Anti-matter: All you need to know

A complete guide to materials composed of antiparticles

By colliding matter and anti-matter particles we can release masses of energy — giving us, theoretically, an unlimited supply of cheap energy. According to scientists, this may hold the answer to one of the greatest mysteries of the universe.

So, how did the story of anti-matter begin?

The history of anti-matter

The story began in 1928, when the British physicist Paul Dirac formulated a theory which described the behaviour of electrons in electric and magnetic fields. Theories like this had been formulated before, but Dirac’s was unique in that it included the effects of Einstein’s special theory of relativity and also the effects of quantum physics.

Dirac’s equation worked very well but, in the same way as the equation x^2 = 4 has two solutions (x = 2 or x = -2), so did this equation predict multiple solutions. This led to a surprising prediction that the electron must have an anti-particle having the same mass but a positive electrical charge, the opposite of a normal electron’s negative charge.

Dirac interpreted this to mean that for every particle that exists there is a corresponding anti-particle, exactly matching the particle but with opposite charge. He won a Nobel Prize for this work and, in his Nobel Lecture, he even went as far as to speculate that there might be an entire universe of anti-matter.

The search for this anti-electron began in the 1930s and, in 1932 Carl Anderson, a young professor at the California Institute of Technology, observed this new particle experimentally and it was named the “positron.” In 1936 he won a Nobel Prize for his discovery.

The search for anti-protons then began, but it wasn’t until 1954, twenty-two years after positrons had been observed, that man had the power to create the necessary energy to produce anti-protons. The machine used to create this was the ‘Bevatron’, built at Berkeley by Nobel Prize winner Ernest Lawrence.

Meanwhile, a team of physicists, headed by Emilio Segre, designed and built a special detector to see the anti-protons. They succeeded in detecting anti-protons, further proving the existence of anti-matter and winning Segre and his team a Nobel prize. Just twelve months after the discovery of the anti-proton, a second team working with the Bevatron discovered the anti-neutron.

Once all three particles that make up atoms (electrons, protons and neutrons) had been discovered, scientists wanted to find whether anti-particles bound together in anti-atoms were the basic units of anti-matter. They wanted to know if matter and anti-matter are exactly equal and opposite as Dirac had implied. In 1965, two teams of scientists, one headed by Antonino Zichichi and the other by Leon Lederman, made simultaneous observations of anti-deuteron, a nucleus made out of an anti-proton plus an anti-neutron.

In 1995, scientists created the first anti-hydrogen atom at the CERN research facility in Europe. Normal hydrogen atoms consist of one proton and one electron, so they created them by combining the anti-proton with a positron. When these anti-hydrogen atoms are produced, they are travelling at nearly the speed of light and typically last only about 40 nanoseconds.

What is anti-matter?

Anti-matter can be described as the mirror of matter, containing anti-particles of the particles that constitute normal matter. Anti-particles are equal and opposite to matter particles in that they have an opposite charge and they rotate in an opposite direction. So whereas matter is composed of atoms, that are made up of the elementary particles (electrons, protons and neutrons), anti-matter is composed of anti-atoms that are made up of positively charged electrons known as positrons, negatively charged protons known as anti-protons, and anti-neutrons. Most theorists believe that at the time of the Big Bang anti-particles and particles were created in almost equal numbers.

Is there anti-matter in the universe now?

If there was anti-matter around us, it would annihilate with matter and we would see light coming out. In terms of anti-matter somewhere else in the universe, most theorists believe that the universe is made up of all matter, however, they are not one hundred per cent sure. Physicists have used special orbiting equipment to measure the sky at a range of energies that should have detected anti-matter annihilation, but none of the instruments have uncovered evidence for vast amounts of anti-matter in the universe. There is evidence that in some isolated spots in the universe some very energetic reactions are taking place that create anti-matter which then annihilates, however, this is not thought to be residual anti-matter left over from the Big Bang. The reason for the lack of anti-matter in the universe since the Big Bang is a matter of scientific debate.

Applications of anti-matter

Currently, the main use for anti-matter is for medical diagnostics, where positrons are used to help identify different diseases with the Positron Emission Tomography or PET scan. When a positron-emitting tracer is injected into a patient’s body or a piece of machinery, the positrons soon annihilate with the surrounding atoms. When this happens they emit a characteristic radiation signature which quickly pinpoints where the annihilations took place. Therefore, these PET radiographs reveal inner structures quickly and with low doses of positrons. They are particularly widely used in brain scans, both for medical diagnosis and for revealing how the brain itself works. The other great use for anti-matter is scientific research.

Future of anti-matter

At the moment, our methods of producing anti-matter are rather inefficient and the current worldwide production rate of anti-matter is less than a gram per year! Much research is being carried out into the possible future applications of anti-matter but first we need a reliable method of producing large amounts of it.

