Is our world actually spatially 4-dimensional

The world has ten dimensions

Scientists are searching for a common theory for the four basic forces in the universe. Norbert Lossau spoke to the spokesman for the research area, Professor Jochen Brüning, about the chance to find a "theory of everything".

Die Welt: The topic of your Collaborative Research Center sounds amazingly comprehensive. What is it about?

Jochen Brüning: It's about the basic categories in which we grasp the world - about spatial expansion, temporal expansion and that which is, so to speak, tangible in space and time, i.e. matter.

Welt: So is it about the famous "theory of everything"?

Brüning: Yes, that is the ultimate goal. But nobody can yet say that they really have the approach to this theory. We are trying different ways to get closer to the big goal. We compare existing mathematical theories and physical approaches and are open to completely new ideas.

Welt: Can you say that you want to use mathematical methods to answer open questions in physics?

Brüning: Physics has found many things that have had an extraordinary effect in mathematics that could not have been found with normal mathematical thinking. This makes mathematicians very interested in better understanding physicists' thinking. Conversely, mathematics has recently kicked off physics. Both sides are dependent on each other.

World: So new knowledge through a dialogue between physicists and mathematicians?

Brüning: Yes, that's the way it is - and for the first time it has been more intense than it has been in a long time. Only together will we be able to answer these big questions and expand them technically.

Welt: But by expanding technically you don't mean applications in society?

Brüning: Yes. Applications from basic research cannot be predicted. Einstein would certainly be very astonished if he could see how the theory of relativity is used technically in GPS today. But if you have really understood a network of effects, technical applications follow with a certain necessity.

Welt: Which questions should be worked on in your Collaborative Research Center?

Brüning: There are various mathematical approaches, some of which have already been tried, but some of which have not. Our goal is to bring these theories together and to let them act together on physics, or to let physics have an effect on them. We expect a lot from this. Our research project is unique worldwide in this combination of different expertise.

World: Can you explain the physical problem in more detail?

Brüning: That is the question of great standardization. The search for a common theory for the four known physical basic forces, which is mathematically free of contradictions and physically meaningful.

Welt: Many researchers have been grappling with this for years. Stagnation can be observed there and nothing has been proven so far.

Brüning: Unfortunately that is true. But I wouldn't call it stagnation anyway. Numerous great ideas have been born here over the past 30 years that have at least had a major impact on the development of mathematics. What is missing so far is the experiment with which predictions from theory can be checked. That could change in 2008 when a new particle accelerator goes into operation at CERN in Geneva.

World: Which of the new ideas do you find most fascinating?

Brüning: The ten-dimensionality of the world is a curious but fundamental idea. The four dimensions that humans can imagine - three spatial and one time dimension - must be supplemented by six dimensions, otherwise the known physical theories cannot be unified without contradictions. Of course, it is difficult to understand why we need these six other dimensions even though we cannot see them. That's because they're very, very small. Therefore you need high energies to make them "audible". The smaller an oscillating particle, the higher its natural frequencies. It's the same with the violin: the shorter a string, the higher its pitch.

Welt: And for that you need even larger particle accelerators with very high energies?

Brüning: Yes, exactly.

Welt: But if there are no predictions that can be checked with such an accelerator, then you are just poking around in the dark.

Brüning: No, there are very precise expectations of what one hopes to be able to see with very high energies. The open question, however, is whether the energy that will soon be available is sufficient to be able to see something. That is not easy to estimate.

Welt: So if you are unlucky, does the new, expensive accelerator not provide any new knowledge at all?

Brüning: You will definitely gain new knowledge. But our real questions may still not be answered.

World: Let's assume that the experiment provides a next step in knowledge. Then the mathematics with which nature can be described would be developed in Berlin.

Brüning: You could definitely say that. If we are lucky, our theories of space, time and matter will be harmonized.