Appearance
3.2 — The Physicists
Physics is a small field with a long memory. Nearly everyone on this page knew, taught, argued with or corrected someone else on it.
Before the twentieth century
Why is Newton considered the greatest, and what was he like?
Isaac Newton (1642–1727) did four things, any one of which would be a career: the three laws of motion, universal gravitation, the decomposition of white light into colours, and — independently of Leibniz — the calculus.
He did much of it in eighteen months from 1665 to 1666, sent home from Cambridge because the university closed for plague. He called it his annus mirabilis.
He was also a difficult and frequently unpleasant man. He conducted a vicious campaign against Leibniz over priority in calculus, including writing an "impartial" report for the Royal Society as its president and then anonymously reviewing it himself favourably. He fell out with Hooke, Flamsteed and others. As Master of the Mint he pursued counterfeiters with genuine enthusiasm and had several hanged.
And the majority of his writing was not physics. He left millions of words on alchemy and on biblical chronology, calculating dates for the end of the world. Keynes, who bought a trunk of his papers at auction in 1936, wrote that Newton was "not the first of the age of reason, he was the last of the magicians" — the last person who believed the universe was a riddle set by God to be read in the evidence, and who happened to be right about several parts of it.
What did Faraday do without any mathematics at all?
Michael Faraday (1791–1867) was a blacksmith's son, apprenticed to a bookbinder, who read the books he was binding. He talked his way into a job washing bottles for Humphry Davy at the Royal Institution and became the greatest experimentalist of the century.
He discovered electromagnetic induction in 1831: move a magnet near a coil of wire and a current flows in the wire. That single fact is every generator and every transformer, and therefore the entire electrical supply of the world. He also discovered electrolysis, diamagnetism, and the rotation of polarised light by a magnetic field, which was the first hint that light and magnetism are the same subject.
His most original contribution is conceptual. Everyone else thought of electricity and magnetism as forces acting instantly across empty space. Faraday could not do the mathematics for that, so he pictured space itself as filled with lines of force — a physical thing, bending and stretching, with the magnet merely a source. He was mocked for it. It is correct, and the modern idea of a field, which is how every fundamental force is now described, is his picture.
He refused a knighthood and refused to work on chemical weapons for the Crimean War. He started the Royal Institution Christmas Lectures for children, which still run.
Why do physicists talk about Maxwell the way they do?
Because James Clerk Maxwell (1831–1879) took Faraday's pictures and turned them into equations, and the equations said something nobody expected.
He assembled the known laws of electricity and magnetism, found them inconsistent, and added a missing term. The resulting set of equations then predicted waves in the electromagnetic field — and when he calculated how fast those waves travel, out came a number that matched the measured speed of light.
Light is an electromagnetic wave. That was the first unification of two apparently unrelated parts of physics, it predicted radio waves before anyone had made one, and it is why Einstein kept a picture of Maxwell on his study wall alongside Newton and Faraday.
He also produced the first colour photograph, worked out the statistical distribution of molecular speeds in a gas, proved that Saturn's rings must be made of many separate particles, and did all of it before dying of abdominal cancer at 48 — the same age his mother had died of the same disease.
The revolution
What is Marie Curie's real distinction?
She is the only person to win Nobel Prizes in two different sciences — physics in 1903, shared with Pierre Curie and Henri Becquerel, and chemistry in 1911 alone.
Born Maria Skłodowska in Warsaw under Russian rule, where universities were closed to women, she attended an illegal underground "Flying University", worked as a governess to fund her sister's studies in Paris on the agreement that the sister would then fund hers, and arrived in Paris at 24.
The physical work was brutal. To isolate radium she processed several tonnes of pitchblende residue by hand in an unheated shed, stirring boiling vats with an iron rod nearly as tall as she was, and ended with about a tenth of a gram of radium chloride. She and Pierre refused to patent the isolation process, on the grounds that it belonged to science.
In the First World War she equipped vans with X-ray machines, trained women to operate them, and drove to the front herself; around a million wounded soldiers were examined with them. She died in 1934 of aplastic anaemia, almost certainly from cumulative radiation exposure.
Her daughter Irène Joliot-Curie won the chemistry Nobel in 1935.
What did Bohr contribute besides the atom picture everybody draws?
Niels Bohr (1885–1962) produced the 1913 model in which electrons occupy fixed orbits and jump between them by emitting or absorbing a precise packet of light. It is wrong in detail and it was the right wrong idea — it explained the exact colours hydrogen emits, which nothing else could, and it forced everyone to accept that atomic energies come in discrete levels.
His larger role was as an institution. His institute in Copenhagen became the place where quantum mechanics was argued into shape, and almost every major figure of the next generation passed through it. The Copenhagen interpretation — that quantum mechanics describes what we can say about a system rather than an underlying reality with definite values — carries the city's name because of him.
His decade-long argument with Einstein is the most famous disagreement in modern physics. Einstein kept constructing thought experiments intended to show quantum mechanics was incomplete; Bohr kept finding the flaw, on at least one occasion using Einstein's own general relativity to do it. Neither convinced the other, and the questions they raised turned out to be experimentally testable decades later, which is the best possible outcome of a philosophical argument.
He escaped occupied Denmark in 1943 in the empty bomb bay of a Mosquito aircraft, passed out from lack of oxygen because the helmet did not fit over his head, and survived.
What did Feynman actually do, apart from the stories?
Richard Feynman (1918–1988) shared the 1965 Nobel Prize for quantum electrodynamics, the theory of how light and matter interact. It is the most precisely tested theory in science: one of its predictions agrees with measurement to about twelve decimal places, which is like measuring the distance from New York to Los Angeles to within the width of a hair.
