Questions to Ask Isaac Newton
Written for the school assignment where you interview Isaac Newton across three centuries, and for any reader who would simply like an hour with him. The questions run in the order of his life: Woolsthorpe and the plague years, the prism, the Principia, the fight with Leibniz over the calculus, the furnace and the Bible, then the Mint, the Royal Society and his last years in London. Each is tied to a letter, a notebook, a dated event or a remark somebody wrote down, so the answer you write for him can be checked.
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The questions
Each question, and why to ask it
Early years
You were born at Woolsthorpe after your father had died, and at three you were left with your grandmother when your mother remarried. What did that do to you?
Why ask it
The facts are firm: Hannah Ayscough married the clergyman Barnabas Smith and moved to his rectory a short ride away. For the feeling, the best evidence is a list of sins he wrote out at nineteen, which includes threatening to burn his mother and stepfather in their house. Quote the list to him and let him decide how much of that boy he still owns.
Your mother pulled you out of school at Grantham to run the farm, and when you did reach Cambridge it was as a subsizar, waiting on other students. What did she want for you?
Why ask it
Her brother William Ayscough, a clergyman who had been to Cambridge, and the Grantham schoolmaster Henry Stokes talked her into sending him back to school. He entered Trinity College in 1661 on the lowest rung although she was comfortably off, and biographers still ask why. The tales of sheep straying while he read under a hedge were collected from neighbors after he was famous, so write them as village memory and not as documented fact.
In your student notebook you wrote that Plato and Aristotle were your friends but truth a greater friend. Which of your teachers' books did you stop believing first?
Why ask it
The notebook is headed with Latin for 'certain philosophical questions' and shows him reading Descartes, Galileo and Boyle while the official course was still Aristotle. Cambridge University Library has put it online, so a student can name the page where he starts arguing back. A good answer picks one claim he tested, such as what Descartes said light was.
The plague closed Cambridge in 1665 and sent you home for most of two years. What did you begin there that you had not begun before?
Why ask it
Half a century later he wrote that in those days he was in the prime of his age for invention. Press him on the word 'begin': the method of fluxions, the work on colors and the first thoughts on gravity all took years more to finish, and some of the mathematics dates from Cambridge before the closure. The tidy story of one miracle year is partly his own later telling.
Did a falling apple really have anything to do with your idea of gravity?
Why ask it
He told the story himself as an old man. William Stukeley wrote down a conversation under the apple trees in 1726 in which Newton said a falling apple set him thinking about why things drop straight toward the Earth's center. Nothing in any account lands on his head, and the story surfaces sixty years after the event, when he cared a great deal about who thought of what first.
In those same years you checked whether the pull on a falling stone might reach as far as the Moon, then put the sums away for nearly twenty years. Why did you stop?
Why ask it
By his own account the numbers agreed 'pretty nearly', which is not the same as agreeing. Two explanations are on offer: a poor figure for the size of the Earth, or the fact that he could not yet show a whole globe pulls as if its matter sat at the center, which he managed around 1685. Let him pick one, then check his choice against those dates.
Light
Plenty of people owned a glass prism. What did you do with yours that they had not?
Why ask it
He darkened his room, let sunlight in through a small hole and gave the colors about twenty-two feet to spread before they hit the far wall, then asked why the patch was long instead of round. His 1672 letter to the Royal Society sets out the arrangement step by step. A class with a prism and a dark room can repeat the first half in ten minutes.
You called one test the crucial experiment: a second prism set in the path of a single color. What result would have made you give the idea up?
Why ask it
Red light sent through the second prism bends but stays red, and that is his case that white light is a mixture and the prism only sorts it. Asking for the outcome that would have sunk him shows whether the student writing the answer understands the logic. Some who tried to repeat it at the time said they could not, so he can be made to defend his method as well.
Your notebook says you slid a blunt needle in beside your own eye and pressed, to see what colors appeared. What were you trying to learn?
Why ask it
The page survives, with his drawing of the eye. He wanted to know whether color is made in the world or in the eye, and he also stared at the Sun's reflection until the afterimage troubled him for days. Use it to ask how far he would go for an answer, and tell younger readers plainly that both were dangerous and neither should be copied.
You counted seven colors in the spectrum. Why seven, and could you honestly see indigo?
