In defence of the indispensable

Of all the technologies of the 20th century, which would you least like to give up? Your car? Air travel? Your computer, mobile phone or television? How about doing without a refrigerator? Can you imagine doing without electricity? These are some of the questions a distinguished group of engineers tried to answer for the US National Academy of Engineering and the American Association of Engineering Societies.

The result is an attractive coffee-table book that lists what they consider to be the top 20 engineering achievements and ranks them according to which have had "the most positive impact on mankind". It is not surprising that "electrification" comes first. Almost anything else one can think of depends on readily available electricity. Scientists might argue that electricity and magnetism were understood in the 19th century, but there is no question that electricity became readily available only from the 1920s.

What about the rest of the ranking? The book does not explain how this was determined. Cars come in second and, given our dependence on them, I suppose that is justified. But why does clean water supply come fourth? The selectors say they sought input from as many sources as possible, but they do not offer any explicit rationalisation of the ranking.

Nevertheless, the 20 achievements make for interesting reading. A chapter is devoted to each one and discusses its history using very good graphics and photographs, along with a timeline that lists the contributions made to a particular technology by different inventors and innovators. We learn, for example, that it was the Wright brothers' ability to control aeroplane roll motion that enabled them to fly. Finally, each chapter has a less interesting page of reflection by a pioneer in the field.

Electronics is ranked fifth. It underlies many of the innovations that come later in the list. Computers depend on the transistor and the integrated circuit. So do telephony, the internet, radio and television, and parts of imaging. Electronics is based on the most important discovery in science in the 20th century, quantum mechanics, and is an achievement of both physics and engineering. Thus, there is ample justification for its ranking.

However, the timeline for electronics omits many important innovations and includes some that, in my view, are not so important. Bob Lucky's adaptive equaliser is included, but what about all the innovation that went into automated design that permits engineers to rapidly design circuits at the logic level while computers automatically turn these logic statements into real circuits?

Also strange is that the invention of the CD-Rom is mentioned but not the magnetic hard disk that surely has played a larger role in computing. Ditto the fact that innovations in lithography, projection optical lithography and electron-beam direct-write machines are ignored while Al Cho's invention of molecular beam epitaxy is cited, despite not being used in silicon technology. Of all the timelines, the one for electronics seems most lacking in judgement. I hope this is not because I know most about electronics.

While reading the book I continually found myself thinking of innovations not included. The chapter on imaging has no mention of the polaroid camera.

It is surely still widely used, although it is being replaced by the digital camera. There was enormous progress in photographic film in the 20th century, but this is not mentioned.

There are many other weaknesses. For example, in the discussion of water supply the illustration clearly shows how supply and the cleaning of waste water play equally important roles. However, there is almost no discussion of waste-water treatment except for the invention of chlorination as a means of killing bacteria, while there is extensive discussion of dam building and the purification of water for the third world. There must surely have been technical innovations associated with the cleaning of our rivers and streams following the environmental movement of the 1970s, but none is mentioned.

An aspect that puzzled me for a while was that the list contains little on medicine and drugs. Then I realised that drugs were not considered part of engineering. As a result, apart from clean water supply, health is in 16th place, with the emphasis on pacemakers, artificial limbs and engineering-based techniques such as laser surgery. One invention, in this case the pacemaker, seems to have been given excessive prominence.

Further down, the list seems to be more arbitrary. Would you rate spacecraft above high-performance materials such as nylon, Dacron, Teflon, steels and glass fibre? I think these materials have had a larger impact on humankind, notwithstanding beautiful and important satellite photos, worldwide television coverage and global positioning system technology; and TV coverage is gradually being taken over by optical-fibre communications that eliminate delays in conversations between reporters around the world.

It will always be hard to decide how to rank progress in materials since it is fundamental to almost all progress in engineering, but it deserves more prominence than it gets here. In electronics, for instance, the ideas behind the ubiquitous field-effect transistor were around for more than ten years before physicists and engineers figured out how to fabricate it using silicon and its oxide. In the optical world, the laser was invented in the late 1950s, but it took another 15 years to learn how to fabricate good semiconductor lasers.

Despite these criticisms, A Century of Innovation covers many of the positive benefits of engineering and makes the reader reflect on the tremendous progress of the past century. The 21st century will surely continue this progress, but it will also have to address the problems created by the very achievements we cherish. We cannot continue putting more carbon dioxide into the atmosphere; we cannot expect to continue using enormous amounts of petroleum. What alternatives can be developed? Possible solutions to the carbon dioxide problem may lie in its sequestration, the revival of nuclear power and more efficient use of resources.

Semiconductor-based light-emitting diodes for general lighting, if they could be made sufficiently inexpensive and were adopted widely, could cut electricity consumption by 5 per cent. Hybrid engines for cars, which could double the mileage of most vehicles for the same consumption of fuel, are coming on the market. Electronics will continue to reduce the power consumption of many devices. What the worldwide web will become is anyone's guess. We already have artificial knees, hips and hearts. What will we develop by 2100 - artificial shoulders and fingers? What else? I only wish I could stay around to find out.

W. F. Brinkman is a senior research physicist, Princeton University, New Jersey, US, and former vice-president of research, Bell Labs.

Top twenty

1 Electrification

2 Cars

3 Aeroplanes

4 Water supply and distribution

5 Electronics

6 Radio and TV

7 Agricultural mechanisation

8 Computers

9 Telephony

10 Air conditioning and refrigeration

11 Highways

12 Spacecraft

13 Internet

14 Imaging

15 Household appliances

16 Health technologies

17 Petroleum and petrochemical technologies

18 Lasers and fibre optics

19 Nuclear technologies

20 High-performance materials