Physics

The life of Albert Einstein

Timeline 1879Born on 14 March in Ulm, in southern Germany. The family soon moves to Munich. 1891At 12, receives a book of Euclidean geometry, which he would call the “holy little book”. 1895Fails the entrance exam of the Zurich Polytechnic, despite high marks in mathematics and physics. 1900Graduates in Zurich. Spends two years without a steady job. 1902Starts work at the patent office in Bern, as a “technical expert, third class”. 1905The miraculous year: four papers that change physics and a doctoral thesis. 1909Leaves the patent office and becomes a professor in Zurich. 1914Moves to Berlin, as a member of the Prussian Academy of Sciences. 1915Presents the equations of general relativity. 1919The eclipse of 29 May, observed in Sobral and on the island of Príncipe, confirms the theory. Einstein becomes world-famous. 1922His Nobel Prize in Physics for 1921 is announced, for the photoelectric effect. 1925Visits Rio de Janeiro, from 4 to 12 May. 1933With the Nazis in power, leaves Germany for good. Settles in Princeton, in the United States. 1939Signs a letter to President Roosevelt about the possibility of an atomic bomb. 1955Dies on 18 April in Princeton. ◀ Previous Follow the journey Next ▶ 1879 UlmBorn on 14 March. The family soon moves away. 1880–1894 MunichHe receives the “holy little book” of geometry and hates his school, where everything is learned by heart. 1894–1895 ItalyAt 15 he leaves school and follows his family, which has moved to Italy. 1895–1896 AarauHaving failed the Zurich exam, he finishes secondary school at a freer Swiss school. 1896–1902 ZurichHe studies at the Polytechnic and graduates in 1900. He spends two years without a steady job. 1902–1909 BernTechnical expert third class at the patent office. In 1905, the miracle year, he writes four papers that change physics. 1911–1912 PragueProfessor at the University of Prague, between two periods in Zurich. 1914–1932 BerlinA member of the Prussian Academy. He presents general relativity (1915) and becomes famous after the 1919 eclipse. 1925 Rio de JaneiroHe spends eight days in Rio, from 4 to 12 May, and is enchanted by the Botanical Garden. 1933–1955 PrincetonWith the Nazis in power, he leaves Germany. He works at the Institute for Advanced Study until his death in 1955. Enable JavaScript to see the map. The stages are listed below. From Ulm to Princeton, with a stop in Rio de Janeiro. Map: © OpenStreetMap contributors

October 14, 2026 Read

The life of James Clerk Maxwell

Timeline 1831Born on 13 June in Edinburgh, Scotland. Spends his childhood on the family estate, Glenlair. 1839His mother dies of cancer, when he is 8. 1846At 14, a paper of his on oval curves is read at the Royal Society of Edinburgh. 1850Enters the University of Cambridge. 1855Presents his theory of colour and the paper “On Faraday’s lines of force”. 1856Becomes a professor in Aberdeen, aged 25. 1859Publishes the essay on Saturn’s rings, which won the Adams Prize. Presents the distribution of molecular speeds. 1860Loses his job when two colleges merge. Moves to King’s College, London. 1861Shows the first colour photograph at the Royal Institution. 1862Calculates that electromagnetic waves travel at the speed of light. 1865Publishes “A dynamical theory of the electromagnetic field” and returns to Glenlair. 1871Becomes the first Cavendish Professor of Experimental Physics, in Cambridge. 1873Publishes the Treatise on Electricity and Magnetism. 1879Dies on 5 November in Cambridge, aged 48. ◀ Previous Follow the journey Next ▶ 1831 EdinburghBorn on 13 June. Later he studies at the Edinburgh Academy and University; at 14 a paper of his on ovals is read at the Royal Society of Edinburgh. 1831–1841 GlenlairHe spends his childhood on the family estate, asking “what’s the go of that?”. His mother dies when he is eight. 1850–1856 CambridgeHe studies at Trinity College. He presents his theory of colours and his paper on Faraday’s lines of force. 1856–1860 AberdeenA professor at 25. He wins the Adams Prize with his essay on Saturn’s rings and loses his job when the colleges merge. 1860–1865 LondonAt King’s College he shows the first colour photograph and discovers that light is an electromagnetic wave. 1865–1871 GlenlairHe returns to the country and writes the Treatise on Electricity and Magnetism. 1871–1879 CambridgeThe first Cavendish Professor, he founds the Cavendish Laboratory. He dies in 1879, aged 48. Enable JavaScript to see the map. The stages are listed below. Maxwell between Scotland and England, always returning to Glenlair. Map: © OpenStreetMap contributors

