Radar

The invention: An electronic system for detecting objects at great

distances, radar was a major factor in the Allied victory ofWorld

War II and now pervades modern life, including scientific research.

The people behind the invention:

Sir Robert Watson-Watt (1892-1973), the father of radar who

proposed the chain air-warning system

Arnold F. Wilkins, the person who first calculated the intensity

of a radio wave

William C. Curtis (1914-1976), an American engineer

Looking for Thunder

Sir RobertWatson-Watt, a scientist with twenty years of experience

in government, led the development of the first radar, an acronym

for radio detection and ranging. “Radar” refers to any instrument

that uses the reflection of radio waves to determine the

distance, direction, and speed of an object.

In 1915, during World War I (1914-1918), Watson-Watt joined

Great Britain’s Meteorological Office. He began work on the detection

and location of thunderstorms at the Royal Aircraft Establishment

in Farnborough and remained there throughout the

war. Thunderstorms were known to be a prolific source of “atmospherics”

(audible disturbances produced in radio receiving apparatus

by atmospheric electrical phenomena), andWatson-Watt

began the design of an elementary radio direction finder that

gave the general position of such storms.





Research continued after

the war and reached a high point in 1922 when sealed-off

cathode-ray tubes first became available. With assistance from

J. F. Herd, a fellow Scot who had joined him at Farnborough, he

constructed an instantaneous direction finder, using the new

cathode-ray tubes, that gave the direction of thunderstorm activity.

It was admittedly of low sensitivity, but it worked, and it was

the first of its kind.Watson-Watt did much of this work at a new site at Ditton Park,

near Slough, where the National Physical Laboratory had a field

station devoted to radio research. In 1927, the two endeavors were

combined as the Radio Research Station; it came under the general

supervision of the National Physical Laboratory, withWatson-Watt

as the first superintendent. This became a center with unrivaled expertise

in direction finding using the cathode-ray tube and in studying

the ionosphere using radio waves. No doubt these facilities

were a factor when Watson-Watt invented radar in 1935.

As radar developed, its practical uses expanded. Meteorological

services around the world, using ground-based radar, gave warning

of approaching rainstorms. Airborne radars proved to be a great

help to aircraft by allowing them to recognize potentially hazardous

storm areas. This type of radar was used also to assist research into

cloud and rain physics. In this type of research, radar-equipped research

aircraft observe the radar echoes inside a cloud as rain develops,

and then fly through the cloud, using on-board instruments to

measure the water content.

Aiming Radar at the Moon

The principles of radar were further developed through the discipline

of radio astronomy. This field began with certain observations

made by the American electrical engineer Karl Jansky in 1933

at the Bell Laboratories at Holmdell, New Jersey. Radio astronomers

learn about objects in space by intercepting the radio waves that

these objects emit.

Jansky found that radio signals were coming to Earth from space.

He called these mysterious pulses “cosmic noise.” In particular, there

was an unusual amount of radar noise when the radio antennas were

pointed at the Sun, which increased at the time of sun-spot activity.

All this information lay dormant until after World War II (1939-

1945), at which time many investigators turned their attention to interpreting

the cosmic noise. The pioneers were Sir Bernard Lovell at

Manchester, England, Sir Martin Ryle at Cambridge, England, and

Joseph Pawsey of the Commonwealth of Science Industrial Research

Organization, in Australia. The intensity of these radio waves was

first calculated by Arnold F.Wilkins.

As more powerful tools became available toward the end of

World War II, curiosity caused experimenters to try to detect radio

signals from the Moon. This was accomplished successfully in the

late 1940’s and led to experiments on other objects in the solar system:

planets, satellites, comets, and asteroids.

Impact

Radar introduced some new and revolutionary concepts into warfare,

and in doing so gave birth to entirely new branches of technology.

In the application of radar to marine navigation, the long-range

navigation system developed during the war was taken up at once

by the merchant fleets that used military-style radar equipment

without modification. In addition, radar systems that could detect

buoys and other ships and obstructions in closed waters, particularly

under conditions of low visibility, proved particularly useful

to peacetime marine navigation.

In the same way, radar was adopted to assist in the navigation of

civil aircraft. The various types of track guidance systems developed after the war were aimed at guiding aircraft in the critical last

hundred kilometers or so of their run into an airport. Subsequent

improvements in the system meant that an aircraft could place itself

on an approach or landing path with great accuracy.

The ability of radar to measure distance to an extraordinary degree

of accuracy resulted in the development of an instrument that

provided pilots with a direct measurement of the distances between

airports. Along with these aids, ground-based radars were developed

for the control of aircraft along the air routes or in the airport

control area.

The development of electronic computers can be traced back to

the enormous advances in circuit design, which were an integral part

of radar research during the war. During that time, some elements

of electronic computing had been built into bombsights and other

weaponry; later, it was realized that a whole range of computing operations

could be performed electronically. By the end of the war,

many pulse-forming networks, pulse-counting circuits, and memory

circuits existed in the form needed for an electronic computer.

Finally, the developing radio technology has continued to help

astronomers explore the universe. Large radio telescopes exist in almost

every country and enable scientists to study the solar system

in great detail. Radar-assisted cosmic background radiation studies

have been a building block for the big bang theory of the origin of

the universe.

Pyrex glass

The invention: Asuperhard and durable glass product with widespread

uses in industry and home products.

The people behind the invention:

Jesse T. Littleton (1888-1966), the chief physicist of Corning

Glass Works’ research department

Eugene G. Sullivan (1872-1962), the founder of Corning’s

research laboratories

William C. Taylor (1886-1958), an assistant to Sullivan

Cooperating with Science

By the twentieth century, Corning GlassWorks had a reputation

as a corporation that cooperated with the world of science to improve

existing products and develop new ones. In the 1870’s, the

company had hired university scientists to advise on improving the

optical quality of glasses, an early example of today’s common practice

of academics consulting for industry.

When Eugene G. Sullivan established Corning’s research laboratory

in 1908 (the first of its kind devoted to glass research), the task

that he undertook withWilliam C. Taylor was that of making a heatresistant

glass for railroad lantern lenses. The problem was that ordinary

flint glass (the kind in bottles and windows, made by melting

together silica sand, soda, and lime) has a fairly high thermal expansion,

but a poor heat conductivity. The glass thus expands

unevenly when exposed to heat. This condition can cause the glass

to break, sometimes violently. Colored lenses for oil or gas railroad

signal lanterns sometimes shattered if they were heated too much

by the flame that produced the light and were then sprayed by rain

or wet snow. This changed a red “stop” light to a clear “proceed”

signal and caused many accidents or near misses in railroading in

the late nineteenth century.



Two solutions were possible: to improve the thermal conductivity

or reduce the thermal expansion. The first is what metals do:

When exposed to heat, most metals have an expansion much greater  

than that of glass, but they conduct heat so quickly that they expand

nearly equally throughout and seldom lose structural integrity from

uneven expansion. Glass, however, is an inherently poor heat conductor,

so this approach was not possible.

Therefore, a formulation had to be found that had little or no

thermal expansivity. Pure silica (one example is quartz) fits this description,

but it is expensive and, with its high melting point, very

difficult to work.

The formulation that Sullivan and Taylor devised was a borosilicate

glass—essentially a soda-lime glass with the lime replaced by

borax, with a small amount of alumina added. This gave the low thermal

expansion needed for signal lenses. It also turned out to have

good acid-resistance, which led to its being used for the battery jars

required for railway telegraph systems and other applications. The

glass was marketed as “Nonex” (for “nonexpansion glass”).

From the Railroad to the Kitchen

Jesse T. Littleton joined Corning’s research laboratory in 1913.

The company had a very successful lens and battery jar material,

but no one had even considered it for cooking or other heat-transfer

applications, because the prevailing opinion was that glass absorbed

and conducted heat poorly. This meant that, in glass pans,

cakes, pies, and the like would cook on the top, where they were exposed

to hot air, but would remain cold and wet (or at least undercooked)

next to the glass surface. As a physicist, Littleton knew that

glass absorbed radiant energy very well. He thought that the heatconduction

problem could be solved by using the glass vessel itself

to absorb and distribute heat. Glass also had a significant advantage

over metal in baking. Metal bakeware mostly reflects radiant energy

to the walls of the oven, where it is lost ultimately to the surroundings.

