sage of Greece,
he founded classical geometry and natural philosophy.
Alchemists have claimed him as one of their own.
The theorem of Thales
(one of two)
is about two triangles with parallel sides:
The pyramid's shadow is to the pyramid what a man's shadow is to the man
he founded the mystic cult of the Phythagoreans,
whose initiated members called themselves mathematikoi.
They are credited with the first proof of the Pythagorean Theorem
(itself known to the Chaldeans
1000 years earlier). Irrational numbers distressed them...
Founder of metaphysics.
Called the weeping philosopher
(as opposed to Democritus, the laughing philosopher)
Heraclitus argued that all things move and nothing remains still,
which led him to a Mach-like principle of Relativity.
Parmenides upheld the extreme view of
He spent some time as a member of the Pythagorean community at Croton.
Zeno was his
At age 65, Parmenides went to Athens and met a youthful Socrates (469-399 BC).
Inventor of rhetoric and borderline charlatan.
His arbitrary explanation of reality with 4 elements (Earth, Air, Fire and Water) and 2 forces (Love and Strife)
dominated Western thought for over two millenia.
Several of his intuitions were correct, though, including the finiteness of the speed of light.
In the most famous of his provocative paradoxes, Zeno asks how
Achilles could overcome a tortoise, since Achilles must first reach the initial
position of the tortoise...
By the time he gets there, the animal is elsewhere and
Achilles is left with a similar challenge, ad infinitum.
A sophist whom
(he portrays him as vain and arrogant, with a wide but shallow knowledge).
Hippias devised the first transcendental curve, known as quadratrix
or trisectrix because the
quadrature of the circle
trisection of an angle
would be trivial if its use was allowed.
The atomists' school in Abdera was founded by his teacher
himself a student of Zeno and a proponent of the law of causality.
Democritus argued that all was made of indivisible atoms
moving in the void.
One of his followers, the alchemist
Bolus of Mendes,
also signed "Democritus".
Revolutionary founder of Western medicine.
said to be a direct descendant (17 or 19 generations) of the legendary
Hippocrates studied philosophy under Democritus and learned rudiments of medicine
from his father, Heraclides, and from Herodicus of Selymbria.
Mathematician and statesman.
Student of Philolaus (an ardent follower of Pythagoras)
and teacher of Eudoxus.
Archytas considered surfaces generated by rotating curves and could
double the cube
by intersecting three of those (defining Archytas' curve in the process).
On a land once owned by someone called Akademos,
Plato created the first institution of higher learning, in 387 BC.
lasted 915 years
(Justinian closed it in 529).
Initiation to Geometry was an entrance requirement.
The aim was to teach or discover ideal laws behind appearances.
His definition of the comparison between ratios of (possibly irrational) numbers
appears in the fifth book of Euclid. It inspired
Dedekind's definition of real numbers (1872).
Eudoxus invented the method
of exhaustion built upon by Archimedes.
He was the first Greek scholar to map the stars.
He shunned mathematics entirely in his natural philosophy
which was lightly based on crude observations. The lack of discussion
of his dogma for two millenia greatly hindered
the development of natural Science, especially
when some Aristotelian misconceptions became part of Church doctrine.
Father of axiomatic geometry and author of the most
enduring textbook in the history of mathematics: The Elements.
His presentation of the mathematics of his times
would become the centerpiece of mathematical teaching for more than 2000 years.
Copernicus credited him for the idea that Earth rotates on its own axis
and revolves around the Sun.
From rough angular measurements, he estimated the distance to the Sun.
As he couldn't detect the parallax of stars, he declared them to be
(which Archimedes wouldn't accept).
Starting out as a barber, he became an engineer and founded the school
of mathematics at the Library of Alexandria
(he may have served as its first head librarian).
He invented a suction pump, a compressed-air catapult,
a water organ and the
(fed by an overflowing vessel).
Also known as Philo Mechanicus, he was an engineer
who journeyed to Rhodes and Alexandria.
He is credited for inventing the
the water mill and the
gimbal suspension (described by Cardano).
Philon constructed the Delian constant
by intersecting a circle and an hyperbola.
A native and resident of
Archimedes studied in Alexandria and maintained
relations with Alexandrian scholars. Although he became famous for designing war
machines, this early physicist was, above all, an
The 14 Archimedean solids
Apollonius named and studied the
He found that a circle consists of all
points M whose distances to two foci (I,J) are in a fixed ratio
He said that planets revolve around the Sun and that the Earth itself might
as well be thought of as moving, like planets do.
The only extant work of Lucretius is the didactic poem
De rerum natura
(On the Nature of Things) where the basic Epicurean
tenets are expressed in a surprisingly modern way.
It's especially so about atomism, randomness
Rutherford's motto is a quote from Lucretius.
Influenced by Ctesibius.
Some of his works were meant to be lecture notes:
Metrica (methods and
formulas for areas and volumes, lost until 1896)
Mechanica (statics & simple machines)
Hero thought light-rays came from the eyes.
Gaius Plinius Secundus was a public official who wrote a lot.
The 37 books of Historia Naturalis (AD 77)
present, in an anthropocentric way, everything the Romans knew about the natural world.
In this, Pliny cites nearly 4000 authors
(his "Ostanes" need not be
the one who cited Miriam).
Earliest female experimentalist on record (signing
Miriam the prophetess, sister of Moses).
and the eponymous balneum Mariae
may be due to her.
F. Hoefer credits her for
The oldest extant alchemical texts (by
Panopolis) quote her as a past master.
Pedanius Dioscorides was the Greek author of the first major
(which never went out of print and remained authoritative for over 1500 years).
The 5 volumes of De Materia Medica (AD 70) present about 600 plants.
A resident of Rome who spent his youth in Alexandria,
he recognized geodesics on a curved surface
as analog to straight lines on a plane.
Shunning arcs of parallels, he defined
spherical triangles as consisting of arcs of great circles.
This was a turning point in
Claudius Ptolemaeus was a Roman citizen
who wrote in Greek
(his first name may have been Tiberius).
His Almagest dominated astronomy for centuries.
Ptolemy's theorem says that a tetragon is cyclic
iff the product of its diagonals
is the sum of the pairwise products of facing sides.
A Roman citizen
of Greek ethnicity, he started out as physician to the gladiators.
He was so prolific (10 million words) that his surviving works (30%) represent
nearly half of the extant literature from ancient Greece.