Below are some arguments and thoughts from leading scientists working in this area.

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.

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.

The Arguments: Sir Martin Rees

Sir Martin Rees is a Royal Society Research Professor and a fellow of King’s College at the University of Cambridge. He also holds the honorary title of Astronomer Royal. He is a cosmologist and is trying to understand why the universe consists of the stars and galaxies we see around us, and how they’ve come to exist over the cosmic evolution that’s extended up for fifteen billion years.

On what it would mean if we could understand where anti-matter went to

The key question is why the universe does seem to consist of ordinary matter, all the stars and all the galaxies seem to be made of matter. If matter and anti-matter have been mixed up within our own galaxy for instance, then we wouldn’t be here, because, during the course of stars forming and exploding, and mixing up the debris, it would all have annihilated, and when matter and anti-matter get together, they annihilate in a flash of energy we call gamma rays. So, we know that matter and anti-matter were separated very early in the universe, and that the anti-matter had somehow disappeared, and how this happened, is one of the mysteries of the early universe, along with why the universe is expanding the way it is, and why it contains the other ingredients we observe. So, it’s a big mystery, why the universe consists of so many atoms but no anti-atoms.

On whether the universe was asymmetrical from the beginning

Well, it might have been, the key question really is whether matter and anti-matter are completely conserved, or whether it’s possible very occasionally, to create an atom of matter without the atom of anti-matter that goes with it. If it was completely conserved, then Fay would have to be right, we’d have to say the asymmetry that’s present in the universe now was there right from the beginning. I think that would be a rather difficult concept because, then we’d have to say, there’s one enormous number in the universe, a number which is one followed by about eighty zeros, that’s the number of atoms in the universe that we can see at the limit of our telescopes. And if we think the universe in a sense started off small, it’s unappealing to imagine there has to be this enormous number imprinted in it from the start.
So that’s why I think most of us prefer the view, that perhaps, everything started off symmetrically, and there was somehow a slight favouritism, and a slight possibility to create matter without the accompanying anti-matter, and this lead to our universe, which is now dominated by matter not anti-matter. And as Graham said earlier, this favouritism need be only quite small because our universe contains lots of radiation. For every atom in the universe, there are about a billion photons quanta of radiation, and we believe what happened is that, as the universe cooled down, we’re talking now about when it was about a microsecond old, matter and anti-matter annihilated, and, for every billion antiparticles, there was a billion plus one particles.
So there were a billion annihilations, but one particle which was left over, and we are made, and the stars are made, of that one that did not find a mate to annihilate with as it were. It’s a small asymmetry, and the mystery which has to await unified theory, is why the laws of physics did allow this small asymmetry to be imprinted very early on. This will have happened we suspect, much earlier than the time which we can simulate in accelerators, because accelerators only allow us to understand the physics that prevailed after the first trillionth of a second. That may seem most of the universe, indeed it is, but if you think on a log scale, lots can happen at even earlier stages, and that’s the era when the physics must have lead to this asymmetry in the universe.

On why the asymmetry in the universe has a tendency to produce matter, rather than anti-matter

Well this really relates to a very deep question, which is the uniformity of the laws of nature, and it does seem that when we look at the light from a distant star or galaxy, and analyse the light with a spectrometer, the atoms which we infer to be there in that distant galaxy, are governed by just the same laws as the ones we study in the lab. So it does look as though, at least all the universe we can now observe with our telescopes, is governed by the same laws, and the C P violation that Graham mentioned will probably prevail everywhere, and that suggests that whatever asymmetry favoured matter over anti-matter would also prevail.

On whether anti-matter could be trapped in some way that made it inaccessible for annihilation with matter

Well, we’d have to ask how it got there, as we have good reason to believe the universe started off with the gas being fairly smooth, and no stars or galaxies forming, and of course, the problem with anti-matter, the problem with the spacecraft that’s powered by anti-matter, is actually confining the stuff because if it comes in contact with ordinary matter, it’s annihilated in a spectacular way. So the only way you could imagine anti-matter being confined, in some futuristic spacecraft or anywhere else, is if it’s confined by some magnetic fields or something like that, so that you can stop it escaping, but keep it quarantined from ordinary matter.

On whether the laws of physics might have been different at very early stages

Well it’s partly a semantic point because, Graham’s right in a sense in saying the laws of nature by definition apply everywhere, but the key thing is what they imply under extreme conditions. We’re used to the idea that the more extreme conditions become, the more we have to jettison or modify our common-sense concepts. We have the spookiness of the quantum world, and the mysteries of space and time in black holes etc. So, we know that when conditions get very extreme, we have to give up some of our cherished common-sense notions, and I think the key question is whether the laws of physics as Graham would define them, apply to the ultra early universe, do allow the production of asymmetry or not. It’s really a question of what the laws of physics are, at those very extreme times.

