At the beginning of this century, before the advent of quantum mechanics, who could have foreseen molecular biology? And in the 1940s, before the discovery of DNA and the development of computers, who could have predicted the Human Genome Project and all of its staggering implications? The scientific exploration of the future is not a trivial exercise, especially when looking further than a few decades ahead. Indeed, unpredictable theoretical or technological breakthroughs in one field can often lead to unexpected developments in unrelated fields – and even open up new fields altogether.

Still, predicting the future (or at least trying to extrapolate major forthcoming developments in science and technology) has always been a big temptation for scientists, as well as for science-fiction writers. Arthur C Clarke’s Profiles of the Future , which was first published 40 years ago, introduced millions of readers to the technological marvels promised by the science of the 1950s. But more important than the predictions themselves was the spirit of exploration that was encapsulated in Clarke’s now famous “laws”. The first law stated that when distinguished, but elderly, scientists say that something is possible, they are almost certainly right; but when they say that something is impossible, they are very probably wrong. Clarke’s second law stated that the only way of discovering the limits of the possible is to venture a little way past them, into the impossible.

As we approach the new millennium, the public’s interest in this kind of futurological essay is expected to rise. In fact, one of the safest predictions is that the number of such publications will explode. Adrian Berry’s The Next 500 Years (1996 W H Freeman) and the late Carl Sagan’s Pale Blue Dot (1995 Random House) have already paved the way, at least as far as our future in space is concerned.

This book by Michio Kaku, a theoretical physicist from the City University of New York, is a serious attempt to present a “unified” view of the scientific and technological landscape of the 21st century. The book is based on a series of interviews with over 150 prominent scientists in various fields, including several Nobel laureates. This impressive list makes the author feel confident that the picture that emerges from the book is quite reliable. However, I do not completely share the author’s optimism – not only because of Clarke’s first law, but also because it is rather well known that socio-economic factors often play a far greater role in shaping the future than techno-scientific ones. In fact, predictions in sociology or economics are notoriously harder to make than those in the physical sciences.

In spite of this, Kaku’s view of the future is well organized around the three main developments in modern science: the quantum revolution, which has enabled us to understand the behaviour of matter; the biomolecular revolution, which has unravelled many (but not yet all) of the secrets of life; and the computer revolution, which Kaku associates, rather fallaciously, with our understanding of the mind. By extrapolating current trends in these fields, he suggests that “predictions about the future of computers and biotechnology can be quantified with reasonable accuracy beyond the year 2020”.

For example, Kaku assumes that computer power and the amount of DNA sequencing will double roughly every two years, and so predicts that by 2020 silicon microprocessors will be as plentiful and as cheap as scrap paper. This will allow us to put “intelligent” systems everywhere, giving us “smart” homes, cars, televisions, clothes and money. The Internet, meanwhile, will evolve into a membrane of millions of computer networks, creating an “intelligent” planet. By 2020 microchip components will shrink to the size of molecules, and quantum effects will necessarily put an end to the reign of silicon. New technologies, involving optical, molecular, biological and – ultimately – quantum computation, will lead to radically new types of computer and reshape the computer industry that we know today.

On the other hand, the automation of DNA sequencing will, by early next century, have unravelled the complete DNA code of thousands of organisms, which will have profound implications for biology and medicine. It will eliminate many genetic diseases and killer viruses, help to treat AIDS and many types of cancer, and enable entire organs – including livers and kidneys – to be grown in the lab. Beyond the year 2020, the understanding of “polygenic” diseases – those involving the complex interaction of many genes – will perhaps enable us to tackle some of our most dreadful chronic enemies, such as heart disease, arthritis and schizophrenia. It may also enable us to clone humans, develop new varieties of disease-resistant plants and animals, and even isolate the fabled “age genes”, which would enable us to extend the lifespan of humans.

The quantum future, meanwhile, will plausibly lead to the further development of nanotechnology, which would allow molecular-sized machines to be built. Carbon nanotubes could be used to create extremely tough fibres – imagine such a cable linking the Earth and a geostationary satellite to allow cheap access to space. Developments in quantum physics could also lead to room-temperature superconductors, which would limit heat losses in electric devices and lead to cheap but powerful magnetic fields that could be used in magnetically levitating trains and cars. Controlled thermonuclear fusion would be another possibility.

These developments will pave the way for us to colonize the solar system, and will ultimately lead to the construction of the first interstellar vehicles. Our civilization will progressively develop into what the Russian astronomer Nikolai Kardashev called a “type I” civilization – one that can master the energy and material resources of a whole planet – and then still further to a “type II” civilization that can use the resources of its solar system.

Despite the lessons of the past, most futurologists take the risk of presenting “time-frames” with approximate dates for when their predictions will come true. For example, in Profiles of the Future, Arthur C Clarke correctly predicted that man would land on the Moon by 1970, but he turned out to be wrong when he said that controlled fusion would be possible by 1990, and that humans would have colonized other planets and created artificial intelligence by the year 2000. Kaku, however, presents a more reasonable, albeit less precise, timetable. He divides the future into three broad periods: up to the year 2020, from 2020 to 2050 and beyond 2050. Still, he isn’t afraid of predicting that the first commercial fusion plant will be up and running by 2035. Taking into account how often the announced celebration of that event has been cancelled in the past, this is not, I think, a very safe bet.

One of the most attractive aspects of the book is that the author does not merely present future developments in various fields as merely a catalogue of isolated, independent events. Instead, Kaku shows clearly the links between the quantum, the biomolecular and the computer revolutions, emphasizing the synergy between these fields. He also considers the potential implications for society. For example, the computer revolution may threaten privacy, bring massive unemployment and, ultimately, make humans obsolete (by producing super-intelligent robots). Progress in biomolecular research may unleash deadly viruses, produce armies of human clones and promote new forms of racism, like the eugenics movement. And although sociologists are probably better placed to discuss such matters, Kaku does not neglect them.

On the other hand, the book has some surprisingly trivial errors in physics and the history of science. For example, the “echo” of the big bang – the 3 K cosmic background radiation – was not discovered by the Cosmic Background Explorer satellite in 1992, as Kaku says, but by Arno Penzias and Robert Wilson in 1965. And Einstein did not say that the universe was “originally a pinpoint”; if the universe is open – as we think today – it is infinite and has always been so.

In fact, the last part of the book is the least satisfactory section, as the author jumps swiftly from Earth-threatening asteroids to extra-terrestrials, from von Neumann machines to time travel, and from wormholes to superstrings and quantum cosmology. Despite this rather disappointing finale, Kaku nevertheless fulfils his aim – of presenting a plausible vision of science and technology in the 21st century.