Science_ The Definitive Visual Guide ( PDFDrive )

MICHAEL FARADAY

was to continue in electromagnetism TIMELINE
what Faraday left unfinished.
O 1791 Michael Faraday is born on September 22
In 1820 the Danish scientist Hans in Newington Butts, south London, England, the
Christian Ørsted showed that around a son of a poor Yorkshire blacksmith.
wire carrying a current there is a
magnetic field, almost like a sleeve O 1805 He is apprenticed to a bookbinder, George
around an arm. Faraday talked about Riebau, in Bloomsbury, London.
this with Davy and William Hyde
Wollaston, and they speculated about O 1812 Goes to a series of lectures given by
whether this sort of magnetism could Humphry Davy (see opposite) at the Royal
be used to generate motion. Institution (RI). He sits in the seat above
the clock, and is entranced. He then writes,
Ground-breaking invention illustrates, and binds a 300-page book based on
his notes from the lectures, and sends it to Davy,
On September 4, 1821 Faraday made asking for a job.
the world’s first electric motor—a wire
dipping into a pool of mercury and O 1813 Davy employs
revolving around a magnet. His Faraday first as secretary
invention paved the way for others and then as chemical
to develop the idea (see pp.162–63). assistant at the RI.
Faraday failed to acknowledge the
Christmas Lecture him on, first as his secretary, and then contribution of Davy and Wollaston O 1813–1815 Davy takes
Faraday gave 19 sets of Christmas as chemistry assistant. When, in 1813, sufficiently, and they argued. Davy Faraday as assistant on
Lectures in what is now called the Davy decided to make a tour of Europe then gave Faraday a useless project his honeymoon tour of
Faraday Lecture Theatre at the with his new wife, a grand heiress investigating various types of glass, Europe, during which
Royal Institution in London. He named Jane Apreece, Faraday was which in effect wasted six years of his he investigates
originated the lectures to introduce asked to go with them as scientific life. Only when Davy died in 1829 was volcanic action.
complex scientific ideas to the assistant. Davy’s valet did not wish to he able to return to electromagnetism; Davy’s valet refuses
public, especially to young people. go, and Faraday was given his duties, Faraday then discovered the process of to go, so Faraday has
too. Jane treated him as just another electromagnetic induction, the basis to act as valet as
servant and he had a miserable time. of transformers and dynamos. well. Davy’s wife
treats him as one of VOLTAMETER USED BY DAVY
For five years after they returned, Later interests the servants, and
Faraday worked on various projects in Faraday becomes so miserable that he is
chemistry. Then, in 1821, he started on Faraday’s broad scientific curiosity tempted to return home and give up science.
what was to become his greatest work, was not confined to the laboratory. He
in electricity and magnetism. investigated the spiritualist movement, O 1821 Marries Sarah Barnard on June 2. She is a
which began in 1848, although he was fellow member of the Protestant Sandemanian
convinced it was all nonsense. He sect, which opposes the Church of Scotland.
devised experiments to show that,
during table-tipping séances, the O 1821 Invents the first electric motor.
sitters themselves were unconsciously
Visionary power moving the table. O 1823 Liquefies chlorine.

Lacking formal education, Faraday had Michael Faraday also was a brilliant O 1824 Elected a Fellow of the Royal Society.
almost no mathematics. Instead he had lecturer and demonstrator. He initiated
an extraordinary ability to visualize the Christmas Lectures at the Royal O 1825 Elected Director of the RI. Initiates the
things. He looked at a magnet and Institution in 1825. And yet he was Christmas Lectures, which are still running today.
could “see” the magnetic field lines humble and self-effacing. He twice
sprouting from the ends and curling refused to be President of the Royal O 1827 Gives his first of 19 sets of Christmas
around from one pole to the other; he Society, and he even refused a Lectures; one of his best-known was called
called them “lines of force,” and we knighthood for religious reasons, “The Chemical History of a Candle.”
still use the expression today. This saying he preferred to remain plain
Electromagnetic rotation visionary power enabled him to make Mr. Faraday to the end of his life. O 1829 Invents the
On September 3, 1821 Faraday performed strides in several branches of chemistry induction ring—the basis
the experiment that was to result in the and physics. His ideas were also crucial of the transformer and
world’s first electric motor. He wrote out to physicist James Clerk Maxwell, who the dynamo.
the details in this laboratory notebook.
O 1831 Observes that a
moving magnet induces
an electric current.

