# Four Hundred Years > Galileo was born in 1564; Turing died in 1954. In the 390 years between them, eleven people worked out how to settle an argument about the world: measure it, publish how, predict something new, and lose in public when the measurement disagrees. Scrub the timeline, see how long each idea waited to be believed, and trace who needed whom. The overview of the Great Scientists series. Interactive film: https://www.planetpast.com/stories/great-scientists-timeline/ Publisher: PlanetPast (https://www.planetpast.com/) · Published 2026-10-13 · History, Physics, Biology ## Prologue ### Four hundred years *Great Scientists* Eleven people and the method they built between them. Galileo was born in 1564. Turing died in 1954. Three hundred and ninety years. In that time eleven people, who mostly never met, worked out a way of settling arguments about the world that does not depend on who is asking. Measure it. Write down how you measured it. Predict something that has not happened yet. And when the measurement disagrees with you, say so in public. This is the map of the whole series. Every bar on it is one episode. ![Everything in this series was argued out in print, in public, and most of it was resisted.](https://www.planetpast.com/stories/great-scientists-timeline/img/c00.jpg) - **11**: people - **390**: years - **1**: method > If I have seen further it is by standing on the shoulders of giants. (Isaac Newton, 1675) Overview · Great Scientists #### Four hundred years Eleven lives, from **1564** to **1954**. Each bar on the timeline is one episode of the series; this film is the map of all of them. How to use: pick a chapter below or press ← → to change step · ▶ plays the step · drag to rotate · three steps have buttons you can press. Sources: [Wikipedia: history of science](https://en.wikipedia.org/wiki/History_of_science); [Wikipedia: the Scientific Revolution](https://en.wikipedia.org/wiki/Scientific_Revolution) ## Chapter I · The method ### Four moves *Chapter I · The method* None of them is clever. Together they are the most powerful thing we have. The method is not complicated, and no single person invented it. Measure something and write the number down. Publish how you measured it, so a stranger can repeat it and disagree. Use it to predict something nobody has seen yet. And when the measurement contradicts you, lose the argument in public. That last move is the hard one. It is also the one that makes the whole thing work. Before about 1600, the usual way to settle a question about nature was to find out what an authority had said about it. After 1600, slowly, it became normal to go and look. ![A lens, a pendulum, a graduated scale. The argument moves from the library to the bench.](https://www.planetpast.com/stories/great-scientists-timeline/img/c01.jpg) - Measure, and write down the number - Publish how you did it, so others can repeat it - Predict something not yet observed - Let the measurement overrule you - **1543**: Copernicus and Vesalius both publish - **1660**: the Royal Society is founded Chapter I · Step 1 #### Four moves Measure it. Publish how. Predict something new. Lose in public when the measurement disagrees. The last move is the one that does the work. Sources: [Wikipedia: the Scientific Revolution](https://en.wikipedia.org/wiki/Scientific_Revolution); [Wikipedia: history of science](https://en.wikipedia.org/wiki/History_of_science) ### Move the year *Chapter I · Interactive* Drag the century and see who is at work. Press the buttons and move the marker along the century. The readout tells you who is alive at that moment and what has just happened. Some of the overlaps are startling. Newton was born at the end of the year Galileo died, by the calendar England was still using. Darwin and Mendel were alive at the same time for sixty years, three days’ travel apart, and neither ever read the other’s most important work. Einstein was alive for every single day of Turing’s life. - Newton was born the year Galileo died - Darwin and Mendel were alive together for sixty years - Einstein was alive for every day of Turing’s life - Lavoisier is the only one killed by a government — until 1952 - **1642/3**: Galileo dies, Newton is born - **1900**: Mendel is