The Arguments: Professor Graham Thompson
Professor Graham Thompson lectures at Queen Mary, University of London, where he is a member of the Particle Physics Group. He is an experimental physicist who took part in the CERN experiments of the 1980s when antiprotons were first produced in bulk form, cooled to make a beam of particles and then accelerated to collide head-on with protons. He uses anti-matter as part of the tools of his trade, doing experiments which use these very small particles, which interact with other particles, to understand, at the energy densities that are interesting, what happened in the early universe, and how matter and anti-matter annihilate.

On the discovery of anti-matter:
"Well I would say that in fact, paradoxically, anti-matter isn't much of a surprise to me. When the anti-proton was first discovered, people said well, why are we surprised, it had to be there, according to the theory, and indeed it was there, and it was formed in exactly the way that it was. I would have thought that the scientists would have been much more surprised, had we not been able to make anti-hydrogen recently, than over the fact that we did make it. It's really quite normal. Also I would say that we do really understand what happens when you put matter and anti-matter together. I would say that the annihilation processes are perfectly well understood, and, it wasn't that anti-matter disappeared, but it annihilated against the matter to give us the extreme radiation that we see in the universe. We see about a billion times more radiation in the universe, than we see particles, and this could be a signature that an awful lot of the particles of the universe did annihilate very early on in the first second of the universe in fact, thus leaving a very small proportion that we see now."

On how to create an anti-particle:
"We don't deliberately create any one particular anti-particle, what we basically do is bang two things together, with terrific energy, with enough energy that will create the extra mass of the antiparticles. Because they didn't exist in the first place, we can create lots of particles, but we do them in pairs; particle, anti-particle pairs. So in most of the collisions that take place in our experiments, we create equal amounts of matter and anti-matter, just as we believe happened in the early universe."

On the amount of anti-matter he has produced:
"Well in my whole career, I'm not sure how much I can personally be responsible for, remember these are very large experiments. But I suppose if we were to actually look and say, what amount of anti-matter we've used as particle beams, we did do a calculation recently, and we reckon it's about a nanogram of material so far that we've actually used. If you ever do any chemistry with milligrams or perhaps micrograms at best, you'll know that we're a factor of a thousand or a million times down on that, this is the total amount of matter I've made in the last twenty five years. It's not going to go an awful long way. If you put all of those antiparticles together, and annihilated them on particles, you'd have just about enough energy to boil a kettle of water, I'm afraid."

On anti-matter as a source of energy:
"One of the things that we've actually got to get across, is that somehow anti-matter is not a source of energy, it could be considered as a way of storing energy. If we ever get to the point where energy is cheap, and that's probably a long, long way away, we could store the energy in the form of antiparticle, and then this would be a very compact way of taking energy with us."

On the possibility of powering a space ship with anti-matter:
"If we did get to the point where we could store anti-matter, then we could think in terms of making anti-matter, holding it, picking up matter along the route, and then annihilating that against the anti-matter that we've got. This is conceivable, it's science fiction, but it's conceivable."

On whether the laws of physics might have been different at very early stages:
"The laws of physics are universal, and I think that most of us would sort of pack up and go home if we if we didn't believe that. If I said the laws of physics are universal, it's different from the natural behaviour. Obviously conditions in the early universe were very different from conditions now, and that's why we believe that that could of course be where the matter was first predominant over the anti-matter. The laws are still the same however, and this is precisely why we as particle physicists can recreate the early universe in our experiments. We can now actually create the energy densities that were existing, round about ten to the minus twelve of a second into the universe, and we are confident, that if it happens in our experiments, and it would have happened as well, at the very beginning of the universe."

On the possibility of making dark matter:
"We have not made dark matter. Dark matter interacts only by the gravitational force, almost by definition. It is dark, we can't see it, there's no electromagnetism, you can't shine light upon it, and you can't see its interactions in any other way. We have dealt with particles like this before. Neutrinos are an example, which are very weakly interacting, but compared with the forces of gravity, the weak interaction is many, many, ten to the forty times stronger, than the force of gravity. So we would need extremely high energies to be able to probe this range, and that I'm afraid is not in the foreseeable future."

On the security of the concept of the Big Bang:
"I think we should distinguish a little bit here about what kinds of evidence are around. For example, we actually know what proportion of various elements are in the universe, and they fit in very well with our theories, and with our experiments so far. So that gets us back to the first minute of the universe. We can actually say from observations that we see from relics of that very early time, we're pretty confident about what happened. What happens next, is that we can actually simulate the conditions of the universe at these very early times, and I would actually volunteer and to say that we can actually explain back to the first ten to the minus twelve of a second, by simulating what happens in the lab here on earth, and then saying, well, this seems to lead to the other things where we know what happened, so we've got good reason to believe this is true, even though we don't see those very relics. The problem comes, is if we push this time further and further back, we actually get to the point that Fay begins to worry about, which is when our, our very theories become inconsistent. We can't go back to the point which is much before ten to the minus thirtieth of a second, because when we do that, our theories are actually disagreeing with each other. We know we need something else."

On whether he’s confident that we will ever will really understand what happened at the start of the universe?
"Once upon a time, of course, we only have to go back about four or five hundred years, and people didn't know that there was going to be an end to geography. You kept discovering new countries, you kept discovering new oceans, new seas, and eventually of course you map the whole thing, and you said yes, I hate to say it in case the geographers are listening but, there is an end to the amount of terrestrial geography that we can learn. Now we don't know yet whether there is an end to the amount of physics that we can learn. So far every time we've taken a layer off the onion, there's been another layer underneath. The present layers have been there for some while now, we call the standard model which we explain the universe, that's been around for about thirty, forty years, and hasn't changed terribly dramatically. We don't know what's going to happen in the future though."

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Content last updated: 16/06/2000

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