Glass would absorb this radiation energy and conduct it evenly to

the cake or pie, giving a better result than that of the metal bakeware.

Moreover, glass would not absorb and carry over flavors from

one baking effort to the next, as some metals do.

Littleton took a cut-off battery jar home and asked his wife to

bake a cake in it. He took it to the laboratory the next day, handing

pieces around and not disclosing the method of baking until all had

agreed that the results were excellent. With this agreement, he was

able to commit laboratory time to developing variations on the

Nonex formula that were more suitable for cooking. The result was

Pyrex, patented and trademarked in May of 1915.

Impact

In the 1930’s, Pyrex “Flameware” was introduced, with a new

glass formulation that could resist the increased heat of stovetop

cooking. In the half century since Flameware was introduced,

Corning went on to produce a variety of other products and materials:

tableware in tempered opal glass; cookware in Pyroceram, a

glass product that during heat treatment gained such mechanical

strength as to be virtually unbreakable; even hot plates and stoves

topped with Pyroceram.

In the same year that Pyrex was marketed for cooking, it was

also introduced for laboratory apparatus. Laboratory glassware

had been coming from Germany at the beginning of the twentieth

century; World War I cut off the supply. Corning filled the gap

with Pyrex beakers, flasks, and other items. The delicate blownglass

equipment that came from Germany was completely displaced

by the more rugged and heat-resistant machine-made Pyrex

ware.

Any number of operations are possible with Pyrex that cannot

be performed safely in flint glass: Test tubes can be thrust directly

into burner flames, with no preliminary warming; beakers and

flasks can be heated on hot plates; and materials that dissolve

when exposed to heat can be made into solutions directly in Pyrex

storage bottles, a process that cannot be performed in regular

glass. The list of such applications is almost endless.

Pyrex has also proved to be the material of choice for lenses in

the great reflector telescopes, beginning in 1934 with that at Mount

Palomar. By its nature, astronomical observation must be done

with the scope open to the weather. This means that the mirror

must not change shape with temperature variations, which rules

out metal mirrors. Silvered (or aluminized) Pyrex serves very well,

and Corning has developed great expertise in casting and machining

Pyrex blanks for mirrors of all sizes.

Propeller-coordinated machine gun

The invention: A mechanism that synchronized machine gun fire

with propeller movement to prevent World War I fighter plane

pilots from shooting off their own propellers during combat.

The people behind the invention:

Anthony Herman Gerard Fokker (1890-1939), a Dutch-born

American entrepreneur, pilot, aircraft designer, and

manufacturer

Roland Garros (1888-1918), a French aviator

Max Immelmann (1890-1916), a German aviator

Raymond Saulnier (1881-1964), a French aircraft designer and

manufacturer

French Innovation

The first true aerial combat ofWorldWar I took place in 1915. Before

then, weapons attached to airplanes were inadequate for any

real combat work. Hand-held weapons and clumsily mounted machine

guns were used by pilots and crew members in attempts to

convert their observation planes into fighters. On April 1, 1915, this

situation changed. From an airfield near Dunkerque, France, a

French airman, Lieutenant Roland Garros, took off in an airplane

equipped with a device that would make his plane the most feared

weapon in the air at that time.

During a visit to Paris, Garros met with Raymond Saulnier, a French

aircraft designer. In April of 1914, Saulnier had applied for a patent on

a device that mechanically linked the trigger of a machine

gun to a cam

on the engine shaft. Theoretically, such an assembly would allow the

gun to fire between the moving blades of the propeller. Unfortunately,

the available machine gun Saulnier used to test his device was a

Hotchkiss gun, which tended to fire at an uneven rate. On Garros’s arrival,

Saulnier showed him a new invention: a steel deflector shield

that, when fastened to the propeller, would deflect the small percentage

of mistimed bullets that would otherwise destroy the blade.

The first test-firing was a disaster, shooting the propeller off and

destroying the fuselage. Modifications were made to the deflector

braces, streamlining its form into a wedge shape with gutterchannels

for deflected bullets. The invention was attached to a

Morane-Saulnier monoplane, and on April 1, Garros took off alone

toward the German lines. Success was immediate. Garros shot

down a German observation plane that morning. During the next

two weeks, Garros shot down five more German aircraft.

German Luck

The German high command, frantic over the effectiveness of the

French “secret weapon,” sent out spies to try to steal the secret and

also ordered engineers to develop a similar weapon. Luck was with

them. On April 18, 1915, despite warnings by his superiors not to fly

over enemy-held territory, Garros was forced to crash-land behind

German lines with engine trouble. Before he could destroy his aircraft,

Garros and his plane were captured by German troops. The secret

weapon was revealed.

The Germans were ecstatic about the opportunity to examine

the new French weapon. Unlike the French, the Germans had the

first air-cooled machine gun, the Parabellum, which shot continuous

bands of one hundred bullets and was reliable enough to be

adapted to a timing mechanism.

In May of 1915, Anthony Herman Gerard Fokker was shown

Garros’s captured plane and was ordered to copy the idea. Instead,

Fokker and his assistant designed a new firing system. It is unclear

whether Fokker and his team were already working on a synchronizer

or to what extent they knew of Saulnier’s previous work in

France.Within several days, however, they had constructed a working

prototype and attached it to a Fokker Eindecker 1 airplane. The

design consisted of a simple linkage of cams and push-rods connected

to the oil-pump drive of an Oberursel engine and the trigger

of a Parabellum machine gun. The firing of the gun had to be timed

precisely to fire its six hundred rounds per minute between the

twelve-hundred-revolutions-per-minute propeller blades.

Fokker took his invention to Doberitz air base, and after a series of exhausting trials before the German high command, both on the

ground and in the air, he was allowed to take two prototypes of the

machine-gun-mounted airplanes to Douai in German-held France.

At Douai, two German pilots crowded into the cockpit with Fokker

and were given demonstrations of the plane’s capabilities. The airmen

were Oswald Boelcke, a test pilot and veteran of forty reconnaissance

missions, and Max Immelmann, a young, skillful aviator

who was assigned to the front.

When the first combat-ready versions of Fokker’s Eindecker 1

were delivered to the front lines, one was assigned to Boelcke, the

other to Immelmann. On August 1, 1915, with their aerodrome under attack from nine English bombers, Boelcke and Immelmann

manned their aircraft and attacked. Boelcke’s gun jammed, and he

was forced to cut off his attack and return to the aerodrome. Immelmann,

however, succeeded in shooting down one of the bombers

with his synchronized machine gun. It was the first victory credited

to the Fokker-designed weapon system.

Impact

At the outbreak of World War I, military strategists and commanders

on both sides saw the wartime function of airplanes as a

means to supply intelligence information behind enemy lines or as

airborne artillery spotting platforms. As the war progressed and aircraft

flew more or less freely across the trenches, providing vital information

to both armies, it became apparent to ground commanders

that while it was important to obtain intelligence on enemy

movements, it was important also to deny the enemy similar information.

Early in the war, the French used airplanes as strategic bombing

platforms. As both armies began to use their air forces for strategic

bombing of troops, railways, ports, and airfields, it became evident

that aircraft would have to be employed against enemy aircraft to

prevent reconnaissance and bombing raids.

With the invention of the synchronized forward-firing machine

gun, pilots could use their aircraft as attack weapons. Apilot finally

could coordinate control of his aircraft and his armaments with

maximum efficiency. This conversion of aircraft from nearly passive

observation platforms to attack fighters is the single greatest innovation

in the history of aerial warfare. The development of fighter

aircraft forced a change in military strategy, tactics, and logistics and

ushered in the era of modern warfare. Fighter planes are responsible

for the battle-tested military adage: Whoever controls the sky controls

the battlefield.

Polystyrene

The invention: A clear, moldable polymer with many industrial

uses whose overuse has also threatened the environment.

