1. Hans Moravec is likely to make this argument in his 1998 book Robot: Mere Machine to Transcendent Mind (Oxford University Press; not yet available as of this writing).

2. One hundred fifty million calculations per second for a 1998 personal computer doubling twenty-seven times by the year 2025 (this assumes doubling both the number of components, and the speed of each component every two years) equals about 20 million billion calculations per second. In 1998, it takes multiple calculations on a conventional personal computer to simulate a neural-connection calculation. However, computers by 2020 will be optimized for the neural-connection calculation (and other highly repetitive calculations needed to simulate neuron functions). Note that neural-connection calculations are simpler and more regular than the general-purpose calculations of a personal computer.

3. Five billion bits per $1,000 in 1998 will be doubled seventeen times by 2023, which is about a million billion bits for $1,000 in 2023.

4. NEC's goals to build a supercomputer with a maximum performance of more than 32 teraflops is chronicled in "NEC Begins Designing World's Fastest Computer," Newsbytes News Network, January 21, 1998.

In 1998, IBM was one of four companies chosen to participate in PathForward, an initiative from the Department of Energy to develop supercomputers for the twenty-first century. Other companies involved in the project are Digital Equipment Corporation; Sun Microsystems, Inc.; and Silicon Graphics/Cray Computer Systems (SGI/Cray). PathForward is part of the Accelerated Strategic Computing Initiative (ASCI).

5. By harnessing the accelerating improvement in both density of components and speed of components, computer power will double every twelve months, or a factor of one thousand every ten years. Based on the projection of $1,000 of computing being equal to the estimated processing power of the human brain (20 million billion calculations per second) by the year 2020, we get a projection of $1,000 of computing being equal to a million human brains in 2040, a billion human brains in 2050, and a trillion human brains in 2060.

6. By 2099, $1,000 of computing will equal 10²⁴ times the processing power of the human brain. Based on an estimate of 10 billion persons, that is 10¹⁴ times the processing power of all human brains. Thus one penny of computing will equal 10⁹ (one billion) times the processing power of all human brains.

7. In the Punctuated Equilibrium theories, evolution is seen to progress in sudden leaps followed by periods of relative stability. Interestingly, we often see similar behavior in the performance of evolutionary algorithms (see chapter 4).

8. Dean Takahashi, "Small Firms Jockeying for Position in 3D Chip Market," Knight-Ridder/Tribune News Service, September 21, 1994, p. 0921K4365.

9. The entire February 1998 issue of Computer (vol. 31, no. 2) explores the status of optical computing and optical storage methods.

Sunny Bains writes of companies using optical computing for fingerprint recognition and other applications in "Small, Hybrid Digital/Electronic Optical Correla- tors Ready to Power Commercial Products: Optical Computing Comes into Focus." EE Times, January 26, 1998, issue 990.

10. For a nontechnical introduction to DNA computing, read Vincent Kiernan, "DNA-Based Computers Could Race Past Supercomputers, Researchers Predict," in the Chronicle of Higher Education (November 28, 1997). Kiernan discusses the research of Dr. Robert Corn from the University of Wisconsin as well as the research of Dr. Leonard Adleman.

Consult research at the University of Wisconsin.

Leonard Adleman's "Molecular Computation of Solutions to Combinatorial Problems" from the November 11, 1994, issue of Science (vol. 266, p. 1021) provides a technical overview of his design of DNA programming for computers.

11. Lambertus Hesselink's research is reported by Phillip F. Schewe and Ben Stein in Physics News Update (no. 219; March 28, 1995).

12. For information on nanotubes and buckyballs, read Janet Rae-Dupree's article "Nanotechnology Could Be Foundation for Next Mechanical Revolution," Knight-Ridder/ Tribune News Service, December 17, 1997, p. 1217K1133.

13. Dr. Sumio Iijima's research on nanotubes is summarized in an article at the NEC site.

14. The research of Isaac Chuang and Neil Gershenfeld is reported in "Cue the Qubits: Quantum Computing," The Economist 342, no. 8005 (February 22, 1997): 91­92; and in an article by Dan Vergano, "Brewing a Quantum Computer in a Coffee Cup," Science News 151, no. 3 (January 18, 1997): 37. More technical details and a list of Chuang and Gershenfeld's publications can be found at the Physics and Media Group/MIT Media Lab and at the Los Alamos National Laboratory.

Other groups working on quantum computation include the Information Mechanics Group at MIT's Lab for Computer Science and the Quantum Computation Group at IBM.

15. "Student Cracks Encryption Code," USA Today Tech Report, September 2, 1997.

16. Mark Buchanan, "Light's Spooky Connections Set Distance Record," New Scientist, June 28, 1997.

17. Roger Penrose, The Emperor's New Mind (New York: Penguin USA, 1990).

18. To understand the concept of tunneling, it is important to understand how transistors on an integrated circuit chip work. An integrated chip is engraved with circuits comprised of thousands or millions of transistors, which electronic devices use to control the flow of electricity. Transistors are made up of a small block of a semiconductor, a material that acts as both an insulator and a conductor of electricity. The first transistors were comprised of germanium and were later replaced with silicon.

Transistors work by holding a pattern of electric charge, allowing that pattern of charge to change millions of times every second. Tunneling refers to the ability of electrons (small particles that circle around the nucleus of an atom) to move or "tunnel" through the silicon. Electrons are said to tunnel through the barrier as a result of the quantum uncertainty as to which side of the barrier they are actually on.

19. Knowledge chunks would be greater than the number of distinct words because words are used in more than one way and with more than one meaning. Each different word meaning or usage is often referred to as a word "sense." It is likely that Shakespeare used more than 100,000 word senses.

20. Quoted from Douglas R. Hofstadter, Gödel, Escher, Bach: An Eternal Golden Braid (New York: Basic Books, 1979).

21. Michael Winerip, "Schizophrenia's Most Zealous Foe," New York Sunday Times, February 22, 1998.

22. The goal of the Visible Human Project is to create highly detailed, three-dimensional views of the male and female human body. The project is collecting transverse CT, MRI, and cryosection images.

23. Researchers Mark Hübener, Doron Shoham, Amiram Grinvald, and Tobias Bonhoeffer published their experiments on optical imaging in "Spatial Relationships among Three Columnar Systems in Cat Area 17," Journal of Neuroscience 17 (1997): 9270­9284. More information on this and other brain-imaging research is located at the Weizmann Institute's web site and at Amiram Grinvald's web site.

24. The work of Dr. Benebid and other researchers is summarized in an online ar- ticle, "Neural Prosthetics Come of Age as Research Continues," by Robert Finn, The Scientist 11, no. 19 (September 29, 1997): 13, 16.

25. From an April 1998 phone interview by the author with Dr. Trosch.

26. Dr. Rizzo's research is also reviewed in Finn's article, "Neural Prosthetics Come of Age as Research Continues."

27. To read more about the "neuron transistor," visit the web site of the Membrane and Neurophysics Department at the Max Planck Institute for Biochemistry.

28. Robert Finn, "Neural Prosthetics Come of Age as Research Continues."

29. Carver Mead's research is described in Physics of Computation on the California Institute of Technology's web site.