The Arguments: Fay Dowker
Dr Fay Dowker is a lecturer in the Theoretical Physics Group in the Department of Physics at Queen Mary, University of London. She does research on quantum gravity, which means she is looking for a theory which would unify and extend Einstein’s theory of general relativity, and quantum theory. She believes that the imbalance that we observe between matter and anti-matter in the universe could be an important piece of data in guiding her research and looking for this theory of quantum gravity.

On whether anti-matter matters:
"Well, as far as my own research area of quantum gravity goes, I hope that this asymmetry between matter and anti-matter that we see, in the fact that we only see matter now, I hope that this will remain a mystery as far as current theories of particle physics and cosmology go. Because I'd like it to be data, that I could use in order to try and explain it using proposals for a theory of quantum gravity. Because one of the problems with quantum gravity is that, there is very little data. We're working pretty much in the dark, trying to put together big principles, and there's very little evidence to go on, very little experimental evidence and observational evidence. So these fundamental constants and parameters in the standard big bang model of cosmology, these are things which I hope will remain mysteries, for me to solve."

On Dirac’s equation, and his postulation that anti-matter existed:
"In an atom the electrons behave non-relativistically, that means they're moving quite slow compared to the speed of light. But when they're moving fast, you need to take account of Einstein’s discovery of special relativity, and the quantum mechanical description of the electron that existed at the time didn't do that. So Dirac wanted to find a description of the electron that would be consistent with special relativity. The result was his famous equation, the Dirac equation, which describes relativistic electrons. But completely unexpectedly, he found that because the relativistic expression for energy gives you the square of the energy, so the solutions for that gives you both positive and negative values for the energy. And that was a problem, and in order to solve that problem, resolve this difficulty of having negative energies, Dirac had to postulate the existence of an anti-particle, counterpart to the electron which has become known as the positron. So the positron doesn't have negative energy. Let me stress that, it has positive energy but it was postulated in order to resolve this theoretical problem that arose when you marry special relativity together with quantum mechanics, and the positron was subsequently discovered in 1932 by Carl Anderson, as a component of cosmic rays."

On the possibility that fundamental laws might not apply at cosmological scales:
"It's absolutely quite possible. The weight of theoretical opinion is towards there being dark matter rather than a different theory of gravity, but it's quite possible that Einstein’s theory of gravity, at larger and larger scales, becomes less and less valid, and that there's a new theory which takes over it, at cosmological scales, so it's quite possible. And in fact there's an interesting historical example of such a thing. The perihelion procession of Mercury was an anomalous observation which couldn't be explained using Newton's theory of gravity, and people proposed that in fact, there was extra stuff around the orbit of Mercury which would distort the orbit, and then make it in agreement with the observation. But in fact what happened, was that the entire theory that we use to describe gravity was altered, and Einstein came up with a new theory, general relativity, which explained this anomalous observation. So there wasn't dark matter in that case, it was a new theory of gravity, and it may be, it's possible that the same is the case now."

On whether the universe will expand forever:
"That seems to be the evidence so far, but we don't know what will happen, what observations we might make tomorrow that would change the picture so as scientists we always have to say that our current picture can alter completely with new observations, new experimental evidence."

On quantum gravity:
"Quantum gravity is the theory which we don't have yet, which we're looking for, which would apply to the universe before the big bang. So, before any of the particle physics models that Graham works on, even at times where even more high energy theories are required. It's the theory of the unknown and it's a theory that would incorporate both quantum mechanics and general relativity, Einstein’s theory of gravity, and extend them both, so in a sense, it's an extension of what Dirac was trying to do. So Dirac was trying to make a theory of the electron which incorporated quantum mechanics and special relativity. Now we want to apply quantum mechanics to space and time themselves, and not just the particles in space time, but space and time themselves, and that theory we hope could lead to tell us why the universe started out, at the very earliest moment of the beginning of the big bang, why it started out in the state that it did, to give us the universe that we see now. So there are many parameters that we have to put into the standard big bang model, which are unexplained at the moment, they're just numbers that we have to assume, they're inputs to the theory. We just assume that certain numbers are what they are, and nobody knows why they are those numbers. Hopefully quantum gravity could tell us why those numbers are the are those numbers. So those inputs to the big bang theory would be outputs of a theory of quantum gravity, they'd be consequences."

On how to approach such abstract concepts as the early universe
:"I think the key is that you get used to things, you extrapolate from what you already know, you boot strap your way, your understanding. I remember when I first saw the Grand Canyon, I couldn't get my head round how big it was, it just looked like a canyon, but then, the way that I understood just how huge it was, was that the rock is very stratified, and if I looked down on the rim that I was standing on, I could see that one of the strata was sort of two hundred metres deep, and then I looked across at the other side, and I saw how many strata there were, and that was five miles away, and then I got some impression of just how deep this canyon really was. But that was the only way I could comprehend it, was by looking at what I knew what was close to me, what was familiar, and then just extrapolating, and saying well then, yes it's really very deep."

On how realistic the idea of a "theory of everything" is:
"Well there are different approaches to quantum gravity, and in some approaches, the hope is that you can unify not only gravity with quantum theory, but also all the other forces in nature as well, and then there would be a good candidate for a so called theory of everything. But then, some people take a more, I don't know conservative approach to quantum gravity and say well, let's just deal with gravity first and see how far we get with that, and maybe we'll think about matter later, or maybe matter will come out naturally if we concentrate on gravity. So, how likely is it? I think all the ideas that exist at the moment, my own research included, I would say are very speculative. The precise odds, I wouldn't like to say."

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Content last updated: 16/06/2000

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