Crude stun weapons called tasers are already available in the US. The weapons
fire two small darts attached to a wire. A pulsing electrical current passes
down the wire and stuns the victim by “tetanisation”. The pulses make the
muscles of the victim contract in unison, rendering them helpless.

The disadvantages of tasers are that they can only be fired once before they
have to be reloaded. They are also classified as firearms because they fire
projectiles.

One attempt to overcome the limitations of tasers uses a stream of liquid
that hits a victim with a 10 000-volt charge. This causes painful muscle spasms
in the victim. But the liquid can split into droplets, breaking the electrical
connection, and is hard to aim.

Herr’s invention uses lasers to generate intense beams of ultraviolet light.
These create a path of ionised air down which precisely modulated electrical
current is sent. The currents can be manipulated to cause painful contractions,
stun a victim painlessly, or induce a heart attack. It has a far longer range
than the taser—over 100 metres—and the beam can penetrate clothing.
The phaser can also fire many shots before it needs reloading.

Using ultraviolet light avoids legal restrictions on weapons that blind with
laser light, since it would take several minutes to damage the retina with the
wavelength of light used by the device.

A hand-held version of the phaser is not yet available because the
argon-fluoride discharge-pumped excimer laser it uses is as big as a kitchen
table. Herr is hoping that others will find ways to make his device smaller and
more powerful, as well as improve its range. He says that any technically
competent person would be able to build a phaser.

Steve Aftergood, a senior research analyst at the Federation of American
�Ӱ�ԭ��s in Washington, says: “At first glance it seems incredible, and rather
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The German company Siemens is developing a £30 000 device called CEREC
2—an update of an older ceramic milling machine called CEREC—that
automates the process of measuring and making ceramic dental prostheses.

Dentists have been making crowns and false teeth from ceramics for years,
because they are nontoxic, hard and white. But fitting ceramic or plastic
prostheses can take several painful sessions, and requires considerable skill on
the part of the dentist to match replacements to surrounding teeth. Normally,
dental laboratories make the plastic or ceramic prostheses from impressions
taken by the dentist.

The Siemens system uses a computer-driven scanner to work out the desired
shape of the false tooth, and then mills the prosthesis from a block of ceramic
material. The scanner uses laser light emitted as a grid of equally spaced
points. This is distorted around teeth, depending on how far from the light
source they are. A camera records the distorted image of the tooth, which is
then used by the computer to re-create a three-dimensional image.

The computer system then matches the damaged tooth to an undamaged model. The
company has created a dental dictionary of tooth shapes with the help of Sven
Gürke of the Fraunhofer Institute for Computer Graphics Research in
Darmstadt. A series of software routines deforms the selected model to match it
to the patient’s tooth.

The data are then passed to the milling machine, which cuts a perfectly
fitting prosthetic. The whole operation takes 20 minutes, claims Siemens.

Chris Coates, from the British Dental Association, says: “Improved equipment
and techniques which make it easier for dentists to deliver dental care will
inevitably be more convenient for patients.” The new machines are expected to
arrive in Britain this year.

Monika is a mannequin created by the University of California at Berkeley’s
Center for the Built Environment to study sick building syndrome. Loaded with
sensors from head to toe, Monika will be masquerading as an office worker to
report on working conditions inside commercial buildings. “If a building causes
people to be distracted, sleepy, or sick, it reduces their productivity,” says
Edward Arens, director of the Berkeley center.

Monika will enable the researchers to study a variety of environmental
conditions, including temperature, humidity, sound and light levels, air quality
and pollution. All these factors can contribute to sick building syndrome.

The model was built at the Technical University of Denmark in Copenhagen and
looks similar to a shop dummy. But Monika is not an empty shell: it is packed
with sensors for measuring the interaction between human bodies and their
working conditions.

The mannequin’s skin is a glass fibre and polyester shell wrapped with nickel
wire. The wire is used to keep the skin warm and measure how office conditions
affect its temperature. Each of Monka’s 16 parts is individually controlled and
monitored by a computer. “It lets us know if its legs are too cold or its face
is too warm or if there is too much difference between the left and right
sides,” says Arens.

Monika also breathes. An artificial lung allows it to inhale and exhale
through the nose and/or mouth. Since the air taken in is strongly influenced by
the convective plume around the human body, analysing what Monika inhales
provides a realistic assessment of what people breathe in.

Arens says that workers in buildings with sealed windows, for instance,
complain of sick building syndrome twice as often as those with windows that
open and close. “This could be air-quality related or it could be partly
psychological, with people feeling less control over their environment.” Monika
should give them a clearer answer.

Monika has a variety of wigs and clothing to simulate the dress habits and
body sizes of both men and women, allowing it to sit inconspicuously in any
office.

Physicists believe that the force of attraction between two neighbouring atoms is generated by the buffeting they receive from particles which are constantly flitting in and out of existence. By reworking quantum equations, Sipko Boersma, an independent physics consultant based in Delft, has proved that 19th-century sailors were right to worry about the attraction between two ships rolling on the waves.

Boersma admits that sailing and quantum mechanics make unusual bedfellows. “Not many people would think of marrying them,” he says. But as a keen yachtsman, he became fascinated by a passage in The Mariner’s Album, a handbook published in 1836 by French nautical guru P.C. Causseé.

When two ships lie in close proximity on a rolling sea with little wind, Causseé warned that they would eventually end up on the crests of neighbouring waves, and be pulled together by a mysterious attractive force. The only way to avoid a disastrous clash of rigging, Causseé wrote, was to lower boats with strong rowers to tow the ships away from one another.

Boersma was struck by the similarity between this effect and the weak attraction, known as the van der Waals force, that pulls atoms together and plays an important role in the condensation of gases.

