From an astrophysicist's point of view, our century is a century with two good and two bad news. The two good news are the following. We have learned a lot about the structure of matter, this has been said and will be said again, and we have learned in particular how our world is made of a structure which goes about like that, which we call the pyramid of complexity, namely we have quarks and electron that builds up to make neutrons and protons that builds up to make atoms, molecule cells organism. And this is the message of physics, chemistry and biology. This is something we understand now. The second thing that science and astronomy has told us is that this pyramid is a result of a history, namely there is what we call the growth of complexity in the universe. What we have learned from astronomy is that 15 billion years ago, this did not exist. It was the big bang: "chaos" in a sense that there was no structure in the universe. The history of the universe, in a few words, is how the pyramid of complexity has build up in time, creating atoms, molecules and on earth cells and organism. There are two good news of the 20th century. We know no more about the structure of nature and we have learned how this structure has come upon years, billions of years through stars and galaxy. These are the good news. Now, for the bad news. The bad news are the following. We have learned 2 ways in our century, 2 ways to destroy ourselves. One is nuclear weapon and here I can say that with the majority of the Frenchmen I deeply regret the decision of President Chirac. This is the very timely subject so I want to mention it Today we fear the proliferation of nuclear weapons. The second bad news is the planetary deterioration. Complexity is threatened on earth but complexity is the results of billions of years of development over the universe and perhaps it exists on another planet too. And it asks the fundamental question, is complexity viable? In an allegoric way, you could say was it a good idea for nature to start on this path of complexity, building more and more complex system. If it is doomed! The answer is not known to anyone. The answer is with us. It is human people who will answer the question of whether complexity is viable and we'll have to answer it in rather near future. We could summarize it "cosmic drama" in 3 sentences. Sentence No. 1 - The universe generate complexity. This is what we have seen over the billions of years. Sentence No. 2 - Complexity generates efficiency. The more complex the system is the more it is efficient, the more it is performing, the more it can do things, it can interact. Now, the drama, Sentence No. 3 - Efficiency may generate nonsense. It is not guaranteed that efficiency will generate sense. What is nonsense? Well, sense, I don't know too much, but nonsense I know. Nonsense would be the following thing. The following thing would be that the universe would have taken 15 billion years to build up complexity with all its marvel life and so on and so forth. And that this complexity represented on earth by human brain would find it impossible and would in fact destroy itself either in 15 minutes via nuclear war or in, I put 150 years but that's just a number, to show that the planet today is deteriorating and this we all know, this deterioration, it could keep some going may well bring the extinction at least of humanity and perhaps of life and certainly of many, many species which have been extinct in the past. These three sentences summarize, I would say, the essence of our problem today: to make sure that efficiency doesn't generate nonsense, namely that we are able to survive with our wonderful brain and that our brain is not a poison gift from nature. In the 21st century? Science and technology has to face many difficulties. The planet is full. We will be 10 to 12 billion in 2050. Can we have 10, 12 billion people live in normal life and not deteriorate completely the planet? n. The natural resources are decreasing, there will be no more oil and coal and gas and no more uranium in a rather short time. It is often said that science and technology are the remedy. I think we have to say something else. Science and technology are necessary but not sufficient. It is clear that science and technology may as well keep on deteriorating or may be used to improve the situation. The main thing required is something that is not scientific but emergence of the planetary consciousness, the planetary conscience; a will to stop the deterioration. For this we need a strong political will on a planetary scale. So I think science is fundamental, we need science, we need technology but more than that we need the real conscious will to say we have to do something to answer the question "Is complexity viable?" No one knows the answer. It depends on what we do, it is our responsibility to do something in order to make the answer "yes."

Hubert Reeves Research Director, National Center for Scientific Research (France, physicist, astrophysics)

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