On whether there is a relationship between dark matter and anti-matter

Well we’re not sure, but we do know that the early universe must have contained not just the atoms that we’re made of, they’re just four percent, plus the radiation, which is the result of the annihilation of matter and anti-matter, but also dark matter. We suspect the dark matter, which is very important gravitationally for holding together galaxies, and clusters of galaxies, is made of some kind of particles, that are also a relic of the very early big bang, some sort of particles with no electric charge, that don’t interact very much. But the big bang must have made these particles, which are very important in the universe today and, it just illustrates how we are mystified as to the basic ingredients as it were of our universe, and to answer the question of what the dark matter is, we need either to find it, by experiments, or to have a better understanding of particle physics. Because if we knew about the physics of high energies, and how particles crash together in the very early universe, we might know whether they’ll produce some kind of particle that would survive to make the dark matter. So it’s a nice link between the physics of the very large and the very small, and it’s embarrassing that most of the universe is unaccounted for in this way, and it’s in the form of dark matter, whose nature we are completely flummoxed about.

On the possibility of making dark matter

I think some people think that a dark matter candidate is a so called super symmetric particle, which might be produced in the next generation of accelerators. So it’s possible that it’ll be produced but it’s pretty unlikely.

On the security of the concept of the Big Bang

Well I think most people would suspect that back to one second is fairly firmly established. The conditions back then are not all that extreme, they’re rather like in the centres of stars, they can easily be simulated in the lab, and we have very good evidence for what the universe was like then, which we can observe with high precision now. So I would say that back to one second, at least, the evidence is as good as what the geologists may tell you about the early history of the earth. Their evidence is less qualitative than we have about the early universe. But, when we get back, certainly into the first trillionth of a second, first ten to the minus twelve seconds, then we encounter a regime where, we have to be agnostic about the basic physics, because it’s beyond what we can directly test. And so here in a way the game changes, because we in astronomy and cosmology are perhaps going to learn about the basic physics, because the universe is the only lab we can ever use, which tells us what conditions were like. So in discussions of the early universe, trying to explain where the dark matter came from, why there’s no anti-matter, why the universe is expanding the way it is, we are, in a sort of symbiotic relationship with fundamental physicists because we need their theories, and the only way their theories will ever be tested, may be in so far as they are corroborated by astronomical observations. So, there’s a different type of interaction between theories of the cosmos and the micro world, the inner space of atoms and the outer space of the universe.

On when the universe is going to end

As far as the universe is concerned, we can never make reliable long range forecasts of course but I can be more confident than if you’d asked me five years ago. In that there’s a strong reason to suspect that the laws of nature are such that the universe is going to go on expanding for ever, perhaps even at an accelerating rate, and that there will not be a big crunch. Now, of course, we could be wrong, it goes back to what we said about whether the laws of nature will apply in the distant future, there could be a change that would trigger a big crunch, but it looks as though the universe is expanding, and the expansion’s even speeding up, not slowing down towards a halt, which would be the precursor of a big crunch. So, it does seem as though, the universe has an infinite future ahead of it , to quote Woody Allen, eternity is very long, especially towards the end, and there’s plenty of time for all the stars to play out their life, and come to a terminal state, before the universe collapses on top of them.

On how to approach such abstract concepts as the early universe

Well, you try and be as concrete as possible and to depend on observations, and my work depends on observations of galaxies and stars etc which, you can visualise in a fairly concrete way. But it’s true that our common-sense notions must be modified drastically when we go down to the very small, the quantum world, or the very large. Fay has emphasised that when we get to the very tiny scale, even space itself has some complicated grainy structure. And in the early universe, we may have to stop our extrapolation back, right in the initial instance, because the whole idea of time breaks down. The idea of three dimensions of space, and clocks ticking away, may have to be generalised. Some ideas for quantum gravity involve extra dimensions, and other deviations from common-sense. But then we do have to think in terms of mathematics but what is amazing is how far we can go, with the laws that we understand here on earth. It’s amazing, we can go back to the first tiny fraction of a second, and study a distant part of the universe through our telescopes and make some sense of it. So I think, what’s amazing is how far we’ve got, not that we eventually come up against a barrier.

On quantum mechanics

We do make use of quantum theory to make calculations on atomic physics, but there are mysteries. Someone once said that your average quantum mechanic is no more philosophical than your average motor mechanic, and that’s certainly true. But nonetheless, the other side of that coin is that, although we use quantum mechanics, there are deep mysteries of a deep philosophical nature, which I’m sure we don’t yet fully understand, and perhaps the deep understanding of those mysteries, will come when we link together, the quantum micro world with cosmology.