The people behind the invention:

Edward Simon, an American chemist

Charles Gerhardt (1816-1856), a French chemist

Marcellin Pierre Berthelot (1827-1907), a French chemist

Polystyrene Is Characterized

In the late eighteenth century, a scientist by the name of Casper

Neuman described the isolation of a chemical called “storax” from a

balsam tree that grew in Asia Minor. This isolation led to the first report

on the physical properties of the substance later known as “styrene.”

The work of Neuman was confirmed and expanded upon

years later, first in 1839 by Edward Simon, who evaluated the temperature

dependence of styrene, and later by Charles Gerhardt,

who proposed its molecular formula. The work of these two men

sparked an interest in styrene and its derivatives.

Polystyrene belongs to a special class of molecules known as

polymers.Apolymer (the name means “many parts”) is a giant molecule

formed by combining small molecular units, called “monomers.”

This combination results in a macromolecule whose physical

properties—especially its strength and flexibility—are significantly

different fromthose of its monomer components. Such polymers are

often simply called “plastics.”

Polystyrene has become an important material in modern society

because it exhibits a variety of physical characteristics that can be

manipulated for the production of consumer products. Polystyrene

is a “thermoplastic,” which means that it can be softened by heat

and then reformed, after which it can be cooled to form a durable

and resilient product.

At 94 degrees Celsius, polystyrene softens; at room temperature,

however, it rings like a metal when struck. Because of the glasslike

nature and high refractive index of polystyrene, products made from it are known for their shine and attractive texture. In addition,

the material is characterized by a high level of water resistance and

by electrical insulating qualities. It is also flammable, can by dissolved

or softened by many solvents, and is sensitive to light. These

qualities make polystyrene a valuable material in the manufacture

of consumer products.

Plastics on the Market

In 1866, Marcellin Pierre Berthelot prepared styrene from ethylene

and benzene mixtures in a heated reaction flask. This was the

first synthetic preparation of polystyrene. In 1925, the Naugatuck

Chemical Company began to operate the first commercial styrene/

polystyrene manufacturing plant. In the 1930’s, the Dow Chemical

Company became involved in the manufacturing and marketing of

styrene/polystyrene products. Dow’s Styron 666 was first marketed

as a general-purpose polystyrene in 1938. This material was

the first plastic product to demonstrate polystyrene’s excellent mechanical

properties and ease of fabrication.

The advent ofWorldWar II increased the need for plastics. When

the Allies’ supply of natural rubber was interrupted, chemists sought

to develop synthetic substitutes. The use of additives with polymer

species was found to alter some of the physical properties of those

species. Adding substances called “elastomers” during the polymerization

process was shown to give a rubberlike quality to a normally

brittle species. An example of this is Dow’s Styron 475, which

was marketed in 1948 as the first “impact” polystyrene. It is called

an impact polystyrene because it also contains butadiene, which increases

the product’s resistance to breakage. The continued characterization

of polystyrene products has led to the development of a

worldwide industry that fills a wide range of consumer needs.

Following World War II, the plastics industry revolutionized

many aspects of modern society. Polystyrene is only one of the

many plastics involved in this process, but it has found its way into

a multitude of consumer products. Disposable kitchen utensils,

trays and packages, cups, videocassettes, insulating foams, egg cartons,

food wrappings, paints, and appliance parts are only a few of

the typical applications of polystyrenes. In fact, the production of polystyrene has grown to exceed 5 billion pounds per year.

The tremendous growth of this industry in the postwar era has

been fueled by a variety of factors. Having studied the physical

and chemical properties of polystyrene, chemists and engineers

were able to envision particular uses and to tailor the manufacture

of the product to fit those uses precisely. Because of its low cost of

production, superior performance, and light weight, polystyrene

has become the material of choice for the packaging industry. The

automobile industry also enjoys its benefits. Polystyrene’s lower

density compared to those of glass and steel makes it appropriate

for use in automobiles, since its light weight means that using

it can reduce the weight of automobiles, thereby increasing gas

efficiency.

Impact

There is no doubt that the marketing of polystyrene has greatly

affected almost every aspect of modern society. Fromcomputer keyboards

to food packaging, the use of polystyrene has had a powerful

impact on both the quality and the prices of products. Its use is not,

however, without drawbacks; it has also presented humankind

with a dilemma. The wholesale use of polystyrene has created an

environmental problem that represents a danger to wildlife, adds to

roadside pollution, and greatly contributes to the volume of solid

waste in landfills.

Polystyrene has become a household commodity because it lasts.

The reciprocal effect of this fact is that it may last forever. Unlike natural

products, which decompose upon burial, polystyrene is very

difficult to convert into degradable forms. The newest challenge facing

engineers and chemists is to provide for the safe and efficient

disposal of plastic products. Thermoplastics such as polystyrene

can be melted down and remolded into new products, which makes

recycling and reuse of polystyrene a viable option, but this option

requires the cooperation of the same consumers who have benefited

from the production of polystyrene products.

Polyethylene

The invention: An artificial polymer with strong insulating properties

and many other applications.

The people behind the invention:

Karl Ziegler (1898-1973), a German chemist

Giulio Natta (1903-1979), an Italian chemist

August Wilhelm von Hofmann (1818-1892), a German chemist

The Development of Synthetic Polymers

In 1841, August Hofmann completed his Ph.D. with Justus von

Liebig, a German chemist and founding father of organic chemistry.

One of Hofmann’s students,William Henry Perkin, discovered that

coal tars could be used to produce brilliant dyes. The German chemical

industry, under Hofmann’s leadership, soon took the lead in

this field, primarily because the discipline of organic chemistry was

much more developed in Germany than elsewhere.

The realities of the early twentieth century found the chemical

industry struggling to produce synthetic substitutes for natural

materials that were in short supply, particularly rubber. Rubber is

a natural polymer, a material composed of a long chain of small

molecules that are linked chemically. An early synthetic rubber,

neoprene, was one of many synthetic polymers (some others were

Bakelite, polyvinyl chloride, and polystyrene) developed in the

1920’s and 1930’s. Another polymer, polyethylene, was developed

in 1936 by Imperial Chemical Industries. Polyethylene was a

tough, waxy material that was produced at high temperature and

at pressures of about one thousand atmospheres. Its method of

production made the material expensive, but it was useful as an insulating

material.

WorldWar II and the material shortages associated with it brought

synthetic materials into the limelight. Many new uses for polymers

were discovered, and after the war they were in demand for the production

of a variety of consumer goods, although polyethylene was

still too expensive to be used widely.

Organometallics Provide the Key

Karl Ziegler, an organic chemist with an excellent international

reputation, spent most of his career in Germany. With his international

reputation and lack of political connections, he was a natural

candidate to take charge of the KaiserWilhelm Institute for Coal Research

(later renamed the Max Planck Institute) in 1943. Wise planners

saw him as a director who would be favored by the conquering

Allies. His appointment was a shrewd one, since he was allowed to

retain his position after World War II ended. Ziegler thus played a

key role in the resurgence of German chemical research after the war.

Before accepting the position at the Kaiser Wilhelm Institute,

Ziegler made it clear that he would take the job only if he could pursue

his own research interests in addition to conducting coal research.

The location of the institute in the Ruhr Valley meant that

abundant supplies of ethylene were available from the local coal industry,

so it is not surprising that Ziegler began experimenting with

that material.

Although Ziegler’s placement as head of the institute was an important

factor in his scientific breakthrough, his previous research

was no less significant. Ziegler devoted much time to the field of

organometallic compounds, which are compounds that contain a

metal atom that is bonded to one or more carbon atoms. Ziegler was

interested in organoaluminum compounds, which are compounds

that contain aluminum-carbon bonds.

Ziegler was also interested in polymerization reactions, which

involve the linking of thousands of smaller molecules into the single

long chain of a polymer. Several synthetic polymers were known,

but chemists could exert little control on the actual process. It was

impossible to regulate the length of the polymer chain, and the extent

of branching in the chain was unpredictable. It was as a result of

studying the effect of organoaluminum compounds on these chain

formation reactions that the key discovery was made.

Ziegler and his coworkers already knew that ethylene would react

with organoaluminum compounds to produce hydrocarbons,

which are compounds that contain only carbon and hydrogen and

that have varying chain lengths. Regulating the product chain length

continued to be a problem.

