What's Next?

By Sir John Maddox

One thing is certain about the century (or even the millennium) ahead. The pace of discovery is sure to be even faster than it is today and the social and ethical dilemmas created by the exploitation of new knowledge even more haunting. Our understanding of the world has deepened at an accelerating rate since the beginning of modern science 500 years ago. Our century, for example, has had the wit to ask how the universe is constructed, how even the tiniest particles of matter move and how life manages to exist in the face of all the odds against it.

Our century has also turned science into the principal agent of technology. When James Watt built the first steam engines 200 years ago, he had intuition but not the laws of thermodynamics to guide him. We do not sufficiently applaud our century's discovery that science can be useful--or the degree to which science has come to depend on technology for its new instruments: powerful telescopes, atom smashers, computers.

The 20th century has made science more exacting. We demand more of its explanations. To say that the earth goes around the sun is no longer sufficient; we insist on knowing why. And in some fields--space research, for example--decades can go by while novel instruments are designed and built. A further complication is that every discovery provokes new questions. The more we know, the more we do not know.

To predict what lies ahead, we must often rely on guesswork. But the nature of our present ignorance points to problems science cannot avoid. The most obvious of these is the question of what happens in our head when we are thinking. Nobody yet has a compelling answer for that. People surmise, but no surmise can yet meet the tyrannical test that every assertion about the nature of the world must be proved by experiment or observation.

Here, then, despite the dangers, is a checklist of some of the scientific and philosophical challenges for the century ahead:

HUMAN EVOLUTION

Human beings and the great apes had a common ancestor about 5 million years ago. The genes of the two groups differ hardly at all, but some of them are differently arranged. By using that information, along with hominid fossils, we shall learn what genetic changes made it possible for the ancestors of modern people to stand upright (about 4 million years ago) and then to speak. As a by-product, we shall be able to trace the migration routes of our human ancestors who emigrated from Africa and came to populate the surface of the earth. A half-century from now, we shall have a rich and authentic history of the human race.

LIFE'S BEGINNING

How life began is a grander question that will occupy most of the next century. The first task is to reconstruct the history of evolution over the past 4 billion years. Modern gene technology can use the DNA in every living thing as a vast repository of historical information. Even dna will not point all the way back to the beginning of life, but it will provide clues to the self-replicating entities first assembled from simple chemicals on the primeval earth. The century ahead will see the first laboratory proof that self-replicating systems can form from ordinary chemicals. Determining whether that is how life really began will take longer.

UNDERSTANDING LIFE

Figuring out how the chemical operations essential for survival are carried out within every cell of living creatures (people included) is a task dominated by complexity. The Human Genome Project aims to specify the location and structure of all 100,000 or so genes in the human body. But that catalog, which will soon be completed, will be simply the springboard for understanding what all the genes do. Only when the network of their interactions with one another has been mapped will enduring benefits follow: in the surer design of drugs, in the growth of replacement organs, in the early detection and treatment of many kinds of diseases, including cancer. Only then shall we understand the subtleties of human behavior and how human personality evolves in the course of early life by the interaction of genetic and environmental influences.

THINKING

How the brain manages to think is a conundrum with a millennial time scale. All animals have brains so as to be able to move about. Signals from the senses--eyes, ears, nostrils or skin, as the case may be--send messages to the spinal cord, which moves the limbs appropriately. But thinking involves the consideration of alternative responses, many of which have not been experienced but have been merely imagined. The faculty of being conscious of what is going on in the head is an extra puzzle. A century from now, electronics shops (or websites) will be advertising all kinds of gadgets that simulate some of the workings of the human brain, but neuroscientists will still be struggling to understand the thinking machine in all our heads.

A THEORY OF EVERYTHING

Only 70 years ago, the universe was found to be expanding, but now there is a model of how it began: the Big Bang. At the beginning, it is said, there was literally nothing ("the void" of Genesis), not even space. Then there came into being a tiny speck of superheated space that contained enough energy to create all the stars and galaxies that fill the sky-with enough left over to drive the expansion of the universe ever since.

One of the intellectual triumphs of our century, which stems from what is called quantum physics, is the understanding of how very high temperatures can create matter. Temperature is inseparable from radiation. Even in empty space, radiation has energy, and thanks to Einstein's special theory of relativity we know that energy is equivalent to mass, or matter. Laboratory scientists have been turning electromagnetic radiation into mass since the 1930s. (The inverse of that process, turning mass into energy, makes nuclear bombs.)

There is something wrong, however, with this account of how the universe began. There is not nearly enough matter in the universe to match the predictions of the Big Bang, and our current list of the particles of matter is almost certainly incomplete. We need a more sophisticated view of what is meant by "empty space," which turns out not to be empty at all. There are also serious philosophical problems created by the Big Bang, which can be described but not explained. Worse, nobody has been able to reconcile quantum physics with the other great triumph of 20th century physics: Einstein's theory of gravitation. Until that is done, the true nature of our universe will remain beyond our ken.

So must we enter the new century in a state of ignorance? There is no shame in that. All previous centuries have been justly proud of their achievements, yet those have been found, in retrospect, to be deficient. We must learn to be patient. We should also discard the idea that scientific inquiry will ever be complete. What we know so far is that each question answered merely spawns another. Why should it not be like that for the rest of time?

Sir John Maddox is the author of What Remains to Be Discovered