October 14, 2026 Read

The life of Blaise Pascal

Timeline 1623Born on 19 June in Clermont, in the Auvergne region of France. 1626His mother, Antoinette Begon, dies. Blaise is 3. 1631His father, Étienne Pascal, moves to Paris with his three children. 1635At 12, he rediscovers on his own that the angles of a triangle add up to two right angles. 1640At 16, he publishes the Essay on conics, with the hexagon theorem. 1642Starts building a calculating machine to help his father, a tax official in Rouen. 1647Publishes the New experiments concerning the vacuum. Descartes visits him. 1648Florin Périer, his brother-in-law, measures the weight of air by climbing the Puy de Dôme. 1654Exchanges letters with Fermat about games of chance and writes the Treatise on the arithmetic triangle. On 23 November he has his “night of fire”. 1656Begins publishing the Provincial letters under a pseudonym. 1658Solves the problems of the cycloid and launches a contest about them. 1662Opens a line of public coaches in Paris. Dies on 19 August, aged 39. 1670His friends publish the Pensées, put together from his notes. ◀ Previous Follow the journey Next ▶ 1623–1631 ClermontHe is born in Clermont, in Auvergne. His mother dies when he is three. 1631–1639 ParisHis father teaches him at home and takes him to Mersenne’s gatherings. At 16 he writes the Essay on conics. 1640–1647 RouenHis father is a tax collector in Normandy. To help him, Blaise builds the Pascaline and carries out his experiments on the vacuum. 1648 Puy de DômeAt Pascal’s request his brother-in-law Florin Périer climbs the mountain with a barometer and shows that the air weighs less at the top. 1647–1662 ParisThe letters to Fermat on games of chance, the night of fire, the Provincial Letters, the cycloid and the public coaches. He dies in 1662, aged 39. 1655 Port-Royal-des-ChampsAfter the night of fire he spends periods at the convent where his sister Jacqueline lives and defends Port-Royal against the Jesuits. Enable JavaScript to see the map. The stages are listed below. Pascal between Clermont, Paris and Rouen, and the mountain that weighed the air. Map: © OpenStreetMap contributors

October 11, 2026 Read

The life of Isaac Newton

Timeline 1643Born on 4 January at Woolsthorpe, England. In English records of the time the date is 25 December 1642. 1661Enters Trinity College, Cambridge, as a poor student. 1665–1667With the university closed by the plague, he returns home. He develops series, fluxions, the theory of colours and his first ideas on gravity. 1669Aged 26, becomes Lucasian Professor of Mathematics, succeeding Isaac Barrow. 1672Presents his reflecting telescope and publishes his theory of light and colours. 1687Publishes the Principia, paid for out of Edmond Halley’s own pocket. 1696Moves to the Royal Mint in London, first as Warden and, from 1699, as Master. 1703Becomes President of the Royal Society. 1704Publishes Opticks. 1727Dies on 31 March in London. He is buried in Westminster Abbey. ◀ Previous Follow the journey Next ▶ 1643–1661 WoolsthorpeHe is born on a farm, the posthumous son of a farmer, and goes to school in nearby Grantham. 1661–1665 CambridgeHe enters Trinity College as a poor student who pays his way by serving other students. 1665–1667 WoolsthorpeWith the university closed by the plague, he goes home. He develops series, fluxions, the theory of colours and his first ideas on gravity. 1667–1696 CambridgeHe holds the Lucasian chair, builds the reflecting telescope and writes the Principia (1687). 1696–1727 LondonHe runs the Royal Mint, at the Tower of London, and presides over the Royal Society. He dies in 1727 and is buried in Westminster Abbey. Enable JavaScript to see the map. The stages are listed below. Newton’s three places, from Woolsthorpe to Cambridge and London. Map: © OpenStreetMap contributors

October 11, 2026 Read

Colour: the spinning top and the tartan ribbon

The science of colour must therefore be regarded as essentially a mental science. — James Clerk Maxwell, “Experiments on colour” (1855) Since Newton it had been known that white light is a mixture of all the colours of the rainbow. But the colour we see is something else: it depends on the eye and the brain. The English physician Thomas Young had proposed, in 1802, that the eye has only three kinds of sensor, and that every colour we perceive is a combination of the responses of those three. It was a bold hypothesis without proof. Maxwell, aged 24, turned it into mathematics.