At this point, fate intervened in the form of a trace of nickel left in a

reactor from a previous experiment. The nickel caused the chain

lengthening to stop after two ethylene molecules had been linked.

Ziegler and his colleagues then tried to determine whether metals

other than nickel caused a similar effect with a longer polymeric

chain. Several metals were tested, and the most important finding

was that a trace of titanium chloride in the reactor caused the deposition

of large quantities of high-density polyethylene at low pressures.

Ziegler licensed the procedure, and within a year, Giulio Natta

had modified the catalysts to give high yields of polymers with

highly ordered side chains branching from the main chain. This

opened the door for the easy production of synthetic rubber. For

their discovery of Ziegler-Natta catalysts, Ziegler and Natta shared

the 1963 Nobel Prize in Chemistry.

Consequences

Ziegler’s process produced polyethylene that was much more

rigid than the material produced at high pressure. His product also

had a higher density and a higher softening temperature. Industrial

exploitation of the process was unusually rapid, and within ten years

more than twenty plants utilizing the process had been built throughout

Europe, producing more than 120,000 metric tons of polyethylene.

This rapid exploitation was one reason Ziegler and Natta were

awarded the Nobel Prize after such a relatively short time.

By the late 1980’s, total production stood at roughly 18 billion

pounds worldwide. Other polymeric materials, including polypropylene,

can be produced by similar means. The ready availability

and low cost of these versatile materials have radically transformed

the packaging industry. Polyethylene bottles are far lighter

than their glass counterparts; in addition, gases and liquids do not

diffuse into polyethylene very easily, and it does not break easily.

As a result, more and more products are bottled in containers

made of polyethylene or other polymers. Other novel materials

possessing properties unparalleled by any naturally occurring material

(Kevlar, for example, which is used to make bullet-resistant

vests) have also been an outgrowth of the availability of low-cost

polymeric materials.

Polyester

The invention: Asynthetic fibrous polymer used especially in fabrics.

The people behind the invention:

Wallace H. Carothers (1896-1937), an American polymer

chemist

Hilaire de Chardonnet (1839-1924), a French polymer chemist

John R. Whinfield (1901-1966), a British polymer chemist

A Story About Threads

Human beings have worn clothing since prehistoric times. At

first, clothing consisted of animal skins sewed together. Later, people

learned to spin threads from the fibers in plant or animal materials

and to weave fabrics from the threads (for example, wool, silk,

and cotton). By the end of the nineteenth century, efforts were begun

to produce synthetic fibers for use in fabrics. These efforts were

motivated by two concerns. First, it seemed likely that natural materials

would become too scarce to meet the needs of a rapidly increasing

world population. Second, a series of natural disasters—

affecting the silk industry in particular—had demonstrated the

problems of relying solely on natural fibers for fabrics.

The first efforts to develop synthetic fabric focused on artificial

silk, because of the high cost of silk, its beauty, and the fact that silk

production had been interrupted by natural disasters more often

than the production of any other material. The first synthetic silk

was rayon, which was originally patented by a French count,

Hilaire de Chardonnet, and was later much improved by other

polymer chemists. Rayon is a semisynthetic material that is made

from wood pulp or cotton.

Because there was a need for synthetic fabrics whose manufacture

did not require natural materials, other avenues were explored. One

of these avenues led to the development of totally synthetic polyester

fibers. In the United States, the best-known of these is Dacron, which

is manufactured by E. I. Du Pont de Nemours. Easily made intthreads, Dacron is widely used in clothing. It is also used to make audiotapes

and videotapes and in automobile and boat bodies.

From Polymers to Polyester

Dacron belongs to a group of chemicals known as “synthetic

polymers.” All polymers are made of giant molecules, each of

which is composed of a large number of simpler molecules (“monomers”)

that have been linked, chemically, to form long strings. Efforts

by industrial chemists to prepare synthetic polymers developed

in the twentieth century after it was discovered that many

natural building materials and fabrics (such as rubber, wood, wool,

silk, and cotton) were polymers, and as the ways in which monomers

could be joined to make polymers became better understood.

One group of chemists who studied polymers sought to make inexpensive

synthetic fibers to replace expensive silk and wool. Their efforts

led to the development of well-known synthetic fibers such as

nylon and Dacron.

Wallace H. Carothers of Du Pont pioneered the development of

polyamide polymers, collectively called “nylon,” and was the first

researcher to attempt to make polyester. It was British polymer

chemists John R. Whinfield and J. T. Dickson of Calico Printers Association

(CPA) Limited, however, who in 1941 perfected and patented

polyester that could be used to manufacture clothing. The

first polyester fiber products were produced in 1950 in Great Britain

by London’s British Imperial Chemical Industries, which had secured

the British patent rights from CPA. This polyester, which was

made of two monomers, terphthalic acid and ethylene glycol, was

called Terylene. In 1951, Du Pont, which had acquired Terylene patent

rights for theWestern Hemisphere, began to market its own version

of this polyester, which was called Dacron. Soon, other companies

around the world were selling polyester materials of similar

composition.

Dacron and other polyesters are used in many items in the

United States. Made into fibers and woven, Dacron becomes cloth.

When pressed into thin sheets, it becomes Mylar, which is used in

videotapes and audiotapes. Dacron polyester, mixed with other materials,

is also used in many industrial items, including motor vehicle and boat bodies. Terylene and similar polyester preparations

serve the same purposes in other countries.

The production of polyester begins when monomers are mixed

in huge reactor tanks and heated, which causes them to form giant

polymer chains composed of thousands of alternating monomer

units. If T represents terphthalic acid and E represents ethylene glycol,

a small part of a necklace-like polymer can be shown in the following

way: (TETETETETE). Once each batch of polyester polymer

has the desired composition, it is processed for storage until it is

needed. In this procedure, the material, in liquid form in the hightemperature

reactor, is passed through a device that cools it and

forms solid strips. These strips are then diced, dried, and stored.

When polyester fiber is desired, the diced polyester is melted and

then forced through tiny holes in a “spinneret” device; this process

is called “extruding.” The extruded polyester cools again, while

passing through the spinneret holes, and becomes fine fibers called

“filaments.” The filaments are immediately wound into threads that

are collected in rolls. These rolls of thread are then dyed and used to

weave various fabrics. If polyester sheets or other forms of polyester

are desired, the melted, diced polyester is processed in other ways.

Polyester preparations are often mixed with cotton, glass fibers, or

other synthetic polymers to produce various products.

Impact

The development of polyester was a natural consequence of the

search for synthetic fibers that developed fromwork on rayon. Once

polyester had been developed, its great utility led to its widespread

use in industry. In addition, the profitability of the material spurred

efforts to produce better synthetic fibers for specific uses. One example

is that of stretchy polymers such as Helance, which is a form

of nylon. In addition, new chemical types of polymer fibers were developed,

including the polyurethane materials known collectively

as “spandex” (for example, Lycra and Vyrenet).

The wide variety of uses for polyester is amazing. Mixed with

cotton, it becomes wash-and-wear clothing; mixed with glass, it is

used to make boat and motor vehicle bodies; combined with other

materials, it is used to make roofing materials, conveyor belts,hoses, and tire cords. In Europe, polyester has become the main

packaging material for consumer goods, and the United States does

not lag far behind in this area.

The future is sure to hold more uses for polyester and the invention

of new polymers. These spinoffs of polyester will be essential in

the development of high technology.

Polio vaccine (Salk)

The invention: Jonas Salk’s vaccine was the first that prevented polio,resulting in the virtual eradication of crippling polio epidemics.The people behind the invention:

Jonas Edward Salk (1914-1995), an American physician,

immunologist, and virologist

Thomas Francis, Jr. (1900-1969), an

American microbiologist

Cause for Celebration

Poliomyelitis (polio) is an infectious disease that can adversely

affect the central nervous system, causing paralysis and great muscle

wasting due to the destruction of motor neurons (nerve cells) in

the spinal cord. Epidemiologists believe that polio has existed since

ancient times, and evidence of its presence in Egypt, circa 1400 b.c.e.,

has been presented. Fortunately, the Salk vaccine and the later vaccine

developed by the American virologist Albert Bruce Sabin can

prevent the disease. Consequently, except in underdeveloped nations,

polio is rare. Moreover, although once a person develops polio,

there is still no cure for it, a large number of polio cases end without

paralysis or any observable effect.