His thinking dominated medicine for more than a thousand years.
Leading commentator of Aristotle, he revived Aristotelian ideas.
Appointed to an endowed chair in Athens
during the co-reign of Septimius Severus and Caracalla (AD 198-209).
He first described the dark band,
named after him, between the brignt primary rainbow and the dim secondary rainbow.
A Diophantine problem is to find an
integer satisfying a polynomial equation
with integer coefficients, or several such equations simultaneously.
Diophantus himself never considered irrational numbers or nonpositive ones.
His age at death was reportedly
x = x/6 + x/12 + x/7 + 5 + x/2 + 4.
Possibly the best mathematician of ancient China, he was a descendant of
Liu Yi, Marquis of Zixiang,
and lived in the state of
Cao Wei (one of the feuding
He expanded the Jiuzhang Suanshu with his own
commentaries and an appendix which became an official surveying manual.
Daughter of the mathematician
Theon (c. 335-405)
last librarian of Alexandria, who raised her like a boy.
Her teaching of science was seen as pagan.
She was ambushed and skinned alive by a mob of Christian fanatics.
Hypatia's murder marks the beginning of the Dark Ages in the West.
Abu Musa Jabir ibn Hayyan al Azdi was born in Tus (Persia) but the
Arabs claim him
as one of their own. Geber (or Jabir) made remarkable scientific advances in
practical chemistry but also produced
eponymous gibberish on occult alchemy.
Al-jabr (transposition from one side of an equation to the other) is the technique
which gave algebra its name.
The term is from the title
of the masterpiece published around 810 by
Abu Abdallah Muhammed bin Musa al Khwarizmi.
Key disciple of the three
brothers, he's best known as Thabit or Thebit.
All later editions of Euclid's Elements were based on his revision.
He was a founder of statics.
He was a Sabian, not a Muslim.
Abu'l-Wafa was the first to build a wall quadrant to observe the stars.
Whenever possible, he determined quantities by giving a ruler
and compass construction for them.
He was an expert in Al-Khwarizmi's "Indian reckoning",
but still wrote out all numbers in arabic letters, for the sake of his audience.
Abu Bekr ibn Muhammad ibn al-Husayn Al-Karaji was probably born in
although his alternative name would imply a connection with
the west part of Baghdad, where he worked most of his life.
He devised the notion of mathematical induction
and used it on the binomial triangle.
Abu Ali Muhammed ibn al-Hasn ibn al-Haytham al-Basri
was hired by Al-Hakim
and had to feign madness to avoid impossible duties,
until the "Mad Caliph" died (1021).
Early proponent of the scientific method,
Alhazen pioneered optics and anticipated
the first law of Newton (who quoted him).
Celebrated polymath who was first exposed to mathematics by associating with
Abu Nasr Mansur (970-1036)
of sine law fame.
Al-Biruni pioneered scientific methods in astronomy and geology.
First mathematician to point out the limited validity
of Brahmagupta's simplified formula.
Last and greatest mathematician in the Golden Age of Indian mathematics.
He developed trigonometry for its own sake, including spherical trigonometry,
and introduced the addition formula:
sin (x+y) = sin x cos y + cos x sin y
He conceived derivatives
and stated Rolle's theorem.
Educated at Oxford University,
of which he became Chancellor in 1215 (until 1221).
Grosseteste introduced the earliest teaching of the
scientific method in Oxford
(comparing theories with observations). After holding other ecclesiastical posts, he became
Bishop of Lincoln in 1235.
Nicknamed Doctor Mirabilis. He went to the University of Paris to take a degree
(1241) and he started lecturing on Aristotle there (1234-1247) before returning
to Oxford. Influenced by Grosseteste, Roger Bacon became the
most active early proponent of the scientific method in Europe.
He was born and raised on the Island of
off the coast of Catalonia.
He was brought up in the Royal Court and would become the dominant figure in Medieval
In 1272, he conceived of reducing all knowledge to first principles.
His work greatly influenced Leibniz.
Arguably, the foremost Medieval logician.
His enduring contribution to natural philosophy is the "principle
of parsimony" known as Occam's Razor
(the simplest explanation compatible with observations is preferred).
In 1327 and 1340, Joannes Buridanus was rector of
where he had studied under Ockham
(whom he condemned in 1340).
Buridan seeded Copernican ideas. He contributed to
probabilities and optics. His concept of
Madhava gave the first examples of
(besides geometric series)
as expansions of trigonometric functions (sin, cos, arctg).
Madhava's knowledge was perpetuated and expanded by the
he founded in Kerala
and may have influenced similar developments later, in the West.
Mathematical prodigy, earliest publisher of printed scientific works.
Johannes Müller von
signed Joannes de Monte Regio.
( "Regiomontanus" was coined in 1534,
Cardano scorned him for publishing
Jabir ibn Aflah's
spherical trigonometry without proper credit.
Artist and full professor of mathematics,
Pacioli invented modern Venitian double-entry accounting in 1494.
He shared living quarters in Milan (1494-1499) with
Leonardo da Vinci, who illustrated Pacioli's second masterpiece
"De divina proportione"
(with iconic polyhedral frames).
A stellar Renaissance painter,
he left 13000 pages of illustrated notes on science and engineering
(in mirror-image cursive). He was taught mathematics by
Luca Pacioli with whom he lived in Milan, while
painting The Last Supper.
(c. 1495) and illustrating Pacioli's
"De divina proportione".
Philippus Aureolus Theophrastus Bombastus von Hohenheim chose the pseudonym
Paracelsus in honor of the encyclopedist
He is the first systematic botanist.
He named zinc (1526)
and revolutonized medicine (without freeing it from superstition) by using
Son of a mounted postman who was murdered when he was only six.
The nickname Tartaglia (stutterer)
came from an infirmity due to the larynx injury he suffered in the
Sack of Brescia
He became a military engineer and founded ballistics (1531).
Solved the cubic on 1535-02-13.
First scholar to use negative numbers routinely.
In 1545, he revealed the solution of cubic equations obtained by
del Ferro (1465-1526)
in 1516 and rediscovered (1535-02-13) by
It had been extended to quartics, in 1540, by his own assistant
Ambroise Paré was a royal military surgeon.
On one occasion on the battlefield, he had to use a makeshift ointment.
He observed that the soldiers so treated recovered much better than those
who underwent the formerly "recommended" treatment (i.e., burning wounds with oil).