Why ask it
Earlier he had named five. Orange and indigo arrived later, bringing the total to the number of notes in a musical scale, a match he wanted. In the Opticks he admits his own eyes were not sharp at telling colors apart and that an assistant marked the boundaries, a detail that goes down well in a room that has just recited the rainbow.
You built a telescope around a curved mirror, and it won you election to the Royal Society. What fault in ordinary telescopes was it meant to cure?
Why ask it
Lenses bend each color by a different amount, so every bright object wore a colored fringe. He decided the fault could never be removed from lenses and went to mirrors instead, grinding the metal himself. He was right about mirrors and wrong about lenses, since color-corrected lenses were being made within a few decades of his death, so ask whether he gave up too soon.
Robert Hooke read your first paper on light and was not persuaded, and about a year later you were asking to leave the Royal Society. Why did criticism cost you so much?
Why ask it
Henry Oldenburg, the Society's secretary, kept the letters, and they show a man who answered every objection at length and then said he wanted no more of it. The same thing happened with a group of English Jesuits at Liege a few years on. Look for whether he says his critics were wrong or merely rude, because he tended to treat the two as one offense.
In 1676 you wrote to Hooke that if you had seen further, it was by standing on the shoulders of giants. Was that praise?
Why ask it
The line was already an old saying, and the letter comes from a short polite truce between the two. A popular reading makes it a dig at Hooke, who was a small, stooped man, but nothing in the letter proves it and most historians doubt it. Read the whole letter before writing his answer, since it is courteous throughout.
Most of the Opticks was thirty years old when you printed it in 1704, the year after Hooke died. Was the timing an accident?
Why ask it
He can deny any motive, and the dates stay where they are. Notice too that he wrote it in English, where the Principia was in Latin, which says something about who he wanted reading each book. Follow up by asking what he lost by keeping the work in a drawer for three decades.
You treated light as a stream of tiny bodies, yet the colored rings you measured between two pieces of glass repeat at regular intervals. How sure were you about what light is?
Why ask it
Less sure than his followers were. He gave rays 'fits' of easy reflection and easy transmission to account for the regular spacing, and he put his thoughts on what light might be among the Queries that close the Opticks, phrased as questions. Later physics needed both the particle and the wave, but do not let him take credit for seeing that coming.
The first Query in your Opticks asks whether bodies act on light at a distance and bend its rays. They do, and it has been measured. Do you want to hear how?
Why ask it
He had in mind light bending as it passes the edge of a knife, but the question as he wrote it has a larger answer: during the solar eclipse of 1919, stars seen close to the Sun were photographed slightly out of place. The shift was about twice what a calculation from his own mechanics gives and agreed with Einstein's theory, so a present-day interviewer can use it to tell him his law of gravity was later amended. Write his reaction from how he took correction in the questions about Hooke.
Gravity
In 1684 Edmond Halley traveled to Cambridge to ask what path a planet would follow if the Sun's pull weakened with the square of the distance. What did you tell him?
Why ask it
The account comes from the mathematician Abraham de Moivre, repeating what Newton told him later: he answered 'an ellipse' at once, said he had calculated it, and then could not find the paper. Whether it was truly lost or he wanted to check it before letting it go is the follow-up. A few months afterwards Halley had a short tract on motion in his hands, and the Principia grew from that.
Halley paid the printer for the Principia from his own pocket. Why did the Royal Society, which had ordered it printed, not pay?
Why ask it
The Society had sunk its money into a handsome history of fishes that would not sell, and the minutes show Halley later receiving part of his salary in unsold copies. He also edited the text and soothed its author through the quarrel with Hooke. Ask Newton directly what he owed him, because the book's preface is where he says so.
Hooke said the inverse-square law was his idea. What exactly do you owe him?
Why ask it
In letters of 1679 and 1680 Hooke proposed treating an orbit as straight-line motion bent by a pull toward the center, and he mentioned the inverse square. Newton's reply, written to Halley in 1686, was that guessing a law is not demonstrating it, and he threatened to hold back the third book. A fair answer keeps the suggestion and the proof apart and gives each man his own share.
State your three laws of motion the way you would to a twelve-year-old. Which one was hardest for people to accept?