October 14, 2026 Read

The photoelectric effect: light comes in packets

It deals with radiation and the energy properties of light and is very revolutionary. — Albert Einstein, letter to Conrad Habicht (May 1905) In May 1905 Einstein wrote to his friend Conrad Habicht announcing four papers. Of the four, he called only one revolutionary, and it was not relativity: it was the paper on light, sent to the Annalen der Physik in March. It was for this paper that Einstein won the Nobel Prize.

October 14, 2026 Read

Pascal's triangle: build it by adding

Write a $1$. Below it, two $1$s. From then on, each row starts and ends with $1$, and each number in between is the sum of the two numbers just above it: $$\begin{array}{ccccccccccc} &&&&&1&&&&&\\ &&&&1&&1&&&&\\ &&&1&&2&&1&&&\\ &&1&&3&&3&&1&&\\ &1&&4&&6&&4&&1&\\ 1&&5&&10&&10&&5&&1 \end{array}$$That is all. A rule a child learns in a minute produces one of the richest tables in mathematics. Today it is called Pascal’s triangle, but Pascal was one of the last to find it.

October 11, 2026 Read

Brownian motion: counting the atoms

If the motion discussed here can actually be observed, then classical thermodynamics can no longer be looked upon as strictly valid for spaces distinguishable under the microscope, and an exact determination of actual atomic dimensions is then possible. — Albert Einstein, Annalen der Physik (May 1905) In 1905 many physicists and chemists still doubted that atoms existed. Chemistry worked very well with the hypothesis, but nobody had seen an atom, and important scientists, such as the Austrian physicist Ernst Mach and the German chemist Wilhelm Ostwald, thought atoms were just a convenient way of doing calculations. Einstein found a way to see them, or almost: through their effect on things big enough to show up under a microscope.

October 14, 2026 Read

Saturn's rings cannot be solid

The only system of rings which can exist is one composed of an indefinite number of unconnected particles, revolving round the planet with different velocities according to their respective distances. — James Clerk Maxwell, On the Stability of the Motion of Saturn's Rings (1859) Galileo looked at Saturn through his telescope in 1610 and thought the planet had “ears”. In 1655 Huygens realised they were a thin, flat ring that does not touch the planet. Two hundred years later, nobody knew what the ring was made of. Was it a solid disc, like a vinyl record? A liquid? A cloud of stones?

October 14, 2026 Read

Combinations: counting without listing

In Brazil’s Mega-Sena lottery you choose 6 numbers out of 60. How many different tickets are there? Listing them all would take a lifetime: there are more than fifty million. But you can count without listing, and Pascal showed how. Choosing without order Start with a small case: in how many ways can you choose 2 people out of a group of 5 to form a committee? If order mattered, there would be $5$ options for the first person and $4$ for the second: $5\cdot4=20$. But on a committee “Ana and Bruno” is the same as “Bruno and Ana”, and every pair has been counted twice. There are $20/2=10$ committees.

October 11, 2026 Read

Special relativity: a clock made of light

If I pursue a beam of light with the velocity c, the velocity of light in a vacuum, I should observe such a beam of light as an electromagnetic field at rest though spatially oscillating. There seems to be no such thing, however. — Albert Einstein, Autobiographical Notes (1949) At 16, at school in Aarau, Einstein asked himself a question: what would I see if I ran alongside a beam of light, at the same speed? According to Newton’s physics, the light would seem to stand still, like a car beside ours on the motorway. But Maxwell’s equations do not allow light at rest: for them, light always travels at $c\approx300{,}000$ km/s. Someone was wrong. Einstein took ten years to find out who.

October 14, 2026 Read

The speeds of molecules: the Maxwell distribution

I have been occupied lately with some questions about the motions and collisions of perfectly elastic spheres, as an exercise in mechanics. — James Clerk Maxwell, letter to George Stokes (30 May 1859) A litre of air contains about $2.5\times10^{22}$ molecules, all moving and colliding billions of times a second. Following each one is impossible. In 1859 Maxwell had an idea that changed physics: not to ask what each molecule does, but what fraction of them has each speed. It was the first time probabilities had been used in a law of physics. He presented the result at a meeting in Aberdeen in 1859 and published it in 1860.

October 14, 2026 Read