Polio is often called “infantile paralysis.” This results from the

fact that it is seen most often in children. It is caused by a virus and

begins with body aches, a stiff neck, and other symptoms that are

very similar to those of a severe case of influenza. In some cases,

within two weeks after its onset, the course of polio begins to lead to

muscle wasting and paralysis.

On April 12, 1955, the world was thrilled with the announcement

that Jonas Edward Salk’s poliomyelitis vaccine could prevent the

disease. It was reported that schools were closed in celebration of

this event. Salk, the son of a New York City garment worker, has

since become one of the most well-known and publicly venerated

medical scientists in the world.

Vaccination is a method of disease prevention by immunization,

whereby a small amount of virus is injected into the body to prevent

a viral disease. The process depends on the production of antibodies

(body proteins that are specifically coded to prevent the disease

spread by the virus) in response to the vaccination. Vaccines are

made of weakened or killed virus preparations.

Electrifying Results

The Salk vaccine was produced in two steps. First, polio viruses

were grown in monkey kidney tissue cultures. These polio viruses

were then killed by treatment with the right amount of formaldehyde

to produce an effective vaccine. The killed-virus polio vaccine

was found to be safe and to cause the production of antibodies

against the disease, a sign that it should prevent polio.

In early 1952, Salk tested a prototype vaccine against Type I polio virus

on children who were afflicted with the disease and were thus

deemed safe from reinfection. This test showed that the vaccination greatly elevated the concentration of polio antibodies in these children.

On July 2, 1952, encouraged by these results, Salk vaccinated fortythree

children who had never had polio with vaccines against each of

the three virus types (Type I, Type II, and Type III). All inoculated children

produced high levels of polio antibodies, and none of them developed

the disease. Consequently, the vaccine appeared to be both safe in

humans and likely to become an effective public health tool.

In 1953, Salk reported these findings in the Journal of the American

Medical Association. In April, 1954, nationwide testing of the Salk

vaccine began, via the mass vaccination of American schoolchildren.

The results of the trial were electrifying. The vaccine was safe,

and it greatly reduced the incidence of the disease. In fact, it was estimated

that Salk’s vaccine gave schoolchildren 60 to 90 percent protection

against polio.

Salk was instantly praised. Then, however, several cases of polio

occurred as a consequence of the vaccine. Its use was immediately

suspended by the U.S. surgeon general, pending a complete examination.

Soon, it was evident that all the cases of vaccine-derived polio

were attributable to faulty batches of vaccine made by one

pharmaceutical company. Salk and his associates were in no way responsible

for the problem. Appropriate steps were taken to ensure

that such an error would not be repeated, and the Salk vaccine was

again released for use by the public.

Consequences

The first reports on the polio epidemic in the United States had

occurred on June 27, 1916, when one hundred residents of Brooklyn,

New York, were afflicted. Soon, the disease had spread. By August,

twenty-seven thousand people had developed polio. Nearly seven

thousand afflicted people died, and many survivors of the epidemic

were permanently paralyzed to varying extents. In New York City

alone, nine thousand people developed polio and two thousand

died. Chaos reigned as large numbers of terrified people attempted

to leave and were turned back by police. Smaller polio epidemics

occurred throughout the nation in the years that followed (for example,

the Catawba County, North Carolina, epidemic of 1944). A

particularly horrible aspect of polio was the fact that more than 70 percent of polio victims were small children. Adults caught it too;

the most famous of these adult polio victims was U.S. President

Franklin D. Roosevelt. There was no cure for the disease. The best

available treatment was physical therapy.

As of August, 1955, more than four million polio vaccines had

been given. The Salk vaccine appeared to work very well. There were

only half as many reported cases of polio in 1956 as there had been in

1955. It appeared that polio was being conquered. By 1957, the number

of cases reported nationwide had fallen below six thousand.

Thus, in two years, its incidence had dropped by about 80 percent.

This was very exciting, and soon other countries clamored for the

vaccine. By 1959, ninety other countries had been supplied with the

Salk vaccine.Worldwide, the disease was being eradicated. The introduction

of an oral polio vaccine by Albert Bruce Sabin supported

this progress.

Salk received many honors, including honorary degrees from

American and foreign universities, the LaskerAward, a Congressional

Medal for Distinguished Civilian Service, and membership in

the French Legion of Honor, yet he received neither the Nobel Prize

nor membership in the American National Academy of Sciences. It

is believed by many that this neglect was a result of the personal antagonism

of some of the members of the scientific community who

strongly disagreed with his theories of viral inactivation.

Polio vaccine (Sabin)

The invention: Albert Bruce Sabin’s vaccine was the first to stimulate

long-lasting immunity against polio without the risk of causing

paralytic disease.

The people behind the invention:

Albert Bruce Sabin (1906-1993), a Russian-born American

virologist

Jonas Edward Salk (1914-1995), an American physician,

immunologist, and virologist

Renato Dulbecco (1914- ), an Italian-born American

virologist who shared the 1975 Nobel Prize in Physiology or

Medicine

The Search for a Living Vaccine

Almost a century ago, the first major poliomyelitis (polio) epidemic

was recorded. Thereafter, epidemics of increasing

frequency

and severity struck the industrialized world. By the 1950’s, as many

as sixteen thousand individuals, most of them children, were being

paralyzed by the disease each year.

Poliovirus enters the body through ingestion by the mouth. It

replicates in the throat and the intestines and establishes an infection

that normally is harmless. From there, the virus can enter the

bloodstream. In some individuals it makes its way to the nervous

system, where it attacks and destroys nerve cells crucial for muscle

movement. The presence of antibodies in the bloodstream will prevent

the virus from reaching the nervous system and causing paralysis.

Thus, the goal of vaccination is to administer poliovirus that

has been altered so that it cannot cause disease but nevertheless will

stimulate the production of antibodies to fight the disease.

Albert Bruce Sabin received his medical degree from New York

University College of Medicine in 1931. Polio was epidemic in 1931,

and for Sabin polio research became a lifelong interest. In 1936,

while working at the Rockefeller Institute, Sabin and Peter Olinsky

successfully grew poliovirus using tissues cultured in vitro. Tissue

culture proved to be an excellent source of virus. Jonas Edward Salk

soon developed an inactive polio vaccine consisting of virus grown

from tissue culture that had been inactivated (killed) by chemical

treatment. This vaccine became available for general use in 1955, almost

fifty years after poliovirus had first been identified.

Sabin, however, was not convinced that an inactivated virus vaccine

was adequate. He believed that it would provide only temporary

protection and that individuals would have to be vaccinated

repeatedly in order to maintain protective levels of antibodies.

Knowing that natural infection with poliovirus induced lifelong immunity,

Sabin believed that a vaccine consisting of a living virus

was necessary to produce long-lasting immunity. Also, unlike the

inactive vaccine, which is injected, a living virus (weakened so that

it would not cause disease) could be taken orally and would invade

the body and replicate of its own accord.

Sabin was not alone in his beliefs. Hilary Koprowski and Harold

Cox also favored a living virus vaccine and had, in fact, begun

searching for weakened strains of poliovirus as early as 1946 by repeatedly

growing the virus in rodents. When Sabin began his search

for weakened virus strains in 1953, a fiercely competitive contest ensued

to achieve an acceptable live virus vaccine.

Rare, Mutant Polioviruses

Sabin’s approach was based on the principle that, as viruses acquire

the ability to replicate in a foreign species or tissue (for example,

in mice), they become less able to replicate in humans and thus

less able to cause disease. Sabin used tissue culture techniques to

isolate those polioviruses that grew most rapidly in monkey kidney

cells. He then employed a technique developed by Renato Dulbecco

that allowed him to recover individual virus particles. The recovered

viruses were injected directly into the brains or spinal cords of

monkeys in order to identify those viruses that did not damage the

nervous system. These meticulously performed experiments, which

involved approximately nine thousand monkeys and more than

one hundred chimpanzees, finally enabled Sabin to isolate rare mutant

polioviruses that would replicate in the intestinal tract but not

in the nervous systems of chimpanzees or, it was hoped, of humans.

