How do you explain the highly emotional discussion that has been sparked by the Long Hadron Collider project?

Well, people in general fear the unknown and that makes sense. If you don't understand something that's potentially dangerous then that's the first thing you want to know about it -- is it something we should be afraid of?

And of course scientists have an aura, still deriving from World War II and the atomic bomb and the nuclear age, and the things they do. This is very, very different, but people on the outside might not be able to see the fine points and the differences -- but this is a completely different kind of thing from any kind of bomb building.

The other thing is that people use the same words for things that are actually quite different, like one of the main things that people were frightened about was the idea that you could produce black holes at LHC. There are some very, very speculative ideas that suggest that you might be able to produce very, very small black holes.

But, although we use the same word, namely black holes, for really, really small ones and really, really big ones, they are very different. Small black holes -- the ones that might be produced at the LHC -- are much smaller than a single atom, much smaller even than a single proton and they exert less gravity than a gram of matter, and they're completely unstable so they live for much less than a second. So, although we call them black holes, they're not at all the kind of thing that might swallow you up or produce a catastrophe.

Perhaps you do not so much have to convince the greater public of the safety of the project, but other scientists, like Professor Roessler of Tuebingen for example. Why has there been no great discussion between scientists?

Oh there has! There's a very, very careful process that we do -- and elaborate reports. Thousands of scientists worked on the LHC and there's a community of tens of thousands with families, with the lives that they live -- they don't want to destroy the world. If there were any real danger, believe me, you would be hearing from thousands of scientists, not just a few isolated fighters, about the potential dangers.

There's an overwhelming scientific consensus that the thing is safe after careful study and very open discussions. There's no conspiracy or secrecy here, everything's out in the open and everything has been carefully discussed. So it gives the wrong impression to say that scientists are arguing with each other about this.

How is this experiment going to change our vision of the world?

We don't know in detail what's going to happen and there may be some big surprises, but I think the three kinds of ideas that look most promising to me -- any one of which would be a major, major contribution to science -- are the following:

Firstly, equations tell us that what appears to us in ordinary life as empty space is actually a material which affects the properties of matter in ways that our very successful equations tell us, but we've never yet really broken down this material to see what it's made out of. So it's as if we have been fish in an ocean, surrounded by water, and for a long time we've taken the water for granted because it's the only thing we know, we couldn't imagine a world without it.

But then if we were smart fish we would eventually realize that we are surrounded by something that is slowing us down and changing the way we move and function, and then the next step would be to figure out what this founding medium is made out of.

That's what the LHC is going to be able to do for the world we actually live in and the complex medium that we call empty space. For the first time we're going to be able to tell what kinds of things it is made out of. This is usually called looking for the “Higgs particle,” but it might not be one particle, it might be a whole bunch of things.

Another idea is that we will be able to make more beautiful equations of physics and combine our descriptions of all the different forces of nature, that at present have separate theories, into a unified field theory. We have very good ideas about doing this, but to do it we have to add to the equations of physics in ways that predict new phenomena.

At LHC we're going to find out whether these ideas about unified field theory and super symmetry -- which is one of the concrete ways of achieving unification -- whether these ideas are right. And if they're right then we'll have much more beautiful, much more powerful equations of physics that will enable us to understand things closer to the Big Bang.

And point three is that astronomers have recently discovered that most of the mass of the universe is not coming from the sort of matter that we've studied in biology and chemistry -- matter that's made out of protons, neutrons, quarks, photons, electrons, these things that we understand very well now -- but something new, that's different from all those, that's called “dark matter,” shows that the universe is in some form that we haven't encountered before and it interacts very, very weakly with normal matter.

Now, one of the remarkable things that comes out of unifying the equations of physics is that if one of the particles in one of these ideas turns out to have the right properties to make this dark matter, and if you figure out how much of it would be produced in the Big Bang, it's about right to make the amount of dark matter we actually observe. That's a very exciting possibility: making a connection between fundamental physics and cosmology by finding out in a laboratory experiment here on Earth what dark matter is made of.

Those are three ideas that I think are concrete and will be tested in the next stages, but there could also be surprises that are harder to anticipate, there are lots of more speculative ideas.

The period of experimentation has now begun, when are we going to hear about the first results?

Well this is really a big engineering step so, if all goes well, we'll have protons circulating all around the tunnel for the first time. It's a milestone, but it won't really be a physics experiment -- they're not yet going to do collisions or study new phenomena -- it's really an engineering step to see if the machine is working properly.

Experiments will really commence if all goes well next year, and when new results will come out depends on what's there. It also depends on how fast we can understand the technicalities of the machine and how the detectors are functioning. So it's hard to give a precise date, but I would expect that by this time next year we should see some very interesting results and, certainly regarding the big ideas that I mentioned, it will be clear whether we are on the right track or in serious trouble within two to three, or up to five years.