rediscovered - 1564–1642: Galileo - 1809–1882: Darwin - 1879–1955: Einstein - 1912–1954: Turing Chapter I · Step 2 · **Interactive** #### Move the year Push the marker along the timeline and watch who is at work. **Newton** was born at the end of the year **Galileo** died; **Darwin** and **Mendel** overlapped for sixty years and never read each other. Buttons move the year by ten or fifty; **Run** sweeps the whole four centuries. Sources: [Wikipedia: Galileo Galilei](https://en.wikipedia.org/wiki/Galileo_Galilei); [Wikipedia: Isaac Newton](https://en.wikipedia.org/wiki/Isaac_Newton); [Wikipedia: Charles Darwin](https://en.wikipedia.org/wiki/Charles_Darwin); [Wikipedia: Gregor Mendel](https://en.wikipedia.org/wiki/Gregor_Mendel) ## Chapter II · The sky and the law ### The sky is not perfect *Chapter II · 1610* Four points of light that did not go round the Earth. Galileo did not invent the telescope, but he built a much better one and pointed it at Jupiter. Four points of light shifted position night after night. They were going round Jupiter, not round the Earth, and that was enough to show the Earth is not the only centre. He also saw mountains on the Moon, spots on the Sun, and the phases of Venus, which Ptolemy’s system cannot produce. For publishing it he was tried in 1633 and spent the rest of his life under house arrest. ![He pointed a nine-power tube at Jupiter and found four things going round it.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-galileo.jpg) - 1609: builds a telescope of about 20× - Jan 1610: four moons beside Jupiter - 1632: the Dialogue - 1633: tried, and under house arrest for life - **4**: moons - **206**: years before Rome gave way Chapter II · Step 3 #### The sky is not perfect Four moons beside Jupiter in January **1610**, mountains on the Moon, and the phases of Venus. Tried in **1633**, house arrest for life. Episode: Four Lights Beside Jupiter Sources: [Wikipedia: Galileo Galilei](https://en.wikipedia.org/wiki/Galileo_Galilei); [Wikipedia: the Galileo affair](https://en.wikipedia.org/wiki/Galileo_affair) ### One law for the apple and the Moon *Chapter II · 1687* Falling is not a special case. It is the general case. Newton was born at the end of 1642, the year Galileo died. His move was to notice that the apple and the Moon are doing the same thing. The Moon is sixty Earth-radii away, so if the force weakens as the square of the distance, its acceleration should be three thousand six hundred times smaller than the apple’s. He worked out what that acceleration actually is from the length of the month, and the numbers matched. The Principia of 1687 turned the sky into arithmetic. It took Europe about fifty years to accept it. ![The same force that drops an apple holds the Moon in its orbit — and he checked the number.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-newton.jpg) $$a_{\text{Moon}} = \frac{g}{60^{2}} \approx 0.0027\ \mathrm{m/s^{2}}$$ The Moon is sixty Earth-radii away, so its acceleration should be 3,600 times smaller than an apple’s. It is. - **1687**: the Principia - **1**: law for everything that falls Chapter II · Step 4 #### One law for the apple and the Moon The Moon is **60** Earth-radii out, so an inverse-square force makes its acceleration **1/3600** of an apple’s — about **0.0027 m/s²**, which is what the month gives. The **Principia**, 1687. Episode: The Apple and the Moon Sources: [Wikipedia: Isaac Newton](https://en.wikipedia.org/wiki/Isaac_Newton) ## Chapter III · Matter ### Nothing is created, nothing is lost *Chapter III · 1789* Weigh the vessel before and after. The number does not move. Lavoisier’s instrument was the balance, and his contribution was to insist on it. Burn something in a sealed vessel and weigh the whole vessel before and afterwards. The mass does not change. Burning is not something leaving the substance; it is something in the air joining it. He named that something oxygen, and in 1789 published the first recognisably modern list of elements. Five years later the Revolution executed him for having been a tax farmer. He was fifty. ![Her drawings and translations are part of the work; the instruments on the table are the argument.