On whether he’s confident that we will ever will really understand what happened at the start of the universe?

Well some people have to be confident or they wouldn’t try and find out, if they don’t try they certainly won’t succeed. But we have to be open minded I suspect that maybe we will never be able to get a full understanding. Maybe the laws of nature, at their deepest level, are at a still deeper level than the ones we apply in our labs, and in our astronomy, and so we have to ask to what extent are our brains matched to the deepest level of reality. It’s amazing we’ve made so much sense, but we may come up against some inherent limitation eventually.

On how realistic the idea of a “theory of everything” is

The phrase theory of everything is sort of hubristic and misleading in my opinion. Because, if we had such a theory, it will be the end of a certain quest, the one that started with Newton and went on through Einstein, to unify the laws, but of course the laws are just the rules of the game, and the way those laws are played out in our universe, and the way they have lead from the big bang, to the immensely complex cosmos around us of which we are a part, that’s an unending challenge, and even if we have the laws then, that’ll be what ninety nine percent of scientists will be doing. And so, it’s the end of a certain part of science, but it’s certainly not the end of science.

Further Reading

Just Six Numbers: The Deep Forces that Shape the Universe
Martin Rees (Basic Books 2001), ISBN: 0465036724

Our Cosmic Habitat
Martin Rees (Princeton University Press, 2001), ISBN: 0297829017

The Discovery of Anti-Matter: The Autobiography of Carl David Anderson, the Youngest Man to Win the Nobel Prize
Richard J Weiss, Editor (World Scientific Publishing Company, 1999), ISBN: 9810236808

The Book of Nothing: Vacuums, Voids, and the Late Latest Ideas About the Origins of the Universe
John D Barrow (Pantheon Books, 2001) ISBN: 0375420991

The Universe in a Nutshell
Stephen Hawking (Bantam Books, 2001), ISBN: 055380202X

Antimatter, the Ultimate Mirror
Gordon Fraser (Cambridge University Press, 2000), ISBN: 0521652529

Mirror Matter: Pioneering antimatter physics
Robert L. Forward and Joel Davis (John Wiley, 1988), ISBN 0380898144

It Must Be Beautiful: Great Equations of Modern Science
Graham Farmelo (Granta Books, 2001), ISBN: 1862074798

Anti-matter jargon-buster

annihilation: spontaneous conversion of a particle and its anti-particle into radiation

anti-atom: the equivalent of an atom, but instead of being composed of protons, neutrons and electrons, they are made up of anti-protons, anti-neutrons and positrons

anti-deuteron: a nucleus of antimatter made out of an anti-proton plus an anti-neutron

anti-hydrogen atom: atom made up of one anti-proton and one positron as opposed to hydrogen which is made up of one proton and one electron

anti-neutron: although neutrons have no overall electric charge, they have small local charges that balance out over the entire particle. These are the opposite in anti-neutrons

anti-particle: a particle type that has exactly the same mass but opposite charge of another particle type

anti-proton: the antiparticle of the proton. It is an equivalent particle but with negative charge

anti-matter: matter composed of the antiparticles of normal matter

atom: the smallest particle of an element that can exist either alone or in combination. Composed of protons, neutrons and electrons

bevatron: a high energy particle accelerator

Big Bang Theory: the theory of an expanding universe that begins as an infinitely dense and hot medium. The initial instant is called the Big Bang

electron: a fundamental particle with a negative electric charge. They are a basic constituent of an atom and are distributed around the nucleus in shells

magnetic field: a field of force that exists around a magnetic body or a current-carrying conductor

matter: an aggregate of material particles that are capable of occupying space

nanosecond: one thousand millionth of a second (1,000,000,000 nanoseconds = 1 second)

neutron: a neutral elementary particle that is stable in the atomic nucleus; They occur in all atomic nuclei except normal hydrogen

nucleus: the central core of an atom that contains most of its mass; It is positively charged and contains protons and neutrons

particle: a subatomic object with a definite mass and charge

PET Scan: also called positron emission tomography scan. An imaging technique that uses a radioactive tracer molecule that emits positrons

positron: the antiparticle of the electron. It is an equivalent particle but with positive charge

proton: an elementary particle that is stable and bears a positive charge, equal in magnitude to that of the electron

quantum mechanics: the laws of physics that apply on very small scales. The essential feature is that electric charge, momentum, and angular momentum, as well as charges, come in discrete amounts called quanta

relativity: two widely accepted theories proposed by Albert Einstein to account for departures from Newtonian mechanics. The special theory of relativity of 1905 refers to non-accelerated frames of reference, while the general theory of 1915, extends to accelerated systems

radiation: energy travelling in the form of electromagnetic waves or photons

radiograph: an x-ray film after it has been exposed to radiation