Breaking with the precepts of Galen,
Andreas Vesalius Bruxellensis revolutionized medicine in 1543
with the first modern book on
human anatomy, based on the detailed observations he made during
the dissections that he carried out in front of medical students
at the University of Padua.
His name is also spelled Viette
(latin: Franciscus Vieta).
Viète pioneered modern algebraic notations,
where known constants and unknown quantities are represented by letters.
law of tangents (c. 1580)
is due to him.
In 1593, he gave an expression of p
as an infinite product.
Tyge Ottesen Brahe was from the high Danish nobility.
His Uraniborg observatory,
on Hven island,
cost 1% of the state budget but allowed precise (naked-eye)
observations of planetary positions which made possible the work of
Flemish engineer who introduced decimal fractions (1583) shortly after
Stevin wrote in Dutch and coined many Dutch scientific terms
(without the Latin/Greek roots used in other languages).
He found that the pressure exerted by a liquid at rest in a vessel depends only on depth (1586).
Known as Neper to the French, he invented an
early version of logarithms
which he spent years tabulating.
This improved upon prosthaphaeresis
(multiplication using trigonometry).
Common (decimal) logarithms are due to his younger contemporary
Henry Briggs (1561-1630).
Harriot discovered the law of refraction in July 1601
(years before Snell or Descartes).
He made the first telescopic drawing of the moon (1609-07-26).
and was first to record sunspots (1610-12-08). He worked out the Sun's rotation.
His research waned after 1613, as he battled skin cancer.
Using his own pulse as a timer,
Galileo discovered the
pendulum isochronism in 1581.
He found that all bodies fall with the same acceleration and
declared mechanical laws valid for all observers in uniform motion.
He made the first telescopic observations of celestial bodies (1609).
Kepler's precise calculations helped establish heliocentric
astronomy. In 1609 and 1619,
he published his famous 3 laws of planetary motion.
He studied optics,
he paved the road to Calculus.
Founder of pneumatic chemistry and biochemistry,
who coined the word gas (1632).
He famously proved that plant bulk doesn't come from soil by weighing a potted
willow tree after 5 years.
His chemical work was published in 1640 by his son,
Van Helmont (1614-1698).
William Harvey started modern experimental medicine with his discovery
of the circulation of the blood.
He had been a student at Padua,
where the Flemish anatomist Andreas Vesalius (1514-1564)
had started encouraging students to observe
rather than conform to the precepts of Galen.
Of modest origins,
Mersenne attended the newly-created Jesuit college of
La Flèche (1604-1609)
then studied in Paris until July 1611, when he joined
the Order of Minims
(founded in 1436). He was ordained one year later.
His informal Academia Parisiensis (1635) had 140 members.
Building on the fundamental results of Pappus,
projective geometry in 1639.
That innovation was largely ignored, except by the likes of Pascal
and La Hire,
until a key manuscript rediscovered in 1845 was published in 1864,
following a remarkable rebirth of the subject.
In Pisa, Cavalieri was mentored by
Benedetto Castelli (1578-1643)
who put him in touch with Galileo.
can be construed as the preliminary conceptual foundations for integral calculus,
stating (in modern terms) that the
integrals of equal functions are equal...
Orphan. Assistant to Castelli, then Galileo.
Torricelli invented the barometer in 1644: He
figured out that what's above a column of 760 mm of mercury is a near-perfect vacuum
(just rarefied mercury vapor). What pushes the liquid up the tube
is the (variable) atmospheric pressure.
At 16, he generalized
the theorem of Pappus. At 19, he built a celebrated
In 1647, Pascal thought of using a Torricelli barometer as
which established experimentally (1648) the origin of atmospheric pressure.
The SI unit of pressure (Pa) is named after him.
In 1660 (as assistant of
his law of elasticity affirmed the notion of force.
After the Great Fire (1666)
he surveyed half of London and designed many new buildings.
For 40 years, he produced new experiments weekly for the Royal Society.
He was a microscopic & telescopic observer.
The Japanese Newton.
Second son of a Samurai warrior.
Adopted by a technocrat (Gorozaemon SEKI )
whose name he took.
Some of Seki's discoveries predate their Western counterparts:
Bernoulli numbers, etc.
He was the teacher of Katahiro TAKEBE (1664-1739).
Also known as Lucrezia Piscopia,
Elena Lucrezia Cornaro-Piscopia was from the
She was an Oblate
of the Order of St. Benedict (1665) and a mathematician...
On 25 June 1678, she became the first woman to be
awarded a doctorate (from Padua).
54 years before Laura Bassi.
In 1691, he proved a statement of Bháscara:
If a polynomial has equal values at two points, then its
derivative vanishes somewhere between those points.
The result was generalized beyond polynomials by Cauchy (1823).
It was first called "Rolle's theorem"
by Drobisch (1834)
and Bellavitis (1846).
Earliest mathematician in a
family that would produce many
(but none among his descendants).
With his younger brother Johann,
Jacob pioneered the calculus of variations
(which Euler would tackle in 1744).
He found Bernoulli numbers (independently of Seki)
and formalized probability theory.
French Huguenot, tutored by
Jacques Ozanam (1640-1718) in 1684-85.
He fled to England shortly after 1685,
eking out a living as a tutor and actuary.
He befriended the likes of
Halley and Newton
and entered all major mathematical societies: London (1697), Berlin
Scottish mathematician (FRS, 1726).
In his first publication Lineae Tertii Ordinis Neutonianae (1717)
he extended to 76 the number of types of planar cubic curves
(Newton had identified 72).
The Stirling series
is a classic example of a divergentasymptotic series.
At 19, Gabrielle-Emilie de Breteuil married the Marquis
Florent-Claude du Chastellet.
She was the lover of Voltaire whom she
and her husband protected in their château.
She was tutored by Maupertuis (1733) and
Clairaut (1735). She
the concept of energy
introduced by Leibniz.
He solved the Basel Problem in 1735.
The most prolific mathematician of all times,
Euler became totally blind in 1771. He still produced nearly half of his 866 works after 1766
(in St. Petersburg)
with the help of several assistants, including
(1755-1826) who joined in 1773.
initiated her to higher mathematics and newtonian physics.
In 1732 (at age 21) Laura Bassi
became the second woman
to earn a doctorate and the first to teach at a European university
She was finally named professor of physics there, in 1776.
Child prodigy and author of the first mathematical book by a woman (1748).