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-lavoisier.jpg) - **40.0 g**: in - **40.0 g**: out, in a sealed vessel - Burning is combination with a gas, not loss of phlogiston - He names oxygen and hydrogen - 1789: the first modern list of elements - 1794: guillotined, aged 50 Chapter III · Step 5 #### Nothing is created, nothing is lost Weigh a sealed vessel before and after burning: the mass is unchanged. Burning is combination with **oxygen**, not loss of phlogiston. The **Traité** of 1789; the guillotine in 1794. Episode: The Balance and the Blade Sources: [Wikipedia: Antoine Lavoisier](https://en.wikipedia.org/wiki/Antoine_Lavoisier) ### The gaps predicted the elements *Chapter III · 1869* A classification that makes predictions is a theory. Mendeleev lined up the sixty-odd known elements by atomic weight and found that their properties repeat. The important decision was what to do when the pattern did not fit. Instead of forcing it, he left the square empty and described the element that would eventually fill it: its weight, its density, the colour of its oxide. Gallium turned up in 1875, scandium in 1879, germanium in 1886. He had predicted a weight of 72.64 for the last one; the measured value is 72.63. A classification that makes predictions has stopped being a filing system. ![He left holes in the table and said what would fit them.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-mendeleev.jpg) - **72.64**: his predicted weight for eka-silicon - **72.63**: germanium, found 1886 - 1869: elements ordered by weight repeat in their properties - He leaves gaps rather than force the fit - Gallium 1875, scandium 1879, germanium 1886 - A table that tells you what you have not found Chapter III · Step 6 #### The gaps predicted the elements Ordered by weight, the elements’ properties repeat. Mendeleev left the misfits as **gaps** and described what would fill them — eka-silicon at **72.64**, germanium measured at **72.63**. Episode: The Gaps He Left Empty Sources: [Wikipedia: Dmitri Mendeleev](https://en.wikipedia.org/wiki/Dmitri_Mendeleev) ## Chapter IV · Life ### Descent with modification *Chapter IV · 1859* Three facts and a conclusion that is hard to escape. Darwin’s argument needs only three observations. More offspring are born than can possibly survive. Individuals differ from each other. Some of those differences are passed on. If all three are true, then the variants that happen to survive will be over-represented in the next generation, and the species will drift. Nobody has to be steering. He had the argument by 1838 and published in 1859, pushed into print by a letter from Alfred Russel Wallace with the same idea in it. On the Galápagos today, average finch beak depth measurably shifts from one drought to the next. ![He sat on the argument for twenty years and then had to publish in a hurry.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-darwin.jpg) - More are born than can survive - Individuals vary, and some variation is inherited - The variants that survive leave more offspring - Repeat for long enough and species change - **1859**: On the Origin of Species - **9.4 → 10.2 mm**: finch beaks after one drought Chapter IV · Step 7 #### Descent with modification More are born than survive; individuals vary; some variation is inherited. Everything else follows. Published in **1859** after twenty years, and only because **Wallace** had found the same idea. Episode: Endless Forms Sources: [Wikipedia: Charles Darwin](https://en.wikipedia.org/wiki/Charles_Darwin) ### Inheritance comes in particles *Chapter IV · 1866* The ratio is three to one, and it will not go away. Darwin had a problem he could not solve: if inheritance blends, variation halves every generation and selection has nothing left to work on. Three hundred kilometres away, a monk counting peas had the answer. Mendel grew about twenty-eight thousand plants and found that the second generation splits three to one. That is what you get if inheritance comes in discrete particles that can hide in one generation and reappear in the next. He published in 1866. It was read by almost nobody, and the result sat unused for thirty-four years. ![Twenty-eight thousand pea plants, counted one at a time.