Why ask it
Usually the first, because everything we push across a floor stops, and it takes an effort to blame friction instead of the nature of motion. Newton credited Galileo with the first two laws, so the answer should not present them as bolts from the blue. Test each law the student writes against one example from the room, such as a cart, a ball or a chair being pushed.
What convinced you that the force bringing down a stone is the same one that holds the Moon in its orbit and raises the tides?
Why ask it
The arithmetic is within reach of a class. The Moon is about sixty Earth radii away, so an inverse-square pull should be 3,600 times weaker there, and the Moon does fall toward the Earth in a minute about as far as a stone falls in a second. Have the student work it through before writing his reply, then ask what the tides and the comet of 1680 added.
You pictured a ball shot from a mountaintop, faster each time. What becomes of the fastest one?
Why ask it
It falls all the way around the Earth without ever landing, which is his picture of what the Moon is doing. The idea is in the opening definitions of the Principia, and the well-known drawing is in a plainer treatise on the system of the world printed in 1728, the year after he died. If the interviewer comes from the present, this is the moment to tell him that satellites now do exactly this, and to ask what he would want measured first.
You wrote that you would frame no hypotheses about what causes gravity. Did you have a private guess?
Why ask it
That sentence belongs to the General Scholium, which he added to the second edition in 1713, a quarter century after the first. In a letter to the scholar Richard Bentley he called it absurd that one body should act on another across empty space with nothing in between, and elsewhere he toyed with a thin ether. The question opens the gap between what he would print and what he would wonder.
A friend reported you as saying you made the Principia hard on purpose, to keep off people with a smattering of mathematics. Did you?
Why ask it
The report is William Derham's, set down after Newton's death, so it is secondhand. Geometry was also simply how a proof was expected to look in the 1680s. John Locke could not follow the demonstrations and is said to have asked Christiaan Huygens whether they could be relied on, which makes a good way to ask who Newton thought his reader was.
You held that space stays fixed whatever moves through it. How does a spinning bucket of water show that?
Why ask it
In the bucket argument the water climbs the sides when it truly spins, whether or not it is moving relative to the bucket, and he took that as a sign of rotation against space itself. Leibniz rejected the idea in his lifetime and later physics dropped it. Let Newton argue his side with what he knew, and keep relativity for a paragraph in your own voice afterwards.
You are reported to have told Halley that working on the Moon's motion made your head ache. What could your theory not do?
Why ask it
The Moon is pulled by the Earth and the Sun at once, and he never got its wanderings to agree with observation as closely as he wanted. It is one of the few places he admitted defeat, so it suits an interviewer who wants a limit and not a triumph. It also leads straight to the man whose measurements he needed.
John Flamsteed, the Astronomer Royal, said you took his star catalog and had it printed against his will. What is your side of it?
Why ask it
Newton's position was that the observations were made in a royal observatory on a royal salary and were overdue, and Flamsteed's was that the work was unfinished and his own. The 1712 edition came out under Halley's hand, and Flamsteed later got hold of most of the print run and burned it. Because Flamsteed's letters are blunt, a pair of students can stage this one as a hearing.
Calculus
What were you trying to work out when you invented fluxions, the mathematics we now call calculus?
Why ask it
He pictured a curve as the track of a moving point, so finding its slope became finding a speed, and finding the area under it became the same problem run backwards. A tract he dated October 1666 presents the method as a way to resolve problems by motion. A student in a first calculus course can ask him to find one tangent his way, which keeps the reply from turning into a speech.
When did you first have the method of fluxions, and who had seen it before Leibniz printed his calculus in 1684?
Why ask it
His papers put the method in 1665 and 1666. In 1669 a short tract went from Isaac Barrow to the London mathematician John Collins, who showed copies around, and that was all the publication it got for decades. The real issue underneath is whether a discovery counts from the day it is made or the day others can read it.
No full account of fluxions was in print until almost forty years after you found the method. What held you back?
Why ask it
Two answers are usually given: the bruising he took over the paper on colors, and booksellers who were wary of mathematics that was costly to set and slow to sell. Neither quite explains four decades. Whatever he says here accounts for the whole priority dispute, so ask it before the questions about Leibniz, not after.
In 1676 you sent Leibniz the heart of your method as a jumble of counted letters. What was the anagram for?