In 1750, she was appointed to the chair of mathematics at Bologna by
Pope Benedict XIV
but she never went there (the first woman to hold
a chair in Europe was thus Laura Bassi, in 1776).
Etienne Montucla was a mathematician and a historian.
He authored the first book on the history of mathematics:
Histoire des mathématiques
The third volume (1799) was completed and published by
who also wrote the fourth and final one (1802).
Dutch-born British physician who discovered the principles of
Building on the work of
Joseph Priestley (1771)
Ingenhousz showed that green plants do require sunlight to produce
oxygen (1779). He was honored by a
on his 287-th Birthday (2017-12-08).
Antoine Lavoisier founded quantitative chemistry by establishing that
mass is conserved in any chemical transformation.
He was infamously executed during the French Revolution because of his
rôle as a tax collector.
Marie, Jean, Antoine, Nicolas de Caritat, Marquis de Condorcet
founded Social Choice Theory
in 1785 with his Essay on the Application of Analysis to the Probability
of Majority Decisions (introducing Condorcet's paradox).
He was a moderate leader during the French revolution.
Correctly interpreting the 1791 observation by
Luigi Galvani (1737-1798) of muscle contractions
in a dead frog, Volta reasoned that electricity is generated upon contact of two different metals.
Replacing living tissue by paper soaked with saline electrolyte, he built the first battery in 1799.
In 1768, he succeeded his mentor
Bossut to the chair of mathematics at the
Monge would use that school as a model for
Ecole Polytechnique, founded in 1794 with himself as Director and
instructor in descriptive
geometry (the drafting technique he had devised in 1765).
Before Jenner, risky variolation and other inocculations were
believed to induce immunity to dangerous diseases
(20% of human deaths were due to smallpox).
Putting some human lives at risk, Jenner proved that innoculation with
harmless cowpox did protect against the dreaded smallpox.
A student of l'abbé Marie (1738-1801)
Legendre grew to be one of the greatest contributors to the mathematics of his times.
Many concepts are named after him.
At left is what seems to be
his only extant portrait
(it was found among 73 caricatures of members of the French academy of Sciences).
In 1776, under Monge,
Meusnier read to the Académie
two papers about surface curvature and the
(both published in 1785).
With Lavoisier, he mass-produced hydrogen
600°C iron with water vapor (1777).
Meusnier fought as a
and died in battle near
Quaker schoolteacher. His first paper was on the genetic
red-green color blindness (Daltonism)
which affected him and 8% of European boys but only 0.64% of the girls.
Studying meteorology, he found the law of partial pressures (1801)
which supported his celebrated atomistic views of chemistry.
In January 1795, Jean-Baptiste Joseph Fourier was the star trainee in the new
Ecole normale de l'an III (the forerunner of
simultaneously teaching at Polytechnique.
He is the founder of
(cf. Fourier transform).
Notorious for his
demonstrating the wavelike nature of light (1802)
and for Young's modulus of elasticity (1807).
Young's rule gives the posology for an n-year old child as
n/(n+12) of the adult dose.
Young paved the way for the decoding of hieroglyphics by
Appointed professor of mathematics at Polytechnique in 1809.
In september 1820, he discovered that
like currents attract each other whereas opposite currents repel.
The effect is now used to define the SI unit of current, which is named after him.
for shady reasons (1793)
he became a student at Ecole Polytechnique upon its creation (1794).
Malus discovered the polarization of light by reflection off non-metallic surfaces (1809)
and by double-refraction (1810)
which brought him multiple honors.
At 13, the story of the death of Archimedes
inspired her to become a mathematician.
She was 18 when Polytechnique opened
(it was male-only until 1972)
and made available Lagrange's lecture notes.
This gave her a start to correspond with him and others
(signing Monsieur LeBlanc at first).
Lorenzo Romano Amedeo Carlo Avogadro, Conte de Quaregna e di Cerreto
was born in Turin to a noble family of
In 1820, he accepted the first chair of mathematical physics at the
University of Turin, which
had to close in 1822. Avogadro got the chair back in Nov. 1834.
At the age of 7, the
Prince of Mathematics found instantly the sum (5050) of all integers
from 1 to 100 (as the sum of 50 pairs, each adding up to 101).
At 19, his breakthrough about
constructible polygons helped him choose
a mathematical career.
Honored by a Doodle on 2018-04-30.
Among his many mathematical contributions is a very abstract construct in
analytical mechanics (Poisson
Brackets, 1809) which helped Dirac
formulate a precise correspondence between classical and quantum
mechanics (Sunday, Sept. 20, 1925).
He taught analysis and geometry at Polytechnique from 1810 to 1830,
at the peak of his creativity (electromagnet, 1820).
A popular left-wing deputy elected in 1830, Arago became Minister of Marine and War
in 1848 and was instrumental in abolishing slavery in the
French Colonies (1848).
In 1814, his observation of the Sun's dark-line spectrum (Fraunhofer lines) marked the
beginning of astrophysics.
Fraunhofer is also remembered for related studies of diffraction in optical systems with small
Fresnel numbers (Fraunhofer diffraction).
Knighted in 1824 (Bavaria).
Caen (1801-1804) then at Polytechnique.
Poor physicist at first...
Augustin Fresnel established (with Arago)
that light is a transverse wave
whose two polarizations don't interfere with each other.
Fresnel lenses for use in lighthouses.
POW in Russia for 15 months (1812-1814) he brought back
the 7 notebooks in which he had invented
modern projective geometry.
Promoted to Colonel in 1845 and General in 1848,
Poncelet headed Polytechnique from 1848 to 1850.
A devout royalist, Cauchy wrote 789 papers in all areas of the mathematics and
theoretical physics of his time. In 1821, his Cours d'analyse
made analysis rigorous.
He originated the calculus of residues (1826) and
complex analysis (1829).
In 1831, Faraday discovered the
Law of Electromagnetic Induction, which
made the electric era possible.
He is widely regarded as one of the greatest
experimentalists who ever lived.
Yet, he had little or no grasp of higher mathematics.
He was Lucasian Professor
(1828-1839) at Cambridge but never taught.
He designed two computing machines:
The Difference Engine (funded in 1822) was never completed.
The more advanced Analytical Engine
would have been the first true computer (Ada Lovelace wrote programs for it).
He gave the terms
(travail) and kinetic energy
their precise mechanical meanings.
At Ponts-et-Chaussées since 1832,
Coriolis inherited the chair of Mechanics there, in 1836, upon the death of
and became director of studies at Polytechnique.