BREAKTHROUGH O 1833 Elected Fullerian
Professor of Chemistry
LAW OF INDUCTION at the RI.

O 1836 Inspired by

Faraday, John Frederic DANIELL AND FARADAY

Faraday’s law of induction, recognized Daniell succeeds in
independently in the US by Joseph Henry,
is a basic law of electromagnetism and making the first battery (see pp.162–63) to
applies to electrical generators. The law
states that the voltage induced in a coil of produce electrical current over a long period.
wire is proportional to the rate at which it
cuts through a magnetic field, multiplied by O 1847 In what could be called the birth of
the strength of the field. In practical terms, a nanoscience (see pp.392–93), Faraday reports
higher voltage can be obtained by spinning that the optical properties of gold colloids differ
a generator more quickly, by using a from those of the bulk metal.
stronger permanent magnet, or by using
Michael Faraday more turns of wire in the input side of an O 1855 Writes a strong letter to The Times
An intuitive physicist, Faraday had an induction ring or transformer. newspaper about the Great Stink, caused by
exceptional gift for visualizing lines foul pollution of the River Thames.
of magnetic force and how they FARADAY’S INDUCTOR
O 1867 Dies on August 25 at his grace-and-favour
interacted with electric current, house in Hampton Court, Surrey.
when both phenomena were
poorly understood. In addition

he was an exceptional
experimental chemist.

171

1700–1890

Accurate Measurement Pointer indicates
object’s weight
Nearly every scientific experiment involves some kind of measurement. Rack-and-pinion links of 7 lb (equivalent
Today scientists can measure to extreme accuracy, using a wide range of spring to pointer to 3.2 kg)
precise measuring devices. They use a logical and clearly defined system
of units called the International System of Units, or SI units. Oval spring deforms
into a more circular
A ccurate measurement in scientific there is an important difference: an Dial shows weight shape when a weight is
investigations became much more object’s mass is the amount of “stuff” it in pounds hung on the hook
important in the 17th century, when contains, while its weight is the force of
people began to use the scientific gravity (see pp.108–109) on that object. Spring balance Weight (7 lb) suspended on
method (see pp.68–69). Experimenters Inside this 18th-century spring balance a hook, which is linked to
became aware that only with reliable In 1678 the English scientist Robert is an oval spring, which deforms when the spring by a metal bar
measurements could their experiments Hooke (see pp.92–93) invented the an object is hung from the hook. The
support or disprove their theories. spring balance, which measures weight greater the mass of the object, the
directly from the extension of a spring. greater its weight and the more the
Along with the measurement of time Although Hooke’s invention is spring deforms. As the spring deforms,
(see pp.120–21), the most frequent convenient, it is not generally very a ratchet connected to it moves a
and important measurements that precise. This is because the force of pointer around a calibrated dial.
scientists make are mass (or weight) gravity varies from place to place.
and length (or distance). An object weighs slightly more at the
poles or near a large mountain range
Mass and weight than at the equator or in the middle
of a desert, for example.
In everyday language, people tend to
confuse the terms “mass” and “weight” In contrast, the lever-arm balance
—both words seem to refer to how gives the same reading wherever you
heavy something is. But to a scientist take it. It works by comparing standard
weights or masses on one side of the
BEFORE pivot with the weight of an object on
the other. A traditional balance would
All the ancient civilizations had systems of even give the same readings on the
weights and measures, which were essential Moon, where an object’s mass is
for many different activities, including unchanged, but its weight is only
building, making items such as clothes, one-sixth of that on Earth.
agriculture, and trade.
Modern chemical balances are
ANCIENT MEASUREMENTS accurate to less than millionth of
The units of measurement in early civilizations a gram (about a 30-millionth of an
were often based on the human body or other ounce), while a device called a mass
natural quantities. For example, the cubit, which spectrometer can select individual
originated in ancient Egypt, was the length of atoms by mass.
the forearm, and in several civilizations the
weight of precious stones was often given in Length or distance
terms of grains of wheat. However, human
bodies and wheat grains vary; so it is impossible In 1631 French physicist Pierre Vernier
to measure consistently and accurately using these. invented the Vernier scale—an add-on
As a result, even in ancient times governments to existing measuring devices to help
and rulers made “standard” weights and scientists measure small distances very
measures against which people could compare accurately. Vernier attached his scale to
their own measuring devices. Nevertheless,
systems of weights and measures remained ENGINEER (1771–1831)
complicated and confusing, and the measurements
people made were probably inaccurate. HENRY MAUDSLAY

