Physicists in Geneva have probably proven the existence of the much-vaunted "God particle". But what does this mean for physics and our view of the world? Oldenburg physicist Christoph Lienau explains why the discovery is so groundbreaking - and raises new questions.
QUESTION: Mr Lienau, what exactly did the scientists in Geneva actually discover? LIENAU: Using the Large Hadron Collider, which went into operation two years ago, they were able to accelerate protons to such high energies that particles with an energy of around 126 giga-electronvolts were released - that corresponds to the mass of 134 protons. These particles are expected to be the long-sought Higgs bosons. QUESTION: Why is the discovery so groundbreaking? LIENAU: Many of us have already learnt at school what the masses of the smallest particles such as electrons or protons are. Some of us may even have memorised the values - and perhaps forgotten them again. However, it was not explained why these particles actually have a mass and why it assumes exactly the values we were taught. Very successful physical models for describing "the world", i.e. elementary particles and their interactions, such as the so-called standard model, cannot do this either. The question of the origin of mass remained completely unanswered for a long time. In 1964, the British physicist Peter Higgs showed that this could be explained by the fact that what we call the vacuum is not really empty. There is also energy there that interacts with the known elementary particles in the background. Higgs surmised that there are "divine" particles in the background that cause this interaction and thus give the other particles their mass.QUESTION: And researchers have been looking for these particles? LIENAU: Yes, since Higgs' hypothesis, which was also developed independently by other Belgian and English researchers. Now researchers have probably proven the existence of the Higgs particles and thus apparently confirmed a possible explanation of the origin of mass. QUESTION: How did this discovery become possible? LIENAU: It is conceptually simple, but technologically highly complex. At the Cern research centre in Geneva, protons are accelerated to 99.9999991 percent of the speed of light in two tubes in a 27-kilometre-long tunnel and then collide with each other. This produces a large number of high-energy particles, which are then analysed. In the Large Hadron Collider, the energy of the protons was now high enough to be able to detect some of the heavy Higgs particles with a mass of 126 giga-electron volts for the first time. So many particles have now been detected that the probability of measurement errors is now only one in a million. We physicists call that a discovery. QUESTION: Is it now possible to fully explain the blueprint of the universe in physical terms? LIENAU: Considerable evidence has been found that Higgs bosons really do exist. This has emphatically confirmed the model proposed by Higgs for interpreting the origin of mass and thus indirectly also the standard model. This is certainly a very important step for elementary particle physics. But a "perfect explanation" is a big word. I, at least, don't know exactly why and how the Big Bang happened or why the mass of the Higgs particle is 126 giga-electronvolts. I suspect that the experts in this field are not doing much better. It seems as if the colleagues at Cern have opened another door into a hidden world. It will be exciting to see what lies behind it. QUESTION: So there is more matter than we know about? LIENAU: Certainly. With our human senses, we only have a very limited horizon of perception. We are rapidly developing ever more sophisticated experiments to see what we could not see before. The discovery of the Higgs boson is one example of this; the search for dark matter and black holes are others. The number of known forms of matter has increased considerably in the last 100 years, and this is likely to continue. QUESTION: Does the Higgs boson now change our view of the world? LIENAU: First of all, the current experiments at Cern are arousing great interest among the general public. Obviously, it's not just us scientists who are very curious. This interest will certainly subside again, but the "world" will certainly no longer be quite the same as it was before. The discovery at Cern will raise so many new questions that we will all certainly learn a lot more about what holds the world together in the years and decades to come. QUESTION: Does the discovery also have an impact on your research field of ultrafast nano-optics? LIENAU: It shows that scientific curiosity and the drive for knowledge are a very important driving force for progress. This applies not only to elementary particle physics, but to all fields of basic research in general. We ourselves use sophisticated optical microscopy techniques with extremely high time resolution to see how individual electrons move in nanostructures. Ultimately, the aim is to recognise the laws according to which certain processes in nature function and to understand how and why complex architectures such as organic solar cells or biological light-harvesting complexes work. It is difficult to predict whether this will one day lead to better, i.e. cheaper or more efficient solar cells. But here too, "progress" and the discovery of new things are closely linked to the technological possibility of seeing things that no one has ever seen before. This is what makes research so exciting.Prof. Dr Christoph Lienau is head of the Ultrafast Nanooptics working group at the Institute of Physics at the University of Oldenburg.