Green worked in his father's bakery and mill.
He entered Cambridge
at the age of 40 (in 1833) 5 years after self-publishing his best work
(extending the work of Poisson in electricity and magnetism)
using self-taught mathematical physics.
Green coined the word potential.
Professeur of geodesy at Polytechnique from 1841 to 1851,
he inaugurated the Sorbonne
chair of projective geometry,
then called higher geometry (1846-1867).
His reputation as a science historian was all but ruined when he
bought forged manuscripts (1861-1869)
from Denis Vrain-Lucas.
He found the law of induction independently of
Faraday (mutual inductance)
and discovered self-inductance (1832).
The SI unit of inductance
was named after him in 1960.
His relay (1835) made practical the
electrical telegraph devised by
Schilling (1832) and patented by
In 1858, using the handiwork of
Heinrich Geissler (1814-1879)
he paved the way for the invention
of the CRT (by Crookes, c. 1875).
He was the doctoral advisor of Klein.
In 1866. Plücker received the
for his work in analytical geometry, magnetism and spectral analysis.
produced many brilliant results during a short life spent in poverty:
Non-solvability of quintic equations by radicals,
double periodicity of the elliptic functions, etc.
An offer for his first professorship
arrived two days after he had succombed to tuberculosis.
A pupil of Lhuilier in
he earned a top prize with Colladon
for measuring the speed of sound in water (1826-27). They both moved to Paris.
Teacher at Rollin (1830)
French citizen (1833). He succeeded Ampère at
Académie des sciences (1836)
and Poisson at Polytechnique (1840).
An inspiring teacher, he was an outstanding and prolific creator of mathematics
who has been likened to Euler.
He introduced ¶ and
Jacobians in 1841.
and proved that they satisfy what's now called
Johann Peter Gustav Lejeune-Dirichlet.
signed Gustav Lejeune Dirichlet, (no hyphen)
published as P.G.L. Dirichlet
and was quoted as Lejeune-Dirichlet. He contributed to
number theory, mechanics and
He was the first to consider unrestricted functions.
Against strong religious animosity (which lasts to this day in the US)
Darwin established that the mechanism of natural selection
was powerful enough to explain the evolution of the humblest ancient lifeforms
into the most advanced modern ones, featuring very sophisticated organs.
he pioneered the modern approach to vectors
and went on to invent exterior algebra (the correct basis
for Cartan's differential forms
Grassmann had little mathematical influence during his own lifetime
(he became successful as a linguist).
Galois theory is about symmetries of polynomials on
fields. Galois "didn't have time" to
extend that to transcendental functions (nobody else has done so).
He died in a stupid duel at the age of 20 and his
fundamental work might have been lost if Liouville hadn't
revived it in 1843.
He introduced the notion of higher-dimensional  vectors
(between 1850 and 1852, full treatise published in 1901).
He pioneered multi-dimensional Riemannian manifolds by considering the
3D-hypersurface of a 4D-hypersphere.
Schläfli also classified
In 1838, he founded the preparatory school at Sainte-Barbe
with Sturm and Liouville.
His left-wing activism damaged his academic career.
He was elected to the French National Assembly.
Catalan's conjecture (1843)
saying that the only solution of
1+xm = yn is 1+23 = 32,
was proved in 2002.
The father of analysis
spent 15 years teaching secondary school before one paper
earned him an honorary doctorate and a professorship.
He gave the rigorous
metric definition of limits and invented the
concept of analytic continuation.
Daughter and heiress of Lord Byron (the poet) whom she never knew.
Ada was introduced by
Mary Somerville to
Charles Babbage on June 5, 1833.
She then developped an intense interest in the mathematics of computation
and is now regarded as the first computer programmer.
[ Video ]
Home-schooled Russian aristocrat. His mathematics tutor was the textbook author
Platon Nikolaevich Pogorelski (1800-1852).
Chebyshev contributed to number theory, algebra, analysis, mechanics, etc.
In 1850, he derived
totient function's asymptotics.
He wrote 996 papers on many mathematical subjects
(200 of these while praticing law, for 14 years).
In 1858, Cayley established (without a formal proof)
the Cayley-Hamilton theorem:
A matrix is a zero of its characteristic polynomial.
We use his initial (H) for
enthalpy, not for the
Helmholtz free energy (F).
Helmholtz is primarily known for his work in physics (thermodynamics, acoustics,
but the fundamental theorem of vector calculus (3D only)
is also named in his honor
Father of genetics.
Mendel communicated his results to
Karl von Nägeli (1817-1891)
who expressed contempt for them and was instrumental in burrying them for three decades.
Mendel's laws of heredity were rediscovered in the 1890s by
Hugo de Vries (1848-1935).
After one year at Polytechnique, the military management
dismissed him because of a congenitally deformed right leg.
Returning as a teacher, five years later, he contributed to number theory,
orthogonal polynomials and elliptic functions.
He proved e transcendental in 1873.
A chemist by training, he separated chiral isomers
by sorting the different crystals they produce.
He proved the germ theory of infectious diseases
and invented pasteurization.
Motto: Fortune favors the prepared mind.
His impoverished family had converted from Judaism to Protestantism before he was born.
Gauss named Eisenstein
one of the top three epoch-making mathematicians in history
(along Archimedes and Newton)
and Weil considered his approach
paramount to modern mathematics. He died at 29.
Famous for his credo "God made the
all else is the work of man", Kronecker
championed constructivism. He strongly opposed his former
student Georg Cantor and the
Born William Thomson, Lord Kelvin was knighted
in 1866 and raised to the peerage in 1892 (Baron Kelvin of Largs).
The SI unit of temperature is named after this
mathematician noted for his engineering work (e.g., transatlantic telegraph).
Applying Pasteur's ideas, he introduced antiseptic surgery while working
at the Glasgow Royal Infirmary.
Lister used carbolic acid (phenol)
to sterilize instruments and clean wounds.
This reduced post-operative infections and made surgery safer.
Baronet in 1883, he became a Baron in 1897.
Pioneer of synthetic organic chemistry.
He was opposed to atomist notations.
He signed his papers P.E.M Berthelot.
Collège de France (1865).
Académie des sciences (1873).
French Minister of education (1886-87) and foreign affairs (1895-96).
Académie française (1901).
In 1865, Kekulé had a revelation of the
cyclic structure of benzene in a daydream where he saw
snakes biting their own tails.