ANCIENT ASSYRIAN WEIGHT English toolmaker and inventor Henry
Maudslay gained early experience of
engineering when he began filling
artillery shells in the Royal Arsenal,
Woolwich, at the age of just 12. Later
he was apprenticed to the English
lockmaker Joseph Bramah, who was

obsessed with precision. In 1791
Maudslay set up on his own, and
in 1800 invented a type of
lathe that enabled standard
screw threads to be mass
produced. He is known as
the “father” of precision
engineering.

172

INVENTION ACCU R ATE M EASU R EM ENT

VERNIER SCALE Lunar laser ranging
The measurement of the distance to the Moon is one of
The Vernier scale was invented in 1631 shown, the approximate reading on the the most precise ever made, accurate to better than one
by French mathematician Pierre Vernier. fixed main scale is somewhere between part in ten billion. It is made possible by reflectors
Here, a Vernier scale is fitted to a calliper, 18 mm and 19 mm. The point at which placed on the lunar surface (left) in 1969 by the crew of
a device whose jaws close around an the markings on the fixed scale and Vernier Apollo 11. Laser beams from observatories on Earth
object (or open into a space to make scale coincide give greater precision. The (below) bounce off the reflectors, and the distance is
internal measurements). In the example actual reading below is 18.64 mm. calculated from the time taken to receive the reflections.

Movable jaws for Vernier scale (in inches) Fixed scale (in inches)
making internal
measurements

Movable jaws for Vernier scale (in mm) Fixed scale (in mm)
making external
measurements

Reading on fixed Vernier scale and fixed
main scale between scale coincide here, giving
18 mm and 19 mm
a reading of 18.64 mm

a quadrant—a device for measuring inch (about 0.0025 mm). One of

angles—but it was later used on Maudslay’s ex-employees, Joseph

the calliper, a device that enables Whitworth, did even more to promote

dimensions of objects to be measured. precision in the 19th century. In 1833,

Around the same time, English having learned the technique from

astronomer and mathematician Maudslay, he produced a new way of

William Gascoigne invented another making extremely flat surfaces. These

device that would revolutionize “surface plates” are used to set up

accuracy: the micrometer. Gascoigne’s accurate measuring devices, and

device was based around a screw: as Whitworth’s technique enabled him to

you turn a screw, it advances make a measuring device

very slowly, and that was accurate to one

incorporating this into a millionth of an inch

measuring device makes (about 0.000025 mm).

it possible to measure

small distances SI units

accurately. Gascoigne By the end of the 19th AFTER
173
used his micrometer in century great accuracy

telescopes, but the was commonplace in

principle was soon being science and engineering. Modern science and technology is so
sophisticated that measurements of
used to engineer tools. However, scientists were unprecedented precision are necessary.