Why ask it
Unscrambled, it gives a Latin sentence stating the two problems of the calculus, finding fluxions from flowing quantities and the reverse. It fixed a date and taught nothing. Leibniz answered the following year by describing his own method openly, so the follow-up writes itself: which of the two behaved better in that exchange?
Did Leibniz take the calculus from you, or did the two of you find it separately?
Why ask it
Historians who have gone through Leibniz's working papers find him arriving at it in 1675 by his own road, with his own symbols. Newton never conceded that, and an answer in his voice should not concede it either. Write his reply as he gave it, then add a line of your own saying what the manuscripts show.
The Royal Society committee that ruled for you in 1712 sat while you were the Society's president, and you drafted its report yourself. Was that a fair hearing?
Why ask it
Leibniz was never asked for his side, and Newton went on to write an unsigned review praising the report in the Society's own journal. An imagined interview that leaves this out has turned into a tribute. Expect him to say the documents speak for themselves, and ask who chose the documents.
We still write dy/dx and the long S for an integral, which are Leibniz's symbols. Does that bother you?
Why ask it
Newton's dot over a letter survives mainly in physics, for change over time. British mathematicians kept to his notation for about a century out of loyalty, and it is often argued that they fell behind the Continent because of it. A lighter question to follow the committee one, and a calculus student can write the same derivative both ways beside his answer.
Alchemy and faith
You left about a million words on alchemy and printed none of them. What were you looking for at the furnace?
Why ask it
The papers were set aside as unfit to print when he died and stayed in the family until a 1936 auction, where the economist John Maynard Keynes bought many of them. Do not let him answer 'gold' and stop. Scholars who have read the notes describe a search for how matter is put together and changes, close kin to his ideas about forces between particles.
Your assistant said the laboratory fire scarcely went out for about six weeks each spring and fall. What were those weeks like?
Why ask it
Humphrey Newton, no relation, was his secretary in the 1680s and described them afterwards: little sleep, meals left untouched, a master he saw laugh only once in five years. It is the closest thing to a day-in-the-life account that exists. Use it for the scene-setting paragraph of a written interview, with the source named.
You advised that Robert Boyle keep 'high silence' about one of his experiments with mercury. Why should some knowledge not be shared?
Why ask it
The advice is in a 1676 letter to the secretary of the Royal Society, a body founded so that its members could share what they found. In his alchemical papers he also signed himself with a Latin anagram of his own name. Ask him to square the secrecy with the open reporting of the prism experiments, and expect him to say the two kinds of knowledge are different.
You were a fellow of Trinity College who had come to reject the doctrine of the Trinity. How did you live with that?
Why ask it
Fellows were expected to take holy orders, and in 1675 a royal dispensation freed the holder of his professorship from the requirement, which spared him ordination. He told almost nobody what he believed, and the papers arguing it stayed unpublished in his lifetime. In a classroom keep the question on secrecy and conscience, and leave the theology itself undecided.
You suggested that the planets' pulls on one another would slowly disorder the solar system until God set it right. Do you stand by that?
Why ask it
The remark is in the Queries of the Opticks. Leibniz seized on it in his exchange of letters with Samuel Clarke, saying it made God a watchmaker who has to keep repairing his watch. This is the place to ask where Newton's physics stopped and his faith took over, and whether he saw any line between them.
You wrote more about Scripture and prophecy than about physics. Which did you think was the more important work?
Why ask it
His study of the prophecies of Daniel and Revelation was printed only after his death, as was a long revision of ancient chronology. He would probably refuse the choice, since he took nature and Scripture to be two records from one author. If the student's Newton picks physics without hesitation, the answer is too modern.
One of your manuscripts reckons from the Book of Daniel that the present age will not end before 2060. Did you mean that as a prediction?
Why ask it
Read the sentences around the number. He says he mentions it not to assert when the end will be, but to stop the rash guesses of people who keep naming early dates and bring prophecy into discredit when they fail. News stories that say Newton predicted the end of the world in 2060 have it close to backwards, which is worth a line in any report.
Later years
In 1693 you sent Samuel Pepys and John Locke strange, accusing letters, and a month later wrote to explain yourself. What happened to you that year?
Why ask it
His own explanation, in the second letter to Locke, was that he had barely slept for a fortnight. Later writers have suggested overwork, the end of a close friendship with the young mathematician Fatio de Duillier, or mercury from his experiments, and none of these can be settled from the surviving evidence. Give him his own account and label the rest as guesses made long afterwards.