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-mendel.jpg) - **3 : 1**: the ratio in the second generation - **34**: years before anyone noticed - Blending inheritance would halve variation every generation - Particles do not: they hide and reappear - Which is exactly what selection needs - Rediscovered in 1900 by three botanists at once Chapter IV · Step 8 #### Inheritance comes in particles Mendel’s peas split **3 : 1** in the second generation — the signature of discrete inherited factors, not blending. Published **1866**, rediscovered **1900**, and it is what makes Darwin’s mechanism work. Episode: Three to One Sources: [Wikipedia: Gregor Mendel](https://en.wikipedia.org/wiki/Gregor_Mendel); [Wikipedia: the modern synthesis](https://en.wikipedia.org/wiki/Modern_synthesis_(20th_century)) ## Chapter V · The invisible ### Matter comes apart by itself *Chapter V · 1898* An atom is not the end of the story. Marie Curie measured the activity of uranium ore with an electrometer and found it was stronger than the uranium in it could account for. Something else was in there. She and Pierre spent four years processing tonnes of pitchblende to get a tenth of a gram of radium chloride, enough to measure an atomic weight. Her real claim was not the new elements. It was that the radiation is a property of the atom itself — which means an atom can fall apart. Two Nobel Prizes, in physics and in chemistry, and a dose that eventually killed her. ![Her instrument was an electrometer: radiation measured as a current, not guessed at.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-curie.jpg) - **0.1 g**: of radium chloride from tonnes of ore - **1903 · 1911**: two Nobel Prizes, in two subjects - Pitchblende is more active than its uranium explains - So something else must be in it - Polonium and radium, 1898 - Radioactivity is a property of the atom itself Chapter V · Step 9 #### Matter comes apart by itself Pitchblende was too active for its uranium, so something else was in it: **polonium** and **radium**, 1898. The deeper claim was that radioactivity belongs to the **atom** — atoms are not permanent. Episode: A Tenth of a Gram Sources: [Wikipedia: Marie Curie](https://en.wikipedia.org/wiki/Marie_Curie) ### Gravity is the shape of spacetime *Chapter V · 1915* Falling is not being pulled. It is going straight in a bent place. Einstein’s starting point was that a person in free fall does not feel their own weight, so gravity and acceleration cannot be told apart locally. Follow that through and gravity stops being a force and becomes the shape of spacetime. Things in free fall go straight; the straight lines are bent. The theory was finished in 1915 and made a prediction nobody could argue with: starlight passing the Sun should bend by a specific amount, twice the Newtonian value. The 1919 eclipse measured it. The satellites above you apply the correction continuously. Without it, GPS would drift about eleven kilometres a day. ![A man in free fall does not feel his own weight. He called it the happiest thought of his life.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-einstein.jpg) $$\Delta t = 38\ \mu\mathrm{s/day} ;\Rightarrow; 11.4\ \mathrm{km/day}$$ Uncorrected, relativity would put GPS positions 11.4 km out after a single day. - **1905**: four papers in one year - **1919**: the eclipse measurement Chapter V · Step 10 #### Gravity is the shape of spacetime Free fall feels like nothing, so gravity is not a force but geometry. Finished **1915**, confirmed by the **1919** eclipse, and applied every second by GPS — uncorrected, it drifts about **11 km a day**. Episode: The Happiest Thought Sources: [Wikipedia: Albert Einstein](https://en.wikipedia.org/wiki/Albert_Einstein) ## Chapter VI · Earth and number ### The continents move *Chapter VI · 1912* Right about the what, wrong about the how — and that was enough to bury it. Wegener put together coastlines that fit, rock belts that continue across oceans, the same fossil plant on five continents, and coal in Antarctica. The conclusion was that the continents were once joined and have moved apart. The evidence was strong and the reaction was hostile, because he could not say what force moves a continent. He died on the Greenland ice in 1930, aged fifty, with the idea still rejected. In the 1960s the sea floor turned out to be spreading, carrying the continents with it, and the magnetic stripes on either side of the ridges are mirror images. He had been right for half a century. ![He was right about the fact and wrong about the mechanism, and the mechanism is what people judged.