In 1948, Hendrik Casimir of the Philips Laboratory in Eindhoven explained this atomic attraction in quantum mechanical terms. According to quantum theory, empty space is not really empty. On the Planck scale—distances of 10⁻³⁷ metres—a vacuum consists of a boiling sea of virtual particles, created in pairs due to fluctuations in the energy of the vacuum. Each particle exists for only about 10⁻²³ seconds, but they fly around before disappearing and their combined effect is to constantly buffet any atoms that they come into contact with, exerting what physicists call “radiation pressure” (see “Nothing like a vacuum”, New �Ӱ�ԭ��, 25 February 1995, p 30).

Casimir showed that when two atoms are brought close together, they create a sheltered region between them in which the radiation pressure is less than in the surrounding space. This pushes the atoms towards each other. Casimir also showed that the same effect causes a measurable force of attraction between two closely spaced metal plates.

Although Casimir explained the effect that now bears his name in terms of virtual particles, quantum theory says that particles can also be considered as waves. So to scale up the Casimir effect to the attraction between ships buffeted by a rolling sea, Boersma reformulated Casimir’s radiation pressure equations in wave terms.

Boersma found that a rolling ship absorbs power from the waves, which it then re-emits as secondary waves emanating in all directions from its hull. If two close ships radiate secondary waves out of phase, these will cancel one other out. This will cause a drop in wave energy between the two ships, similar to the reduction in radiation pressure between atoms. The ships will then be pushed together by the outside wave energy (American Journal of Physics, vol 64, p 539).

Causseé’s conclusion that this was only a danger in relatively windless conditions also makes sense, says Boersma, as even a light breeze would damp down the ships’ rolling motion and diminish the secondary waves. Also, the attractive force turns out to be relatively weak and Boersma has calculated that rowing boats could indeed pull the ships out of danger.

Some biologists argue that anything that can reliably reproduce itself, or
replicate, is alive. And while other researchers have difficulty seeing computer
viruses, for example, as living organisms, many accept that you can learn about
evolution by modelling the process inside a computer. The most famous of these
artificial worlds is Tierra, designed by Thomas Ray of the ATR Human Information
Processing Research Laboratories in Kyoto, Japan, in which a single digital
organism can evolve into a complete ecosystem (“Life and death in a digital
world”, New �Ӱ�ԭ��, 22 February 1992, p 36).

Ray had to play God by creating the first organism in Tierra, but Pargellis’s
program, called Amoeba, goes one step further by modelling the spontaneous
creation of life. “It is a significant advance,” says Ray. “Pargellis is the
first to spontaneously generate self-replicators in any medium.”

Pargellis’s primordial soup was housed within a virtual “stack” in his
computer’s memory. This stack contained 1000 slots, 700 of which initially
contained a random set of computer instructions, the remaining 300 being left
empty. Although computation is different from biochemistry, Pargellis argues
that the random strings of computer instructions in the memory slots are similar
to the babble of genetic information in the first nucleic acids.

The instructions were drawn from a set of 16 different operations, this
number being chosen to mimic closely the 20 amino acids produced by the genetic
code while keeping the number of possible combinations manageably low. Some of
the instructions were neutral directions such as “skip the next instruction”.
But others, if put together in exactly the right combination, would allow a
string of code to make a copy of itself and insert this into a vacant slot
within the stack. The total number of instructions in each slot initially varied
between 1 and 25, so many slots contained duplicates.

Pargellis then asked the computer to process the instructions in each memory
slot, to mimic the biochemical activity of nucleic acids. The program also
contained a routine called “reaper” that simulated the continual destruction and
creation of new nucleic acids in the primordial soup. Each time the computer
read 100 000 instructions, the reaper wiped out 7 per cent of the slots and
replaced them with new, randomly generated strings of code.

Most of the time, the computer routinely read through the random babble of
code. But occasionally it would move or copy pieces of computer code from slot
to slot. In 3 per cent of cases, these “mutations” gave rise to replicating
strings of code that could copy themselves into other positions in the stack
(Physica D, vol 91, p 86).

On average, the first replicating string of code arose after the reaper had
been activated 500 times. In 30 per cent of the computer runs, the ancestral
replicator was immediately able to copy itself efficiently. The rest of the
time, however, the first digital organism that reached this “biotic” state
evolved from an unwieldy, inefficient replicator, which did not replicate in
every cycle of the program and often failed to do so accurately.

As soon as an efficient replicator did appear, it rapidly filled all of the
vacant slots. When this happened, a modified version of the reaper routine came
into play, which was designed to mimic the death of the digital organisms. This
deleted 300 slots, mostly the oldest, each time the stack was filled and added
50 fresh, random strings of code. As in Ray’s Tierra, the replicators then began
to evolve through further mutations. Typically, they lost redundant instructions
that did not help them replicate, and later gained others that let them
replicate even more efficiently.

So does Pargellis’s program provide a good idea of what went on in the
Earth’s primordial soup? It is too early to tell, but more attempts to model the
creation of life could provide some answers. “As we collect more independent
examples of evolution, we should be able to begin to recognise some very
high-level properties that are common to most,” says Ray. “But we are not ready
for that yet. The sample size is two, the Earth and this program.”

Pargellis, meanwhile, has big plans. He notes that the genomes of viruses,
the simplest forms of life, are limited to about 4000 “words” of the genetic
code. If their genomes were larger, they would accumulate too many damaging
mutations to be viable. But higher organisms have evolved DNA repair mechanisms
to put right the damage. “I hope to see whether I can generate a similar
self-repair system within my digital species,” says Pargellis.