He first proposed a planar molecule of trigonal symmetry,
with alternating single and double bonds
(instead of the currently accepted perfect hexagonal symmetry).
Julius Wilhelm Richard Dedekind was
the last doctoral student of Gauss
but he also learned much from Dirichlet
after his doctorate. On 24 November 1858, he defined every real number
as a Dedekind cut
of rationals. In 1871, he introduced algebraic
he presented a classification of chemical elements
(based mostly on atomic masses) which showed periodic patterns in their chemical properties.
He predicted the properties of 3 unknown elements which were discovered shortly thereafter:
Ga (1871), Sc (1879) and Ge (1886).
Bringing to a great conclusion the works of
on non-Euclidean geometry, he showed that geodesics matched straight lines on the plane only
for surfaces of constant
curvature. His pseudosphere
(generated by rotating a tractrix) is the key example (1868).
Johannes Diderik van der Waals
obtained a doctorate in his native town of Leiden
only when classical languages requirements were lifted in Science (he was 36).
At a time when the very existence of molecules was doubted, his thesis
showed how molecule interactions explain gas liquefaction.
A universal mathematician and one of the greatest teachers of the 19-th century,
he inspired Lie, Klein,
Borel and Lebesgue.
He invented the topological concept of
Camille Jordan was appointed professor of Analysis at Polytechnique in 1876.
Mach would only consider relative motion between objects, irrespective of
absolute Newtonian space.
He studied the shockwaves produced by fast projectiles
(the Mach number of a projectile is the ratio of its speed
to the speed of sound in the surrounding fluid).
Mach was Pauli's godfather.
Founder of modern optics.
His industrial commitments to the instrument-maker
Carl Zeiss (1816-1888) and
the glassmaker Otto Schott (1851-1935)
prevented Abbe from accepting a professorship at
(offered by Helmholtz).
He tied his definition of integrals (1870)
to that of Riemann in 1875.
The Darboux formulas define the normal
and geodesic curvatures as well as the geodesic torsion for a curve drawn on a surface.
He was a biographer of Poincaré.
Darboux was elected to the Académie des Sciences in 1884.
With Felix Klein,
Sophus Lie originated the investigation of the continuous
groups of symmetry now named after him.
The study of Lie groups and the related
Lie algebras would become a major branch of
20-th century mathematics, with applications to
A proponent of atomic theory and the father of
statistical physics. We call
the coefficient of proportionality between entropy
(in J/K) and the natural logarithm of
the number W
of allowed physical states.
Cantor's diagonal argument shows that
the points of a line are not countable.
states that no function from a set to its powerset
can possibly be surjective,
which establishes an infinite sequence of increasing
The most successfull
His 1093 US patents cover the phonograph,
light-bulb, motion picture camera...
In 1876, he created the first industrial research laboratory at
Menlo Park, NJ.
He favored DC current, which lost out to Tesla's
AC generation and distribution of electric power.
Investigating Lie groups independently of Lie and Klein,
he fully classified simple Lie groups in 1887
(as confirmed by Cartan in 1894):
5 exceptional Lie groups
and three regular families:
special linear groups SL(n),
orthogonal groups O(n), symplectic groups Sp(2n).
Born on 1849-4-25 (432, 22, 52 )
to a Prussian government official, he married the granddaughter
of Hegel in 1875.
The noncyclic group of order 4 bears his name.
As first president of the
ICMI (1908) he was instrumental in bringing
Calculus (back) to secondary schools worldwide.
Sofia Vasilyevna Kovalevskaya was born Sonya Korvin-Krukovskaya.
Weierstrass tutored her privately (1870-1874) and helped her
become the first female professor at a European university (Stockholm, 1889)
since the days of Laura Bassi (1776) or
Among the many contributions of H.A. Lorentz is
the coordinate transformation
which is the cornerstone of Special Relativity.
In 1892, Lorentz proposed a
theory of the
electron (discovered by Perrin in 1895 and
J.J. Thomson in 1897,
who measured the mass-to-charge ratio).
He was originally trained as a mechanical engineer.
At least 272 patents
were awarded to Tesla in 25 countries.
His work is the basis of modern alternating current
(AC) electric power distribution.
In 1960, the
SI unit of
magnetic induction (magnetic flux density) was named after him.
In 1887, Heinrich Rudolf Hertz
discovered the photoelectric effect, whose
explanation by Einstein, in 1905, would establish the existence
In 1888, he made the first transmission of a signal by
The SI unit of frequency
(symbol Hz) was named after him, in 1960.
Peano joined the staff at Turin
where he succeeded
(1817-1889) to the chair of Calculus, in 1890.
Peano defined the integers axiomatically (1889) and found a
space-filling curve (1890).
He invented symboliclogic (1895) and
devised a new natural language (1903).
One of the most powerful mathematicians ever, David Hilbert gave a famous
list of 23 unsolved problems in 1900. Quantum Theory
is based on the complex normed vector spaces
which are named after him. In 1931, Gödel
shattered the dream Hilbert had voiced in 1930 ("we will know").
Pioneering convex geometry, he proved
an early version of the separation theorem (of Hahn-Banach)
and called A+B the set of all sums with one addend
in A and the other in B.
His name was given to the Lptriangular inequality (1896)
and to the relativisticscalar product
in spacetime (1908).
In 1892, he obtained his doctorate and was awarded the French Academy's Grand Prix
for completing the work of Riemann on the Zeta function.
He authored one of the first two proofs of the Prime number theorem in 1896.
He gave functional analysis its name in 1910.
Madame Curie (née Maria Salomea Sklodowska )
was the first woman to earn a Nobel prize and the first person to earn two.
In 1898, she isolated two new elements (polonium and radium)
by tracking their ionizing radiation, using the electrometer
of Jacques and Pierre Curie
In 1908, Henrietta Swan Leavitt
published the period-luminosity relationship for Cepheid variable stars,
which reveals their actual distances, even when stellar parallax is undetectable.
This paved the way for the first measurement of the expansion of the Universe
by Edwin Hubble (1929).
In a Hausdorff space (1914) two distinct points
are always disconnected.
In 1919, he introduced fractional dimensions
and defined d-dimensional measures.
Hausdorff published literary work as Paul Mongré.
Unable to escape the Nazis, he committed suicide with his wife and sister-in-law.
In 1913, Cartan established, from a purely geometrical standpoint, the relations that
lead to the quantization of spin.