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-wegener.jpg) - The coastlines fit, and so do the rock belts across them - The same fossil plant lies on five separated continents - Coal in Antarctica; glacier scars in India - But he had no force that could move a continent - **1912**: he proposes it - **~1965**: the sea floor supplies the mechanism Chapter VI · Step 11 #### The continents move Fitting coastlines, continuous rock belts, one fossil plant on five continents, coal in Antarctica — and no mechanism, which is why it was rejected until **sea-floor spreading** supplied one around 1965. Episode: The Fit Sources: [Wikipedia: Alfred Wegener](https://en.wikipedia.org/wiki/Alfred_Wegener); [Wikipedia: plate tectonics](https://en.wikipedia.org/wiki/Plate_tectonics) ### Formulas from nowhere *Chapter VI · 1913* Hardy had to decide whether it was a crank or a genius. It took him an evening. In January 1913 a clerk in Madras posted nine pages of formulas to a Cambridge mathematician he had never met, with no proofs attached. Hardy later said they must be true, because nobody would have had the imagination to invent them. Their joint work on partitions produced a formula that is accurate enough to pin down an exact integer: the number of ways to write a hundred as a sum of positive integers is one hundred and ninety million, five hundred and sixty-nine thousand, two hundred and ninety-two. Ramanujan died in 1920 at thirty-two, leaving notebooks that mathematicians were still proving results from seventy years later. ![Nine pages of formulas with no proofs, from a shipping clerk, in January 1913.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-ramanujan.jpg) $$p(100) = 190{,}569{,}292$$ The Hardy–Ramanujan series gives 190,569,291.996 — round it and it is exact. - **~3,900**: results in his notebooks - **32**: years old when he died Chapter VI · Step 12 #### Formulas from nowhere A letter from Madras in **1913**, nine pages of unproved formulas. The Hardy–Ramanujan series for partitions gives **190,569,291.996** for *p*(100) — rounding to the exact **190,569,292**. Episode: A Letter from Madras Sources: [Wikipedia: Srinivasa Ramanujan](https://en.wikipedia.org/wiki/Srinivasa_Ramanujan) ## Chapter VII · The machine ### One machine can be any machine *Chapter VII · 1936* The computer began as a step in a proof. Turing answered the last great question of the series, which was about the limits of proof itself. To show that no fixed procedure can decide every mathematical statement, he first had to define a procedure — so he described a machine with a tape, a head and a table of rules. Write a machine’s rules onto the tape as data, and one machine can imitate any other. That is a computer, and the description is software. Then he showed that no machine can decide, in general, whether a program will stop. Three years later he was at Bletchley Park. In 1952 his own government convicted him for being gay. ![He invented the computer as a step in a proof about what proof cannot do.](https://www.planetpast.com/stories/great-scientists-timeline/img/p-turing.jpg) - **1.59 × 10²⁰**: Enigma settings - **1**: machine that can be any machine - A tape, a head, a state, a table of rules - Write the rules on the tape and one machine runs them all - No machine can decide whether a program halts - Bletchley Park, 1939–45, and a conviction in 1952 Chapter VII · Step 13 #### One machine can be any machine A tape, a head, a table of rules — defined in **1936** to prove that no procedure decides every mathematical question. Rules written as data make one **universal machine**, which is every computer since. Episode: The Universal Machine Sources: [Wikipedia: Alan Turing](https://en.wikipedia.org/wiki/Alan_Turing) ## Epilogue ### How long they waited *Epilogue · Interactive* Press a name. The bar is the years between the claim and the end of the argument. Here is the same eleven, measured a different way: the years between making the claim and the argument