TEDGlobal 2005 Transcript

Slightly expanded version of the talk I gave at the TEDGlobal Conference, Oxford, July 2005

We’ve been asked to go out on a limb, stick our necks out. I’ll try to do that, but I want to start with two things that everyone already knows. The first is something that has been known for most of human history, namely that the planet Earth – the solar system – our environment – is uniquely suited to sustaining our evolution (or creation as they used to think), our present existence, and most importantly our future survival. Nowadays this idea has a dramatic name: Spaceship Earth. And the idea is that outside the spaceship, the universe is implacably hostile. Inside is all we have, all we depend on. And we only get the one chance. If we mess up our spaceship, we have nowhere else to go.

The second thing that everyone already knows is that, contrary to what was believed from most of history, human beings not the hub of existence. As Stephen Hawking famously put it, we’re just a chemical scum on the surface of a typical planet that’s in orbit round a typical star on the outskirts of a typical galaxy, and so on.

Now, the first of those two ‘ideas that everyone knows’ is saying that we’re at a very untypical, special place: uniquely suited, and so on. The second is saying that we are at a typical place. So, especially if you regard them as deep truths to form cornerstones of your world view and inform your life-decisions, they appear somewhat in opposition to each other – but nevertheless, that does not prevent them from both being completely false.

In fact, if you were looking for a pair of great truths, so true and important that it’s worth carving them on blocks of stone and reciting them every morning before breakfast, you could do a lot worse than to carve the negations of those two statements.

Let me take the second one first: is this a typical place? Let’s look around. Look in a random direction; what do you see? Walls. Chemical scum. But that’s not typical of the universe. All you have to do is go out another couple of hundred miles in that direction and look back, and you’ll see a blue planet, but you won’t see any walls or chemical scum. If you go out further than that, you’ll see the sun and the solar system and stars and so on. But that’s not typical either, because stars come in galaxies, and most places in the universe are not in a galaxy. So, go out even further until you get outside the galaxy, and look back, and you’ll see the huge spiral-armed thing laid out in front of you. At this point you are about 100,000 light years away from here. But you still haven’t reached a typical place in the universe, because a typical place is not even near any galaxy. To get to a typical place you’ll have to go about a thousand times as far as that. Then you’ll be in deep, intergalactic space. What does that look like?

Sparing no expense, TED has laid on a fully-surround, high-resolution, virtual reality rendering of deep, intergalactic space. So, can we have the lights off please, and I’ll show it to you.


Yes, deep, intergalactic space is completely dark. It is so dark that if you were to look at the nearest star to you, and that star were to explode as a supernova, and you were staring directly at it at the moment when its light reached you, then you still wouldn’t see even a glimmer. And that’s despite the fact that a supernova explosion is so luminous that it would kill you stone dead at a range of several light years. And yet, at intergalactic distances you wouldn’t see it at all.

It’s also very cold out there. Less than three degrees above absolute zero. And it’s very empty: less than one millionth of the density of the highest vacuum that our best technology can currently attain on Earth. That is how unlike our location a typical location is. And that is a measure of how untypical our environment is of the universe. Can we have the lights back on now please.


David Deutsch at TEDGlobal

How do we know so much about an environment that is so far away and so different from ours? The Earth, our environment, in the form of us, has been creating knowledge. What does that mean?

Take a telescope and look even further out than where we’ve just been, and see a thing that looks like star. It’s called a ‘quasar’, which used to stand for ‘quasi-stellar object’, which means ‘thing that looks like a star’. But we know that it isn’t a star, and we now know what it really is. Billions of years ago, and billions of light years away, the material at the centre of some galaxy collapsed under its own weight towards a super-massive black hole. Intense magnetic fields directed some of the matter and gravitational energy of that collapse back out into narrow jets travelling near the speed of light, illuminating surrounding lobes of gas with the brightness of – I think it’s atrillion suns.

The physics of the human brain could hardly be more unlike the physics of that jet. We couldn’t survive for an instant there. It would be a bit like facing a supernova explosion, at point blank range, for millions of years at a time. And yet that jet happened in precisely such a way that billions of years later on the other side of the universe, a chemical scum can accurately describe, and model, and predict, and explain what that jet really is. So the one physical system, the human brain, contains an accurate working model of the other, the quasar. Not just a superficial image of it (though it contains that as well) but an explanatory model that embodies the same mathematical relationships and causal structure. That’s knowledge.

And if that weren’t amazing enough, the faithfulness with which the one structure resembles the other is steadily increasing. That’s the growth of knowledge. So the laws of physics have this special property that physical objects very unlike each other can sometimes have the same mathematical and causal structure embodied in them – and that this can become more so over time.

Therefore we are chemical scum that’s different. This chemical scum has universality. Its structure contains, with ever-increasing precision, the structure of everything. This place, and not other places in the universe, is a hub that contains within itself the structural and causal essence of the whole of the rest of physical reality. And so, far from being insignificant, the fact that the laws of physics permit – and even mandate – the existence of such a hub is one of the most important facts about the physical world.

Now, how does the solar system acquire this relationship with the rest of the universe? Well, one thing that’s true about Hawking’s remark – well, it’s entirely true, just misleading – is that it doesn’t require any special physics. No special dispensation or miracle is involved. It does it with three things that we have here in abundance: The first is matter. That’s because the growth of knowledge is a kind of information processing, and information processing is computation, which requires a computer, and there is no known way of making a computer without matter. So the open-ended creation of knowledge requires the presence of matter. It also requires energy – to build the computer and to manufacture the media onto which we record knowledge, and so on. And it also requires a third thing which is less tangible but just as essential, namely evidence. We need evidence to choose between our rival explanations of what is really out there. We got round to testing, say, Newton’s law of gravity a few hundred years ago, but the evidence that we used to test it had already been inundating every square metre of the surface of the Earth for billions of years before that, and will continue to do so for billions of years hence. So our location is inundated with evidence of astronomy, and the same for all the other sciences.