He developed exterior calculus
and published his Theory of Spinors as a textbook
in 1935. Godfather of Bourbaki and father of
key Bourbakist Henri Cartan
A Sainte-Barbe bursar, he ranked first in the top three
French academic competitions of 1889:
Polytechnique, Ecole Normale.
He chose to enter the latter.
Borel developed point-set topology and
founded Measure theory.
Elected to the Académie des Sciences in 1921.
British physicist born in Nelson, New Zealand.
His investigations of alpha and beta decay (which he so named) earned him
a Nobel prize before he moved to
Manchester, where he
supervised the Geiger-Marsden
experiment (1909) and inferred the planetary model of the atom (1911).
Building on the work of Jordan and
Borel (his advisor) he laid the goundwork of
measure theory in 1901 and went on to revolutionize the notion of
definite integration in his doctoral dissertation (1902).
Lebesgue was elected to the Académie des Sciences on 29 May 1922.
Known only by his initials G.H. (for Godfrey Harold)
Hardy was asexual, entirely devoted to mathematics and cricket
(a nonpractising homosexual, said Littlewood).
His collaboration with Littlewood is legendary.
So is the way Hardy
recognized and guided Ramanujan's raw genius.
A student of Ludwig Boltzmann, she became a collaborator
of Otto Hahn who was awarded a
Nobel prize (1944)
for their joint work.
With Otto Frisch (her nephew) Lise Meitner gave
nuclear fission its name (Kernspaltung).
She correctly explained the related
mass defect (1938).
Early in his career, Bertus Brouwer
founded modern topology.
He later championed the incompatible philosophy of
which considers only sets whose elements can be shown to belong in finitely many steps.
As topology isn't intuitionistic, he wouldn't teach it at all!
Born in Budapest.
Visiting Paris in March 1908, he saw early aviation flights and decided he'd apply mathematics to aeronautics.
He became director of the Aeronautical Institute at
Aachen in 1912.
He emmigrated to the US in 1930 and received the firstNational Medal of Science, in 1963.
Born's probabilistic interpretation of Schrödinger's wave function
ended determinism in physics but provided a firm ground for
Irene Born, the eldest of his 3 children, is the mother of
Born had a Google Doodle on his 135-th Birthday (2007-12-11)
22 doctoral students
but, like Hardy, never bothered to take a doctoral degree himself.
In 1910 or 1911, he started a prolific collaboration with
G.H. Hardy which spanned 35 years.
He was so discreet that rumors once circulated that he was just a
figment of Hardy's imagination.
In 1913, Bohr started the quantum revolution
with a model where
the orbital angular momentum
of an electron only has discrete values.
He later spearheaded the Copenhagen interpretation
(i.e., probabilistic measurements cause the collapse of otherwise
linearly-evolving quantum states).
In 1926, Schrödinger matched observed quantum behavior with the properties of
a continuous nonrelativistic wave obeying the
In 1935, he challenged Bohr's Copenhagen Interpretation,
with the famous tale of Schrödinger's cat.
He lived in Dublin from 1939 to 1955.
Ramanujan lacked a formal mathematical education but, in 1913, a few of his early results
managed to startle G.H. Hardy (1877-1947) and
J.E. Littlewood (1885-1977) who invited him to
Cambridge in 1914.
Ramanujan has left an unusual legacy of brilliant unconventional results.
Born in Philadelphia
to Lithuanian parents, he was inspired by second-hand textbooks and
conceived the mad project of competing
for a Cambridge
scholarship. Against all odds, Mordell placed first (1906).
His results would set the tone for modern views of number theory
(cf. elliptic curves).
In 1929, with sketchy observational data, he saw that
galaxiesrecede at speeds proportional
to their distances from us. The coefficient of proportionality Ho
(Hubble's constant) varies inversely as the age of the Universe
(thus proved to be expanding,
by the cosmological principle).
In 1923, he proposed that any particle could behave
like a wave of
wavelength inversely proportional to its momentum
(this helps justify Schrödinger's equation).
He predicted interferences for an electron beam hitting a crystal.
The Hasse-Minkowski theorem (1921)
transfers arithmetical questions to
The Hasse invariant of a non-singular algebraic curve over a finite field is the
rank of its Hasse-Witt matrix.
In 1937, Hasse's application to the Nazi party was denied because
he had a Jewish great-grandmother.
In 1925, Wolfgang Pauli formulated the exclusion principle
which explains the entire table of elements.
His Godfather was Ernst Mach.
Pauli's sharp tongue was legendary; he once said about a bad paper:
"This isn't right; this isn't even wrong."
In 1926, Fermi helped formulate the Fermi-Dirac statistics
obeyed by what we now call fermions.
He identified the neutrino in beta-decay.
He discovered slow neutrons and the radioactivity they induce.
On December 2, 1942, Fermi produced the first self-sustaining nuclear
He is credited with the
stored program architecture (1946) whereby a computer uses
its primary memory space to store both the data it operates on and the
codes for the programs it executes.
Von Neumann pioneered game theory,
automata theory and fault-tolerant systems.
Son of Elie Cartan (1869-1951).
A key founder, with Weil, of the
Bourbaki group (1935) which would consume a
large part of his research activities.
He was the leading professor at ENS for several decades.
Cartan was instrumental in reconciling French and German mahematics after WWII.
In 1944, Thomas Harold Flowers built the first large-scale electronic
computer (Colossus) at
As the accomplishment remained classified for decades, Flowers was deprived
of the glory which went instead to
Eckert for the
ENIAC (Philadelphia, 1946).
The completeness theorem in his dissertation (1929)
states that a statement true in everymodel of an axiomatic
system is provable in it. His more famous incompleteness theorem
says that, in any model of a set of axioms covering arithmetic,
some true statements are not provable.
Brother of the philosopher Simone
Weil (1909-1943) but unrelated to the politician
Simone Veil (1927-2017).
He was the leading founder of Bourbaki.
Weil established the field of algebraic geometry
and, arguably, charted the course of much abstract mathematics
in the twentieth century.
He fled Germany in 1933, after losing his post at
because of his Jewish ancestry.
In 1935, he got a position at Cornell,
which he never left except for wartime work at MIT and
(as head of the theoretical division).
Nobel prize for his work on nuclear fusion in
stars of all sizes.