In 1696 you left Cambridge to be Warden of the Mint, a post earlier holders had treated as easy money. Why take it, and why work so hard at it?
Why ask it
The offer came through Charles Montagu, a Trinity man who was by then Chancellor of the Exchequer, in the middle of a recoinage that was calling in the country's worn silver and striking it afresh. Ambition, salary and weariness with Cambridge are all defensible answers. One checkable detail: he kept his professorship until 1701, so he did not burn the bridge at once.
You questioned coiners and informers in person, and the counterfeiter William Chaloner was hanged in 1699. Did that trouble you?
Why ask it
Counterfeiting the coin was treason in law, and Chaloner had also accused the Mint of incompetence before Parliament, so this was personal as well as official. His last letter begging Newton for mercy survives, and no reply is known. With younger students the question can stay on duty and proportion: how far should a careful man go for an accurate coinage?
No portrait of Robert Hooke is known to have survived, and you were president of the Royal Society when it moved house in 1710. Did you have anything to do with that?
Why ask it
The story that he had the painting destroyed, or saw to it that it was left behind, is repeated everywhere and rests on no document. That makes it a useful exercise: the student has to write an answer the evidence cannot settle. Have him deny it, and say in a note that nobody can show otherwise.
As Master of the Mint you advised the Treasury in 1717 on what a gold guinea should be worth in silver. Did you see what would follow?
Why ask it
The guinea was set at twenty-one shillings on his report. That still valued gold more highly than the rest of Europe did, so silver went abroad, gold stayed, and Britain drifted onto gold as its standard. Most historians call that an accident and not a plan, which makes it a fair test of whether the student's Newton claims too much foresight.
You lost heavily when South Sea Company shares collapsed in 1720. What did you get wrong?
Why ask it
His niece remembered the loss as about twenty thousand pounds. The famous remark that he could calculate the motions of the heavenly bodies but not the madness of people reached print secondhand and may have been polished on the way, so quote it as reported. The more interesting line of questioning is why a man that careful with evidence seems to have bought back in when the price was near its peak.
You never married and kept few close friends. Who knew you best?
Why ask it
Candidates include John Wickins, who shared his college rooms for about twenty years, his niece Catherine Barton, who kept his London house, and her husband John Conduitt, who gathered recollections for a biography. Each saw a different man. Choose one, find what that person wrote down, and build his answer from it.
The last edition of the Principia came out the year before you died. What had you changed your mind about since the first?
Why ask it
Comparing editions is the nearest thing to hearing him revise aloud. The General Scholium and its remarks on God arrived in 1713, the rules of reasoning were reworked, a passage that had named Leibniz was rewritten without him, and Flamsteed's name was thinned out. A translation that marks the differences between editions lets a student confirm each of these.
People asked how you made your discoveries, and you are reported to have said it was by keeping the problem constantly in front of you. Is that all there was to it?
Why ask it
The remark reaches us secondhand, so introduce it as reported. It fits what his secretary saw in the 1680s: a man who would break off a walk in the garden, run upstairs and write at his desk standing up sooner than stop to pull over a chair. Set it against the apple and ask him which is nearer the truth, the sudden idea or the long siege.
In 1669 you wrote a friend a letter of advice before he traveled abroad. What would you tell a student setting out now?
Why ask it
The friend was Francis Aston, another fellow of Trinity, and the letter survives. It tells him to put his talk as questions and doubts instead of flat assertions, to let an insult pass in a foreign country, and to find out about mines and the working of metals wherever he goes. Newton never left England himself, which is worth putting to him, and an answer built from the letter will sound more like him than one about following your dreams.
Of everything you did, which discovery would you put first?
Why ask it
At twenty-nine he told the Royal Society that his finding about colors was the oddest, if not the most considerable, detection yet made in the workings of nature. Ask whether he still ranked it there after the Principia. If he names neither and chooses his reading of prophecy, that is consistent with the papers he left.
Near the end you are said to have likened yourself to a boy on the seashore, pleased with a smoother pebble while the great ocean of truth lay undiscovered. What was in the ocean?
Why ask it
The saying was written down after his death by people repeating what they had heard, so introduce it as reported. The strongest follow-up asks him to name the open problems, and he left a list: the Queries that close the Opticks ask what causes gravity, what light is and why matter holds together. It makes a natural last question because it ends on what he did not know.