In addition, the weakened virus strains were shown to stimulate antibodies when they were fed to chimpanzees; this was a critical attribute

for a vaccine strain.

By 1957, Sabin had identified three strains of attenuated viruses that

were ready for small experimental trials in humans. Asmall group of

volunteers, including Sabin’s own wife and children, were fed the vaccine

with promising results. Sabin then gave his vaccine to virologists

in the Soviet Union, Eastern Europe, Mexico, and Holland for further

testing. Combined with smaller studies in the United States, these trials

established the effectiveness and safety of his oral vaccine.

During this period, the strains developed by Cox and by Koprowski

were being tested also in millions of persons in field trials

around the world. In 1958, two laboratories independently compared

the vaccine strains and concluded that the Sabin strains were

superior. In 1962, after four years of deliberation by the U.S. Public

Health Service, all three of Sabin’s vaccine strains were licensed for

general use.Consequences

The development of polio vaccines ranks as one of the triumphs of

modern medicine. In the early 1950’s, paralytic polio struck 13,500

out of every 100 million Americans. The use of the Salk vaccine

greatly reduced the incidence of polio, but outbreaks of paralytic disease

continued to occur: Fifty-seven hundred cases were reported in

1959 and twenty-five hundred cases in 1960. In 1962, the oral Sabin

vaccine became the vaccine of choice in the United States. Since its

widespread use, the number of paralytic cases in the United States

has dropped precipitously, eventually averaging fewer than ten per

year. Worldwide, the oral vaccine prevented an estimated 5 million

cases of paralytic poliomyelitis between 1970 and 1990.

The oral vaccine is not without problems. Occasionally, the living

virus mutates to a disease-causing (virulent) form as it multiplies in

the vaccinated person. When this occurs, the person may develop

paralytic poliomyelitis. The inactive vaccine, in contrast, cannot

mutate to a virulent form. Ironically, nearly every incidence of polio

in the United States is caused by the vaccine itself.

In the developing countries of the world, the issue of vaccination is

more pressing. Millions receive neither form of polio vaccine; as a result,

at least 250,000 individuals are paralyzed or die each year. The World

Health Organization and other health providers continue to work toward

the very practical goal of completely eradicating this disease.

Pocket calculator

The invention: The first portable and reliable hand-held calculator

capable of performing a wide range of mathematical computations.

The people behind the invention:

Jack St. Clair Kilby (1923- ), the inventor of the

semiconductor microchip

Jerry D. Merryman (1932- ), the first project manager of the

team that invented the first portable calculator

James Van Tassel (1929- ), an inventor and expert on

semiconductor components

An Ancient Dream

In the earliest accounts of civilizations that developed number

systems to perform mathematical calculations, evidence has been

found of efforts to fashion a device that would permit people to perform

these calculations with reduced effort and increased accuracy.

The ancient Babylonians are regarded as the inventors of the first

abacus (or counting board, from the Greek abakos, meaning “board”

or “tablet”). It was originally little more than a row of shallow

grooves with pebbles or bone fragments as counters.

The next step in mechanical calculation did not occur until the

early seventeenth century. John Napier, a Scottish baron and mathematician,

originated the concept of “logarithms” as a mathematical

device to make calculating easier. This concept led to the first slide

rule, created by the English mathematician William Oughtred of

Cambridge. Oughtred’s invention consisted of two identical, circular

logarithmic scales held together and adjusted by hand. The slide

rule made it possible to perform rough but rapid multiplication and

division. Oughtred’s invention in 1623 was paralleled by the work

of a German professor,Wilhelm Schickard, who built a “calculating

clock” the same year. Because the record of Schickard’s work was

lost until 1935, however, the French mathematician Blaise Pascal

was generally thought to have built the first mechanical calculator,

the “Pascaline,” in 1645.Other versions of mechanical calculators were built in later centuries,

but none was rapid or compact enough to be useful beyond specific

laboratory or mercantile situations. Meanwhile, the dream of

such a machine continued to fascinate scientists and mathematicians.

The development that made a fast, small calculator possible did

not occur until the middle of the twentieth century, when Jack St.

Clair Kilby of Texas Instruments invented the silicon microchip (or

integrated circuit) in 1958. An integrated circuit is a tiny complex of

electronic components and their connections that is produced in or

on a small slice of semiconductor material such as silicon. Patrick

Haggerty, then president of Texas Instruments, wrote in 1964 that

“integrated electronics” would “remove limitations” that determined

the size of instruments, and he recognized that Kilby’s invention

of the microchip made possible the creation of a portable,

hand-held calculator. He challenged Kilby to put together a team to

design a calculator that would be as powerful as the large, electromechanical

models in use at the time but small enough to fit into a

coat pocket. Working with Jerry D. Merryman and James Van Tassel,

Kilby began to work on the project in October, 1965.

An Amazing Reality

At the outset, there were basically five elements that had to be designed.

These were the logic designs that enabled the machine to

perform the actual calculations, the keyboard or keypad, the power

supply, the readout display, and the outer case. Kilby recalls that

once a particular size for the unit had been determined (something

that could be easily held in the hand), project manager Merryman

was able to develop the initial logic designs in three days.Van Tassel

contributed his experience with semiconductor components to solve

the problems of packaging the integrated circuit. The display required

a thermal printer that would work on a low power source.

The machine also had to include a microencapsulated ink source so

that the paper readouts could be imprinted clearly. Then the paper

had to be advanced for the next calculation. Kilby, Merryman, and

Van Tassel filed for a patent on their work in 1967.

Although this relatively small, working prototype of the minicalculator

made obsolete the transistor-operated design of the much larger desk calculators, the cost of setting up new production lines

and the need to develop a market made it impractical to begin production

immediately. Instead, Texas Instruments and Canon of Tokyo

formed a joint venture, which led to the introduction of the

Canon Pocketronic Printing Calculator in Japan in April, 1970, and

in the United States that fall. Built entirely of Texas Instruments

parts, this four-function machine with three metal oxide semiconductor (MOS) circuits was similar to the prototype designed in 1967.

The calculator was priced at $400, weighed 740 grams, and measured

101 millimeters wide by 208 millimeters long by 49 millimeters

high. It could perform twelve-digit calculations and worked up

to four decimal places.

In September, 1972, Texas Instruments put the Datamath, its first

commercial hand-held calculator using a single MOS chip, on the

retail market. It weighed 340 grams and measured 75 millimeters

wide by 137 millimeters long by 42 millimeters high. The Datamath

was priced at $120 and included a full-floating decimal point that

could appear anywhere among the numbers on its eight-digit, lightemitting

diode (LED) display. It came with a rechargeable battery

that could also be connected to a standard alternating current (AC)

outlet. The Datamath also had the ability to conserve power while

awaiting the next keyboard entry. Finally, the machine had a built-in

limited amount of memory storage.Consequences

Prior to 1970, most calculating machines were of such dimensions

that professional mathematicians and engineers were either tied to

their desks or else carried slide rules whenever they had to be away

from their offices. By 1975, Keuffel&Esser, the largest slide rule manufacturer

in the world, was producing its last model, and mechanical

engineers found that problems that had previously taken a week

could now be solved in an hour using the new machines.

That year, the Smithsonian Institution accepted the world’s first

miniature electronic calculator for its permanent collection, noting

that it was the forerunner of more than one hundred million pocket

calculators then in use. By the 1990’s, more than fifty million portable

units were being sold each year in the United States. In general,

the electronic pocket calculator revolutionized the way in which

people related to the world of numbers.

Moreover, the portability of the hand-held calculator made it

ideal for use in remote locations, such as those a petroleum engineer

might have to explore. Its rapidity and reliability made it an indispensable

instrument for construction engineers, architects, and real

estate agents, who could figure the volume of a room and other

building dimensions almost instantly and then produce cost estimates

almost on the spot.

Plastic

The invention: The first totally synthetic thermosetting plastic,

which paved the way for modern materials science.