Arguably the most brilliant of a dozen
Via Panisperna boys
selected by Fermi (including the likes of
Majorana published only 9 scientific papers but left a huge 10,000-page legacy
of notebooks written between 1927 and 1932.
He organized his own disappearance in March 1938.
Claude Chevalley was born in Johannesburg,
where his father was serving as French Consul.
His parents were the authors of the Oxford Concise French Dictionary.
He entered ENS at the early age of 17.
He was the youngest founding Bourbakist (1935).
He revived Clifford algebras.
Chandra was the nephew of Raman
(1888-1970; Nobel 1930).
On Chandra's 107th birthday, Google's home page in 28 countries featured an animation illustrating the
Chandrasekhar limit (1.44 solar masses)
beyond which a star's death can only yield a
neutron star or a black hole.
Top code-breaker of Bletchley Park
A Turing Machine is a finite automaton endowed with an infinite
read/write tape on which it can move back and forth, one step at a time.
Turing showed that such a machine is capable
of computing anything that any other machine could.
Paul Erdös wrote over 1500 papers with 511 collaborators.
He contributed many conjectures and proved some great ones.
Faced with antisemitism, he left Hungary in 1934 and spent the
rest of his frugal life on the road, touring mathematical centers.
"One night in 1944", he figured out that the distributions
used in theoretical physics
(including Dirac's delta) weren't pointwise functions
but linear forms over a restricted set of
smooth test functions. The Fourier transform turns out to
be a linear automorphism
among tempered distributions.
In 1949, he introduced
to describe the relativistic quantum theory of
electromagnetic interactions known as
electrodynamics (QED) using perturbation theory.
This has helped visualize all other types of fundamental interactions ever since.
Robinson's non-standard analysis (1961)
gave a rigorous footing to the infinitesimals
introduced by Leibniz (1675)
thus providing an alternative basis for analysis
(competing with the approach made standard by Cauchy
This was an early application of
With Robert Mills (1927-1999) in 1954,
Frank Yang generalized the
of Weyl (1919).
Yang-Mills theory, is now the paradigm for the modern description of all interactions.
With T.D. Lee
and Chien-Shiung Wu (1912-1997)
Yang found beta-decay to violate parity (1956).
Born in England, Dyson went to
Cornell as a student
(1947) and went on
to replace Feynman there, without ever getting a doctorate.
In 1949, he showed Feynman's QEDdiagrams to be equivalent,
to the methods of Schwinger or
Dyson joined the IAS in Princeton in 1953 and never left.
A Bourbakist noted for broad contributions in fields like
topology, group theory and number theory
(particularly Galois representations and modular forms).
First prize for mathematics in
Concours Général (1944).
Youngest Fields medalist (in 1954) and first Abel prize recipient (2003).
In his 1950 thesis about non-cooperative games)
The notion of a
makes game theory relevant
to many real-life situations. Nash battled
schizophrenia for decades,
but willed it off before receiving
the Nobel prize in economics, at 66, and the
Abel prize, at 86 (2015).
John Stewart Bell earned his PhD in nuclear physics at
Birmingham in 1956.
In 1960, he and his wife
gave up tenured positions to work at
CERN for the rest of their careers.
After a year-long sabbatical from CERN, John published his masterpiece:
"On the EPR paradox" (1964).
In algebraic geometry,
the index theorem (1963) equates the topological index
of an elliptic differential operator, on a compact manifold,
to its algebraic index (pertaining to the dimension of the space of solutions).
This very general theorem has many specializations and applications.
An early proponent of the chirality of weak interactions (1958)
he dubbed strangeness one
they don't conserve.
Gell-Mann gave "quarks" their name and
called color what they trade.
The same scheme was independently proposed by
George Zweig (1937-) using the word aces.
His father, Lionel,
was a geneticist. His mother, Margaret, was a physician.
His older brother, Oliver,
became a professor of mathematics. His younger brother,
was 10 times British Chess Champion, perhaps the most talented ever.
Roger penrose put forth twistors in 1967.
In 1967, he formulated the electroweak unification of the
weak nuclear force and electromagnetism,
predicting a massive neutral messenger
particle (the Z boson) which was first observed in 1979.
Steven Weinberg gave the Standard Model its name.
["To Explain the World", 2015.]
His invention of the technique of forcing revolutionized logic
and allowed him to prove, in 1963, the undecidability of Cantor's
continuum hypothesis (CH):
Gödel had shown CH to be compatible with the
axioms of set theory and
Cohen proved the same for the negation of CH...
In 1970, Conway found the simple rules of a cellular automaton
(the Game of Life)
capable of self-replication and universal computation.
His many other original contributions include
the ultimate extension of the ordered number line:
surreal numbers (1973).
Donald Ervin Knuth made the
rigorous analysis of algorithms a key aspect of computer science.
theory studies the best possible
performance of all procedures that can solve a given problem
(running time and/or memory-space used, as functions of input data size).
Diagnosed with ALS
at age 21, he wasn't expected to reach his 25th birthday, but went on to establish
the pointlike nature of the Universe's origin.
Communicating only via one cheek muscle,
he achieved a legendary status in the public eye. Hawking's fame in physics
is second only to Einstein's.
Dame Jocelyn Bell Burnell discovered the first pulsar
(neutron star) in July 1967 and the
next three shortly thereafter.
She was then a Ph.D. student supervised by Antony Hewish
(who would be awarded a Nobel prize in physics,
for their subsequent joint work).
Alan Guth (MIT) came up with the idea of cosmic inflation
in 1979 to explain the extremely even distribution of the contents of the Universe at the beginning
of the Big Bang. For this, he shared the 2002
ICTP Dirac Medal
with Andrei Linde
(Stanford) and Paul Steinhardt (Princeton).
He was awarded a Fields Medal (1990) for his mathematical contributions to
a physical theory
(String Theory) which captured the hearts of generations
of physicists without any empirical support.
In 1995, Witten unified the 5 or 6 flavors of that theory under a single umbrella
he called M-Theory.
He worked secretly on a proof of Fermat's last theorem
for seven years before offering it for publication in 1993.
A flaw discovered by Nick Katz
required new insights and the collaboration of
By resolving the issue on 1994-09-19, Andrew Wiles
achieved worldwide fame!
Grigori Yakovlevich Perelman turned down the Fields Medal (2006)
and a million-dollar Clay prize (2010) for his 2002 proof of
Thurston's geometrization conjecture,
implying the legendary
Poincaré conjecture (1904).
Since 2005, Perelman has been living as a