His distinctive contribution is the Feynman diagram, a way of drawing an interaction between particles as lines and vertices, where each diagram corresponds to a specific mathematical term. It turned an intractable calculation into a bookkeeping exercise a graduate student could do, and it is now how physicists think about particles, not merely how they compute.
He also worked out how superfluid helium behaves, proposed a model of the proton's insides, and gave a 1959 lecture called "There's Plenty of Room at the Bottom" that anticipated nanotechnology.
And he did the thing on the Challenger commission. Investigating the 1986 shuttle disaster, he cut through months of institutional evasion by dropping a piece of the O-ring seal material into a glass of ice water on live television and showing it lost its resilience. His appendix to the report ends with a line worth memorising: "For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled."
India's physicists
Why is it called a boson?
After Satyendra Nath Bose (1894–1974), who worked at Dhaka University and, in 1924, derived Planck's radiation law from scratch by counting the ways identical particles of light can be distributed among energy states — treating photons as genuinely indistinguishable, so that swapping two of them does not produce a different arrangement.
The paper was rejected by a British journal. He sent it directly to Einstein, who recognised what it was, translated it into German himself, and had it published — then extended the method to atoms, which is why the statistics are called Bose-Einstein.
Every particle in the universe is either a boson or a fermion, depending on whether it follows Bose's statistics or Fermi's. Bosons can pile into the same state without limit, which is what makes a laser and a superconductor possible; fermions cannot, which is what makes atoms have structure and matter take up space.
Bose was never awarded a Nobel Prize. Asked about it, he said he had received all the recognition he deserved.
What is the Raman effect, and why does it matter?
C. V. Raman (1888–1970) noticed on a voyage back from England that the Mediterranean was a deeper blue than could be explained by reflection of the sky, and spent years working out why. The answer was scattering of light by the water molecules themselves.
Pursuing it further, he and K. S. Krishnan found in 1928 that when light passes through a transparent substance, a very small fraction of it comes out at a slightly different colour — having given up or gained a precise amount of energy to a vibration of the molecule it hit.
That shift is a fingerprint. Since every molecule vibrates at its own set of frequencies, measuring the shifted light identifies the substance without touching it, without destroying it, and through glass or plastic packaging. Raman spectroscopy is now used in pharmaceutical quality control, art conservation, gemstone identification, airport security, and by the Mars rovers.
He did it with equipment costing a few hundred rupees, and won the Nobel Prize in 1930 — the first Asian to win it in any science. He had booked his tickets to Stockholm before the announcement.
What is the Chandrasekhar limit?
Subrahmanyan Chandrasekhar (1910–1995) worked it out at nineteen, on a ship from Madras to England.
When a star runs out of fuel it collapses until the pressure of its own tightly packed electrons stops it — a white dwarf. Chandrasekhar calculated what happens when the star is heavy: the electrons are squeezed to near light speed, relativity changes how their pressure behaves, and above about 1.4 times the mass of the sun the pressure cannot win. The star keeps collapsing.
Arthur Eddington, then the most powerful astrophysicist alive and Chandrasekhar's own mentor, ridiculed the result publicly at a Royal Astronomical Society meeting in 1935, saying there must be a law of nature preventing a star from behaving so absurdly. Chandrasekhar was 24, and the community sided with Eddington.
He was right, and the absurd behaviour is a neutron star or a black hole. He left the field, moved to Chicago, and rebuilt his career several times over in different areas of astrophysics. He received the Nobel Prize in 1983, almost fifty years later. NASA's Chandra X-ray Observatory is named for him.
His uncle was C. V. Raman.
Two more worth knowing
Who was Lise Meitner?
The physicist who explained nuclear fission and was left off the Nobel Prize for it.
Meitner (1878–1968) worked with the chemist Otto Hahn in Berlin for thirty years. She was Jewish, and in 1938 fled to Sweden with almost nothing. Hahn continued the experiments and got a result he could not explain: bombarding uranium with neutrons produced barium, an element half its size.
He wrote to Meitner. She and her nephew Otto Frisch worked it out walking in the snow over Christmas — the nucleus was splitting in two, and using Einstein's mass-energy relation they calculated the energy released, which was enormous. Frisch named it fission after the division of a biological cell.
Hahn received the 1944 Nobel Prize in Chemistry alone. Meitner was nominated dozens of times and never won. She refused to work on the atomic bomb, saying she would have nothing to do with it, and later said she was ashamed the discovery had been used that way. Element 109 is named meitnerium.
Was Tesla a genius or a myth?
Both, and separating them is worth doing.
The real achievements are enormous. Nikola Tesla (1856–1943) developed the polyphase alternating current system — the generators, motors and transmission arrangement that the world's electricity grid still uses. The induction motor, which runs a very large fraction of the world's industrial machinery, is his. He did fundamental work on radio, and the US Supreme Court upheld his patent priority over Marconi's in 1943. The unit of magnetic field strength is named after him.
The myth is the later Tesla. He claimed a death ray, wireless power transmission to the whole planet, and communication with Mars, and produced no working evidence for any of it. He died in a New York hotel room, in debt, having spent decades on projects that did not come off.
The popular contrast with Edison as a heroic inventor versus a greedy businessman is too simple in both directions. Edison was a formidable inventor and a ruthless competitor; Tesla was a formidable inventor and a poor businessman who signed away his royalties. The lesson people take from Tesla — that being right is not sufficient — is the accurate one.
What comes next
The next page covers the people who worked on living things: the chemists who found what matter is made of, the doctors who worked out what makes us ill, and the researcher whose photograph solved DNA and whose name was left off the paper.