being effectively over. Einstein waited four years, because he had made a prediction that an eclipse could check. Mendeleev waited six, for gallium to be dug up. Mendel waited thirty-four, because nobody read him. Wegener waited fifty, because he had no mechanism. Darwin’s natural selection waited roughly eighty for genetics to catch up with it. And Galileo waited two hundred and six, because the question had stopped being about astronomy. Press a name and the readout gives the two dates. - Galileo: 206 years - Darwin: 80 years - Newton: 50 years - Wegener: 50 years - Mendel: 34 years - Turing: 12 years - Lavoisier: 11 years - Mendeleev: 6 years - Curie: 5 years - Einstein: 4 years - Ramanujan: 0 years - Fast when there is a number to check - Slow when the claim has no mechanism - Slowest when somebody powerful has taken a side - Being right early is not the same as being believed - **4**: years: Einstein - **206**: years: Galileo Epilogue · Step 14 · **Interactive** #### How long they waited Years from the published claim to the end of the argument: **Einstein 4**, **Curie 5**, **Mendeleev 6**, **Lavoisier 11**, **Turing 12**, **Mendel 34**, **Newton ~50**, **Wegener ~50**, **Darwin ~80**, **Galileo 206**. “Over” is a judgement, so treat the long bars as approximate. The pattern is not: a checkable prediction ends an argument fast; a missing mechanism, or an authority with a position, makes it last. Sources: [Wikipedia: the Galileo affair](https://en.wikipedia.org/wiki/Galileo_affair); [Wikipedia: the modern synthesis](https://en.wikipedia.org/wiki/Modern_synthesis_(20th_century)); [Wikipedia: plate tectonics](https://en.wikipedia.org/wiki/Plate_tectonics); [Wikipedia: Gregor Mendel](https://en.wikipedia.org/wiki/Gregor_Mendel) ### Nobody did it alone *Epilogue* Press a name to see what they were standing on. The last thing worth saying is that none of these people worked alone, and none of them started from nothing. Newton had Galileo’s falling bodies and Kepler’s orbits. Mendeleev had Lavoisier’s list of elements. The theory of evolution only became quantitative when Mendel’s peas were rediscovered thirty-four years after he published. Turing had Hilbert’s question and Gödel’s answer. Press a name and the readout says what each of them was standing on. Eleven episodes follow this one. The chapter stills are AI-generated; the portraits and documents are real, credited where they appear, and the sources are listed in every step. - Newton needed Galileo and Kepler - Mendeleev needed Lavoisier’s element list - Darwin needed Lyell’s deep time; the synthesis needed Mendel - Turing needed Hilbert’s question and Gödel’s answer ![The method outlived every one of them, which was the point of writing it all down.](https://www.planetpast.com/stories/great-scientists-timeline/img/c08.jpg) - **11**: episodes - **1**: argument, continued Epilogue · Step 15 · **Interactive** #### Nobody did it alone Every one of them inherited a question, an instrument or a number from somebody else. Press a name to see what they were standing on. - II Galileo · Newton - III Lavoisier · Mendeleev - IV Darwin · Mendel - V Curie · Einstein - VI Wegener · Ramanujan - VII Turing Chapter stills in this film are AI-generated illustrations. The portraits and the letter are real historical images, credited where they appear. Sources: [Wikipedia: history of science](https://en.wikipedia.org/wiki/History_of_science); [Wikipedia: Galileo Galilei](https://en.wikipedia.org/wiki/Galileo_Galilei); [Wikipedia: Isaac Newton](https://en.wikipedia.org/wiki/Isaac_Newton); [Wikipedia: Antoine Lavoisier](https://en.wikipedia.org/wiki/Antoine_Lavoisier); [Wikipedia: Charles Darwin](https://en.wikipedia.org/wiki/Charles_Darwin); [Wikipedia: Gregor Mendel](https://en.wikipedia.org/wiki/Gregor_Mendel); [Wikipedia: Dmitri Mendeleev](https://en.wikipedia.org/wiki/Dmitri_Mendeleev); [Wikipedia: Marie Curie](https://en.wikipedia.org/wiki/Marie_Curie); [Wikipedia: Albert Einstein](https://en.wikipedia.org/wiki/Albert_Einstein); [Wikipedia: Alfred Wegener](https://en.wikipedia.org/wiki/Alfred_Wegener); [Wikipedia: Srinivasa Ramanujan](https://en.wikipedia.org/wiki/Srinivasa_Ramanujan); [Wikipedia: Alan Turing](https://en.wikipedia.org/wiki/Alan_Turing)