after already having been quizzed at the Vatican and run around the city chasing lost cardinals for at least an hour. That can’t be done (minimum flight time Boston to Rome is a little under eight hours, call it seven with a fast private jet, and there is a six-hour time difference, plus a minimum hour to/from the airports, so on the clock you can’t make it in less than 14 hours, add to that the time he had already spent in Rome and it would have been after 11pm, too late to see the sun set). Nobody objected because nobody noticed. So the bottom line is that Hollywood directors think they can include gross scientific errors in their plots because their audience won’t notice, and given the frequency with which you see people claim that anti-matter could be an energy source, they appear to be right. The solution is obvious, if difficult to implement — raise the general level of scientific awareness. I am afraid that is a job we can’t (and shouldn’t) leave to Hollywood.

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