In 1800 Henry Maudslay Standard kilogram still using traditional

invented the screw-cutting Of all the SI units, the kilogram is systems of measurement,

lathe, which made it the only one defined in terms of with the result that EXTREME PRECISION
It is now possible to measure the distances
possible to cut standard a physical object—the meter, for different systems between individual atoms using an instrument
screw threads. Until then example, is defined by the distance were being used in called an atomic force microscope. This works
nuts and bolts were made light travels in a certain time. The different countries. by measuring the tiny forces between atoms on
in pairs, and only a International Prototype Kilogram the microscope’s probe and those on a surface,
matching pair could be (IPK) was made in 1889, and is With science becoming enabling the surface atoms to be mapped.
held under controlled conditions in increasingly international Microelectronics is another area where extreme
precision is needed, with components measured
guaranteed to work a vault in Sèvres, France. during the 20th century, it in nanometers (millionths of a millimeter). A
2004 satellite-based experiment, called Gravity
together, but Maudslay’s became important for Probe B, used nearly perfect spheres, accurate to
within 40 atoms’ thickness, to measure effects
invention enabled engineers to mass there to be a single measurement predicted by Einstein’s general theory of relativity.

produce screws, nuts, and bolts. system. The Système International,

Maudslay used his expertise with or SI units system (see pp.422–23),

screw threads to produce an extremely was introduced in 1960, enabling

accurate micrometer that was capable scientists to share the results of their

of measuring to an unprecedented measurements and calculations GRAVITY PROBE B

accuracy of one ten-thousandth of an meaningfully in international journals.

1700–1890

Calculating
and Computing

From the last years of the 18th century onward the demands of science
and industry prompted the development of techniques that ultimately
gave us the computer. These techniques included the forerunners of
apparently modern concepts such as programs and computer languages.

A s the Industrial Revolution spread Although various calculating
across Europe, a demand arose for machines had been invented, they
more automated machinery. At the were limited in capability and were
same time scientific discovery called for not always accurate. A more useful
increasingly complex calculations. tool was the slide rule, which was
reasonably accurate and easy to use,
BEFORE but for large and difficult calculations
logarithms provided the best solution.
For millennia, people have used mechanical The main problem with logarithms,
aids for calculation. Tools such as the however, was that their use depended
abacus, Napier’s bones, and the slide rule on sets of tables—which themselves
are the direct ancestors of our computers. had to be calculated.

LOGARITHMS AND NAPIER’S BONES In 1792 Napoleon Bonaparte
First set out by Scottish mathematician John appointed the French mathematician
Napier, logarithms make calculations easier by Gaspard de Prony to compile a set of
allowing multiplication and division to be more comprehensive and accurate
simplified to addition and subtraction. Napier logarithmic tables. To do so, de Prony
also invented Napier’s bones, a set of rods or employed a hierarchy of workers.
cylinders marked with multiplication tables Mathematicians devised the formulae,
for numbers 1 to 9, as a calculating tool. assistants broke the calculations down

INVENTOR (1791–1871)

CHARLES BABBAGE

Born in London, England, Charles Babbage
was already widely read in mathematics
by the time he went to Cambridge
University. He was Lucasian Professor of
Mathematics from 1828 to 1839, and
was an eminent spokesman for science.
To his dismay, none of his calculating
machines was built during his lifetime.
He did, however, manage to build part of
his Difference Engine for demonstration
purposes; this is recognized as the first
automatic calculator.

NAPIER’S BONES

SLIDE RULE
The slide rule is a mechanical computer
invented in 1622 by English clergyman William
Oughtred. The device comprises two sliding
bars marked with logarithmic scales, plus
a marker, or cursor. Deceptively simple in
appearance, slide rules enabled users to do
highly complex calculations. They were
essential in science and engineering until the
1970s—even being used in the Apollo missions.

ff SEE ALSO NS
pp.30–31 A C
pp.88–89 M

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