The people behind the invention:

John Wesley Hyatt (1837-1920), an American inventor

Leo Hendrik Baekeland (1863-1944), a Belgian-born chemist,

consultant, and inventor

Christian Friedrich Schönbein (1799-1868), a German chemist

who produced guncotton, the first artificial polymer

Adolf von Baeyer (1835-1917), a German chemist

Exploding Billiard Balls

In the 1860’s, the firm of Phelan and Collender offered a prize of

ten thousand dollars to anyone producing a substance that could

serve as an inexpensive substitute for ivory, which was somewhat

difficult to obtain in large quantities at reasonable prices. Earlier,

Christian Friedrich Schönbein had laid the groundwork for a breakthrough

in the quest for a new material in 1846 by the serendipitous

discovery of nitrocellulose, more commonly known as “guncotton,”

which was produced by the reaction of nitric acid with cotton.

An American inventor, John Wesley Hyatt, while looking for a

substitute for ivory as a material for making billiard balls, discovered

that the addition of camphor to nitrocellulose under certain

conditions led to the formation of a white material that could be

molded and machined. He dubbed this substance “celluloid,” and

this product is now acknowledged as the first synthetic plastic. Celluloid

won the prize for Hyatt, and he promptly set out to exploit his

product. Celluloid was used to make baby rattles, collars, dentures,

and other manufactured goods.

As a billiard ball substitute, however, it was not really adequate,

for various reasons. First, it is thermoplastic—in other words, a material

that softens when heated and can then be easily deformed or

molded. It was thus too soft for billiard ball use. Second, it was

highly flammable, hardly a desirable characteristic. Awidely circulated, perhaps apocryphal, story claimed that celluloid billiard balls

detonated when they collided.

Truly Artificial

Since celluloid can be viewed as a derivative of a natural product,

it is not a completely synthetic substance. Leo Hendrik Baekeland

has the distinction of being the first to produce a completely artificial

plastic. Born in Ghent, Belgium, Baekeland emigrated to the

United States in 1889 to pursue applied research, a pursuit not encouraged

in Europe at the time. One area in which Baekeland hoped

to make an inroad was in the development of an artificial shellac.

Shellac at the time was a natural and therefore expensive product,

and there would be a wide market for any reasonably priced substitute.

Baekeland’s research scheme, begun in 1905, focused on finding

a solvent that could dissolve the resinous products from a certain

class of organic chemical reaction.

The particular resins he used had been reported in the mid-

1800’s by the German chemist Adolf von Baeyer. These resins were

produced by the condensation reaction of formaldehyde with a

class of chemicals called “phenols.” Baeyer found that frequently

the major product of such a reaction was a gummy residue that was

virtually impossible to remove from glassware. Baekeland focused

on finding a material that could dissolve these resinous products.

Such a substance would prove to be the shellac substitute he sought.

These efforts proved frustrating, as an adequate solvent for these

resins could not be found. After repeated attempts to dissolve these

residues, Baekeland shifted the orientation of his work. Abandoning

the quest to dissolve the resin, he set about trying to develop a resin

that would be impervious to any solvent, reasoning that such a material

would have useful applications.

Baekeland’s experiments involved the manipulation of phenolformaldehyde

reactions through precise control of the temperature

and pressure at which the reactions were performed. Many of these

experiments were performed in a 1.5-meter-tall reactor vessel, which

he called a “Bakelizer.” In 1907, these meticulous experiments paid

off when Baekeland opened the reactor to reveal a clear solid that

was heat resistant, nonconducting, and machinable. Experimentation proved that the material could be dyed practically any color in

the manufacturing process, with no effect on the physical properties

of the solid.

Baekeland filed a patent for this new material in 1907. (This patent

was filed one day before that filed by James Swinburne, a British electrical engineer who had developed a similar material in his

quest to produce an insulating material.) Baekeland dubbed his new

creation “Bakelite” and announced its existence to the scientific

community on February 15, 1909, at the annual meeting of the American

Chemical Society. Among its first uses was in the manufacture

of ignition parts for the rapidly growing automobile industry.

Impact

Bakelite proved to be the first of a class of compounds called

“synthetic polymers.” Polymers are long chains of molecules chemically

linked together. There are many natural polymers, such as cotton.

The discovery of synthetic polymers led to vigorous research

into the field and attempts to produce other useful artificial materials.

These efforts met with a fair amount of success; by 1940, a multitude

of new products unlike anything found in nature had been discovered.

These included such items as polystyrene and low-density

polyethylene. In addition, artificial substitutes for natural polymers,

such as rubber, were a goal of polymer chemists. One of the results

of this research was the development of neoprene.

Industries also were interested in developing synthetic polymers

to produce materials that could be used in place of natural fibers

such as cotton. The most dramatic success in this area was achieved

by Du Pont chemist Wallace Carothers, who had also developed

neoprene. Carothers focused his energies on forming a synthetic fiber

similar to silk, resulting in the synthesis of nylon.

Synthetic polymers constitute one branch of a broad area known

as “materials science.” Novel, useful materials produced synthetically

from a variety of natural materials have allowed for tremendous

progress in many areas. Examples of these new materials include

high-temperature superconductors, composites, ceramics, and

plastics. These materials are used to make the structural components

of aircraft, artificial limbs and implants, tennis rackets, garbage

bags, and many other common objects.

Photovoltaic cell

Photovoltaic cell

The invention: Drawing their energy directly from the Sun, the

first photovoltaic cells powered instruments on early space vehicles

and held out hope for future uses of solar energy.

The people behind the invention:

Daryl M. Chapin (1906-1995), an American physicist

Calvin S. Fuller (1902-1994), an American chemist

Gerald L. Pearson (1905- ), an American physicist

Unlimited Energy Source

All the energy that the world has at its disposal ultimately comes

from the Sun. Some of this solar energy was trapped millions of years

ago in the form of vegetable and animal matter that became the coal,

oil, and natural gas that the world relies upon for energy. Some of this

fuel is used directly to heat homes and to power factories and gasoline

vehicles. Much of this fossil fuel, however, is burned to produce

the electricity on which modern society depends.

The amount of energy available from the Sun is difficult to imagine,

but some comparisons may be helpful. During each forty-hour

period, the Sun provides the earth with as much energy as the

earth’s total reserves of coal, oil, and natural gas. It has been estimated

that the amount of energy provided by the sun’s radiation

matches the earth’s reserves of nuclear fuel every forty days. The

annual solar radiation that falls on about twelve hundred square

miles of land in Arizona matched the world’s estimated total annual

energy requirement for 1960. Scientists have been searching for

many decades for inexpensive, efficient means of converting this

vast supply of solar radiation directly into electricity.

The Bell Solar Cell

Throughout its history, Bell Systems has needed to be able to

transmit, modulate, and amplify electrical signals. Until the 1930’s,

these tasks were accomplished by using insulators and metallic conductors. At that time, semiconductors, which have electrical properties

that are between those of insulators and those of conductors,

were developed. One of the most important semiconductor materials

is silicon, which is one of the most common elements on the

earth. Unfortunately, silicon is usually found in the form of compounds

such as sand or quartz, and it must be refined and purified

before it can be used in electrical circuits. This process required

much initial research, and very pure silicon was not available until

the early 1950’s.

Electric conduction in silicon is the result of the movement of

negative charges (electrons) or positive charges (holes). One way of

accomplishing this is by deliberately adding to the silicon phosphorus

or arsenic atoms, which have five outer electrons. This addition

creates a type of semiconductor that has excess negative charges (an

n-type semiconductor). Adding boron atoms, which have three

outer electrons, creates a semiconductor that has excess positive

charges (a p-type semiconductor). Calvin Fuller made an important

study of the formation of p-n junctions, which are the points at

which p-type and n-type semiconductors meet, by using the process

of diffusing impurity atoms—that is, adding atoms of materials that

would increase the level of positive or negative charges, as described

above. Fuller’s work stimulated interested in using the process

of impurity diffusion to create cells that would turn solar energy

into electricity. Fuller and Gerald Pearson made the first largearea

p-n junction by using the diffusion process. Daryl Chapin,

Fuller, and Pearson made a similar p-n junction very close to the

surface of a silicon crystal, which was then exposed to sunlight.