It is inundated with all three of these prerequisites – matter, energy and evidence – for the open-ended creation of knowledge. But out there in intergalactic space, those three prerequisites are at their lowest possible supply: it’s empty, it’s cold, and it’s dark. Or is it?

Actually, that’s yet another a parochial misconception, because – Imagine a cube, out there in intergalactic space, the same size as our home, the solar system. That cube is indeed incredibly empty, by our standards, but that still means that it contains a million tons of matter. Which is more than enough, say, to build a space station containing a colony of scientists who might be creating an open-ended stream of knowledge just as we are. The matter out there is in the form of hydrogen at the moment, so to make a space station out of it, and chemical scum and so on, you’d have to transmute it into other elements first. That’s beyond our present technology, but in a comprehensible universe, if something isn’t forbidden by the laws of physics – and this isn’t – then what could prevent us from doing it other than the knowledge of how to? And that would automatically become an energy supply as well, because the transmutation device would be a nuclear fusion reactor and would provide power. And as for evidence – well, again, it’s dark out there by human standards, but all you’d have to do is take a telescope, even one of present-day design, and you’d see, all around you, galaxies just as we do. And with a more powerful telescope you could see stars in those galaxies, and planets, and you could do astrophysics and learn the laws of physics. Locally, you could build particle accelerators and learn elementary particle physics, and chemistry, and so on.

The hardest science to do would probably be biology field trips, because to get to the nearest life-bearing planet and back would be a journey of several hundred million years at least. But – I never did like biology field trips (sorry Richard) so I guess that one every few hundred million years is going to be enough.

So, anyway, that means that intergalactic space contains all the prerequisites for the open-ended creation of knowledge. Any such cube could become a hub, if the knowledge of how to do so were present there. And therefore we are not in a uniquely hospitable place after all. Because if intergalactic space is capable of creating an open-ended stream of explanations, given the right knowledge to start it off, then so is almost any other environment. So is the Earth. And so also is a polluted or messed-up Earth. The limiting factor, there and here, is not resources but knowledge.

Now, this cosmic, knowledge-based, view may make us feel very special. But it should also make us feel vulnerable, because it means that without the specific knowledge needed to survive each of the ongoing challenges of the universe, we won’t survive them. All it takes is a supernova a few light years away, and we’ll all be dead. Martin Rees has written a book about our vulnerability to various dangers ranging from astrophysics to scientific accidents to terrorism using weapons of mass destruction. He thinks that civilisation has only a 50% chance of surviving this century. I don’t think that probability is the right category to discuss this issue, but I do agree about this: we can survive, and we can fail to survive, but this depends not on chance but on whether we create the relevant knowledge in time.

This danger is not at all unprecedented. Species go extinct. All the time. Civilisations end. The vast majority of all species and all civilisations that have ever existed are now history. If we want to be exceptions to that, then logically, our only hope is to make use of the one feature of us that distinguishes our species and our civilisation from the others, namely our special relationship with the laws of physics. Our ability to create new knowledge. To be a hub of existence.

So let me apply this to one issue of current controversy – not because I want to advocate any particular solution, but just to illustrate the kind of thinking I’m advocating. The issue is global warming. I’m a physicist but not knowledgeable about the relevant physics. So for these purposes I am a layman. And for a layman, the rational thing to do is to take seriously the prevailing scientific theory. And according to that theory, it is already too late to avoid a disaster. Because if it’s true that our best option currently is to prevent carbon dioxide emissions via the Kyoto protocol with its constraints on economic activity and its cost of hundreds of billions of dollars and so on, then that’s already a disaster by any reasonable measure. And these actions aren’t even purported to solve the problem, merely to postpone it a little.

So it’s too late to avoid it, and most likely it was already too late to avoid it even before anyone knew about it. It was already too late in the 70s when the best available science was telling us that industrial emissions were about to precipitate a new Ice Age in which billions of people would die. And so the lesson of that seems very clear to me, and I don’t know why it isn’t informing public debate, namely: we can’t always know. When we know of an impending disaster, and how to avoid it at a cost less than that of the disaster itself, then there isn’t going to be much argument. But no precautions, and no precautionary principle, can avoid problems that we do not yet foresee. Hence, we need a stance of problem-fixing not just problem avoidance.

It is true that an ounce of prevention equals a pound of cure. But that’s only when we know what to prevent. If you’ve been punched on the nose, then medical science does not consist of teaching you how to avoid being punched in the future. If medical science stopped seeking cures, and concentrated only on prevention, then it would achieve very little of either.

The world is currently buzzing with plans to force reductions in gas emissions. At all costs! But it ought to be buzzing more with plans to reduce the temperature, or with plans for how to live with a higher temperature. And not at all costs but efficiently and cheaply. Some such plans exist: things like swarms of mirrors in space that would deflect sunlight away from the Earth; encouraging aquatic organisms to eat more carbon dioxide, and so on. But at the moment these are fringe research. They are not central to the human effort to face this problem or problems like it. But with problems that we are not aware of yet, the ability to put things right, not the sheer good luck of avoiding them indefinitely, is our only hope not just of solving them but of survival. So take those two stone tablets, and here’s a better way of phrasing the two denials I spoke of: On the first tablet, carve: problems are inevitable. And on the second, carve: problems are soluble.

Thank you.