Writing an imagined interview with Newton that holds up
Practical guidance for the conversation itself
Before the first question
Pick the year you are visiting
A Newton of 1666 is twenty-three, unknown, and has never heard of Leibniz and has no idea he will one day run the Mint. A Newton of 1726 is Sir Isaac, president of the Royal Society, and can look back on all of it. Put the year in the first line of the interview and drop any question he could not yet answer.
Say which calendar you are using
England still ran on the old Julian calendar in his lifetime. By it he was born on Christmas Day 1642, and by the calendar we use now the date is 4 January 1643, which is why reference books disagree. Choose one, say so once, and keep to it for every date in the piece.
Choose eight or ten, not the whole list
A class interview usually runs to a page or two. Take one or two questions from each group so the piece covers the farm boy, the experimenter, the author of the Principia, the disputant, the private scholar and the public official. An interview built only from the gravity questions describes about a third of the man.
Decide who is holding the notebook
A reporter from the present can ask about the apple and the 2060 manuscript, and can tell him about satellites and the eclipse of 1919. Halley, visiting in 1684, can only ask about orbits. Naming the interviewer settles what vocabulary is allowed and keeps the questions from drifting into things no visitor of that year could know.
Writing what he says back
Use his sentences where they exist
For the prism there is the 1672 letter, for gravity the General Scholium, for his doubts the Queries of the Opticks. A short phrase in quotation marks, with the source in brackets, carries more weight than a paragraph of invented speech. Mark clearly which words are his and which are yours.
Keep his temper
People who dealt with him describe a guarded man, slow to publish, quick to take offense and unforgiving once crossed. A Newton who chats warmly and laughs at himself is easier to write and is not the one in the letters. Short answers, a correction of the interviewer's wording and the occasional refusal are closer.
Give him only what he knew
He had no word 'scientist' and called his subject natural philosophy. He knew nothing of atoms as chemistry later understood them, of energy as a quantity, or of anything Einstein wrote. When the modern answer matters, step outside the interview and give it in a sentence under your own name.
Let him decline
On alchemy and on the Trinity he told almost no one anything while he lived. An honest version has him change the subject, and then a line from you explains what his private papers contain. The refusal is itself accurate reporting.
Taking an answer back to the evidence
Find the document behind the question
Nearly every question here leans on a letter, a notebook page or a printed passage. Cambridge University Library has digitized many of his papers, and the Newton Project publishes transcriptions that can be searched by word. Before writing a reply, find the passage and read a little on either side of it.
Ask who told the story, and when
The apple was written down in 1726, the seashore after his death, the remark about the madness of people at second hand. The dog Diamond, supposed to have upset a candle onto his papers, enters print decades after he died, and his own secretary recalled no dog in his rooms. A late story can still go in if the interview says it is late.
Read one opponent in his own words
Hooke, Leibniz and Flamsteed each left their side, and none of them comes off as a fool in it. Even one paragraph from the other man changes how the question should be put, and it stops the interview from becoming Newton's case argued twice.
Separate what is known from what is argued
That Halley paid for the Principia is known. Why Newton shelved the Moon calculation, what made him ill in 1693 and what became of Hooke's portrait are argued. A good interview shows the difference, with a plain 'historians disagree' where they do.
Four ways the exercise goes flat
The apple on the head
It is the first thing every reader expects, and it is not in any early account. Ask the apple question, have him tell it the way Stukeley recorded it, and the piece has corrected a legend in its opening lines.
The genius who needed nobody
Barrow passed his work on, Collins copied it, Oldenburg carried his letters, Halley paid and edited, Flamsteed supplied the measurements and Roger Cotes saw the second edition through the press. An interview that names none of them has described a statue.
Alchemy as an embarrassing hobby
He gave the furnace and the prophecies as much care as the prism. Treating them as a lapse, or leaving them out, produces a modern physicist in a wig. Keynes, who had read the papers, called him the last of the magicians, and a few questions from that group keep that side of him on the page.
Questions that only admire
If every question could be answered with thanks, add the committee of 1712, Flamsteed's catalog or the Chaloner case. He was at his most revealing when he was defending himself, and those are the answers a teacher or reader will remember.