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MARIN MERSENNE
1588–1648
The French monk Marin Mersenne
is best remembered today for his
work on prime numbers, showing
that if the number 2n–1 is prime,
then n must also be prime. He
also conducted extensive studies
in many scientific fields, including
harmonics, in which he figured out
the laws that govern the frequency
of vibrations of a stretched string.
Mersenne lived in Paris, where he
collaborated with René Descartes,
and corresponded extensively with
Galileo, whose works he translated
into French. He strongly advocated
experiment as the key to scientific
understanding, stressing the need
for accurate data and criticizing
many of his contemporaries for
their lack of rigor. In 1635, he
founded the Académie Parisienne,
a private scientific association with
more than 100 members across
Europe, which would later become
the French Academy of Sciences.
See also: Galileo Galilei 42–43
RENÉ DESCARTES
1596–1650
The French philosopher René
Descartes was a key figure in
the Scientific Revolution of the
17th century, traveling widely
across Europe and working with
many of the prominent figures of
his day. He helped European
scientists to finally overcome
Aristotle’s nonempirical approach
by applying a thorough scepticism
to assumed knowledge. Descartes
produced a four-pronged method
of scientific inquiry, based on
mathematics: accept nothing as
true unless it is self-evident; divide
problems into their simplest parts;
solve the problems by moving from
the simple to the complex; and,
lastly, check your results. He also
developed the Cartesian system
of coordinates—with x, y, and z
axes—to represent points in space
using numbers. This allowed
shapes to be expressed as numbers
and numbers to be expressed as
shapes, founding the mathematical
field of analytical geometry.
See also: Galileo Galilei 42–43 ■
Francis Bacon 45HENNIG BRAND
c.1630–c.1710Little is known about the early life
of German chemist Hennig Brand.
We do know that he fought in the
Thirty Years’ War and dedicated
himself to alchemy on leaving the
army, searching for the elusive
philosopher’s stone that would
turn base metal into gold. In 1669,
Brand produced a waxy, white
material by heating the residue of
boiled-down urine. He called this
material “phosphorus” (“light-
carrier”) because it glowed in the
dark. Phosphorus is highly reactive
and never found as a free element
on Earth, and this marked the first
time that such an element had been
isolated. Brand kept his method
secret, but phosphorus was
discovered independently by
Robert Boyle in 1680.
See also: Robert Boyle 46–49GOTTFRIED LEIBNIZ
1646–1716The German Gottfrield Leibniz
studied law at the University of
Leipzig. During his studies, he
became increasingly interested inscience as he discovered the ideas
of Descartes, Bacon, and Galileo,
which marked the start of a
lifelong quest to collate all human
knowledge. He later studied
mathematics in Paris under
Christiaan Huygens, and it was
here that he began to develop
calculus—a mathematical means
of calculating rates of change
that was to prove crucial to
the development of science. He
developed calculus at the same
time as Isaac Newton, with whom
he corresponded and then fell out.
Leibniz actively promoted the study
of science, corresponding with
more than 600 scientists across
Europe and setting up academies
in Berlin, Dresden, Vienna, and
St. Petersburg.
See also: Christiaan Huygens
50–51 ■ Isaac Newton 62–69DENIS PAPIN
1647–1712As a young man, French-born
English physicist and inventor
Denis Papin assisted both
Christiaan Huygens and Robert
Boyle in their experiments on air
and pressure, and in 1679, he
invented the pressure cooker.
Observing how the steam in
the cooker tended to raise the lid,
Papin then came up with the idea
of using steam to drive a piston
in a cylinder, and produced the
first design for a steam engine.
Papin never built a steam
engine himself, but in 1709, he
constructed a paddle wheel that
demonstrated the practicability
of using paddles instead of oars
in steam-powered ships.
See also: Robert Boyle 46–49 ■
Christiaan Huygens 50–51 ■
Joseph Black 76–77DIRECTORY