The cell was constructed by first making an ingot of arsenicdoped

silicon that was then cut into very thin slices. Then a very

thin layer of p-type silicon was formed over the surface of the n-type

wafer, providing a p-n junction close to the surface of the cell. Once

the cell cooled, the p-type layer was removed from the back of the

cell and lead wires were attached to the two surfaces. When light

was absorbed at the p-n junction, electron-hole pairs were produced,

and the electric field that was present at the junction forced

the electrons to the n side and the holes to the p side.

The recombination of the electrons and holes takes place after the

electrons have traveled through the external wires, where they do useful work. Chapin, Fuller, and Pearson announced in 1954 that

the resulting photovoltaic cell was the most efficient (6 percent)

means then available for converting sunlight into electricity.

The first experimental use of the silicon solar battery was in amplifiers

for electrical telephone signals in rural areas. An array of 432

silicon cells, capable of supplying 9 watts of power in bright sunlight,

was used to charge a nickel-cadmium storage battery. This, in

turn, powered the amplifier for the telephone signal. The electrical

energy derived from sunlight during the day was sufficient to keep

the storage battery charged for continuous operation. The system

was successfully tested for six months of continuous use in Americus,

Georgia, in 1956. Although it was a technical success, the silicon solar

cell was not ready to compete economically with conventional

means of producing electrical power.

Consequences

One of the immediate applications of the solar cell was to supply

electrical energy for Telstar satellites. These cells are used extensively

on all satellites to generate power. The success of the U.S. satellite program prompted serious suggestions in 1965 for the use of

an orbiting power satellite. A large satellite could be placed into a

synchronous orbit of the earth. It would collect sunlight, convert it

to microwave radiation, and beam the energy to an Earth-based receiving

station. Many technical problems must be solved, however,

before this dream can become a reality.

Solar cells are used in small-scale applications such as power

sources for calculators. Large-scale applications are still not economically

competitive with more traditional means of generating

electric power. The development of the ThirdWorld countries, however,

may provide the incentive to search for less-expensive solar

cells that can be used, for example, to provide energy in remote villages.

As the standards of living in such areas improve, the need for

electric power will grow. Solar cells may be able to provide the necessary

energy while safeguarding the environment for future generations.

Photoelectric cell

The invention: The first devices to make practical use of the photoelectric

effect, photoelectric cells were of decisive importance in

the electron theory of metals.

The people behind the invention:

Julius Elster (1854-1920), a German experimental physicist

Hans Friedrich Geitel (1855-1923), a German physicist

Wilhelm Hallwachs (1859-1922), a German physicist

Early Photoelectric Cells

The photoelectric effect was known to science in the early

nineteenth century when the French physicist Alexandre-Edmond

Becquerel wrote of it in connection with his work on glass-enclosed

primary batteries. He discovered that the voltage of his batteries increased

with intensified illumination and that green light produced

the highest voltage. Since Becquerel researched batteries exclusively,

however, the liquid-type photocell was not discovered until

1929, when the Wein and Arcturus cells were introduced commercially.

These cells were miniature voltaic cells arranged so that light

falling on one side of the front plate generated a considerable

amount of electrical energy. The cells had short lives, unfortunately;

when subjected to cold, the electrolyte froze, and when subjected to

heat, the gas generated would expand and explode the cells.

What came to be known as the photoelectric cell, a device connecting

light and electricity, had its beginnings in the 1880’s. At

that time, scientists noticed that a negatively charged metal plate

lost its charge much more quickly in the light (especially ultraviolet

light) than in the dark. Several years later, researchers demonstrated

that this phenomenon was not an “ionization” effect because

of the air’s increased conductivity, since the phenomenon

took place in a vacuum but did not take place if the plate were positively

charged. Instead, the phenomenon had to be attributed to

the light that excited the electrons of the metal and caused them to

fly off: Aneutral plate even acquired a slight positive charge under the influence of strong light. Study of this effect not only contributed

evidence to an electronic theory of matter—and, as a result of

some brilliant mathematical work by the physicist Albert Einstein,

later increased knowledge of the nature of radiant energy—but

also further linked the studies of light and electricity. It even explained

certain chemical phenomena, such as the process of photography.

It is important to note that all the experimental work on

photoelectricity accomplished prior to the work of Julius Elster

and Hans Friedrich Geitel was carried out before the existence of

the electron was known.

Explaining Photoelectric Emission

After the English physicist Sir Joseph John Thomson’s discovery

of the electron in 1897, investigators soon realized that the photoelectric

effect was caused by the emission of electrons under the influence

of radiation. The fundamental theory of photoelectric emission

was put forward by Einstein in 1905 on the basis of the German

physicist Max Planck’s quantum theory (1900). Thus, it was not surprising

that light was found to have an electronic effect. Since it was

known that the longer radio waves could shake electrons into resonant

oscillations and the shorter X rays could detach electrons from

the atoms of gases, the intermediate waves of visual light would

have been expected to have some effect upon electrons—such as detaching

them from metal plates and therefore setting up a difference

of potential. The photoelectric cell, developed by Elster and Geitel

in 1904, was a practical device that made use of this effect.

In 1888,Wilhelm Hallwachs observed that an electrically charged

zinc electrode loses its charge when exposed to ultraviolet radiation

if the charge is negative, but is able to retain a positive charge under

the same conditions. The following year, Elster and Geitel discovered

a photoelectric effect caused by visible light; however, they

used the alkali metals potassium and sodium for their experiments

instead of zinc.

The Elster-Geitel photocell (a vacuum emission cell, as opposed to

a gas-filled cell) consisted of an evacuated glass bulb containing two

electrodes. The cathode consisted of a thin film of a rare, chemically

active metal (such as potassium) that lost its electrons fairly readily; the anode was simply a wire sealed in to complete the circuit. This anode

was maintained at a positive potential in order to collect the negative

charges released by light from the cathode. The Elster-Geitel

photocell resembled two other types of vacuum tubes in existence at

the time: the cathode-ray tube, in which the cathode emitted electrons

under the influence of a high potential, and the thermionic

valve (a valve that permits the passage of current in one direction only), in which it emitted electrons under the influence of heat. Like

both of these vacuum tubes, the photoelectric cell could be classified

as an “electronic” device.

The new cell, then, emitted electrons when stimulated by light, and

at a rate proportional to the intensity of the light. Hence, a current

could be obtained from the cell. Yet Elster and Geitel found that their

photoelectric currents fell off gradually; they therefore spoke of “fatigue”

(instability). It was discovered later that most of this change was

not a direct effect of a photoelectric current’s passage; it was not even

an indirect effect but was caused by oxidation of the cathode by the air.

Since all modern cathodes are enclosed in sealed vessels, that source of

change has been completely abolished. Nevertheless, the changes that

persist in modern cathodes often are indirect effects of light that can be

produced independently of any photoelectric current.

Impact

The Elster-Geitel photocell was, for some twenty years, used in

all emission cells adapted for the visible spectrum, and throughout

the twentieth century, the photoelectric cell has had a wide variety

of applications in numerous fields. For example, if products leaving

a factory on a conveyor belt were passed between a light and a cell,

they could be counted as they interrupted the beam. Persons entering

a building could be counted also, and if invisible ultraviolet rays

were used, those persons could be detected without their knowledge.

Simple relay circuits could be arranged that would automatically

switch on street lamps when it grew dark. The sensitivity of

the cell with an amplifying circuit enabled it to “see” objects too

faint for the human eye, such as minor stars or certain lines in the

spectra of elements excited by a flame or discharge. The fact that the

current depended on the intensity of the light made it possible to

construct photoelectric meters that could judge the strength of illumination

without risking human error—for example, to determine

the right exposure for a photograph.

A further use for the cell was to make talking films possible. The

early “talkies” had depended on gramophone records, but it was very

difficult to keep the records in time with the film. Now, the waves of

speech and music could be recorded in a “sound track” by turning the sound first into current through a microphone and then into light with

a neon tube or magnetic shutter; next, the variations in the intensity of

this light on the side of the film were photographed. By reversing the

process and running the film between a light and a photoelectric cell,

the visual signals could be converted back to sound.